CONTACT! Magazing Issue 87 Mazda Rotary Special

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CONTACT! ISSUE 87 PAGE 1

By Patrick Panzera

PO BOX 1382 Hanford CA 93232-1382 United States of America 559-584-3306 Editor@CONTACTMagazine.com

Volume 15 Number 4 Mar-Apr 2007

Issue #87 MISSION CONTACT! Magazine is published bi-monthly by Aeronautics Education Enterprises (AEE), an Arizona nonprofit corporation, established in 1990 to promote aeronautical education. CONTACT! promotes the experimental development, expansion and exchange of aeronautical concepts, information, and experience. In this corporate age of task specialization many individuals have chosen to seek fresh, unencumbered avenues in the pursuit of improvements in aircraft and powerplants. In so doing, they have revitalized the progress of aeronautical design, particularly in the general aviation area. Flight efficiency improvements, in terms of operating costs as well as airframe drag, have come from these efforts. We fully expect that such individual efforts will continue and that they will provide additional incentives for the advancement of aeronautics.

EDITORIAL POLICY CONTACT! pages are open to the publication of these individual efforts. Views expressed are exclusively those of the individual authors. Experimenters are encouraged to submit articles and photos of their work. Materials exclusive to CONTACT! are welcome but are returnable only if accompanied by return postage. Every effort will be made to balance articles reporting on commercial developments. Commercial advertising is not accepted. All rights with respect to reproduction, are reserved. Nothing whole or in part may be reproduced without the permission of the publisher.

SUBSCRIPTIONS Six issue subscription in U.S. funds is $24.00 for USA, $28.00 for Canada and Mexico, $40.00 for overseas air orders. CONTACT! is mailed to U.S. addresses at nonprofit organization rates mid January, March, May, July, September and November. Please allow time for processing and delivery of first issue from time of order.

ADDRESS CHANGES / RENEWALS The last line of your label contains the number of your last issue. Please check label for correctness. This magazine does not forward. Please notify us of your date of address change consistent with our bimonthly mailing dates to avoid missing any issues.

COPYRIGHT 2007 BY AEE, Inc.

You may have noticed a bit of a change in this issue of CONTACT! Magazine, namely, we are almost double in size! 40 pages of content as opposed to the usual 24.

This happened due to a plea made to a few e-mail groups for rotary PROJECTS in PROGRESS engine articles. I was inundated Another change in this issue is with quality articles and had more somewhat taboo with aviation magthan I could possibly use for the azines, but something I’d like to time and budget allotted. I still have start doing on a regular basis; that several articles that didn’t make this would be publishing articles on proissue that will be printed in subsejects that are not “done”. As an exquent issues. I wish to express sinperimenter myself, and being natucere gratitude to everyone who rally inquisitive, I’m equally interestsubmitted an article, and apologize ed in what people are doing, as I to those who worked hard to meet am in what they have done. It’s our deadline and I was unable to great to read about one’s trials and print their article in this issue. tribulations and their ultimate success with or without failure, but I think we all can learn and/or be inspired by reading about someContinued on page 38

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Rotary Progress and Update. Ed Anderson gives us an update on his 13B installation powering his RV-6A that we reported on in earlier copies of CONTACT! Magazine.

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A new offering from a new supplier, Propelled Engineering. Art and Cheryl Reudko along with Ted Alexander are embarking on a new endeavor of bringing the convenience of a FWF package to the RV community first, and others as demand dictates. By Earnest Kerr

13 X is for Experimental; A Rotary Odyssey. A long anticipated article from rotary engine guru Tracy Crook that brings us up to date with his trials and tribulations of taming his record-breaking RV-4.

28 One-off, single rotor conversion for an Avid. A work in progress is described, detailing building a single rotor engine from a mix of available OEM parts and a few custom parts, gets the weight down and power up while hopefully not sacrificing reliability. By Richard Sohn 31 Bill and Linda Eslick’s rotary powered RV-6. With a $5,000 FWF investment, Bill and Linda have done a remarkable job with their creation. By Bill Eslick 34 Decisions, Decisions, Decisions. Considering a rotary engine for your experimental aircraft? This article does its best to bring you up to speed by detailing what has worked and what may not work while the author describes his Cozy Mark IV. By John Slade 39 Duckt is now ductless! Perry Mick picks up where he left off in this follow-up article on his adventure into his ducted fan experiment, carried out with the use of his sleek Long-EZ. By Perry Mick On the cover: Tracy Crook’s Renisis (Mazda rotary) powered RV-4. Photo courtesy of Ed Hicks.

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By Ed Anderson eanderson@carolina.rr.com Ed Anderson first appeared in CONTACT! Magazine with his three part article series, spanning issues #49-51. He was then kind enough to write a follow up article in issue #63. We are especially appreciative of his supPhoto: Pat Panzera port of our magazine and thank him for his past and current We caught up with Ed at the 2006 Sun ‘n Fun Fly-in and found him sitting contributions. In addition to be- comfortably in the auto engine parking area. ing a prolific writer for us, Ed is first an electronic engineer and a pilot who obviously RV-6A flown by me, Ed Anderson, all taxiing to parking loves things mechanical. He makes no claim to exrow 19 (better known as Rotary Row). We were later pertise in any area but does have a broad underjoined by another rotary powered RV-6 by Bill Eslick from standing of electronics, mechanics and engines.

Texas. (Read about Bill’s plane on page 31 as well as Like most true experimenters, he enjoys technical Tracy’s plane on page 13)This made five rotary powered challenges and is happy to pass along his successaircraft at Sun & Fun, another first for the rotary folks. In es and mistakes so that others may learn from them. fact, the rotary powered aircraft outnumbered all other ~Pat type auto conversions put together.

Aviation "firsts" of any kind, tend to attract attention; the more radical they are, the more attention they get. When radical, inexpensive, successful and FAST team up, well that really attracts attention. At the annual Sun ‘n Fun flyin, the Rotary Engine crowd has received their fair share of attention, and then some. There was the first-ever four ship formation of aircraft powered by the Mazda 13B rotary (Wankel) engine that roared in from the North like a bunch of noisy barbarian upstarts. Landing in trail at Lakeland, the unsettling and raspy note of their exhaust pipes told even the uninitiated that something different lurked under their cowls.

Well, it did not take long for other "Firsts" to be garnered when Tracy Crook (Real World Solutions) of Bell, Florida flew his rotary powered RV-4 to the winning time for the Sun ‘n Fun 100 in the 160 HP class. Despite having a fixed-pitch prop, a somewhat aerodynamically dirty airframe, a muffler hanging in the slipstream and some defective ballooning race tape, his racer #29 launched, rapidly overtook, and passed all his competitors. His speed was clocked at an average of 180 Kts (209 mph) from a standing start. He has now exceeded 220 MPH with his new Renesis engine from the Mazda RX-8 sports car.

As these events at recent Sun ‘n Fun airshows indicate, the rotary crowd has come a long way since I wrote a series of articles for CONTACT! (Issues 49, 50, 51) describing the rotary engine installation in my RV-6A. I provided an update of lessons learned and changes made since then in issue #63 in 2002. Well, here we are five years later and change continues.

SLOW START Photo courtesy of Chuck Dunlap.

The rotary powered RV formation looked like an advertisement from Van's aircraft for rotary powered experimentals. There was an RV-3 flown by Finn Lassen, RV-4 piloted by Tracy Crook, RV-6 pilot Chuck Dunlap and an www.ContactMagazine.com

A little background for those not familiar with the history of the Mazda rotary (Wankel) engine in aircraft. When I started my project in 1992, there were less that a handful of folks that had actually become airborne with a rotary engine – and that with mixed results. The rotary engine was a new and different beast and it took a while to understand its peculiarities. Not to detract from those earli-

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er attempts, but in my opinion, Tracy Crook garners the credit for demonstrating the rotary as a reliable and viable aircraft powerplant. (See Tracy's article immediately following this article.) While others had flown previously as experiments, Tracy’s installation flew and has flow regularly since 1994 (over 1650 hours accumulated as of this writing), clearly demonstrating a mature operational FWF installation. Other individuals have contributed with their experience and knowledge ranging from Rotary Racers to those just loving to dive into the theory of the rotary, thermodynamics, aerodynamics, combustion processes, etc, etc. Recognition has grown to the point that a Swiss company is developing a rotary powered aircraft powerplant package that is designed for, and is close to, certification.

A strong contributor to the rotary growth has been the number of vendors with products for the rotary. Again, Tracy Crook was first and foremost by providing electronic modules as well as a planetary PSRU, and now many improved components for the rotary engine itself.

Motor mounts, cowlings, exhausts and engines can now be acquired if you have more money than time or the lack of skills to produce your own.

Rotary powered aircraft have twice won “Best Auto Conversion” at Sun & Fun of which my rotary powered RV6A was so honored in 2001. As previously stated, Tracy Crook won his HP class in the Sun & Fun 100 air race in 2003 but also took home “Best Auto Conversion” that year. There have been as many as seven flying rotaries parked at Sun & Fun. It was great being part of the first rotary formation flights on the way to Sun ‘n Fun. These are just a few examples of the rapid growth in interest surrounding the use of the Mazda Rotary 13B and now the new, improved and more powerful RX-8 Renesis engine in aircraft.

It’s hard to compare that time period with today, when rotary enthusiast can communicate and share with hundreds of others via e-mail and the Internet. Needless to say, sharing the lessons-learned has shortened the time and risk of those doing such conversions today. With this brief history overview out of the way, I’ll now turn to the latest changes made to my own rotary installation.

MY ROTARY STORY (CONTINUED FROM 2001)

exhausts, and engines, I realize that of my original firewall forward installation, the only original components remaining are the engine mount, exhaust headers and the ignition system. All else has been replaced as my understanding of the engine, cooling and induction systems grew over the years. This exemplifies the heart of experimentation – you experiment and you learn. The steady growth of folks who have installed rotary engines and their contribution to our body of knowledge has provided a synergistic effect in understanding what works, what works well and what does not work.

SUMMARY OF CHANGES So why my latest changes? Basically because a better way or improvement was found and proven. My very first flights encountered high oil temperatures, elevated coolant temps and while performance was safe, it was short of sterling. The original induction system was based on what worked for the rotary race car industry, which as it turns out, is not appropriate for the rpm ranges we fly with the rotary engine. The most significant changes since 2001 have been the:  Propeller speed reduction unit  Propeller  Induction system  Cooling ducts  Fuel Injection monitoring system The original 1986 naturally aspirated 13B was swapped out in 2001 for a 1991 turbo block. High compression rotors were installed and a new intake was designed. By this time, I junked the aftermarket automobile EFI system which had failed (fortunately on the ground), for one of Tracy Crook’s Real World Solutions, EC2. This unit combined computerized ignition and fuel injection modules which added significantly to the ease of tuning the fuel maps and to peace-of-mind with the unit’s redundant CPUs and sensors.

As mentioned, the original induction design was based on what had proven effective for the rotary automobile racing crowd. However, they were winding engines past 9000 rpm whereas our rotaries were operating between 5000-6500 rpm. Short, large diameter intakes provide benefits at higher RPM, whereas just the opposite configuration is needed at (comparatively) lower RPM for

This article updates the changes to my rotary installation since the August, 2001 update in issue #63 of CONTACT! and the adjacent photo shows my rotary powered RV-6A, N494BW, which first flew in Sept 1998. The photo was taken shortly after it was painted in 2000. A fairly conservative looking RV-6A other than the air intake under the spinner and louvers along the side of the cowl, there is not much to indicate the radical power plant underneath. I now have 350 flying hours with the rotary with a 2600-mile trip being the longest single trip.

As I reflect on the years and hours of flying that have passed, not to mention the experiments with intakes, www.ContactMagazine.com

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maximum torque and power. Also, with the lack of a shiftable gearbox, the propeller load may well prevent achieving the RPM that would result in the power that you were hoping for.

COOLING SYSTEM Increased power output is a great result of modifications to engine and systems.

However, you may find your cooling system is no longer adequate to reject the additional heat generated. The rotary is perhaps more sensitive than piston engine to heat excursions out of its nominal operating limits. You can always add larger radiators, but that adds weight and drag, not to mention time and money, so gaining the maximum cooling with a given installation is always advantageous. It turns out ducting in and out of the cowl and heat exchangers are crucially important.

The basic coolant system design remains unchanged, but improvements to ducting, mounting and using lighter fittings were made. It was quite a learning experience and it turns out that intuition about how and what airflow should do can frequently be incorrect. Theory often points out a direction, but until you try it you just don’t know how well it will work in your particular application.

One thing that has become apparent is that unless you copy or duplicate a cooling approach exactly, the results may be surprisingly different. That’s the reason that what worked for “Joe” frequently does not work as well for “Bill”. Small and subtle differences in installation can make a big difference in performance.

Finally, we really need information to understand what our alternative engine is doing under the cowl. I ended up developing my own EFI System Monitor, which fits in a 2 ¼” instrument hole and provides information about the engine’s fuel system.

REAL WORLD SOLUTION PSRU The propeller speed reduction unit (PSRU), gear ratio, and propeller have all been changed, with the PSRU being changed essentially two times. The first time was because my original Ross 2.17:1 redrive showed signs of gear galling after approximately 160 hours, so that one was removed and replaced with one from Real World Solutions (RWS 2.17:1 unit), and then with a RWS 2.85:1 gearbox. As a result of a lower gear ratio (and more power from the new engine), a much larger propeller was possible. The prop has gone from a 68” diameter (72” pitch) to a much larger 76” diameter x88”, made by Clark Lydic of Performance Propellers. The transformation was completed and the performance goals I long sought were achieved when I switched gear ratios. All this was done after Tracy Crook demonstrated to me what his rotary powered RV-4 could do with the lower 2.85 gear ratio. The lower gear ratio off-loads the engine www.ContactMagazine.com

permitting higher static engine rpm and power and the greatly multiplied torque permitted switching to a larger propeller. The difference was awesome! Take-off acceleration was significantly improved and rate of climb increased to the 1500-1700 fpm range, depending on OAT and weight. My RV-6A is approximately 110 lbs. heavier empty than the norm.

TORQUE I quickly found that my plane did not have sufficient rudder control for a WOT take off with this new combination, requiring judicious use of differential braking to remain on my narrow 35 foot wide runway, with ponds off each side to add to the excitement. So the “fear” factor plus wanting to hit 6,000 engine rpm static on take off led me to remove two inches from the prop diameter making it 74x88, still an aggressive prop. Take-off with the rpm staged to airspeed increases have made the take-off just as impressive, but a bit less hair raising. I am now very pleased with the performance, particularly in getting out of short grass strips and over tall trees. An additional benefit was my top speed now hits 200 MPH TAS. As an aside, I decided to have the body of the RWS PSRU nickel-plated instead of anodized based on the recommendations of a local plating shop. This has turned out to work fine with the gold toned nickel plating protecting the aluminum from oxidation and corrosion as well being considerably less expensive. However, a problem did result. After flying with the nickel-plated gearbox for approximately 10 hours, I went out one morning to fly and found that the propeller would not rotate without considerable effort. To make the story short, I discovered on disassembly that the nickel plating had also covered the bronze pressure bearing. The gold tone of the nickel plating blended with the bronze of the pressure bearing and was not immediately noticeable. So even though the plating shop was told to protect the

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bearing, their efforts were not completely successful.

After returning the PSRU to RWS, Tracy bore out the nickel plating that had flaked off the bronze and had become compressed around the shaft to the point that there was no clearance between the bearing and shaft.

Fortunately, no damage was done and I have added nearly 160 hours of flying with it.

lengths and port timing there is a mini-supercharging effect that if properly capitalized on can add 15% in torque. The 65 mm dia throttle body is from a Ford Mustang, much simpler and several pounds lighter than the original Mazda throttle body used.

The message here is that selection of the correct ratio of the speed reduction unit (be it belt or gear drive) is very important to the overall performance of an alternative engine installation. I also learned that large diameter, relatively slow turning propellers and the mass of air they accelerate with each revolution can really supercharge the take-off and climb-out performance. It has taken a number of years to finally arrive at the ideal match for my installation. Other type aircraft, engines and flight regimes may demand a different combination to achieve the desired goal, but it is something well worth spending time on.

INDUCTION SYSTEM The only substantial change in the induction system since 2001 has been to replace the rather crude throttle body mount (made of fiberglass enclosed in a metal shell) with a plastic casting. I was rather amazed at the capability of modern polyurethane resins so I decided to see if I could improve on the earlier ugly fiberglass/metal throttle body mount, which was not only ugly, but heavy as well, by casting a new, improved one from plastic.

Above is a photo of the adjustable intake and polyurethane cast throttle body mount installed. Not only is it much easier and quicker to pour the resin into a simple mold, but the end product takes much less finishing than fiberglass and is also lighter. I have over three years of flight time using the two part polyurethane resin poured into a foam board mold and no sign of deterioration due to the heat and caustic environment under the cowl.

COOLING AND AIR DUCTS Up until the last few years, probably no rotary installation became airborne without one of the first things noticed by the pilot is that the engine cooling was less than adequate, sometimes way less than adequate! Research and experimentation has provided a lot of useful information about what cools and what does not. Recent installations have benefited by making their first-flights without worrying about steam blowing from beneath the cowl.

The above photo shows the mold and silicon cores (for the air passages), as they would hang down into the mold cavity, where the polyurethane resin was poured.

Once cured, I removed the new part and cut a hole in its front for the throttle body air passage. Aluminum tubes were then inserted through an aluminum plate (to which the plastic casting is bolted), into the air channels left when the silicon cores were removed from the casting.

The bible for liquid engine cooling is undoubtedly the Kuchmann and Weber (K&W) tome written back in the 1940s. Chapter 12 is probably the most pertinent, if you have the patience to wade through the pages of math.

After a lot of study and experimentation, I believe I have

An additional induction refinement shown in the adjacent photo, is the use of telescoping aluminum tubes to adjust intake runner length. I have a total adjustment range of 4� and fly in the winter with the runners at maximum length and in the warmer months at minimum length.

Mazda technical papers reveal that for certain manifold www.ContactMagazine.com

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come to understand what makes a ducting system work.

I have changed and reshaped the plenums for my radiators six times since 2001. I started out with a total of 48 square inches total opening for my two radiator cores and have now reduced that to 32 square inches. In the meantime, power has increased from around 150 HP to 180 HP, increasing the amount of heat to be rejected, so I believe this is a fair indication of the increased effectiveness of the ducts based on the K&W information.

the core), therefore the turbulence shadow cast on the core was smaller. According to K&W a perfectly implemented “streamline duct” (the bell shape) would theoretically recover 82% of the possible static pressure recoverable from the kinetic energy of the air in the duct. I apologize for my poor explanation, but suffice it to say that I found my attempts at implementing the K&W findings improved my cooling system considerably.

Above is a photo showing the reduction in plenum opening area (and therefore drag) from earlier attempts. The newer plenum features a considerable reduction in opening area as well as pinched shape to the cross section area of the duct. While somewhat difficult to see, the white area is foam used to fill in the plenum and make the area conform to a bell shape, which expands in area/ volume just before the radiator core.

This last photo shows the pinched center and “bell” flare of the plenum just before the radiator core. The pinched center is my own innovation. The K&W Streamline duct requires more room than I had available in my installation, so I reasoned that if I could maintain the boundary layer attachment by speeding up the duct airflow using the Bernoulli principle (narrowing duct increases airspeed), that would assist in delaying flow separation and improve cooling. Certainly not as effective as the full implementation of the Streamline duct, but I believe it was a good compromise based on the understanding I gained. Suffice it to say it meets my cooling needs with a minimum of duct opening and drag.

It is fairly clear that the most significant factor in reducing cooling effectiveness of a duct is where separation of the boundary layer occurs. My first attempt (with the wide opening) was the traditional sinusoidal shape commonly shown in most drawings of cooling ducts. It expands dramatically once past the opening. As it turns out, this theory was based on the shape of streamlines observed by flowing streams of smoke and observing their flow pattern around a free standing radiator core.

It was assumed that since these smoke trails were the “natural” airflow, it should be the way to shape your duct.

For reasons too involved to go into here, it turns out this is about the worst possible shape for a cooling duct. The basic reason is that the rapid expansion near the entrance essentially ensured that boundary flow separation would (and did) occur. This separation caused “eddies” as the flow separated and rotated. The eddy, in effect, cast a shadow downstream that grew in size until it reached the radiator core.

The area of the core covered by the shadow of turbulent airflow had its cooling effectiveness considerably reduced. K&W pointed out that if the duct was shaped like a trumpet bell with a long mouth, that the airflow boundary layer would maintain its speed in the non-expanding portion of the duct thereby delaying separation. To achieve the desired pressure recovery, the duct was then rapidly expanded in a bell shape just before the core. Any separation that did occur was up in the far corner of the bell duct and near the radiator (very close to www.ContactMagazine.com

ELECTRONIC FUEL INJECTION SYSTEM MONITOR Knowing what is transpiring under the cowl is crucial to succeeding with an alternative engine. I started out with basically RPM, manifold pressure and EGT. I quickly realized that I wanted more information. I looked around at the aircraft fuel monitoring systems and decided they were way too expensive and failed to provide all the information I wanted, so I developed my own.

The first one (shown here) was built following an analog system approach (Yes, I do go that far back). It provided air/ fuel ratio indication, fuel flow and total fuel used. However, it was large, complex, had a high part count and no flexibility to add such things as alarms or other features without a complete redesign.

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With a sigh, I decided to go digital. After a couple of years learning to program those small microchips and design circuit boards, I developed a digital version shown in the photos below. The digital version provides: ● Fuel flow rate. ● Air/fuel ratio. ● Fuel used. ● Fuel remaining. ● Time remaining.

(Current burn rate). ● Switch tank alarm. ● Low fuel warning. ● RPM. ● Power (calculated based on fuel burn). ● Semi-automatic calibration.

Fuel remaining as well as the pilot’s selected alarms are stored in non-volatile memory so when you shut down the engine, the system “remembers” the fuel you have remaining, and any alarm changes made, etc. I recently added the capability to display graphically the fuel map of the electronic fuel injection computer as well as modify it and the ignition timing (also computer controlled). This graphical display makes it much easier to see if you have “valleys” or “hills” in your fuel map that could adversely effect engine performance.

I believe a unique feature of my design is that it requires no expensive fuel flow transducers and in fact, no connection to the fuel plumbing at all. There is also no need to subtract fuel returned to the tank from the main fuel flow, which frequently requires the use of two expensive fuel flow transducers. The new digital design is much smaller and has fewer parts-count enabling it to easily fit in a 2 ¼” instrument hole. The only thing I was not entirely happy about was the display. Finding a suitable display that will fit inside the 2 ¼” constraint was not easy.

The design is now modified to use one of the new Organic Light Emitting Diode (OLED) displays. These provide a brilliant color display that is much easier to read in all lighting conditions. I am in the process of redesigning the circuit board to use surface mount devices (very, very tiny little components) and hope to have this version with OLED display ready for Sun & Fun 2007. Another electronic projects include an angle of attack indicator using pressure sensors and LEDs. It’s functioning in the bench prototype stage but has not flown as yet.

CONCLUSION Taking on an alternative engine project is not for the faint of heart. I tell folks it’s like a miniature research and development project; it will almost certainly take longer than expected and cost more. However, nothing provides the thrill and satisfaction that successfully flying behind your “own” powerplant in your “own” aircraft does. If you simply want to fly, then put a Lycoming in your bird and go enjoy. But, if you like a challenge and have the patience to “tinker” with your installation to find the optimum configuration, then this is probably for you. www.ContactMagazine.com

Each airframe type seems to have its own unique problems to solve. We now have a FWF configuration for the RV aircraft that we know will work, as a number of flying installations demonstrate. A number of canard airframe builders have wrestled with their own unique challenges, primarily cooling problems, but it appears that a working standard for that airframe is rapidly maturing. However, there are still many areas where different and better approaches are still awaiting someone to tackle them and demonstrate their validity.

The rotary community now has a number of means of communicating and sharing information. We have two email lists and numerous builders’ web sites of rotary powered projects. I strongly recommend that anyone interested in rotary aviation to at least joint the rotary email lists and “lurk”. You will find a great deal of information and not just a few opinions. It can save you time and money as well as lessen risk. CONTACT! Magazine is also an excellent source of information and contacts and if you don’t subscribe, I recommend that you do.

The rotary engine has proven to be an excellent alternative engine for an aircraft power plant, but like any alternative engine, it demands attention to detail and understanding that there are risks associated. Approach it with your eyes and mind open and enjoy a community of folks with interests and characteristics similar to your own.

I want to thank Pat for his invitation to provide an update on my project. I hope you have found the update informative and interesting.

Ed Anderson aka Rotary_Ed RV-6A N494BW Rotary Powered eanderson@carolina.rr.com

Flying Rotary Engine Information Sources: FlyRotary Group web page: www.flyrotary.com RotaryEngine Group (Hosted by Paul Lamar ) Web Page: www.home.earthlink.net/~rotaryeng/ACRE.html List of Rotary aviators and their projects web page: www.members.aol.com/_ht_a/rotaryroster/flying.html

Rotary Best Practices Web page (maintained by Mark Wrathall) accumulates the lessons learned, the good, the bad and the Ugly regarding flying rotary engines. web page: www.members.aon.at/wrathall/rotary Edward Klepeis, Paducah, Ky, creates custom radiators for the flyers as well as motor mounts, exhausts, you name it. 1-270-898-3776 Web-site: www.techwelding.com And last my own web page of the history of my RV-6A rotary powered project, hosted by Don Mack on this RV webpage. www.dmack.net/mazda/index.html

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Nothing can withstand the force of an idea whose time has come.

Ernie is a retired advertising copy writer, photographer and illustrator with 45 years experience, as well as being a rotary engine fan.

He’s in the process of forming a Florida corporation called the “Association of Rotary Powered Aircraft” (ARPA) and beginning in November, 2007, Ernie plans to publish an annual “State of the Art for Rotary Engines in Aircraft”. We’ll stay in touch with Ernie and keep our readers updated with his progress. ~Pat

By Ernest Kerr Ehkerr@aol.com

The 13B firewall forward package being offered by Propelled Engineering.

Could this be the time for a standardized, firewallforward, Wankel rotary engine package? In this issue of CONTACT! Magazine you will learn why the Mazda Wankel Rotary engine is potentially more suited for aviation than just about any other automobile engine and potentially better suited than certified piston aircraft engines. Those who fly rotaries swear by them. A rotary engine has three moving parts which in and of themselves historically don’t fail. Other things such as hoses, electronics, and even seals can fail but in most cases, other than a loss of oil, the pilot of a broken rotary will fly to the nearest airport. An oil loss will seize the rotors and the aircraft will dead stick like any other. However, unlike any other water cooled engine, a rotary will actually fly for some time with a coolant loss. Vibration is the cause of a serious amount of aircraft maintenance from metal fatigue to shaken electronics. The rotary though, is like an electric motor; it spins, and that spells s-m-o-o-t-h. It’s a rotary exclusive that that motion blends perfectly with a spinning propeller. It can burn 87 Octane automobile fuel so the savings in operating costs will more than pay for overhauls, if ever needed. It will also burn 100LL when the FBO doesn’t offer mo-gas. It’s compact, it has high power-to-weight ratio and is the perfect replacement for any design specifying an O-320 or O-360.

WHY AREN’T THERE MORE FLYING? OK, if the rotary is so perfect for airplanes why isn’t everyone flying them? There are several reasons. Familiarity, tradition, resale value, and aviation insurance top the list. Aircraft manufacturers can only use certified aircraft engines and they don’t make many changes in those engines because of the recertification expense, so it seems common sense to continue with what has been the norm for several generations. Then too, kit builders today typically avoid experimenting in the building process; they rely on the kit manufacturers to do the experi-

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menting. Automotive engine converters follow the same strategy. A proven auto engine, that everyone is familiar with, is repackaged for aircraft and the cost savings make the sale. The rotary has not been able to follow suit because the rotary is so strange and the community of rotary experimenters is so small that progress in modifying the rotary for aircraft use has been painfully slow.

There are many unique features of the rotary that must be modified and it has taken until now to reach the point where a FWF package could possibly be assembled from the steady stream of contributions from those experimenters and even commercially proven components.

THE TIME HAS COME For years It has been the aspiration of rotary enthusiasts to assemble a standardized FWF package. Twenty years ago a NASA study found the rotary engine to be superior to both diesels and small turbines. Oregon based Powersport, Inc. www.powersportaviation.com was the first commercial FWF offering. However, they sold their project to Ratech Machine, located in Osceola, Wisconsin www.ratechmachine.com. Ratech then announced their intention to continue the Powersport business plan with installations for a variety of experimental aircraft. Few were ever sold though because a complete installation would cost over $35,000 USD. Then Mistral Engines, LLC, a Switzerland company with offices in Daytona Beach, Florida www.mistral-engines.com was so convinced that rotaries are the future for aviation that they have invested millions of dollars to completely design, manufacture and certify a rotary engine for the commercial aviation market. It’s flying now in a Piper Arrow and it’s a beautiful package but, no surprise here, priced way beyond the kit builders’ budget. However, Mistral has been known to sell certain components to kit builders.

The need for a reasonably priced FWF package, then, still remains unfilled and awaits a champion.

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MISTRAL Liquid-cooled 2 rotor engine for light aircraft, including propeller speed reduction unit and digital engine management system, offers 193 HP NA, as described on the previous page.

That champion may well be Propelled Engineering, Inc., located at the North Tampa Airport (KX39) in Tampa, FL. Propelled Engineering www.propelledengineering.com is a new start-up, less than a year old, but represents the culmination of decades of planning and study by the founders, Art and Cheryl Rudko. Ted Alexander, an aviation structural engineer, completes the team. Art started life as a Canadian farm boy who began his career in aviation with bush flying in some of the most remote Northwest Territories. It took special skills to fly and repair those bush planes and, over the years, Art earned a fistful of certificates and ratings. He even flew top secret missions under contract, with the US Navy, involving rendezvous with Trident submarines as they surfaced up through arctic and Antarctic ice. After 17,000 flight hours, Art retired from the Masonite Corporation and Lear jets.

He recalls that it was over 10 years ago when he first read an article by Tracy Crook and was so impressed that he located Tracy and introduced himself; they have critiqued each others’ ideas ever since. Ted Alexander is also a Canadian airman but has specialized in hands-on engineering. Ted has extensive experience in aircraft reconstruction from Convairs to wrecked FedEx cargo planes. Art says that Ted’s work was so good that no one could tell a major reconstruction had been done. Ted is also an avid plans-built experimental aircraft builder as well, having finished a CH-300 and Kestrel Hawk. Cheryl, Art’s wife, is the chief financial officer and cheerleader, and a very fine SWMBO. (computer geek acronym for “She Who Must Be Obeyed”) Their investments over the years allow them the self employment to pursue this rotary engine obsession which has been, for months now, a very intense labor.

THE SHOP I visited the workshop at Propelled Engineering and I was very impressed with the facilities. All new equipment and a very professional attitude. The shop mantra is “Aircraft Grade” and I heard it often. I understood just what they meant when I examined their work. Everything was, indeed, aircraft grade. Art has already invested over $200,000 in equipment and has completed business arrangements for materials and components. The first complete assembly is on the test stand now and as of this writing, the team is laboring to add polish for the www.ContactMagazine.com

The “James Holy Cowl”, designed as part of the FWF offering for the RV series of experimental aircraft is shown here, covering the engine (on the test stand) pictured on the previous page.

2007 SnF week-long daily demonstrations. The “James Holy Cowl”, which is not included in the FWF package, might even be painted - just for showmanship. After calculating parts and labor the team has settled on a price of $27,995 USD for a FWF installation of which two have already been sold at that price. Of course, certain accessories and shipping are extra. Every engine is blueprinted to Mazda specs and builders are assured of after -sale support either by personal visit, e-mail, fax or phone. These NA, 2 rotor, 13B engines will be rated at around 180 HP and will weigh less than the lightest 0320, 150 HP Lycoming, FWF.

THE BUILD PROCESS In the design of Propelled Engineering’s FWF package Art Rudko’s guiding principle is to use techniques and components that have a proven record of safety and reliability. For reference, the racing community has proven many solutions and there are several rotary powered aircraft with hundreds of flight hours on other major components. Art starts with a low time, single servo, second generation (RX-7), 13B engine imported from Japan.

Japan requires all autos to meet strict emission and safety standards and often the body of the car will fail the test while the engine is hardly broken in. Imported, these low time engines are a gift to rebuilders and careful inspection before a complete rebuild to factory specs is the established procedure. In every case so far, disassembly has found no discernible wear and yet Art will replace all critical parts such as gears, thrust bearings, oil pump chain, and, of course all seals. At first Art would send center and side housings to Racing Beat (a wellestablished, Southern California expert in rotary engines), for refinishing but had them returned untouched as they simply were not worn.

The 13B has an oil injection system to lubricate the apex seals, but this poorly burned engine oil will form carbon deposits which have been known to break free only to lock a rotor or even fracture apex seals. To avoid such an event, Art disables the factory oil injection system and instructs the operator to add clean burning two-cycle synthetic oil (one ounce per gallon) to the fuel for apex

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seal lubrication. This has become standard operating procedure for flying rotaries. NASCAR racing fuel filters are installed which allow the operator to easily clean and reuse the filter.

Custom intake plenum with mass airflow sensor.

also incorporates custom made swirl pots in the coolant line to remove steam as steam will reduce cooling efficiency because steam bubbles will lessen the water-tometal contact in the radiators and heat exchanger. Swirl pots were common in WWII liquid cooled engines. The pressure cap on the coolant system is rated at 27-29 PSI and improves cooling efficiency by raising the boiling point where steam is formed. Art uses the same 50-50 glycol to water mix as recommended by Mazda. The glycol also serves as a corrosion inhibitor in the aluminum engine rotor housings and radiators.

The exhaust system will be of particular interest to kit builders as virtually everyone has had difficulty in fabricating one that survives the somewhat high rotary engine exhaust heat. Art uses the Racing Beat U bends and Y collector which is a proven assembly of thick-wall stainless steel. Art will also incorporate a silencer in the exhaust even though his conversion isn’t exceptionally loud. The unique sound of the rotary has been interpreted as exceptionally loud but decibel tests show the rotary and a 150 HP Lycoming to be nearly identical, measured at 300 feet.

The rotary engine normally operates at 6,500 RPM and Art uses Tracy Crook’s well respected RWS 2.85:1 planthe Propelled Engineering intake manifold is custom etary PSRU www.rotaryaviation.com and for propellers, made with runner lengths tuned for maximum torque at that RPM. Runner length for autos is 11”-16” but aircraft Art has a dealership with Vesta, Inc. Their all-composite require 19”-22” in order to move the torque curve higher. NASCAR also contributed the in-line oil filter which is easily disassembled at the 50 hour inspection and quickly reveals any engine problems. Oil not only serves as lubrication for the rotary engine rotors but carries away nearly 30% of the heat. Most flying installations have used an oil radiator which transfers the heat to ram air. However, the most efficient thermal transfer occurs with oil to water rather than oil to air.

Here Art has once again used the racing solution and installed a custom made heat exchanger using the engine coolant to cool the oil. This method is not only 35 -60% more efficient, but since the heat exchanger is mounted on the firewall, it eliminates the need The custom built oil-to-water heat exchanger mounts to the firewall and has for an under engine radiator. Art no need for outside air for cooling, saving space and reducing drag. www.ContactMagazine.com

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propellers are nicely crafted and are gaining acceptance among the higher powered experimental aviation community. www.vestav8.com And, especially noteworthy, as an option, Art will supply an all new constant speed pitch control. This automatic pitch control will maintain whatever constant RPM the pilot sets and it does so electrically, without the need for hydraulics. At long last the rotary has a system that mimics a constant speed propeller.

List of components in the Propelled Engineering Firewall-Forward package:

 Mazda RX-7 NA 13B Engine, starter, alternator, water pump assembly, and 70 MM throttle body.

 Moroso water fill and overflow.  Real World Solutions PSRU and

EC2 Computer for

ignition and fuel injection control.

 Modified NASCAR oil filter.  Modified fuel pump, gascolator and fuel injection final filter.

 Custom

intake manifold, exhaust system, swirl pots, motor mount, engine mounts, coolant radiators, heat exchanger, heat shields, oil filter lines, and a custom made panel for coils.

Options available:

 Real World Solutions monitor  Dual Battery Bus  Electric, continuously variable propeller pitch control.

CONCLUSION Utilizing the stock (automobile) motor mount locations, Propelled Engineering fabricates an adapter for mating the engine to an aircraft engine mount.

There are many features of Art’s assembly that are proprietary but the following list of components will give the reader a better understanding of the considerable contribution Art’s team has made to standardize the rotary engine for aircraft.

What makes the work of this team especially exciting to homebuilders is that not only can one purchase a FWF package but one can save several thousand dollars by doing their own assembly using Art’s components and following his installation methods. It has always been the trial and error of assembly, with cooling the toughest nut, that has dissuaded kit builders from the rotary engine.

Every flying rotary has been unique, with experimental aircraft builders solving the same problems in different ways. But a new day is dawning; Art’s team is dedicated to standardizing the rotary installation for certain experimental models. The first and most significant kit to design for was the RV series, but assemblies for many other experimentals are in the works. Art will install an engine package on his just finished Thorp T-18 for the trip to OSH in July and I saw a Mustang II, still in the crate, which will be next.

There is a roster of experimental, amateur-built aircraft www.members.aol.com/_ht_a/rotaryroster/index.html that use a rotary engine. RVs are the largest group and the second largest group is the category of Long EZ, Cozy, and Velocity pushers. But the list includes everything from an F1 Rocket to a Starduster -- seems no end to the rotary applications. For “Rotor Heads”, Sun ‘n Fun 2007 will be a “happening” and, with Propelled Engineering’s FWF package of components, that list of builders may well be expanding. So, if you want a concentrated rotary experience, be at the Sun ‘n Fun Fly-In, Lakeland, Florida, April 17-23. Look for the Rudko team’s demo at the Engine Workshop tent; the workshop volunteers also disassemble a Mazda 12A rotary engine every day during the airshow. If not Lakeland in April, then July 23-29 at EAA Airventure, Oshkosh, WI.

Top motor mount adapter. www.ContactMagazine.com

Ernest Kerr

Ehkerr@aol.com

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Tracy Crook has graced the pages of CONTACT! Magazine twice before, first in issue #34 where he reported on the installation of a Mazda RX-7 engine in his RV-4, then in issue #64 where he detailed his approach to electronic engine control. In issue #34 Mick Myal wrote the following: ”Tracy has done a commendable job with his installation. It surely will be copied”.

Mick was absolutely correct. ~Pat Photo: Pat Panzera

By Tracy Crook, Bell, FL Real World Solutions, Inc. support@rotaryaviation.com

Tracy Crook, (far right) holding court at his Mazda Renisis powered RV-4 “RVotter” during the 2006 Sun ‘n Fun fly-in.

Stories about successful alternative engines are among my favorite things to read, but I often find myself wanting to know what it took to get there as well as the end result. The following is my admittedly long winded version of the 15 years spent building and flying my Mazda rotary powered RV-4. The plane has been flying continuously since January 1995 and has accumulated over 1600 flight hours. I have previously written about some aspects of its development but I hope you enjoy “The rest of the story”.

Through some twist of fate I was never exposed to airplanes, pilots, airports or anything else connected to aviation while I was growing up. I have no idea where my attraction to flying machines came from, but one of my earliest memories is of a children’s book called, “The Little Golden Book of Airplanes”. I spent countless hours staring at it instead of doing the schoolwork I was supposed to be doing in second grade. I especially remember the picture of the Bell X-1. The book explained that the “X” meant that it was “Experimental.” That exotic sounding word fired my imagination so strongly that I knew, without a doubt, that someday I would build a sleek little metal airplane with that word on it. I flunked second grade and forty more years went by, but eventually I did build that plane. It was indeed experimental in every sense of the word and was labeled appropriately.

I initially planned to fly 1,000 hours in the two years following its construction, but as John Lennon said, "Life is what happens to you when you’re busy making other plans." It took roughly six years to reach that magic number, but on the other hand, I never could have predicted that a simple choice of engines would lead me on such an incredible odyssey of fun, adventure and friends. www.ContactMagazine.com

For those who didn't see my earlier articles, I’ll briefly describe the initial development process. I chose the Mazda 13B rotary for two basic reasons: its simplicity (only three basic moving parts) and the fact that it was the only alternative engine available at the time that would deliver the same power and weight as the O-320, (the recommended engine for my RV-4). My hopes were that the simplicity would equate to reliability and that the low weight would not push it over aerobatic gross as some other alternatives would. I was not disappointed.

THE ODYSSEY BEGINS When an FAA designee issued my airworthiness certificate back in December, 1994 he specified the usual 40 hour test period before leaving the flight test area or carrying passengers. In my usual optimistic view I thought this was unnecessarily long, but it turned out to take considerably longer to iron out all the wrinkles.

The complications began long before the first flight, when I decided the stock automotive ECU was not appropriate for aircraft use and designed my own ignition controller at a cost of around 300 hours. It took an additional 30 hours of flight-testing and fine tuning before I was satisfied. Three Mikuni motorcycle carburetors took the place of the stock fuel injection and these took another 10 hours to properly tune. Solving a stubborn propeller reduction drive oil leak and optimizing the water and oil cooling systems took even more time. Going experimental has its price.

Finally, at the 80 hour mark, I felt confident enough to fly the 1,200 miles from Florida to Oshkosh ‘95. It was on this trip that I experienced the now familiar blown front

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cover oil passage O-ring problem that later plagued several other rotary plane builders. The failed O-ring causes the oil pressure to fall to around 37 psi. I flew most of the trip at a reduced power setting and made it home without incident, but the abnormal oil pressure made it a nervewracking experience. The cause and solution to the problem were very simple and it taught me that problems could strike well after the 40 hour mark.

I was feeling quite confident with the engine when my first and only power failure occurred, at 130 hours. One of the carburetors overheated due to its close proximity to the exhaust system. Fortunately, I had enough altitude and time to get the engine restarted, but it was sobering to think that the problem had been lurking under the cowl just waiting for the right conditions and a hot summer day to show up. Had it occurred on takeoff, this story might have been much shorter and had a very different ending.

A simple aluminum heat shield under the carbs eliminated the overheating problem.

Finally, eight months after the first flight, I felt like the airplane had truly earned its airworthiness certificate and was confident enough to start taking up passengers. By this time, the plane had acquired the name "RVotter", a mangled contraction of the terms RV, aviator and Otter which is my wife's pet name for me (don't ask - it's another long story).

stay up awhile and return for more. The RV's panoramic view of water and sky worked its magic and within a few weeks, flying just offshore along the barrier islands became a regular ritual. It didn't happen immediately, but Laura eventually became almost as hooked on seeing the world from above as I.

FROM EXPERIMENTAL TO WORKHORSE Pure utility was not top priority when I decided to build this plane. Although the RV-4 has a wide flight envelope and does a lot of things well, its primary mission is focused on one thing: Fun. The controls are so responsive and well coordinated that they beg to be used. The urge is so strong that cross-country flights must be punctuated by an occasional aileron or barrel roll.

Similarly, my choice of engines was not based on pure utility. Bolting on a Lycoming will get you up and flying a lot sooner and with fewer unknowns to figure out. To tackle an alternative engine you should probably be the type that gets a thrill from just hearing the sound of something different under the cowl, even if it means more work. As we will see later, even simple things like mufflers can be a challenge. I was also prepared to do more maintenance than a typical Lycoming requires.

This was not my first experience with alternative engines and on one previous airplane, I spent 10 hours on maintenance and repairs for every hour of flight. I was counting on better results with the rotary.

Having said all this, I am pleasantly surprised by how much use we get from the airplane. After those first 130 hours of development, the RV became a tool that we would come to depend on for years on end.

It had long been my dream to live on an airstrip so several years prior to starting the RV project I bought a vacant lot at Shady Bend Airpark, a remote grass strip near the Suwannee River in north Florida. The plan was to build a house there in our spare time, but a grueling 3-1/2 hour drive each way made progress very slow. That all changed once the RV reached operational status. Instead of dreading the Saturday morning trip for a weekend of construction Original 13B configuration with Mikuni carbs and Ross gear drive. work, I would wake up eagerly anticipating the break from my electronics engineering COME FLY WITH ME job and, best of all, I got to fly. On almost every weekend for several years we would load up the plane with food, Although not generally recognized as an official mileclothes and tools and make the one-hour flight to Shady stone, getting your significant other to share your enthuBend. Not once during those years did we have to scrub siasm for flight can be a make or break factor in how a flight for mechanical problems. The certified avionics in much flying you do. My wife, Laura, was game enough to my panel caused the only down time for the plane. buck a few rivets on the RV-4 on the morning of our wedding day but she could, at best, be described as a Between 130 and 650 hours, the only engine related "reluctant flyer". She finally agreed to go up for a short problem was a gradual increase in play in the planetary flight on the condition that we land immediately if she felt gear drive, which became noticeable around the 200 uncomfortable. We took off from Clearwater, Florida and hour mark. The problem turned out to be the mounting I was counting on the 'eye candy' aerial view of blue sky scheme for the planet carrier rather than the gears themand long sandy beaches to be an irresistible incentive to www.ContactMagazine.com

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selves and was easily fixed. Other than this, these hours were wonderfully uneventful and the Mazda 13B engine core did not give even a hint of trouble. I flew the RVotter to Sun 'n Fun and Oshkosh every year and met a growing number of builders who were either in the process of installing or interested in using the Mazda rotary. Many of them have come to be good friends - another welcome surprise resulting from a simple choice of engines.

Of course I ended up installing the EFI system and it went so smoothly that it was almost anticlimactic. The simple onboard setup pane, mounted permanently on my instrument panel, proved to be a good choice. Tuning an EFI system for best economy must be done under actual flight conditions and an aircraft cockpit is no place to be fumbling around with a laptop computer, as required by many aftermarket EFI systems.

MORE POWER, SCOTTY

In addition to the expected fuel economy benefits there was a healthy boost in maximum power as well. The airplane felt more muscular and the improved fuel distribution made the engine even smoother. Based on comparisons with Lycoming powered RVs, I estimate that I gained 20 horsepower, mainly due to the tuned intake manifold. Pilot perceptions of a change are sometimes hard to evaluate in numbers but the overall effect of this one I would describe as “confidence inspiring”. Laura and I spent many more uneventful hours in the plane traveling on vacations, breakfast flights with the Florida chapter of Van’s Air Force and afternoon joy rides, with never a hint of trouble.

Although the bank of three motorcycle carbs had served well up to this point, I knew they were far from the optimum intake system. For one thing, the intake was not tuned, with almost zero intake runner length. The engine was making between 150 and 160 HP and even though the airplane performed quite well, I started thinking about how it would fly with (to quote Tim the Tool Man) “more power”. Secondly, I was learning about the speed and economy advantages of flying at higher altitudes. The constant velocity carbs compensated for altitude to some extent but about 8500 feet is all they could manage before starting to run rich.

With these thoughts in mind, I began to design an EFI system optimized for aircraft use. Using it in an aircraft meant that it had to run on 100 LL avgas at least some of the time, so this ruled out using oxygen sensors to control mixture as in automotive systems. I used mogas directories and flight planning websites like Airnav.com to pick fuel stops where auto fuel was available, but for one reason or another, I ended up burning avgas on at least one leg of every long cross country flight. The engine runs fine on avgas but spark plug life is reduced.

Another personal requirement was redundancy. The rotary has dual plugs per chamber and separate coils for each plug. On one occasion this feature prevented an inflight power failure when an igniter module failed. Having been saved by redundancy once, I wanted a backup system in place wherever it was practical.

A WESTERN ADVENTURE In October, 1998, I set out on my second trip to Arizona, for the COPPERSTATE Fly In. The trip started great. I had tweaked the EFI for excellent fuel economy (about 10% better than the carburetors) and I was thinking how blissfully “operational” the rotary engine and the RV-4 had been for the past few years. After a quick refueling stop, and still grinning over the reliability of my installation, I applied full throttle for take off and felt the reassuring tug of the engine. My celebration ended abruptly when shortly after liftoff the power sagged and my head went on red alert. The engine was still making about 60% power, but had a very uncertain feel to it.

Development and testing of the EFI controller took almost 18 months and was done on the ground with an engine test stand. Finally the day came when it was time to put it on my airplane, but I felt strangely reluctant As I stood there admiring it, I was surprised at the unexpected emotion that swept over me. I was reluctant to unbolt my old Mikuni carbs.

I lowered the nose to maintain airspeed and scanned the instruments for clues to the problem. The EIS was not flashing the bright red warning light, so all parameters were still within limits. The EGTs did catch my eye, as they were about 300 degrees apart. Rotor one looked slightly high and rotor two was much lower than normal. I used the mixture control knob to tune for best power and settled on the setting where it seemed to run the best although it was still way down on power. This all happened in a matter of seconds and I was over the numbers at the end of the runway and too late to abort.

"Where the hell did that come from?" I wondered. Then I began to think about all that I had been through with those carburetors. They had flown for over three years and 600 hours of flight. During that time they have reliably fed over 4,000 gallons of fuel to the engine and carried me over 100,000 miles of open fields, mountains and a lot of water.

They've worked in dry desert heat, driving rain and multiple other situations I was fool enough to get into. In short, they had proven that they worked. If just listening to the hum of that rotary for 600 hours could make me feel this attachment to a set of old motorcycle carbs, maybe I can start to understand why Lycoming pilots look askance at my rotary engine. I call this “The Lycoming effect”.

Making an early turn to down wind, I nursed it up to pattern altitude and prepared for a possible emergency landing. Now is where the hard decisions start. Do I land immediately and start checking things on the ground or spend a few moments gathering data on the problem?

Even at maximum gross weight and 60% power the RV4 was soon at a safe altitude circling the airport so I opt for getting the data. Past experience has shown that many problems like this can mysteriously disappear when back on the ground only to return and bite you the next time you are airborne. Taking a little time to positively identify the problem now could avoid a bigger risk later.. at least that's the way it sometimes works.

www.ContactMagazine.com

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The obvious factor you think of when EGT changes is fuel mixture (or detonation), so I carefully studied the EGTs and how they responded to the mixture control.

Past experience with engines taught me that EGT goes up with leaner mixture and down with rich. If you start leaning a traditional (piston) engine past the peak EGT it starts a lean stumble before you get very far. Things are a bit different for the Mazda rotary engine however. The lean misfire (stumble) is almost totally absent on the rotary where, instead, the main indication of lean mixture is a decline in power and a drop in EGT. Only after the power has fallen under 50% does it begin to cough, but by then it will sputter to a stop.

Back to my in-flight dilemma - I could not immediately tell if the low EGT on rotor 2 meant it was too rich or too lean. It was also apparent to me that the many hours of trouble free flying had dulled my response to in-flight engine emergencies. I had previously conditioned myself to think "P - I - F" at the first sign of trouble. PIF was an acronym for Pump, Ignition, Fuel. A single cough of the engine and my hands would automatically switch on the backup fuel Pump, select the backup engine controller and switch to the other Fuel tank. Belatedly, I switched to backup on the EFI controller but nothing changed. Fuel pressure looked normal but I switched on the backup pump momentarily just to be sure. Still no joy.

After climbing to a safe altitude and throttling back, the EGTs moved into their normal range and the engine resumed its rock-steady hum. Everything looked and felt so normal that I began to think that the problem might be related to the fuel I had just picked up. Maybe the fuel had water in it or other contaminates. Maybe the Marvel Mystery Oil I had poured into the tank did not mix with the added fuel and fouled the engine. The sudden onset of the problem seemed to fit this possibility. I briefly applied full throttle again and the engine ran perfectly. After another five minutes of thinking about it I was satisfied with this theory and continued my flight..

Taking off from Frisco, Texas, I was still a little nervous about the engine so I used a power setting of about 75%.

It took a little longer to occur but the same sag in power happened again and it cleared up when I backed off the throttle.

Struggling for an explanation, I start thinking the problem might be a partially clogged fuel injector, allowing enough fuel at low throttle but not at high. Following this logic I started experimenting with the independent rotor mixture adjustments on the EFI. Since it looked like rotor two mixture was going haywire I adjusted it richer and found that the problem could be almost eliminated if I set it to the full rich setting and left rotor one set to nominal.

This gave me the right EGTs at full throttle, but then rotor two was too rich when I backed off to cruise power. No problem, I said, I would use A controller with the rich rotor two setting for takeoff just switch to controller B (backup controller) at cruise. Are you saying to yourself "This guy must be nuts"? Read on. www.ContactMagazine.com

Feeling completely confident in my ability to diagnose and compensate for the problem, I pointed the RV toward the West Texas badlands and the mountains of New Mexico without a care in the world. The scenery from this point on was so beautiful that I sometimes forgot there was a problem.

Further evidence that I wasn’t at thinking at 100% showed up when I found one more way to screw up fuel management. The fuel system I now use always draws fuel and returns it to the left wing tank. When this tank gets low, I transfer fuel to it from the right wing tank using a low pressure electric fuel pump. This eliminated the complicated valves & plumbing to switch both feed and return lines (return lines being required with EFI) between tanks but did introduce one additional factor. If you forget to turn off the transfer pump, you may suffer some bruises when you realize that you have been pumping fuel overboard from the left tank vent. I’ve inadvertently sprinkled about a gallon over west Texas this way. The bruises, by the way, are from kicking yourself. (I've since installed a light on the panel to remind myself that the transfer pump is on.)

I arrived safely and even enjoyed the fly in. Back in the RVotter for the return trip home, I again experienced the strange sensation that possesses me on every take off. I have come home, a creature of the air returning to my natural environment. Now accustomed to the engine’s odd behavior, I stayed below 70% power on take off and made it to my fuel stop in Bastrop, LA without further mishaps. Louisiana must be bad mojo for engines, as shortly after take off, the power sags again. This time it is down to around 50% power. There is never a hint of a miss or pop, the engine just goes weak in the knees and sounds like it is on the verge of fuel starvation. I circled the airport to sort things out and found that at just under 50%, the EGTs return to normal and the engine feels solid. Thoughts of stopping to work on the engine are again over-ruled by the difficulties of doing this so far from home. If my home at Shady Bend Airpark had not been my next landing point I would have stopped anyway but for better or worse, I headed for home.

DIGGING IN I was never in doubt that the trouble was fuel system related and the fuel injectors were at the top of the most likely cause list. My hopes for an easy ‘find’ disappeared when I removed them and found nothing obvious. The little screen filters built into the inlets were clean and the electrical resistance checked good on all of them. Next I tried replacing them with other used injectors I had laying around. I was fairly sure this would be the fix but, after warm up and a brief full throttle test, the problem returned and my confidence took another beating. Test after test revealed nothing so I began to question everything. Maybe there was a latent software bug in the EFI controller. Maybe the engine really could not take the constant higher power settings I had been using and there was a mechanical problem. Maybe this engine was a mistake after all.

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Feeling exhausted and defeated, I sat next to the engine and stared at it, too tired to even think about the problem anymore. My eyes came to rest on the oil cooler. It was from a 1978 Mazda Cosmo (rotary powered) that my brother Barry had owned and driven for around 130,000 miles before he retired it due to high oil consumption.

Barry had also donated one of the air conditioner evaporator cores I use as radiators. It was from a 70’s era Buick Electra station wagon that he had affectionately called “Miss Piggy”. (Do you see a long family tradition of recycling auto parts here?) I remembered Laura walking into the garage and asking where “that thing” came from when I first mounted it on the RV. She knew about Barry’s old Buick so I just said “Miss Piggy flies again”. She rolled her eyes and went back in the house.

With these thoughts drifting through my head, I happened to recall a comment Barry made about the Cosmo. He said something to the effect that the first sign of needing new plugs was that the engine would crap out at full throttle. I assumed at the time that this meant it would start missing like most engines with worn out plugs do.

Then it occurred to me that it had been a very long time since the plugs were changed on this engine. In the past, I changed the spark plugs at around 200 flight hours. I did this mainly on general principles because they were still working just fine and certainly weren’t showing any signs of deterioration. My aircraft maintenance log was back at my old house, in Clearwater, so I couldn’t check to see how long these plugs had been in service. For lack of any other ideas, I pulled the plugs to have a look at them.

In spite of all the indications of fuel related problems, one look at the plugs is all it took to know that this had to be the cause. The center electrode was eroded all the way down to the insulator and even the four massive ground electrodes were noticeably worn. The gap in rotary spark plugs is quite large when new (about .050” and not adjustable) but the gap had grown to at least twice this amount. I was amazed that the engine ran as well as it did. A later check of my maintenance log showed the plugs had been in service for 289 hours. Complacency had struck again.

I felt like a real dummy for failing to diagnose a simple case of worn out spark plugs after more than a day of troubleshooting, especially when I remembered there was a brand new set in the box of spare parts that I carry with me on long trips. The only thing I can say in my defense is that the characteristics were very different from my previous piston engine experience. You might think that after four years and 750 hours of flying this airplane I would know every nuance of its behavior; obviously, I’m still learning things about the rotary.

As to why the problem seemed to get better when I adjusted the mixture to the individual rotors, I don’t have a good answer. The explanation is probably based on combustion physics way beyond my understanding. Anyway, I installed $18.00 worth of new plugs, reset the EFI www.ContactMagazine.com

controller to the default settings and the engine ran perfectly. Next time I’ll know.

Whaaa Whaaa Whaaaa The Ross gear drive on my plane had generally performed well with only a couple of minor and easily fixed problems. My only real complaint was a persistent rhythmic vibration that could be heard and felt. It was similar to the feel of a twin engine aircraft with the engines running at slightly different speeds. It seemed to be related to the play in the prop shaft bearings that would allow the shaft to wobble. While this was not causing any operational problems, it bothered me enough to start working on a gear drive of my own design. Since there was no pressing need, progress was slow. This all changed during an annual inspection when I found some galling on the teeth of the drive’s sun gear. Further inspection turned up a bad thrust bearing on the prop shaft. After some delay, Ross fixed the drive but this gave me the incentive to complete my own design.

THINGS GET MESSY At 856 hours on the Hobbs, my new drive was ready to install. After getting over another case of ‘The Lycoming Effect’, I pulled the refurbished Ross drive off and saw an odd pattern on the end of the crankshaft. This turned out to be the spline pattern of the gear drive input shaft that was pounding itself into the engine. The old drive did not have its own thrust bearing but instead relied on the engine thrust bearing to absorb the thrust caused by the helical cut gear teeth. Most people (including me) had assumed that the propeller would produce the highest thrust loads. As it turns out, the thrust produced by a prop absorbing 180 HP at the full throttle airspeed of my RV-4 (208 MPH) is only about 250 pounds. I was shocked and amazed when I calculated the thrust load produced by the helical gears at over 800 pounds! After seeing the number on paper I immediately wondered how the engine thrust bearing had held up to this load. I grabbed the counterweight on the end of the crankshaft and shook it. A clunk at each end of the travel told me that I would have to dig into the engine. Measuring the end play with a dial indicator showed that it was 10 times higher than the factory spec. I got another shock when visual inspection showed the bearing to be on the verge of catastrophic failure. Fortunately, the new gear drive design included an input shaft thrust bearing.

1,000 HOURS OR BUST? From the very start, it had been my plan to fly the engine for 1,000 hours and then do a careful tear down and inspection report. Since the engine core did not have to be opened to replace the thrust bearing, it would have been possible to continue flying this engine and reach the magic number.

Tearing it down before getting there almost seemed like admitting defeat, but a combination of factors made replacing the engine the easiest way to go. When ace rotary engine builder, Bruce Turrentine, offered to build up another engine to my specifications, I couldn’t resist. My current engine was a box stock junkyard dog engine that had been given a minimal overhaul. As I accumulated more experi-

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ence and knowledge about the Mazda rotary, I had been mentally building a modified engine that I thought would be the optimum configuration for aircraft use. Bruce was another of the many wonderful people I met as a result of picking the rotary and now he was offering me a painless way to try out the engine of my dreams. I said OK and a week later Bruce arrived with a zero-timed engine and said “let’s get this thing installed!”.

SNOWBALLING CHANGES Swapping the engine itself took only hours but it wasn’t that simple when it came to the new gear drive. It was the same length as the Ross PSRU but the adapter between engine and gearbox was shaped differently and required that the right side radiator be moved about an inch further to the right. This, in turn, required that the oil cooler be moved as well. After remaking the mounting hardware for both, the cooling air inlets and ducts didn’t match up. Arrggh! Time for more of the dreaded fiberglass work. After all was said and done it took 4 weeks of steady work to make everything fit again.

With everything double checked and all the fluids topped off, it was time to try it out. The engine lit off nicely and all the gauges were soon in the green. Two things were immediately apparent. The new drive and engine would idle much lower, without the rattling experienced with the Ross drive at anything less than 1400 rpm. Now it could idle smoothly down to 800 rpm. The other obvious change was the exhaust note. The new engine used turbo rotor housings that do not have what Mazda calls “splitters” in the exhaust ports of normally aspirated engines. This gave the engine a more aggressive bark. It would also cause me a few other headaches down the road, but I’ll discuss more about that later.

After about an hour of ground running for engine break-in, it was time for flight-testing. As I look the plane over before flying any new hardware, I always have a flashback to that scene in the movie “The Right Stuff”. It’s the one where Chuck Yeager walks around the Bell X-1 as some technicians do some ground tests just prior to his record setting flight. Even the ominous movie music is playing in my head.

I really love this part of home building. Some people are in favor of renaming the FAA amateur built designation of ‘experimental’ with something less threatening like the ‘sport plane’ category, but that just doesn’t have the same romantic appeal. Call me Walter Mitty, but I love seeing that EXPERIMENTAL placard on my plane.

On takeoff, there was a noticeable improvement in power as soon as the throttle was shoved forward. The tail wheel came up almost immediately and rotation speed was reached in about 400 feet, even with a cruise prop installed.

After reaching 120 mph where my cooling system starts working best, I pitch up and set elevator trim to hold this speed. Flown solo with a light load of fuel, the RV-4 normally pegs the 2,000 FPM VSI but seat of the pants indications tell me that the climb rate is even better. The engine tachometer also confirms that power is up by indicating a 250 rpm increase during climb. www.ContactMagazine.com

The 13B engine provided by Bruce Turrentine. EFI and 2.17:1 RD-1B gear reduction drive, designed by Tracy.

MISSING NOISE Leveling off at 1,500 feet I turned downwind to stay in the pattern, throttled back and verified that all the gauges were in the green. Something seemed different than usual and it took several minutes before I realized that the warbling drone of the old redrive was gone! This pleased me even more than the increased engine power, because my enjoyment of flight is, generally, inversely proportional to the amount of noise and vibration in the cockpit. The exhaust note was a little louder than before but the improvement in the drive more than made up for it.

THE VERDICT It took more than 30 hours of flight testing to get an accurate picture of the performance differences between the two engines. The comparison is complicated by the fact that we are comparing a well-worn engine to a fresh, zero-timed one, so that factor alone could account for some if not a lot of the improvement. After making all these disclaimers, here is what I concluded: The major functional difference between the two engines was the porting. The old engine was a normally aspirated six port engine. To accurately describe the differences in porting would be a bit tedious so I’ll just summarize it by saying that the six port engine has a very “dirty” arrangement with large changes in cross sectional area and some ‘square’ corners. Its one redeeming feature is that the outer ports have a very long duration with a late closing time. This tends to raise the torque peak to the high rpm range, which of course is where we want it for non direct drive aircraft use. The new engine is essentially the turbocharged version of the 13B (without the turbo) with the high compression rotors of the normally aspirated engine. I hoped the much cleaner and larger turbo ports would flow better, even though their port closing time was significantly earlier than the normally aspirated ports. The results were pretty much in line with what I expected. I use a fixed pitch prop so engine rpm during climb is well below maximum. This is where the new engine really shines as indicated by the increase in climb engine speed and climb rate, which was about 300 fpm higher than before.

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I was hoping that the power at maximum rpm would not be sacrificed for the boost in lower speed torque and I wasn’t disappointed. The new engine makes slightly more power at high speed, too, but the difference is far less. This resulted in a small increase in top speed from somewhere between 204 and 208 mph.

clean. Maybe it was the Hylomar gasket dressing I used during assembly.

Side Seal Oil Seal

INSIDE THE OLD ENGINE Reading details about the innards of an old engine doesn’t sound like a lot of fun but many readers of those earlier articles tell me that they’ve been sitting on the edge of their seats waiting to hear the results. OK fellow gear heads, here’s what you’ve been waiting for.

Even though I did not make it to the magic 1,000 hour mark, 856 hours is long enough to show what we can expect of the 13B rotary in aircraft service. The engine was still running fine when removed. It was only the excessive end play in the thrust bearing (and a chance to try out the new engine) that prompted the engine swap.

To properly evaluate the results, it should be remembered that this was a used 1988 13B engine with approximately 50 to 70 thousand miles on it when I gave it a minimal overhaul. When I first rescued it from the junkyard, it ran well but had been overheated enough to ruin the oil seal o-rings, and it smoked badly. I lavished a great deal of love and attention upon it but being a little short of cash at the time, the only parts replaced were the apex seals, oil seal o-rings and some side seal springs. This is the piston-engine equivalent of honing the cylinders and slapping in a new set of rings. At the time, this was the first rotary I had ever seen so I didn’t know what to expect. Now, after tearing down about a dozen 13Bs with various mileages, I know it was not in particularly good shape when I got it. I have seen 130,000 mile engines in better condition.

CLEAN MACHINE Taking the engine apart after 856 hours of service, the first thing I noticed was how little carbon there was in the seal grooves. Until you have torn down a typical 13B from a car you can't appreciate this, but almost all the rotor seals fell out of their grooves with nothing more than gravity to help. Even the side seal springs came out with just a gentle tug. The first time I took this same engine apart, I had to dig the originals out with the help of a X-Acto knife and most of them broke in the process.

There was a moderate amount of carbon on the faces of the rotors, but it was the soft, easily removed variety which took only a few minutes with a single edge razor blade and a brass wire brush to get rid of. I estimate that total cleaning time to prepare this engine for reuse would be about an hour. I spent two full DAYS cleaning it the first time. I attribute the lack of carbon in the grooves to mixing an ounce of two-stroke oil per gallon of fuel instead of using the factory oil injection system.

The water jacket o-rings looked good, and I was able to pull them out in one piece (which is unusual). The oil I used would not explain why these grooves were so www.ContactMagazine.com

Apex Seal The above photo is one I nabbed off the internet for the purposes of illustrating apex and side seals, as well as the condition of a rotor as pulled from a running engine, complete with carbon deposits. This is not the rotor that came from Tracy’s engine. ~Pat The part with the hardest life in the rotary engine is the apex seal. My estimate of TBO is mainly based on the wear measured on the height of these parts. I knew that the experiment was a success when I found that the wear was the smallest I have seen on any engine so far.

All the car engines I’ve checked had between 25 and 40 thousandths of wear here. The wear rate appears to be very non-linear with most of the wear occurring during the first 20,000 miles. The airplane engine had only .017” wear. The face of the seal was perfectly smooth and rounded with no chamfering.

The side seals were the original to the junkyard engine.

As mentioned before, they were not replaced when I gave it the “minimal overhaul”. They had a total of .002” wear (height measurement) when I reassembled the engine. After five years of flying they had only an additional .00025 - .00050" of wear. The side seals are definitely not the weak link in the engine.

Wear on main and rotor bearings and the eccentric shaft was not measurable. These parts almost never seem to be worn. Since the combustion chamber rotates around the axis of the crankshaft in the rotary, the bearings are not subjected to the unidirectional pounding that the piston engine gives its bearings. This helps maintain the lubricating oil film.

The most expensive parts in a rotary are the rotor housings, so I was especially interested in how these had

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da’s rotary. Typically, about 3 to 4 thousandths are removed during lapping, which could conceivably remove all of the hardened material. So the question is: Is it better to tolerate a small amount of step-wear when doing an overhaul or to start with zero wear and risk an accelerated wear rate due to removing the hardened surface?

I do not know the answer, and I have not found anyone who has run the engine to TBO a second time after lapping the side housings. This would typically represent a total of about 300,000 miles of driving. After this much use, very few car owners go to the trouble of opening the engine to see what it looks like. The new engine in my plane did have the housings lapped, so someday I may have the answer, but that day is probably 5 to 10 years away.

The odd looking pattern on the end of the eccentric shaft was caused by the Ross redrive input shaft hammering its spline into the engine. fared. Even prior to putting 856 hours on the engine, these were not in very good condition compared with what I now consider to be ‘good.’ Judging the condition of these housings tends to be somewhat subjective since it is the chrome plated wearing surface that determines the health of these parts. Minor scratches are OK but flaking or peeling chrome is a reject. Mine were in so-so condition when put back in service but they had held up remarkably well. The groove worn by the apex seal corner piece had not increased in depth and there was no further ‘chipping’ of the chrome between the groove and edge (we are talking about very tiny chips here). There were no scratches and no noticeable wear on the chrome surface in spite of the fact that I never ran an air cleaner. Basically, they looked exactly the way they looked when I put the engine together 7 years ago. If I were putting together an engine for my airplane today I'd probably replace them, but on the other hand, I'd fly them again if money was an issue.

The other expensive parts that I hoped were still in good shape were the side housings. The point of maximum wear is a step near the minor axis on the sparkplug side where the side and corner seals exert maximum pressure. The step measured about .002" when overhauled.

The step had increased to .00225 - .00250"; still well under the factory limit of .00390".

If the step wear on the side housings is over the limit, they can be lapped with a Blanchard grinder to eliminate the step. The question of whether or not to lap the side housings (even if they are under the wear limit) is a subject of much debate. In theory, it is always better to start with factory new specifications. This should result in the longest TBO. The only reason I would question this wisdom relates to the nitriding process that Mazda used on the side housings in 1986 and later engines. Nitriding greatly increases the hardness and wear resistance of cast iron. The depth of the nitriding can vary between 2 and 7 thousandths, depending on the process used. I have been unable to determine how deep it is on Mazwww.ContactMagazine.com

The last parts examined were the stationary and rotor gears, (stationary gears not shown in the photo below) which showed no signs of wear. I was not expecting any problem with these parts because their behavior has been thoroughly explored by Mazda and the automobile Side Housing (Rear)

Rotor Counter-balance

Apex Rotor Rotor Gear

Counter-balance

Side seal Eccentric shaft

The above photo is not a depiction of Tracy’s engine. It was stag internal pieces of a typical rotary engine. The entire case assemb

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racing community. There seems to be a clearly defined threshold at which the gears start giving problems and this point is well beyond where we operate the rotary in aircraft service. The car racers tell me that the engine will run all day in stock form up to about 8000 rpm. Above 8500 rpm you can be sure that stationary gears will shed their teeth and the rotor gears will begin to creep off their roll pins. This is why many rotary car racers recommend using specially heat-treated and hardened stationary gears, and rotors machined to accept snap rings to retain the rotor gears. At only 6500 to 7000 rpm these measures are just a waste of money.

By the time the inspection was finished, I was completely convinced (and still am) of the rotary’s suitability for aircraft use. One of the most frequent questions I receive concerns the expected TBO. Up until now all I could offer was a guess, but based on these inspection results I am confident that as long as the PSRU does not put thrust on the engine shaft and that the factory oil injection system is not used, a 2,000 hour TBO is achievable.

Rotor Housing Cast from aluminum with an Integral, thin, iron (chrome plated) wear surface.

Side Housing (Middle)

Side Housing (Front)

With the extra power of the turbo ported engine, (and with power comes heat) something had to give.

THE NOSE KNOWS Making any change to an aircraft should always put you on alert until the alteration is fully proven. In spite of how well the new PSRU was working, it was different, so I expected it to be the source of any new problem. After several months of trouble-free flight and the absence of the annoying prop shaft wobble, it seemed so rock solid that I declared it operational and Laura and I resumed our normal flying activities. On the return flight from a local fly-in, Laura said she smelled something like smoke or exhaust fumes. I didn’t smell anything and a quick look at the Carbon Monoxide tag showed nothing so I wrote it off as yet another false alarm from her notoriously sensitive nose. The rest of the flight was without incident but I did make a mental note to remove the cowl and do a close inspection.

Taking the top cowl off showed nothing out of the ordinary. The gear drive was not leaking any oil and the gear lash and prop shaft axial endplay had not changed. Still smiling about how well this thing was working, I removed the bottom cowl and saw something that ended my little celebration. The muffler looked as if a grenade had gone off inside. The front end was bulged out and it had ruptured at the very bottom. Only a thin aluminum shield on the bottom of the cowl had kept the exhaust off the fiberglass and it was almost burned through.

EATING CROW (EXHAUST SYSTEM WOES)

e Accessory case (Aluminum) All other pieces shown are ferrous, either iron or steel, unless otherwise noted.

ged and provided by Lynn Hanover so that we could illustrate the bly is held together with long through-bolts. www.ContactMagazine.com

One of the many stories I had heard about the rotary was that the exhaust was notoriously hard to tame. The first year I flew to Oshkosh, several rotary experts there had predicted that my exhaust system would fail after only a few hours. The headers, muffler and tailpipe were all fabricated out of thin wall (.035”) 321 stainless steel in order to save weight. I had assumed that stress was behind the failures that the experts had seen so my simple solution to this problem was to eliminate stress on the header pipes by suspending the muffler independently and using a flexible coupling between headers and muffler. Cantilevering the system from the exhaust flange will result in early failure unless made from very thick wall material or exotic material like Inconel®. The reason for this is due to the higher EGT, which is about 200° hotter

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than a piston engine. The strength of metal goes down very rapidly with increasing temperature. My assumptions about the stress and how to deal with it were successful so I assumed that the horror stories about rotary exhaust were greatly exaggerated.

Since the muffler had been in service for about 1000 hours at this point, I figured its life was simply up and it was time to replace it. The original muffler had been a labor-intensive thing to build and my much-anticipated third trip to the COPPERSTATE fly-in was quickly approaching. It was time to try out another idea that had been incubating for some time.

I really enjoy listening to music on long flights and this requires a fairly quiet cockpit. Due to environmental regulations, the Swiss have enacted laws that prompted development of the world’s quietest aircraft exhaust systems. These usually entail what has come to be called the “Swiss Muffler” which, due to its length, is mounted outside the cowl and slung underneath the fuselage. Not only does this result in a quiet system but also I figured it would allow the use of an off-the-shelf muffler. There was not time to mail-order stainless steel parts to fabricate the collector and tailpipes needed, so a quick trip to the local NAPA store netted the parts in mild steel that I figured would last for one trip to COPPERSTATE. The muffler was a sleek looking “Cherry Bomb” glass pack that was a bit heavy but had a nice low drag profile. It only took a few hours to fabricate and mount the system since I had already installed the required hard points on the underside of the RV’s fuselage.

I was absolutely delighted with the flight test results. The glass-pack was not as quiet as I would have liked, but was acceptable and the character of the exhaust note was just plain fun to listen to, much like a racing Porsche at full song. There were also a couple of unexpected benefits. Without the hot muffler under the cowl, water and oil cooling were improved. This was partly due to the elimination of radiated heat from the muffler and partly to the cleaner path to the cooling air outlet. The longer header length and the use of a collector seemed to have improved exhaust scavenging as well. Maximum power was up slightly and fuel burn was slightly lower at any given airspeed. What more could you ask for!

Psyched about the better than ever performance, I loaded my camping gear in the plane and headed for COPPERSTATE where Mick Myal was going to present me with CONTACT! magazine’s achievement award for reaching 1000 hours of rotary powered flight. This time the weather was perfect and I made it to my overnight stop in McKinney Texas in record time. Just to be sure, I removed the cowl and re-tightened the clamps on the exhaust system.

After a pleasant overnight stay with Rob and Julia Johnson, I got an early start the next morning. I saw a low cloud layer rapidly approaching from the southeast and as soon as I departed the pattern heading northwest I www.ContactMagazine.com

heard the tower report to an inbound aircraft that the field had gone IFR. Good timing for me, or so I thought.

About four minutes later I heard a subtle change in the exhaust note. I thought it was probably just my imagination, but it seemed to get slightly louder with each passing moment. When the smell of hot fiberglass made its way to my nose I ruled out imaginary causes and reduced engine power to minimum level flight setting. I then hit the “go to nearest” function on the GPS, altered course to the indicated airport (which was about four miles away) and reduced power even more to start my descent. The GPS also gave me the unicom frequency and runway heading as I announced a straight in emergency landing. The GPS has bailed me out so many times now that I call it the second most important piece of safety gear you can have; a reliable engine being first.

Aero Country airport seemed to be deserted this morning so I killed the engine after touchdown and rolled out onto the apron in front of the closest hangar, grabbed my fire extinguisher and made an expedited exit from the cockpit. There was no visible smoke or fire so I got out my tools and started removing the cowl just as the low cloud layer I had been running from rolled over the airport.

THE CAUSE I saw immediately that the flex-pipe couplers between the headers and collector were loose and slipping off.

The leaking exhaust had scorched the inside of the cowl but no real damage had been done. It was now apparent that the muffler clamps were not maintaining clamping pressure on the mild steel pipes, probably because they are going soft at the elevated exhaust temperatures of the rotary. My box of emergency tools and parts didn’t have anything appropriate to make temporary repairs so I went in search of help. There was a mechanic working on a tired looking Cessna 150 a few hangars down and I begged some safety wire and hose clamps that I used to patch up the exhaust system.

By the time I got everything back together, the low cloud layer was beginning to break up. As badly as I wanted to make it to COPPERSTATE, the thought of flying over the Texas badlands and mountains to the west while worrying about the exhaust plumbing was too much even for me. I set a course for home and flew high, keeping an airport within gliding distance whenever possible.

I arrived back at Shady Bend with no further problems and a sigh of relief. After leaving a message to let Mick Myal know I wasn’t going to make it to COPPERSTATE, I got back to work on the exhaust. I would have enjoyed picking it up in person, but Mick was kind enough to ship the very nice achievement award to me anyway.

Laura and I had a breakfast flight with the local chapter of Van’s Air force scheduled for the following weekend so the temporary exhaust system had one more mission to fly before being retired. I set about welding some tabs on the mild steel pipes to which I attached springs to hold the system together. This actually worked pretty

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well because it did not depend on the rigidity of the pipes to remain clamped in place. The real challenge at this point was convincing Laura to get in the plane. My powers of persuasion must be much better than I thought because she actually did.

The mild steel exhaust system held together for that last flight but a replacement was mandatory at this point. The fiberglass packing in the Cherry Bomb was completely blown out and the noise level was approaching the threshold of pain. The stainless steel exhaust components I had ordered arrived and a higher quality stainless steel racing muffler was fitted. My exhaust problems were far from over though. That muffler lasted about 20 hours before self-destructing. This was the beginning of a long series of failed muffler experiments that left me scratching my head in confusion.

Why did that first crude home-made muffler last almost 1,000 hours, and why did even the best racing mufflers now fall apart after only a few? The answer came when I finally focused on the fact that my exhaust problems started shortly after I installed the new engine with the turbo exhaust ports. Without the splitters used on the normally aspirated engine, the exhaust pulse exits with explosive force and wreaks havoc on the exhaust system. So why don’t turbo RX-7 car owners have this problem? Because turbo RX-7s have a turbocharger that breaks up the pulse before it gets to the exhaust system.

As Homer Simpson would say, D’oh! After this revelation, my exhaust experiments started going much better, but, I’m still optimizing things.

DRAGGED KICKING AND SCREAMING Shortly before the RV-4 was completed I took early retirement from my engineering job at Lockheed Martin and was looking forward to having more time to fly and pursue some other interests. Writing had always interested me, so I wrote up my early rotary experiences and published them in a book called ‘Aviator’s Guide to Mazda Rotary Conversion’. A title like that is not likely to turn up on the best-sellers list but I was astounded at the number of builders who responded to the tiny classified ad I put in KITPLANES magazine. If it had sold 50 copies I would have considered it a smashing success. 10 years and over 1200 copies later I still can’t believe it. There is obviously a pent up demand for information on the subject of alternative engines. Tracy’s book is available from his website or by phone, for a mere $35 plus a very minimal shipping charge. Contact information is available at the end of this article. ~Pat The book sales resulted in a growing interest in my EFI and redrive development. The last thing I wanted was to start a business after I retired, but I was being nudged in that direction by builders who wanted copies of what I was flying on my plane. On the other hand, doing real R&D work on aircraft engines and systems was a fantasy that I had not dared to even think about, and here I was, being offered a chance to do just that. So in January, 1997, I paid the State of Florida $70.00 to incorporate and became the CEO, chief engineer and janitor of Real www.ContactMagazine.com

World Solutions Inc. The EFI controller was refined enough to offer as a product and after redesigning the gear drive for better manufacturability, I found there was a ready market for both of them.

Before putting the redrive on the market I wanted to change the input shaft thrust bearing to something better. The needle thrust bearing only had a calculated L10 life of about 300 hours. L10 life is the industry term for the numbers of revolutions that a group of sample bearings will endure at the specified load before 10 percent of them have failed. I selected a ball type thrust bearing and calculated the life at about 3,000 hours and retrofitted the drive on my plane with it. An inspection at 10 hours showed no indications of wear or premature failure so in 1999, I confidently shipped the first batch of five production drives with the new bearing.

The initial redrive design was intended for use with fixed pitch wood propellers, which is what most experimentals are equipped with. The prop shaft (made from the Ford C6 output shaft) would allow recreational aerobatics with this type prop, but I was getting a lot of inquires about using much heavier metal props and competition aerobatics. The shaft was not suitable for this use so I went back to the drawing board and redesigned the drive with a larger diameter shaft, machined from a 4340 steel forging. To keep the weight down and allow for possible future use of constant speed props, the shaft was gun drilled. A few months later the new drive was ready.

I’m always a bit excited when the time finally comes to test a new project but as I removed the drive to replace it, my excitement turned to horror when I saw the input shaft thrust bearing. It had deteriorated to the point where it was on the verge of catastrophic failure.

Yikes! Failed bearing from drive on left compared to new one on right.

It was bad enough that Laura and I had just gotten back from a cross country flight with this ticking time bomb, but my horror turned to absolute panic when I thought about the five redrives I had already shipped with this same bearing installed. Writing the “Do not fly until this problem is resolved” letter to customers was painful to say the least.

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I was totally mystified as to what the problem was. A double check of the bearing specifications and the math for the bearing life equations failed to reveal to me any reason for the problem (failure). After several agonizing days of head scratching, I finally found where things had gone wrong. The formula I used for bearing life on ball bearings is the same as for needle or roller bearings, no problem here… But what is not the same is a load factor in one part of the formula. It was not immediately evident in the design guide I was using, but the static load rating is used in the formula for roller thrust bearings whereas the fatigue load rating for ball thrust bearings is used. I assume this is because roller bearings distribute their loads over a much greater area than the limited point contact of a ball.

Figuring it was time to get some outside advice on the subject, I called my bearing supplier, gave them the operating parameters of the bearing, and asked for their recommendation. While I was waiting for their answer, I went back and looked for a more suitable bearing myself.

I took it as a good sign when the supplier came up with the same bearing I did. The good news was that the new bearing (a roller type) would fit the same envelope as the old one, with only a minor amount of machining to the input shaft assembly. The bad news was that the cost was 300% higher. My panic caused me to slip into a rare “cost is no object” mode so I immediately ordered them.

After 75 hours of flight testing on the new roller thrust bearing and triple checking the bearing life calculations I was satisfied that they would work. I then retrofitted all customer re-drives with the new bearing.

NEVER ENDING STORY Like any good odyssey, this one seemed to take on a life of its own. Redrives and EFI controllers for Mazda rotaries are about as “niche market” as you can get and I always expected that the demand for them would fall off quickly and I could get back to doing other things. It hasn’t worked that way. To date, we’ve delivered just over 200 redrives, 100 engine monitors (introduced in 2003) and over 300 EFI/engine controller units. I’m currently working on a fly-by-wire system as well as a “black box for experimental aircraft” data logging device. I’m still trying to figure out what happened to those mythical days of retirement.

I NEED MORE POWER SCOTTY! With more people starting to fly behind rotary engine conversions, the word was getting out that this really was a viable option for experimental aircraft. The 13B, tworotor engine from the “second generation” (1986-1991) RX-7 was an excellent match for aircraft designed around the O–320 and O–360 but it was not quite enough for planes calling for the larger six cylinder Lycomings and Continentals, especially the turbocharged versions.

It was not long before builders started hearing about the 13B’s bigger brother. The “Cosmo Luce” was a car sold only in Japan and was powered by a twin turbocharged 20B (three rotor) engine, conservatively rated at 325 – 350 HP. A few of these engines had found their way into the hands of car racers in the U.S.A. and inevitably, some horsepower crazed aircraft builders as well. It was

dynamic pressure needNote the lack of throttle ed to get thick heat excable to the throttle changers to work. The body. Power control is oil cooler is 3 ½” thick.

Fly-By-Wire. Heat exThe “crude but effective” changer on the left is an intake manifold looks like oil cooler made from an a shoe box and is made air conditioner evaporafrom ¼” plywood with tor core. The single rafiberglass laminated to diator on the right (top in both sides. This design photo) is a Griffin racing has worked well on the rad that was the thickest Renesis engine I am off-the-shelf model they flying and is low cost and make. It’s 2.625” thick easy to fabricate. I’ll but I would have premake an all-aluminum ferred 3 to 3 ¼”. How replacement when time thick the rad should be is allows. The intake runa subject of great debate ners are 6061-T6 alumiin the experimental airnum tubing and run alcraft community. I tend most to the far side of to be of the “Thick rads The 20B engine on Tracy’s soon-to-fly RV-8. the plenum chamber to are better” school if the give maximum length for “ram tuning”. The small black aircraft is in the 200 mph or higher category. The canishose going to the plenum chamber goes to the manifold ter sticking up between the two rear sets of coils is an oil pressure sensor of the EC2 engine controller. The inlet accumulator from Moroso. It reduces the magnitude of air temp sensor sitting on top goes the same place. This the pulsations from the gear-type oil pump. This is hopeengine is getting close to final form but there are many fully my solution to the problem of fatigue failures in oil refinements needed before first flight. For example, the coolers made from evaporator cores that some builders top coolant hose is a little close to the alternator pulley. have experienced. Note the shape of the air diffuser on the oil cooler. This is a critical part of getting maximum Tracy Crook www.ContactMagazine.com

CONTACT! ISSUE 87 PAGE 24

not long before they were asking for 20B versions of my EFI and redrives, so it was back to the drawing board.

The EFI wasn’t too hard to change for an additional rotor, mainly just a matter of modifying the program for the microcontroller chips (I’d already modified it to work on Subaru and Chevy engines). Of course changes are never that simple and in this case it was complicated by the fact that engine accessories like the three coil 20B ignition modules never seem to make it over from Japan with the engine. This required finding a suitable replacement that met all the requirements of availability, quality and affordability. For me, balancing these three factors practically defines the task of developing alternative engines and systems for aircraft use. Anyone with the basic skills and a CAD program can design high quality systems, at least on paper. The real challenge is adapting low cost mass produced hardware to do the job at an affordable price. In this case the off-the-shelf solution was a very lightweight coil/igniter module used on the Corvette LS-1 engine.

Modifying the gear drive PSRU for the 20B was not as simple. I felt that the heavy duty four pinion Ford C6 planetary gear that I was using was pretty well maxed out at 200 HP. Even normally aspirated, the 20B will develop 260 – 300 HP. Starting from scratch was out of the question if I ever wanted to get back to flying and writing, so I looked for the simplest way to modify the existing planetary design.

All side loads are canceled out inside the ring gear thus minimizing bearing loads and simplifying the design. The easiest way to add power-handling capability to a planetary gear drive is to increase the number of planet gears transferring torque between the sun and ring gears. I was already using Ford’s heavy-duty truck version with four instead of the standard three gears. The only limit to how many planets can be used is the space available inside the ring gear. There is room for six gears, but Ford never made the C6 with that many.

The planetary gear set shown along with the input and propeller shaft.

The first solution was having a custom planet carrier for six planet gears machined. I would then rob the gears from two standard duty (3 pinion) Ford carriers to populate the custom carrier. The prototype was built this way and it looked beautiful, but when I sat down to analyze the cost in machining and labor to disassemble stock carriers and load the new one, it just didn’t make sense. I was about to give up on the project when a minor miracle occurred. Ford introduced a super duty version of its lat-

Ford’s super duty version of its latest AOD six pinion planetary gear set, as used in Tracy’s RD-1C PSRU. The planetary gear configuration is a marvel of mechanical efficiency in terms of size, weight and power handling capability. A gear drive’s power handling capability is basically determined by the gear tooth loading. The planet gear teeth in Ford’s C6 transmission are only .875” wide but since there are four gears sharing the load, this makes it equivalent to a pair of spur gears 3 ½ inches wide. Another advantage of the planetary configuration is the absence of radial loads on input and output shafts. www.ContactMagazine.com

The prop shaft used in all RD-1 drives. The front bearing is retained on the prop shaft by a lock ring pressed on with a force of 15 tons. Note the hole in the gun drilled prop shaft used to transfer oil from the external oil fitting to the internals of the gear set.

Getting the oil where it needs to be is a key requirement on planetary gear drives.

CONTACT! ISSUE 87 PAGE 25

for me because I had gone out on a limb six years before and predicted that the rotary would come to be the dominant alternative engine in this category. I made this prediction back when the Subaru was the odds-on favorite to take the title. My thanks to all you fellow rotor-heads out there who believed in it.

2004 TO PRESENT

The internals of the RD-1C alongside the housing. est AOD automatic transmission, with a six pinion planet set. Best of all, the helix angle and dimensions were compatible with the C6 ring and pinion gears! It was not a total “drop in” replacement but all that was needed was a minor change to the housing on the redrive. This configuration is the one currently installed on my RV-4 and soon to fly 20B powered RV-8.

THE BEAT GOES ON This sort of thing pretty well set the pattern for life since the decision 15 years ago to use a rotary engine. It was a lot more work than I anticipated, but I have enjoyed every minute of it. The places it has taken me, the priceless hours spent aloft and, best of all, the people I’ve met along the way have made life better than I could have imagined. After “How do you like it?”, the second most frequently asked question I get is “Would you do it again?”.

Building an airplane is a monumental task and to be honest, I wasn’t sure if I could ever get psyched up enough to build another one. The incentive to do it finally came when we tried (and failed) to squeeze Laura and a weeks worth of camping gear into the RVotter for a trip to Oshkosh. (To ensure continued domestic tranquility, I should add that at 110 pounds, it was not Laura’s fault.)

With the advent of the Mazda RX-8 and the latest version of the rotary engine called the Renesis, I once again had the urge to swap power plants. With over 500 flawless hours on the 1989 4-port 13B, I removed it and had Bruce Turrentine build me an RX-8 engine from parts, since Mazda was not yet selling crate engines and I was too impatient to wait for someone to total their new car.

After the usual complications, it went on the RV-4 (pictured below) and testing began to verify if all the promised benefits were real. After 250 hours on this engine I’m happy with the results even though some of the improvements were less than expected. The full report will have to wait for a future article as the 20B powered RV-8 is nearing completion and demanding all my time.

For those wanting more of the gory details of rotary engine conversion, EFI, gear drive PSRU and other developments, further information can be found on my website at www.rotaryaviation.com Tracy Crook 5500 NW 72 Way Bell, FL, 32619 386-935-2973

tcrook@rotaryaviation.com laura@rotaryaviation.com

Now there is an RV-8 (cleverly named the RV8R) sitting in the hangar with a 20B engine mounted on the firewall 90% complete with 50% to go, so, yes, I’d do it again. I am cautiously optimistic that it will fly this year.

EPILOGUE 2001 With the Hobbs sitting at 1,108 hours, I had just returned from Oshkosh (Airventure) 2001 where no less than six rotary powered planes from every corner of the country attended. This was far more than any other alternative engine type in the 150–200 HP range. This was an especially sweet sight

With no forethought to an “all rotary” issue of CONTACT! Magazine in the future, I took the above photo of Tracy’s Renesis engine installation at SnF, 2006. Not paying attention to the background, I inadvertently captured Ed Anderson’s plane just beyond (Ed is featured on page 3 of this issue). Another coincidence is that Ken Millard’s Subaru EG33 powered Comp Monster (that graced the cover of the last issue, #86) appears in the upper left hand corner of this photo. ~Pat

www.ContactMagazine.com

CONTACT! ISSUE 87 PAGE 26

On page 21, Tracy Crook casually mentions an “exotic” material called Inconel® for use with exhaust systems.

Having no idea what Inconel is, I looked it up. It just so happened that the best information I could find on it was from an exhaust system component supplier that I’ve done business with before, Burns Stainless, Costa Mesa CA. This is in no way meant to be an advertisement for them, but since I’m quoting the below from their website, I feel obligated to credit the information to them. www.burnsstainless.com (949) 631-5120

For a few more details on Tracy’s RV-8 20B installation, see the sidebar at the bottom of page 24.

Inconel® refers to a family of trademarked high-strength austenitic nickel-chromium-iron alloys that have exceptional anti-corrosion and heat-resistance properties. These alloys contain high levels of nickel and can be thought of as super -stainless steels. Inconel alloys are used for a variety of extreme applications including navy boat exhaust ducts, submarine propulsion motors, undersea cable sheathing, heat exchanger tubing and gas turbine shroud rings.

For many years, Inconel has been used for Formula One and Champ Car exhaust systems. More recently, several Winston Cup racing teams have utilized Inconel for producing ultra-light, high-durability exhaust headers.

A shot of the 20B exhaust manifold. The manifold is ceramic coated to reduce radiated heat under the cowl. Coating was from Jet Hot, this was the Jet Hot 2000 process because the more popular chrome colored coating was only good up to 1,300 degrees, not high enough for the rotary’s hotter exhaust.

All rotary installations don’t have to be of the “Crude but effective” variety like Tracy’s. Here is a more meticulous Renesis installation. It uses the James Aircraft rotary engine cowl with the lower air inlet suited for heat exchangers mounted under the engine. www.ContactMagazine.com

Burns Stainless recommends Inconel 625 alloy for exhaust systems due to its excellent strength, corrosion resistance and fabricability. This alloy also exhibits high creep and rupture strength; outstanding fatigue and thermal-fatigue strength; as well as excellent weldability (though the guy welding it might have a different opinion!). Inconel 625 contains molybdenum and columbium, which stiffens and strengthens the nickel-chromium matrix without precipitation hardening treatments. Some hardening however does occur when heated to intermediate temperatures (1200 F to 1600 F) increasing room temperature strength. Also, this alloy retains over 75% of its room temperature strength at 1200 F. This alloy is available in a wide variety of forms including tubing, sheet, bar, plates and castings. Burns Stainless typically stocks welded and drawn Inconel 625 tubing. The tubing specification is SAE AMS 5581, Nickel Alloy, Corrosion and Heat Resistant, Seamless or Welded Tubing. Due to the high nickel content, Inconel is 3-4 times more expensive that traditional stainless steel.

Inconel 625 can be welded using conventional stainless steel TIG welding techniques. Inconel Filler Metal 625 rod is used to weld Inconel to Inconel as well as to dissimilar metals including stainless steel. Inconel weldments are high strength and are highly resistant to corrosion and oxidation. Many welders describe that welding Inconel as "dirty". In other words, the weld pool appears to be under a "skin" and is not well defined. In addition, the weld pool is somewhat "sluggish" as compared with steel or stainless steel. These characteristics tend to result in a "coarse" appearing weldment as compared to stainless steel. Welding Inconel is not necessarily more difficult to weld than stainless, just different. By following the welding procedures outlined in the header construction tips article, (on our website) successful welds with Inconel 625 are possible.

CONTACT! ISSUE 87 PAGE 27

Richard Sohn is currently flying an Avid Flyer, powered by his own Subaru EA81 conversion. In search of a better engine solution for his airplane, he joined the rotary engine community and began to pioneer new ground. Although he’s not the first to ever cut a multiple cylinder engine in half in order to net a smaller, lighter package, he may be the first (certainly among the first) to ”cut” a Mazda 12A rotary engine in half. ~Pat Photos and story by Richard Sohn Through the “Fly Rotary” e-mail discussion group, I was informed about the intention of CONTACT! Magazine to dedicate an entire issue to the rotary (Wankel) engine.

Therefore I would like to offer this narrative of my work on perhaps a better engine solution for my airplane, and any other aircraft in the same power range.

After solving the weight/CG issue on the Avid with the EA81, more or less, I started looking at rotary engines as a possible better suitable powerplant for my airplane.

The first obstacle I hit was an obvious one; the Mazda RX-7 engine is just too powerful and too heavy. Other rotaries in my power range where either not available, too expensive, or I could not trust what was offered.

This situation left me only one choice, building my own.

My smart (ha…ha) decision, to build my own single rotor engine was an uphill battle from the beginning, plagued with problems, both foreseeable and unforeseen. The solution was to use as many factory Mazda parts as humanly possible, modify what I could get away with and build from scratch what was absolutely necessary.

GETTING STARTED: CONSTRUCTION On the weight reduction side, the first order of business was the doing away with all automotive driven features and design elements specific to automobile applications.

Just to name a few, flywheel size, bell housing attachment, ignition distributor, alternator, fuel delivery and exhaust as well as emissions come to mind quickly.

Next was getting rid of the heavy cast iron side housings.

(See pages 16-17 for an exploded view of a typical rotary engine) A side housing made of aluminum, if available, has not been demonstrated with a reliable running surface coating. If it were commercially available it would probably be too expensive anyway. So the solution, in my mind, is to produce the piece from aluminum and sandwich a piece of cast iron between it and the rotor housing. After all, cast iron is the specified material or choice; I just chose to support it with aluminum. Note too that the rotor housing is a “compound” casting using aluminum for the bulk of the part and a chrome plated iron wear surface.

One big issue in using all Mazda parts is weight. I believe some single-rotor (essentially ½ RX-7) engines currently available, weigh anything from 180 pounds on up, for the equivalent of a single rotor long-block.

The design goal I set for this engine was 100 hp and a FWF weight of 170 lbs. The whole thing turned out to be a real evolution, as far as engine configuration is concerned. The good part is general engine dimensional details were not an issue, since there is a wealth of information available from books and reports on research done primarily by Mazda. Also, the highly regarded rotary automobile racing community has generated a wealth of knowledge, in particular about the ultimate performance limits of a rotary engine.

Considering all of that led to two primary areas of modification. First, weight reduction, and second, increasing power. As it turned out, the second one is by far the easier of the two. www.ContactMagazine.com

Figure 1. Aluminum side housing w/o iron plate.

CONTACT! ISSUE 87 PAGE 28

This compound side housing configuration was used in my engine from day one to present. In the first engine I experimented with, I used a machined down cast iron Mazda housing with an aluminum back-plate and bearing carrier. This was relatively simple on the power-takeoff end of the engine (Fig 1., opposite page), because this end requires no stationary gear for a one-rotor application. The water pump side housing was a little trickier due to the need of a stationary gear, oil return opening and the oil pump (see photo below). Thanks to JB Weld, nothing is impossible while in the R&D phase.

Figure 3. The running test engine (Mazda 12A) complete with custom compound side housings. negative influence on engine idle. Playing with the numbers, it turns out not to be that much of an issue. For example, on my configuration with a 3:1 gear ratio, and 7500 rpm redline, if I want the prop to idle at 500 rpm, the engine is running at 1,500 revs, which is not low enough to be a problem. The test engine is now idling at 1200, with temporary, not optimized, carburetion. So, there does not seem to be a problem.

IT SEEMS TO BE WORKING

For the water pump, I picked one from a Subaru engine because it is essentially self-contained and does not need any cavities on the engine side; it just mounts on a flat surface with an opening for the coolant outlet. All these modifications cut the weight of the engine, compared to a single rotor using all stock Mazda. And all this with limited technical risk.

The final design for the compound side housing, consisting of a cast aluminum section and a cast iron insert (Fig. 2), has been running in the test engine since 3/05/07 (Fig. 3).

MORE POWER On the power increase, as I said before, it was a simple modification changing to what is called a “peripheral intake port configuration� (Fig. 4, next page). The upper hole in the rotor housing is called a peripheral intake port.

This configuration makes the engine breathe better at higher RPM at the expense of lower RPM torque. This may be an issue in an automotive application, but not for airplane use.

This configuration also has a

The engine in Fig. 5 (next page) is the second running version used for proof of concept. This configuration already had a one-piece aluminum housing, but still a large cast iron running surface section. The naked engine of this configuration weighs 90 pounds vs. 170 pounds for the same size engine using all Mazda parts. It can potentially develop 115 hp at 7500 RPM. This engine has absorbed many successful hours on the test stand so far, including extreme temperature cycles and over-temperature runs, for the purpose of fully taxing the seals and other components under worst-case conditions. Power output has not been demonstrated yet, mainly due to of the lack of a dynamometer.

Figure 2. Compound side housing; notice the lack of intake porting.

www.ContactMagazine.com

I consider this conversion to be not overly risky since all parts and technologies involved in the combustion cycle are original Mazda. Fig. 6 (next page) shows the eccentric shaft , made from a two-rotor shaft. This shaft is one of the only two moving parts in this rotary engine; the other one is the rotor itself. This is the big fascination about this rotary engine, two moving parts, that’s it.

The flywheel in Fig. 8 (next page) had to be made from scratch.

CONTACT! ISSUE 87 PAGE 29

The stock intake ports on a Mazda rotary engine deliver air/fuel into the combustion chamber through the side plates. When one does a “peripheral port” job on a rotary, these ports are welded closed and a hole is drilled through the rotor housing (through the water jacket) and then sleeved as shown in the photo to the left. A flange is then welded to the protruding sleeve allowing for the attachment of the intake manifold runner.

Figure 4. The rotor housing.

BALANCE The holes shown in the flywheel are for balance and are calculated. The balancing on the single rotor consists of one counter balance on each side of the rotor. One can be seen attached to the eccentric shaft in the photo (on the preceding page) of the accessory plate. The size of the counter balance depends on its distance from the rotor. Both balances together have to have the same momentum as the rotor/eccentric shaft combination. It can be calculated fairly closely, however, in an engine going in an airplane, it will have to be verified/refined by dynamic balancing on a spin balancing machine.

A two-rotor, as installed in the RX-7/RX-8 also has two balance weights; a discrete one in the front of the engine, and another one in the rear. In an automobile application there is a discrete balance in the case of an auto trans, or a balanced flywheel with a manual transmission. For aircraft use, it will always be the configuration for automatic transmission, mainly for weight reasons.

OUTLOOK

Figure 5. Completed Avid firewall forward w/ Rotax C PSRU.

The next step is, making an “airworthy” version and developing the FWF installation. The final design compound side housing is the first step in this direction. I am looking forward to a new set of challenges like cooling and exhaust muffler, just to mention two important issues. Once I feel comfortable with the ground testing up to full power, I will install it into the Avid and fly. When might that be? The short answer is, as soon as everything is completely ready.

Figure 6. The eccentric shaft, made from a twin rotor shaft.

I’d like to take this opportunity to openly express my appreciation to everyone on the two rotary e-mail discussion groups “Fly Rotary” and “Rotary Engine”, for providing so much knowledge and information. I would probably still be struggling where I was five years ago, without all these great people. www.ContactMagazine.com

Richard Sohn Defuniak Springs, FL unicorn@gdsys.net Avid Flyer S/N 589 N2071U

CONTACT! ISSUE 87 PAGE 30

By Bill Eslick wgeslick@gmail.com Bill Eslick has been flying since 1966. He received a BS in Electrical Engineering from Washington State University prior to flying the F-4C/D/E with the USAF where he also obtained a Master’s in HRM. He has survived 11 years of wheat farming in S.E. Washington State, aerial crop spraying, over 20 years with the worlds largest airline, the marriages of two daughters, and coming up on 40 years with the world’s best wife. He has flown ultralights at 300 lbs and the DC-10-30 at 565,000 lbs. He has cruised at 40 mph and at Mach 2.25. It turns out the most fun is playing with his new granddaughter, Allison. Bill has owned and updated a 1955 Tri-Pacer, a 1967 Mooney MK-21, and a 1969 Cessna 180. His first project was a fiberglass Goldwing canard in 1982 that taught him how much easier it is to use rivets.

The year was 1992. I had been drooling over kit plane articles for years when it dawned on me that the only way to get one built was to take step #1 – START! The rest of the story is familiar to many of us. I called Van’s, got the tail kit and time moved on. Kids grew up, work interfered quite a bit, the constellations shifted position ever so slightly, and 10 years passed by before the first flight. (No such thing as a quick-build in those days!)

ENGINE CHOICES I am not sure when I first considered a rotary engine, but when Pat put out a call for articles, I discovered Issue #1 of CONTACT! Magazine in my collection. It contains quite a bit of information about rotary power, and is dated 1991. Also consider that (1) I am cheap (Lycoming = $$$) and (2) as a reformed wheat farmer with a lifetime of shop experience, engines have always held a special interest. By doing the rebuild and mount myself, I held the firewall forward cost to $5,000 including prop and Tracy Crook’s redrive!

I looked at many engines but kept coming back to the Mazda rotary. I read and re-read articles from CONTACT! Magazine and bought Tracy’s manual describing his RV-4 installation. I followed Ed Anderson’s cooling adventures and looked at both of their installations (in person) every chance I got.

Having absolutely no rotary engine experience, I was fortunate to find (in my neighborhood) a used 1986 RX-7 at a fire-sale price . It would not start and the owner was ready to dump it. Turns out it was just flooded! That is www.ContactMagazine.com

when I learned about the dripping injector problem that plagues some models. The answer seemed painfully obvious to me. When it is time to shut down, just turn off the fuel pump! No need for bypass orifices to drain the residual pressure. To this day, that is how I shut down the RV-6, and this is the reason why.

To become familiar with the engine, I pulled it out of the car and spread it all over my little shop. I believed Tracy when he wrote that normal shop tools and a Haynes manual would suffice to remove the mystery of this little engine’s internals, and he was right. With over 100,000 miles, it was in good shape, but the finish on the edge of each rotor housing surface was worn. Not a big deal, but I wanted an AIRPLANE engine, so perfection was desired. Being a real deep thinker, I went to a salvage yard and bought another engine with 100,000 miles on it to get better parts. DUH. Looked just like mine inside. In the end, I purchased two new rotor housings and two of the “iron” sections from Mazdatrix and had the third “iron” resurfaced. New seals and gaskets and all was good!

ENGINE MODS I made the mods that Tracy recommended, including grooving the water jacket with a Dremel tool inside the plug area, installing a permanent bypass in the eccentric shaft oil passage, and changing the size of the rotor oil jets. He also removed the rotary valves from the highspeed ports on the intake and smoothed the passages with JB Weld. I did the same.

ENGINE MOUNT How do I hang this thing on the RV? The only commercial mount available was from Atkins. I tried to buy one, but his supplier was not producing, so I bit the bullet and welded my own. I used photos from the internet of working installations and stirred that in with farm experience to produce what is flying today. It began as a conical mount from Van’s, as the landing gear mount is integral with the engine mount. I cut off everything but the gear mounts, mocked the mount with PVC pipe, then gas

CONTACT! ISSUE 87 PAGE 31

COOLING All the articles seemed to point to cooling as the weak link, so I copied Ed’s installation as much as I could, since he seemed to be enjoying success. The radiators are A/C evaporator cores out of an ‘86 Caprice, and the oil cooler is stock ’86 RX-7.

welded it out of 4130. The isolators are modified Barry mounts and work fine.

BREATHING CONSIDERATIONS Intake and exhaust systems are always cause for much discussion, deliberation, and aggravation. I am on intake manifold #2. The first was much too short and restrictive even though I spent many hours designing to take advantage of the dynamic charging effect peculiar to the rotary. Just turns out that I had no clue.

I tried to have more clues on #2, but all I know for sure is that it is much longer and works much better, which is the real goal. It increased my static rpm by 300, which is a LOT. It seems some people can just bolt on a tomato can and go 200 mph, but that never works for me. Maybe I am just not a good liar?

My first exhaust system was a tangential can muffler of my own design inside the cowl. It was quite successful and very quiet, but finally disintegrated internally after a couple of hundred hours. I then fell to convention and installed a two-into-one header to a Flowmaster muffler under the belly. I also had a Spintech which worked just fine, but my neighbors chided me for not having an “aerodynamic” muffler, so now I “look” faster. www.ContactMagazine.com

I have fooled with the ducts into the radiators several times and measured pressures all over the radiator face and throughout the cowl. I never did see measurable improvement with any of my “upgrades”, and truth be told, I may have made it a little worse. The addition of a large cowl flap made the most difference. It can also be used as a speed brake (unfortunately) and requires a flap actuator jackscrew to position it. (See my website for more details) At that point, I decided good enough was good enough. Incremental improvement is great, but I enjoy flying! My current setup does cool adequately except full-throttle-climbs at speeds below 120 MPH when the OAT is over about 90° F. In those situations, reducing the power a little or leveling and letting it run fast will still keep things in check.

Intakes are standard RV at the top, and standard "Ed" for the oil cooler.

My temperature alarms are on the conservative side when compared to some, but I use 200° F on the oil and 210° F on the coolant (50/50 Prestone). I keep the coolant pre-pressurized to 10-15 PSI via a Schrader valve and a small hand pump (strut pump for Harleys) to eliminate the nuisance alarm for low coolant pressure. I use a 21 lb cap, and the system retains positive pressure for over a month.

CONTACT! ISSUE 87 PAGE 32

If I were to ever start over, I would be inclined to try the single large radiator method as it seems to be working well for Jason Hutchison who lives down the street. He is developing more power and speed with his 3rd generation engine, 2:85/1 redrive, and large prop and now has too much cooling!

There are no valves to leave in the wrong position, the left tank can be totally emptied without scaring anyone. (I scared the heck out of my brother-in-law a few years ago emptying a tank in a Tri-Pacer.) Fuel is the lowest grade of auto gas with 1 oz/gallon of TC-W3 two-stroke oil added to lubricate the rotor apex seals.

PERFORMANCE Like I always say, I am no good at lying. I keep forgetting what I told the last guy, so sticking to the truth is much easier. Like all aircraft, it loves gulping cold air and in mid -winter it feels like somebody strapped on JATO bottles for takeoff! My power is estimated by flying with other RV -6s with wood props, but O-320 powered.

ELECTRICAL Electrical systems are routed through an EXP2 Load Center switch panel from Control Vision. The switched feeds are protected by electronic circuit breakers which will reset by recycling the switch if the problem was momentary. Avionics are taken off line automatically when the starter is activated. The alternator is stock with the mod described in CONTACT! Magazine #46 to allow shutting down the field in case of over-voltage, which is sensed and controlled by the load center. The only conventional circuit breaker in the cockpit is a 60 amp unit for the alternator feed. I really like the EXP2 package, but I also have engine-critical power (injectors, fuel pump, ignition and controller) connected to a switch which is hard-wired straight to the battery. If the engine suddenly quits, it is the first “go-to” switch on the list. If a smoke situation arises, this allows shutting off the master switch and powering down everything but the engine. In over 450 hours, the only time I have touched this switch is to test it!

Since the Mazda engine comes with a low-level float switch in the oil pan, I wired it to a big red light on my panel and added a lead to a similar low-level warning in my right tank. This is the “land this thing NOW light”.

FUEL I copied Tracy Crook’s fuel plumbing philosophy. The engine feed and return lines go to the right tank. The left tank feeds the right one through a facet pump which transfers about 1 GPM. I really like simplicity, but it was inevitable that I would get distracted when transferring fuel and forget to turn off the pump, so I installed a 3minute timer which transfers 3 gallons then shuts off. My right-seater’s job is to watch the fuel gauges and push the little red button between the gauges when 3 gallons will get us back in balance. I use two high-pressure fuel injection pumps in parallel (each with its own filter), to feed the go-juice. One pump runs all the time, and the other is only used below 1,000 AGL. Fuel pressure runs at 30-35 PSI. The second pump increases the pressure 3 or 4 PSI during the run up, so I know it is running. www.ContactMagazine.com

Estimated HP: 160 Normal cruise: 140 KTS True 7.8 GPH at 7500’ MSL @ 5300 RPM Redrive: RWS RD-1 at 2.17/1 Prop: Felix wood 68 X 72 Static RPM: 5000 First flight: Total time:

June, 2002 450+ hours as of 3/07

MAINTENANCE ISSUES I have had only one issue that required repair on this drive train and it was not urgent. In ‘06, I was doing a lot of short flights investigating low-pressure areas on my cowl. That came to nothing, but in the process I got tired of the idle, which had been kind of ratty for a year or so.

Above high idle, everything was smooth, but low idle was not. The problem was discovered through a compression check. This revealed a leaking apex seal on one rotor.

The tear-down was surprisingly quick, and I found a corner of the seal had broken off but was still in place. I swear it must have been like that for a year! New seals from RWS put it back like new and the engine performs exactly the same, but the idle is now smooth. While it was apart, I inspected the Redrive and found a TINY bit of galling on the drive (sun) gear teeth. After a conversation and e-mailing of photos, Tracy Crook sent me an updated gear gratis (mine is a very early version) and I buttoned it all up. Thank you, Tracy.

Every time I hear about another Lycoming cylinder or crankshaft recall, I just smile and go flying.

Bill Eslick More information about the RV-6: www.weslick.com

Bill and Linda Eslick, 2005 AirVenture Cup, 142.37 MPH

CONTACT! ISSUE 87 PAGE 33

By John Slade sladerj@sbcglobal.net John Slade built Cozy Mark IV N96PM, aka “Slick Kitten” on his patio in West Palm Beach, FL. For the story of the build in excruciating detail, visit his website (address at the end of this article). As of this writing, the aircraft has logged 84 hours and is now based at KWST in Rhode Island.

Thus far, the top speed attained by the Kitten was a triangle averaged GPS ground speed of 269 mph.

We hope to publish a detailed article on the engine installation and performance in a future issue. ~Pat

John Slade’s spectacular Cozy Mark IV.

Installing a non-standard engine in an aircraft is all about decisions. You’re faced with a string of them. Most decisions have a few right answers and plenty of wrong ones. It is said that if you’re not making mistakes, you’re not moving forward. During the past five years I moved forward quite a bit, and made my share of mistakes. The following is some of what I learned along the way.

The more of a particular engine type that’s flying, the easier the job is going to be. It’s like a minefield; if you’re the first to cross, the odds are that you’ll step on a couple of mines, if you run across you might be lucky. Moving slowly doesn’t really help unless you have the time to search out and dig around every single mine. Early rotary aviators have each stepped on their share of mines leaving flags, and occasional holes in the ground for others to avoid. As more and more rotaries “break the surly bonds of earth” the safe path through the minefield becomes wider and clearer.

Consider this article a guided tour though the minefield.

No. Stop. That sounds too negative. It used to be a minefield. These days it’s beautifully landscaped parkland, with rivers, trees and picnic tables …and a few unexploded mines hidden under the well-manicured lawn.

WHICH ENGINE? The rotary is a simple engine at its core. It’s robust, has few moving parts and, once running, it’s an energizer bunny. It produces very little vibration, which cuts down on fatigue both, of the pilot and the airframe. While it burns about the same as, or maybe a little more fuel than it’s certified brethren, it’s happy with automotive gas.

Most trips can be done there-and-back on full tanks and I’ve found that refueling from five gallon cans is simple, quick and convenient. In 84 hours I’ve burned about 15 www.ContactMagazine.com

gallons of Avgas. The rest was automotive. It’s not the gallons per hour that count, it’s the dollars per hour. I’m averaging about $20 per hour.

There are numerous models of rotary to choose from.

The early 12A, and four generations of 13B (including Renesis). Each generation of 13B was an improvement over its predecessor. There are also Cosmo and turbo or normally aspirated (NA) versions and the three rotor 20B. Most flyers use the second generation RX-7 (1987 – 1990) 13B. My choice was the FD model third generation RX-7 (1993 to be specific) 13B-REW turbo, with non -turbo 9.3:1 rotors and 3 mm RWS apex seals. The 13BREW was the first-ever mass-produced sequential twinturbocharger system to export from Japan, boosting power to 255 HP in 1993 and finally 276 hp by the time production ended in Japan in 2002.

The fourth generation (Renesis) was not available at the time I made my decision. Would I choose the Renesis if I were doing it again? Perhaps. The current Renesis model has a 10.1:1 compression ratio. Theoretically this makes it more susceptible to detonation under boost.

Turbo normalized, it should be fine, but what’s the point of having a turbo and not using it for take-off? Some after -market vendors are now adding turbos to the RX-8, but the stock road turbos probably wont hold up in aircraft use. In contrast to the REW, which was last made in 1996, the engine’s are new, and parts are easily found.

It’s close, but on balance I think I’d go with the same engine I have. Peripheral porting (i.e. grinding out the intake and exhaust ports) produces more power, but can make the engine rough at idle.

REBUILD IT YOURSELF? This depends on you’re background and/or your determination to understand and master every detail and, yes, even a brand new Renesis from Mazda parts will need

CONTACT! ISSUE 87 PAGE 34

opening up. Once you’ve learned the skills a second rebuild, should you ever need one, is only going to cost you $1200 or so, plus your labor. I’d prefer not to need one but if I do I’ll gladly pay the price tag to have it done by a professional. The savings from re-building it yourself are probably in the region of $3000. This is a very low percentage of the total cost of your airplane. Weight this against the relative importance of the function provided. I called upon Bruce Turrentine. 919-557-6512 One last thought on this topic – if you use an expert; make sure he or she really IS an expert and is conversant with the modifications needed for aviation use.

GOT CORE? NOW WHAT? The core 13B is a relatively small cube. Once you’ve surrounded it with fuel supply, ignition, turbo, intercooler, coolant and oil supply parts, hoses and fittings it more than doubles in size. Weight is about the same as an equally equipped IO-360.

They say “the devil is in the details”. In the case of the rotary, he’s in the peripherals. Rotaries don’t suffer from pistons poking through the block or from blown cylinder heads but, as with any combustion engine, a rotary will stop running if you remove spark, fuel or cooling. The answer is here redundancy. Try to have backups for all critical systems.

Most flyers disable the automatic oil metering (injection) for apex seal lubrication and add 1oz/gal of 2-stroke oil to the fuel. One less system to fail. One more thing to remember. Adding the oil is easy and soon becomes a natural part of the refueling procedure.

TURBO OR NATURALLY ASPIRATED? A turbo serves well as a muffler and it gets you to altitude quickly. Some would argue with this statement, but I think of the turbo as a safety feature. There’s a period in every flight when it’s too late to land back down and stop safely, and too early to turn back. I call it this the “Oh S#%&!” zone because that’s what you say if something goes wrong. A turbo either dramatically minimizes the length of this zone, or eliminates it completely. It also gets you out of short or highdensity altitude fields more www.ContactMagazine.com

easily and gives you more power (and speed) at cruise altitudes. On the negative side, turbos are HOT: they add about 40 pounds: cost a couple of grand all installed and they add complexity as well as additional failure modes.

Thankfully the failure modes are mostly fairly benign. I know this because I’ve tested most of them. Blowing off an intake hose can get your attention at 300’ on take-off, but the aircraft can still climb without boost so the only damage is probably to your underwear.

Know now that the stock turbo is not a satisfactory solution for aviation. They’re not that well-built, they don’t stand up under constant boost, and they over-speed and blow up at altitude. When this happens the oil gallery can leak into the exhaust leaving you about 30 minutes to land safely and costing you another 30 minutes listening to phone messages about the black smoke you were trailing in the pattern. Eventually I installed a Turbonetics T04E-50 big shaft tangential with P trim, wet housing, an aspect ratio of 0.96 and a TiAL Sport 46 mm wastegate.

The stainless manifold came from XSPower. This now has 40+ hours on it with no problems other than somewhat high indicated EGTs which, hopefully, will reduce with some fine tuning of timing and mixture when I get around to it.

WHICH ECU? Another tough decision. I installed the RWS EC2 from rotaryaviation.com. This is the unit used by the majority of rotary flyers. It’s a little complex to set up, but it handles both ignition and fuel injection and has redundancy modes in both that the stock and aftermarket ECUs don’t have. Some aftermarket units have sophisticated data logging and leading/trailing spark separation (which is apparently good for turbos), but redundancy is key.

Loose a set of coils – fly home. Loose an injector - double the flow to the other two. Fly home. Two very important little words.

PLUMBING THE FUEL SYSTEM The fuel-injected rotary uses a high-pressure fuel system with a return from the rail. This means that two tank aircraft need to switch both the feed and the return. Switching can be done with expensive duplex valves and lots of pipes or with an electric solenoid. I chose the solenoid approach and have had no problems with it other than dealing with cross-feed when taking off on both pumps and a full left tank. The solution I found was “don’t do that”. Another option is Tracy Crook’s method of one main tank and one reserve. He runs a transfer pump to move fuel from reserve to main when needed. This costs you the principal of entirely redundant fuel supply systems. Perhaps an emergency feed from the reserve

CONTACT! ISSUE 87 PAGE 35

could be added, but this adds complexity. Another solution, that I’m not personally fond of, is the central sump tank. This has it’s own peculiarities and failure modes.

There is no right answer to the fuel system question. If in doubt, copy something that works … and copy it exactly, including pipe diameters and component placement. Oh, by the way, use aircraft quality AN fittings, no 90’s, all sweeps instead, and stainless steel braided hoses. Absolutely no barbed fittings with hose clamps! Doing it right is more expensive; just write the check.

GOT VOLTS? A fuel-injected rotary must have a continuous supply of positively charged electrons for the ECU, fuel pumps and the coils, otherwise it simply stops rotating. A backup battery is absolutely essential. Some add a backup alternator too, but there’s no easy way to do this in a rotary, so I installed a low voltage warning (voice) and a minimal systems power circuit (essential buss). I replace the batteries frequently. It may be possible to add magneto type backup for ignition and a carburetion or even hand prime type backup for injection. It doesn’t take much in the way of accuracy to keep the engine running once its started.

As always, increased redundancy adds increased complexity and more failure modes.

ENGINE MOUNT Off-the-shelf mount’s can be found, but use caution; one vendor seems to be taking deposits but not delivering products. COD only would be my suggestion. For pushers, the choice is EZ. Contact the Cozy Girrrls www.cozygirrrl.com (There’s excellent article about them in the March issue of EAA’s Sport Aviation). I’m not sure if there’s an commercial solution for the Renesis yet.

Building your own mount (with the aid of a skilled welder in my case) can be expensive and time consuming, but it can be done. Learning TIG welding from scratch in order to build your own mount wasn’t my choice. Metal has a nasty habit of loosing strength when heated and cooled improperly and welds that look good can, in fact, be very weak. The bottom line in this case is to either do it right, or have someone else do it right.

about to have a very bad day.

Making your own intake is relatively easy.

Just find a good TIG welder guy (skilled in aluminum welding), give him the engine, the throttle body, some thick walled aluminum tube and four injector bosses, then tell him to stick them all together with aluminum. Remember to mention that it all has to fit under the cowl. My intake puts the throttle body on the cold side, has four aluminum runners over the engine and has the two secondary injectors in bosses close to the intake end. I used the stock primary rail in the housing.

COWLING Building your own cowl can be fun. Some install the engine, prop and spinner and then build the cowl to fit around it. My approach was to make the cowl first, then force the engine to fit under it. The alternator mount and water pump had to be “adjusted”, but otherwise it worked out well for me.

WHICH PROP?

INTAKE: HOME BREW OR STORE-BOUGHT? Other than mufflers, this is the one remaining area that’s lacking a good off-the-shelf solution. Mistral sell one, but it’s very expensive and has the rail on the hot side right in the way of the turbo. Atkins Rotary sells one, but it’s for NA only and, incredibly, dispenses with the stock redundant injectors by using two larger ones. If just one of these two injectors fails or becomes blocked, you’re www.ContactMagazine.com

Although John ended up with a composite IVO Magnum, it’s hard to beat the looks of a nicely crafted wood prop. The end product of the cowl construction is exceptional.

I started with a three-blade wood version optimized for cruise. I was able to operate from a 3,000’ strip but take-off and climb were about equal to a stock Cozy. The inflight adjustable 3 blade IVO Magnum I’m using now seems to be an excellent solution so far. It’s very well built, quiet and accu-

CONTACT! ISSUE 87 PAGE 36

rately balanced. Blades are also comparatively cheap to replace if you strike them on landing… but that’s a whole other story. My take-off roll is drastically reduced with the IVO and climb is simply exhilarating. Wa-hoo is the best way to describe it. I haven’t had the chance to test highspeed cruise numbers on the IVO yet.

John’s firewall mockup including his RWS PSRU.

WHICH REDRIVE? This one’s easy, since Tracy Crook’s product is well proven. The 2.17 ratio RD1-B or the 2.8 ratio RD1-C from Real World Solutions. The C will get you higher engine rpm, thus higher power and the higher engine wear and noise that come with it. I like the lower ratio.

COOLING SYSTEM Once black magic, cooling and airflow is gradually becoming a know entity on the FlyRotary e-mail list, www.flyrotary.com. Early rotary flyers were plagued with cooling problems. These days, most first-flights are problem free in this area. The cooling system for my Cozy IV consists of the stock NACA inlet leading to a sealed plenum formed as part of the lower cowl. The roof of the plenum is a 16” x 26” x 2” aluminum radiator, and in the sides are two stock third generation (twin turbo RX-7) oil coolers, plumbed in series. There are outlets from the plenum for filtered intake air, intercooler air and a blasttube for the Chevrolet LS1 ignition coils. A manually actuated cowl flap allows air out of the rear of the cowl V tail for use during high altitude cruise. Rudimentary exhaust augmentation is achieved by extending the stock turbo heat shield beyond the end of the exhaust with an oval of stainless steel. Eric Westland vortex generators on the belly help get the air into the NACA inlet.

sonally I think experimental aviation is a lot safer than jumping off bridges with an elastic band tied to your waste, or jumping out of perfectly good airplanes, but every man to his own.

A well-installed rotary is probably the most robust alternative light aviation power plant available today and, in the unlikely event that it fails in flight, at least the famous $18,000 silence during the glide down with a dead Lycoming is replaced by the thought that “this can’t possibly cost me more than $6000 to repair”.

I have had some surprises while flight-testing the airplane. I’ve experienced blocked fuel filters, ignition failure, fuel pump failure, turbo failure (one of which took out the apex seals on one rotor), ECU problems, wiring problems and a few issues with the big nut in the left seat.

Not once have I experienced “the sound of silence” while airborne. I have zero glider time and no off-field or even wrong field landings. On each occasion in which I had a problem, the engine continued to run and brought me to home base safely. Often this was partly because “home base” was 10,000’ directly below me during many long circular test flights.

I have found the exercise of installing a rotary to be one of the most satisfying and rewarding endeavors of my life. Building and flying your own plane is a tremendous achievement. Building and flying your own engine installation is twice as hard and three times as rewarding.

Cruising in the rotary is surprisingly quiet and extremely smooth. The engine is responsive and powerful. Many ask, if I knew what I know now, would I do it again. The answer is a resounding YES. My advise for those who choose to fly where even angels fear to tread - Make informed decisions, C.Y.A. with redundancy wherever possible, don’t even THINK about venturing out of that cone of safety for the first 40 hours, and try to make your mistakes be little ones.

John Slade

sladerj@sbcglobal.net http://canardaviation.com/cozy

CONCLUSION Installing and flying a non-standard engine in an airplane is not for the faint of heart, nor the feint of bowel. It will most likely take a lot more time and probably isn’t going to save you money in the initial installation. It is, however, the essence of “experimental aviation” where you effectively put your keister where your mouth is. Let me rephrase that. As in any extreme sport, your life is on the line and a small mistake can end the fun – quickly.

Cheating death is part of the thrill. In our sport you have a lot more, if not complete, control over the odds. Perwww.ContactMagazine.com

CONTACT! ISSUE 87 PAGE 37

SWITCH ON! Continued from page 2

thing that’s a work in progress. Some people think that any idea that’s not “flight proven” is not worth investigating, but EVERY good idea was at one time in fact, not flight proven. On the flip side, every bad idea that was proven to be bad through flight testing was once held in high esteem by its innovator and had the potential to be published as I’m proposing. But here’s how we are different. CONTACT! is more than just a magazine. On the cover of every issue we make the claim to be a newsforum, and as such, we encourage communication directly to the author, hence the contact information in every article. The vast majority of our readers are engineers and/or talented mechanics or at a minimum, creative thinkers and it’s not uncommon for them to spot potential issues and bring them to the attention of the author.

With this, I feel that bringing unfinished works to the pages of CONTACT! furthers our mission of education, but on a two-way street basis. However this is not the last word. I’d like to hear from you on this subject and find out if you agree or not that works in progress should remain taboo.

GIFT SUBSCRIPTIONS In my last editorial I made a request for help with increasing our subscription base. Many of you stepped up and took my suggestion to buy gift subscriptions for friends and family. With that, I would like to send a sincere thank you to each and every one of you who did just that. Some of you even went over the top and purchased gift subscriptions for multiple people. I can’t express enough gratitude to those of you who support our work.

WHAT’S IN A WORD? There’s a phrase bandied about throughout our community which is used (and almost universally accepted as a correct term) to describe what it is that we do. But I feel it fails to capture the true essence of our passion and waters down the impact of just how special it is. The term I’m speaking of is “homebuilt”, or “homebuilder”. Sure, most of us either have built or are building our projects at home, in our garage, basement, carport or patio, (some of us real hard-core builders even use the living room!) but that’s not the heart and soul of it as much as the fact that we have the freedom to experiment. While laying out Tracy Crook’s article, I came across something he wrote that does a better job of expressing what I’m trying to convey here, and it’s worth repeating.

“I have no idea where my attraction to flying machines came from, but one of my earliest memories is of a children’s book called, “The Little Golden Book of Airplanes”.

I spent countless hours staring at it instead of doing the schoolwork I was supposed to be doing in second grade.

I especially remember the picture of the Bell X-1. The book explained that the “X” meant that it was “Experimental.” That exotic sounding word fired my imagination so strongly that I knew, without a doubt, that someday I would build a sleek little metal airplane with that word on it. I flunked second grade and forty more years went by, but eventually I did build that plane. It was indeed experimental in every sense of the word and was www.ContactMagazine.com

labeled appropriately.”

Although it seems for the most part that our beloved EAA would rather sweep the E under the carpet, I (among countless others) on the other hand wish to embrace it and bring it to the forefront where it belongs.

We are EXPERIMENTERS involved with EXPERIMENTAL AVIATION. We’re not homebuilders… we don’t build houses. We are amateur builders of experimental aircraft with 2” letters and a metal plate on our planes that says so! This is intended to be a warning to any possible passengers, but for me, it’s a badge of honor, bragging rights if you will, not some caveat or something to be embarrassed by and certainly not something to be swept under the carpet or dumbed-down with a phrase such as “homebuilt”. So if you feel as I do about this I would like to ask that we remove this reference from our vernacular and call EXPERIMENTAL AVIATION exactly what it is.

BOOK SALES The vast majority of you reading this probably already know that we have published two books in the past and are currently working on a third. The long and short of it is that each volume of ALTERNATIVE ENGINES is a compilation of approximately five years worth of CONTACT! Magazine articles that highlight or otherwise feature alternative engines. It’s not a reprint of all the back issues, as not every article printed in our magazine is engine related. Volume I covers the first five years, Volume II the second five years and Volume III, which we are currently pre-selling, covers the most recent five years. Volumes I and II are still available directly from us and can be ordered at any time. We have bundle specials if you elect to order both Volume I and II, for $42 each, we’ll sell you a year’s subscription for an additional $5. If you want just Volume I or II, we’ll sell you a subscription for $10 off. Volume III is already discounted for those who want to help us with the printing costs by preordering at the price of $34.95. Once Volume III is printed, the price will go up to $39.95. All prices include shipping inside the United States. See the inside of the attached protective cover-wrap for more information.

BACK ISSUES We keep in stock all the back issues starting with issue #1. You may order one or all of them any time you wish.

The vast majority of them are completely original, but many of the early issues are photocopies. We usually have a full selection of back issues at every show or event we attend. You can buy them right then and there or order them through the mail for $5.00 each. Of course in bulk, they get cheaper: 2 through 6 issues are $4.00 each.

7 or more issues are $3.50 each.

The entire collection, $3.00 each.

A complete key-word searchable listing with minimal descriptions can be found on our back issue webpage www.contactmagazine.com/backissu.html or if you do not have access to the internet ~Pat

CONTACT! ISSUE 87 PAGE 38

Photo courtesy Claus Bohm

By Perry Mick McMinnville, OR pjmick@verizon.net Long-EZ (Duckt) N7XR, 650 hours TT News Flash, February 2005! Duckt was converted from ducted fan propulsion to PSRU/prop December, 2004 (still powered by a rotary engine - of course!). The short story is: takeoff distance remains the same, climb rate improved, cruise speed much improved. Ducted fans remain a viable alternative, especially for slower applications such as Light Sport Aircraft and gyrocopters. The Long-EZ, other than being a pusher, was probably not the ideal test bed to develop the ducted fan, but I did get almost 500 enjoyable flight hours in over 5 years from the configuration.

Since I wrote the article for CONTACT! Magazine back in issue #60, (Jan-Feb, 2001), I've made many changes and have had a lot of travel adventures in my rotarypowered Long-EZ.

Mazdatrix, reinstalled in the Long-EZ, and has been on the plane ever since, accumulating 500 hours in the last six years.

During the almost eight years that I have been flying this airplane, I've made many trips up and down the West Coast, three trips to Kansas, and two trips to Arizona. I attended the Arlington Washington EAA Fly-In 2000, 2002, and 2006, and the Copperstate AZ Fly-In 2002.

I won the "Best Non-Metal Aircraft" award at the North Bend Oregon Airfair 8-31-2001 and I won the "Farthest Distance Traveled" award at the CONTACT! Magazine Alternative Engine Round-up, Laughlin, NV, 3-19-2004.

The Long-EZ engine installation originally used the stock RX-7 intake system that sits on top of the engine. A new custom intake manifold was built in 2003 that put the whole thing in the right wing root area of the Long-EZ. This got the bulk off the top of the engine and allowed the ugly bumps to be removed from the upper cowl.

I flew the first 500 hours, July 1999 to December 2004, with the rotary, direct-drive ducted fan installation. Almost all that time was flown with "Duct2" and "Fan3", as described on my website, www.ductedfan.com. "Duct2" was a duct design with a highly cambered, venturishaped internal surface. This duct shape developed great static and low speed thrust, but limited top speed in cruise to 135 knots. I built and flew an experimental "Duct3" that had less internal camber. Theoretically it should have been faster, but it lugged the engine down more and ended up having the same cruise speed.

The first 165 hours were flown with a junkyard engine that had 120,000 miles in its previous installation in a 1986 RX-7. The engine and all accessories were removed in running condition from a car that had rear end damage. In May 2001 this engine was overhauled by www.ContactMagazine.com

With a new intake system, a new induction scoop.

When Tracy Crook came out with his RD-1C 2.85 ratio reduction drive for the Renesis engine, there was a fad among rotary RV people to make the switch from the 2.17:1 drive, and turn large diameter props slower. They

CONTACT! ISSUE 87 PAGE 39

were getting tremendous climb rates with no loss of top end speed. One of these builders put his RD-1B 2.17:1 redrive on the market with only 30 hours on it. I wasn't looking for a reduction drive at the time, I even had plans on the drawing board for a new experimental duct for the ducted fan installation, but the price was good so I bought it. I wanted to keep flying as long as possible, so I built a new propeller for the reduction drive and didn't do the conversion to PSRU/prop until the prop was complete and all other conversion parts in hand. The plane was only down for one week during the changeover. Duct, fan, direct-drive extension, and flywheel were removed. Automatic transmission flexplate, RD-1B, and prop Duckt is indeed ductless. We caught up with N7XR (and took were installed without removing the engine these photos) at the 2006 Cinco de Mayo Canard Fly-in held at from the airplane. 50 pounds were removed Columbia, CA, (O22). This year’s event will be held on May 4&5. from the installation in the changeover. CG that were a bit short. I hit on the idea of converting the was recovered by removing an inop WX radar antenna design to three narrower chord blades so the hub could from the nose cone and the WX display from the instrube made thinner to accept the short bolts. ment panel netting additional weight loss.

In 2001 I replaced the original air-conditioning cores I was using as a radiator, with a more “conventional” design; a custom, single-pass aluminum radiator from C&R Racing. This radiator was only 13" wide by 17" long with a core 1.25" thick and 2" thick tanks. Cooling was a little marginal on hot days.

With the installation of the PSRU and prop, I was able to turn the engine up in cruise to 6400 RPM, up from 5400 RPM with the ducted fan.

With the additional power available (more power usually means more heat), in the summer of 2005 I replaced the single-pass radiator with a double-pass design of the same dimensions, just twice as thick. This radiator has two 1.25" cores, two 2" thick tanks on the front end and one 4" thick tank on the rear end. See the photo to the left. It was also built for me by C&R Racing. Cooling is no issue at all even on the hottest days.

A very unique aspect of Perry’s propeller is the shape and size of the hub, being that it follows the natural contour of the cowling and the spinner and is exposed, as opposed to being hidden under a fullsized spinner with cut-outs.

The new propeller was built using the same techniques that I used when building my fans. In this case, the blades are all-composite carbon fiber, laid up in three molds simultaneously. The blades are interconnected in the center around a 2.25" inside diameter fiberglass tube. After cure a laminated hardwood hub is built around the blades. Because of this method of contraction, I was able to build a taper into the hub so that the hub itself forms part of the "spinner". The rest of the spinner is a cone that bolts to flanges on the backside of the hub. This propeller started out as a two-blade design, but I had some prop bolts laying around that I wanted to use www.ContactMagazine.com

The airplane is pure joy to fly, and cruises at 165 knots these days. The only modification I would like to pursue now is the installation of a variable-pitch propeller to shorten takeoff distance, especially at high density altitude airports. To learn more about installing a rotary engine in a Long-EZ, see my webpage: www.bridgingworlds.com/LEZ13B/LEZ13B.htm As for ducted fans, I eventually would like to build a canard Light Sport Aircraft using a rotary-powered directdrive ducted fan, much like what I had in my Long-EZ. The ducted fan is ideal for slower aircraft such as LSA with an enforced 120 knot speed limit. I have a website describing this concept, as well as other canard LSA concepts and actual aircraft: bridgingworlds.com/LSA.htm Perry Mick

CONTACT! ISSUE 87 PAGE 40

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