Model Engineer issue 4717 - 20 PAGE PREVIEW

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THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS Vol. 230 No. 4717 19 May – 1 June 2023

Join our online community www.model-engineer.co.uk COVER FEATURE

Gauge 2

Can it be revived?

Braking

How do we make them stop?

Machines Do they have a soul?

TRACK CIRCUITS Where’s our train?

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676

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News, views and comment on the world of model engineering.

669 THE FORGOTTEN RAILWAY SYSTEM - GAUGE 2

John Arrowsmith discovers that Gauge 2 is still with us and awaiting a revival.

PUBLISHING Sales and distribution manager: Carl Smith Marketing manager: Charlotte Park Commercial director: Nigel Hole Publishing director: Dan Savage

672 RAILWAY BRAKING FOR MODEL ENGINEERS

Bob Bramson explains the science and the practicalities of stopping trains.

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Mike Hanscomb describes the signalling system at the Beer Heights Light Railway at Pecorama in Devon.

692 BOOK REVIEW

Roger Backhouse reads John Hannavy’s history of the gas tramcar.

693 ABOUT MACHINES AND THEIR CREATORS Mikhail Chernyshev sees the magic in the mundane.

694 SLOTTING ON THE LATHE

678 BASIC OSCILLATOR STEAM ENGINE IN CAD

698 LNER B1 LOCOMOTIVE

Luis Trincão leads us through the creation of a 3D CAD model of an oscillating steam engine.

Jacques Maurel presents an attachment for creating slots on a small lathe.

Doug Hewson presents a true to scale 5 inch gauge model of Thompson’s B1.

702 POSTBAG

Readers’ letters.

682 A FIVE-INCH GAUGE 0-4-0 PADARN RAILWAY TENDER LOCOMOTIVE

704 KMYCA – A NEW RAISED MINIATURE RAILWAY

686 THE STATIONARY STEAM ENGINE

709 THE EATING OF ELEPHANTS

Luker presents Fire Queen, a Welsh slate quarry locomotive.

Ron Fitzgerald tells the story of the development of the stationary steam engine.

689 CLUB DIARY Future Events

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690 BEER HEIGHTS LIGHT RAILWAY SIGNALLING

676 GRASSHOPPER BEAM ENGINE

Martin Gearing describes a half beam engine suitable for a beginner.

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THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS Vol. 230 No. 4717 19 May – 1 June 2023

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Gauge 2

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Can it be revived?

Luc Hoorelbeke tells the story of the relocation of the Koninklijke Model Yacht Club’s track in Antwerp.

Steve Goodbody argues that anything is possible if you take it a bite at a time.

712 CLUB NEWS

Geoff Theasby compiles the latest from model engineering clubs around the world.

ON THE COVER...

Henry Greenly’s 0-6-0-6-0 articulated shunting engine in Gauge 2 (photo: John Arrowsmith).

Braking

How do we make them stop?

Machines

Do they have a soul?

TRACK CIRCUITS Where’s our train?

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Steam Traction World

MARTIN EVANS Editor

DIANE CARNEY Assistant Editor

Well known miniature traction engine kit company Steam Traction World continues to grow as a business and has recently invested significantly in new machinery for their Daventry factory. The company supplies traction engine kits that are fully machined and ready for assembly after final de-burring, sanding and then painting. Most models tend to be purchased over a fixed period of time so the kits arrive at regular intervals to enable the builder to build as they pay for each kit.

To continue to back their operation in January 2023 year managing director Dean Rogers decided to invest capital into the purchase of a new £100,000 CNC lathe, a Puma GT2600L. With a gap of 1.2 meters between turret and spindle this lathe will enable work to be completed on all the longer items in the production process such as axles and boiler barrels. With the previous lathe being over 25 years old it has clearly been a great opportunity to benefit from new technology too. This now takes their number of CNC machines to nine, as well have having manual machines too such as their gear cutter.

Since the leaving of the EU, Steam Traction World have

Joe Simon’s four inch double crank compound Burrell, seen in his tidy workshop, is well advanced now on its build. Joe didn’t opt for the ‘fast track’ option but has taken his time to create a fine-looking engine finished in Oxford Blue livery and it will be a striking exhibit on the rally field once completed.

668

Dimensions of the plate above the axleboxes in Fire Queen’s front frame. been required to resubmit each of the 20 different boiler designs for reapproval, as dual certification is now need – CA for the UK, and CE for the rest of the world, which was a significant piece of work to undertake. All of this has been completed with a backdrop of continued business growth, as more and more people have joined the ranks of miniature engine builders. So much enthusiasm has been shown that Steam Traction World has introduced a ‘fast track’ purchase scheme, where kits are provided in three stages over a 12 month period to respond to customers wanting to complete a build at pace.

One area that Steam Traction World has previously faced criticism from customers about has been the supply of spare parts. A key advantage of their engines is that all the parts are catalogued with the vast majority available ‘off the shelf’. However, the business struggled to find a way to service this area in an efficient way for their customers. They have now introduced an online shop for parts and have a dedicated member of staff, Traci, who oversees matters regarding spares. Feedback is now much more positive for this important area of the business, and with over £400,000 of stock in spare parts most are available via the shop or by email query.

Their biggest selling engine remains their four inch Burrell agricultural traction engine, of which they have sold a staggering 524 kits, but their

current most popular is the double crank compound four inch Burrell road locomotive which has 38 being built currently compared to 14 of the Showman’s variant in build.

In total now 1343 Steam Traction World engines have been built, or are the process of being built, which is a remarkable achievement, and a tribute to the way the company has responded to their customers’ requirements and created good quality products.

Fire Queen

In Fire Queen, part 2 (M.E.4714, April 7) fig 2 omits some of the dimensions for the plate above the axleboxes in the front frames. The key missing dimension is the width of the plate, which is 58.8 mm, as shown in the figure above.

The holes shown in blue are positioned as in the original drawing but the positioning of the holes shown in red is discretionary. Some suggested positions for these holes are shown in the figure. The material is 1.6 mm bright mild steel and all holes are 2mm diameter.

Martin Evans can be contacted on the mobile number or email below and would be delighted to receive your contributions, in the form of items of correspondence, comment or articles.

07710-192953 MEeditor@mortons.co.uk

Model Engineer 19 May 2023

The Forgotten Railway System - Gauge 2 T

1 John Arrowsmith explores a short-lived gauge that expired about a century ago but hopes for a revival one day.

The main station on the Gauge 2 layout at Bicester.

2

Another view of the Bicester event with a rake of six coaches built by H. B. Jervis in 1912.

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his relatively unknown gauge was first introduced by the German company Märklin at the 1891 Leipzig Toy Fair. Gauge 2 is equivalent to a scale of 1:22.5 or 7/16 inch to 1 foot. It was originally built to 64mm or 2½ inch gauge but in 1909 was standardised to 2 inch or 50.8mm, often described as 54mm when measured between the rail centres, and this is how it has stayed through all the years. Its use was strongly discouraged by Bassett Lowke, Greenly and others in 1917 in the interests of post war standardisation and it has fallen into disuse but collectors have maintained a small selection of rolling stock and locomotives in the hope that one day it might be revived.

A new group of modellers have now built a new 2 inch gauge 40 x 20 foot oval layout and this was demonstrated recently at the G1MRA75 event held at Bicester in October 2022 by kind permission of the G1 Association who

3

David Viewing prepares the Carson Precursor for its turn on the track.

>> 669

4

5

A good head of steam as the Precursor waits for the signal.

Greenley’s 0-6-0-6-0 Tank locomotive (circa 1911).

6

The Greenly engine operating at Bicester. were the organisers of the event. It was perhaps the largest gathering of Gauge 2 locomotives and rolling stock since the First World War and

where most of the world’s operating locomotives were in action. The photographs show almost all of these locomotives located at the shed on the new

7

Pages from Greenly’s book and the construction details of his engine.

670

layout displayed at the Bicester exhibition.

David Viewing is the prime mover in this resurgence and he was highly delighted to

be able to use a new layout to demonstrate this (almost) long-lost system. The track was scratch built using code 330 rail (similar to the modern LGB rail) so that a wide range of both locomotives and stock, from early tinplate to later scale models, could run. Most of the small amount of surviving original Gauge 2 track was deployed in extensive sidings.

Scale Gauge 2 engines and carriages need a minimum of 10 foot radius track to operate successfully. The other consideration was the provision of electricity for other locomotives and a powered track did not seem feasible so the electric models have been converted for R/C use using lithium batteries, which obviate the need for powered rails. It is appreciated that this method is perhaps not in keeping with the history of the models but it

8

The 0-6-0-6-0 on a 40 wagon goods train in a suitable garden layout.

Model Engineer 19 May 2023

GAUGE 2

9

A superb example from the 1920s based on a LB&SR J1 Class.

10

The Jubb Atlantic and a 4-4-2 in the siding with the J1 passing through the station.

11

A majority of the world’s surviving serviceable Gauge 2 locomotives. From left, clockwise: • Saint George, Bing for Bassett Lowke, 1913 (live steam, awaiting restoration); • a pair of LNWR Bowen Cooke 4-6-2 tanks, Bing for Bassett Lowke, 1912; • Great Central 9N 4-6-2 Tank, Bing for Bassett Lowke, clockwork; • (in shed) 4-4-0 Metropolitan Tank, modern, Ned Williams; • Peckett 0-4-0 Tank, Carette for B-L 1910 • (on turntable) Experiment 4-6-0, Bassett Lowke • (on road behind) 0-6-6-0 Tank, Greenly, 1911 • 0-4-0 Tank, F. W. Jubb for B-L, c. 1910 • Abergavenny - LBSC 4-6-2 Tank, Butcher & Co., c. 1911 • (turntable road) Sydney, Bing for Bassett Lowke, c. 1908 • GNR N1 Tank, Bing for Bassett Lowke, c. 1910 • Precursor 4-4-0, James Carson, 1911 now named Carson (live steam) • 4-4-2 Atlantic, F. W. Jubb 1911, live steam.

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does mean that they can now be operated on any suitable track, either indoors or out.

The two operating steam locomotives have a very interesting history which can be traced back to their original owners. The Jubb Atlantic is the engine described by Mr. W. H. Jubb in Henry Greenly’s Models, Locomotives And Railways and was built in 1911. It is still running today in original condition. The other steam engine operating at this event was the Carson 4-4-0 Precursor locomotive which is now 110 years old and still going strong. Probably the most unusual locomotive performing at the show was Henry Greenly’s 0-6-0-6-0 articulated shunting engine (circa 1911) which he never completed but which now runs in this configuration.

The engine is the only known example of a model locomotive built by Greenly himself. riginally it was fitted with twin clockwork mechanisms but today it is powered by two 3D printed lithium powered engine units. Working well, it can pull 40 Gauge 2 wagons, without difficulty, for two hours non-stop.

Another unique survivor from those early days is the 4-6-2 tank locomotive Abergavenny

by C. Butcher & Co. which

is based on the LB&SC J1 class. This engine has been refurbished and is fitted with lithium batteries. It has also been fitted with an intermediate bevel gear, 3D printed in SLS Nylon to replace the one lost in the 1920s. To preserve the original paintwork it has been clothed in a printed vinyl covering displaying the colours of the original locomotive.

The weekend event at Bicester has appeared to give this forgotten gauge system a new lease of life, so it will be interesting to see if it has generated additional interest and can move the gauge forward towards being as popular as Gauge 1, or Gauge 3 which is the ‘scenic’ version of the 2½ inch gauge.

More information on the Gauge 2 Model Railway can be found by scanning the QR code.

tinyurl.com/2p96myd9 ME 671

Railway Braking for Model Engineers

PART 1

the completion process. Not only that but it is evident that there is a knowledge gap and this article is intended to help bridge that gap and stimulate interest in the subject.

Throughout this article, the Imperial system of weights and measures is used.

Why adopt power braking?

Introduction

Bob Bramson explains the important business of bringing trains to a halt in a controlled manner.

672

Throughout the past century of our hobby, there have been many developments in improving the performance and reliability of miniature steam locomotives but very little on the subject of braking.

A relatively small number of articles have appeared in the model engineering press but no real efforts have been made to adopt continuous and automatic braking, possibly because the additional effort needed to equip miniatures with a well-engineered braking system adds quite a significant number of hours to

The author’s first experience with the business of braking was after constructing his 3½ inch gauge tank locomotive Jubilee. He set up about 30 feet of track in the garden and steamed the engine. He was fairly young then and naturally eager to see it go. Bystander No.1, elder brother, remarked, “Now you’ve made it go how do you stop it?” This was followed by both heels digging two tramlines into his dad’s fondly manicured lawn, not to mention hot ash setting it on fire. The experiment came to an abrupt conclusion but the lesson had been well and truly learned. Given the small scale of model locomotives and the light loads of the day, braking was generally achieved using hand brakes on drivers’ trollies, which is still the norm today in the smaller gauges. In 1966, the author visited the ‘Surrey Hills Live Steamers’ in Melbourne, Australia and was offered a drive of a five-inch gauge petrol driven locomotive fitted with air brakes. Two things stuck in his mind about that experience the hospitality and friendship of the club members extended to a seafaring ‘pommie’ and the superb braking control of the engine and its train.

Since those early days the hobby has graduated to larger and larger scales.

Nature decrees that as the linear dimension of an object increases, its volume expands in relation to its cube. On this principle, a 3½ inch gauge standard gauge type engine might weigh say 70 lb and doubling this to 7¼ inch gauge the weight goes up to around 600 lbs. A 3½ inch gauge passenger engine might pull four passengers and a couple of cars with an all up weight of some 800 lb. Its 7¼ inch gauge counterpart could be hauling an all up weight of some 5,000 lb at speeds up to 10 mph.

Under those conditions, it is uite impossible to expect a trolley brake to dissipate the considerable amount of kinetic energy of such a train - an effective braking system acting on all vehicles is essential.

In the late 1970s, our society became set on the road of the so called ‘service economy’ with the litigation industry forming a prime ‘service’. This has bred plenty of opportunity for claims against clubs, societies and even individual drivers if accidents occur. Our legal framework rightly requires us to exercise a duty of care to limit risks to the safety of ourselves and our fellow citizens.

The rules

The regulatory framework for the operation of miniature railways is predicated on the Health and Safety at Work Regulations 1974. In pursuance of this legislation, the current ‘Guidance’ HS2020

Model Engineer 19 May 2023

BRAKING

Brake system continuity. for ‘Managing the health and safety at passenger carrying miniature railways’ is now in place. On the subject of braking, Clause 41(d) states ‘the vehicle has adequate braking provisions for parking, normal and emergency braking’. Whilst the author considers this statement rather feeble it is the effective law that attends should an enquiry or prosecution be brought in the event of a mishap.

(Author’s note The former TN produced by HMRI was more specific on this topic and is worthy of consultation.)

So now we know the rules which apply to our gauges.

This puts the onus on us all to ensure that our operating practices are safe. Let’s keep it that way.

Braking principles

The scientific principles which govern the braking of miniature trains are in essence no different to that of their main line counterparts. For main line operation the theoretical and practical lessons have been well learned resulting in the publication of the ‘Railway Group Standards’ which mandate how safety of operation on Network Rail is achieved. Braking is covered in several of these standards (available on the web at www. rssb.co.uk) the most relevant being GM/RT2045 ‘Braking Principles for Rail Vehicles’.

This document sets out some prime requirements which apply equally to miniature gauges, these are

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● Brake systems must be safe and reliable. ● Continuous and automatic operation of the power brake must be provided. ● The system must operate in all foreseeable weather and climatic conditions. ● A parking brake must be provided.

It should thus be obvious that whatever medium is used to power a braking system, it must be safe and always work when required.

‘Continuous’ means there is a series of brake system connections throughout the train as shown in fig 1.

‘Automatic’ means whenever there is any interruption of the continuity system, the train is automatically brought to a stand. For instance, if a train division occurs, the ‘pass comm (communication cord)’ is operated or the guard applies his brake valve.

‘Fail Safe’ means that if any critical system component fails, the system cannot be rendered inoperative. In all safety systems, the principle of ‘de-energise to apply’ is adopted to ensure fail safe operation. ther relevant provisions are ● A guard’s brake valve must be fitted to enable the brake to be applied by the guard and the brake continuity proved. ● The normal convention for operation of the driver’s brake valve on steam locomotives is anticlockwise to apply and clockwise to release or

towards you to apply and away for release (different on modern trains!).

Friction

Friction is the primary means used to dissipate the energy of motion. What is friction? ● It is difficult to define precisely but we can observe its effect. ● It occurs when materials are either in contact or rub together in sliding contact under the influence of a mechanical force. ● Different materials exhibit varying frictional characteristics. ● Friction varies with speed, pressure and temperature. ● The energy due to motion (kinetic and wheel rotational energy) is

normally dissipated by FRICTION. The principle of ‘Conservation of Energy’ applies (heat is work and work is heat). ● With electric drives, the energy can also be dissipated by dynamic braking but a friction medium is still necessary to provide braking to a stand. ● The rate at which a train can be braked depends on three main variables friction, brake force and speed.

The coefficient of friction (pronounced mu) is simply the force applied to a material in contact with another divided by the normal reaction.

For example, if a force of 20 lb is applied to one of the materials and a force of 100 lb is applied normally (at 90 degrees) to both of them, the coefficient of friction would be 0.2. The friction at the point where sliding just takes place is known as the coefficient of limiting friction.

Figure 2 shows a rail vehicle brake block applied to a wheel.

When the product of brake force F and the coefficient of friction between the brake block and the wheel rim is less than the product of the coefficient of friction between the wheel rim and the rail and the normal force on the wheel Q – wheel slide will not occur. For this reason, it is always necessary

Fig 2 Q μB x F Block retarding force F Brake force

Direction of travel

μR x Q Retarding force at rail

μR = Mu at rail μB = Mu at block

μR x Q has to be greater than μB x F to avoid wheel slide

Friction and braking forces

>> 673

Fig 3 At 80mph, wheel F has a peripheral speed of 7040ft/min Ø6' 2"

At 10mph, wheel S rotates at 360rpm Both wheels have the same rim speed at the rail - 880ft/min

Ø9.25”

Wheel F (Full size)

Wheel S (1 1/2” : 1’)

he benefit of scale.

674

increased, a great advantage for miniatures. One downside however, is that during a prolonged brake application, the temperature of the brake block/wheel interface will increase leading to lower effective brake force and possible wheel damage, a plague in full size but hardly an issue with miniatures.

So now the influence of friction, brake force and speed on the rate of braking can be appreciated.

Brake systems

A brake system is the arrangement of the various

components which are interconnected to provide the control and functionality of the brakes.

There are basically three systems which can practicably be used for the braking of miniature trains ● Vacuum (atmospheric air). ● Compressed air. ● Spring applied.

Each system has its own advantages and disadvantages. Spring applied brakes are not considered in this article because the means of isolating this type of brake adds complication when working trains.

Fig 4 Block Retarding Force

to limit the brake force F so that wheel sliding and consequent wheel flats do not occur. This limit is referred to as the ‘brake percentage’.

In fig 3, an essential truth by which we, as model engineers benefit, is the fact that a model 7¼ inch gauge wheel, of say 9¼ inches diameter, would be the th scale e uivalent of a 6 foot 2 inch full size wheel.

The rim speed of the model wheel at 10 mph works out at 880 ft per minute and it rotates at 360 rpm. The full size wheel at this speed has the same peripheral speed but only rotates at 45.4 rpm.

At eighty mph the wheel revolves at 360 rpm and has a rim speed of 7,040 ft per minute. The issue here is that friction at the higher speeds is much reduced and the model operates at a speed where the available friction is comparatively high.

Figure 4 illustrates how the friction force varies with speed. At high speeds (above 60 mph) the friction is low, both between the rail and block interfaces with the wheel and thus the rate of retardation is correspondingly low. To the left of the diagram, the friction effect can be seen to be significantly

The vacuum brake system is eminently suited to steam locomotives. Vacuum is easily created by use of an ejector worked by a small flow of live steam. Provided the system is well engineered, it should be very safe and reliable. There are a number of dos and don’ts to observe in designing and making such a system and if these are satisfied the result will prove most acceptable.

A (simple) air brake system is perhaps better suited to battery or I.C. engined locomotives.

There are a few more components to make for an air operated system but it can be just as safe and reliable as an equivalent vacuum system.

The advantage of the vacuum system lies in its simplicity but it does require relatively large brake cylinders since a system operating at 21 inches of mercury only has a maximum air pressure of 10 lb/in2 to work the brake. An air brake system may work at any safe desired pressure and the brake cylinders may be correspondingly small yet provide the same brake force as an equivalent vacuum system.

The crunch comes when considering the rolling stock that needs to be compatible with the installed system.

British Railways spent a significant fortune in fitting dual braked systems in the 1950s and 60s during the change over from vacuum to air braking. So, which system do you fit The choice

μ at rail - low speed Adhesion envelope at rail μ at rail - high speed

μB x F Train Speed

he variability of brake retarding force with speed.

Model Engineer 19 May 2023

BRAKING

Fig 5

Continuous brake pipe

Release cords

Brake cylinder

NRV

Stored energy (air/vacuum)

Guard’s brake valve

Brake diagram for a trailer vehicle.

Fig 6

Train pipe

Gauges

Chamber

1 3

2

4

5

6

Non-return valve

Vacuum reservoir

1. Ejector steam valve 2. Vacuum ejector 3. Exhaust elbow 4. Non-return valve 5. Driver’s brake valve 6. Vacuum release valve

Brake cylinder

Drain valves

acuum brake system for a miniature steam locomotive.

Fig 7 MR

10

3

6

1 Prime mover

BC

5

9

4 Main reservoir

2

7

To be continued.

Brake cylinder

Brake reservoir 8

1. Air compressor 2. Electric clutch 3. Electric decompressor 4. Non-return valve

simple brake system for an

11

ABP

depends on several factors and should be well thought out by individual clubs and societies.

Figure 5 shows a typical system for a trailer car.

The brake cylinders of both vacuum and air operated systems described herein employ a balanced piston principle. When the brake is released, both sides of the piston (ignoring the small area of the piston rod) are balanced either by equal vacuum or equal air pressure.

When one side is ‘released’ air pressure of the atmosphere or from the air brake reservoir applies the brake.

Figure 6 shows a vacuum brake scheme for a steam locomotive. The resistance to leakage of any vacuum system is a key requirement.

It should be remembered that the old axiom, nature abhors a vacuum’ applies absolutely.

Figure 7 illustrates a simple air brake system, the heart of which is the air compressor.

The air brake system described differs greatly from that used in full si e being simplified to work in the inverse manner as the vacuum brake.

It will be noted that on all three diagrams a release valve is shown. The purpose of this is to allow a train to be moved when there is a system failure or the train requires to be shunted with the brake isolated. This is accomplished by venting the reservoir side to atmosphere when either the vacuum or compressed air is vented from the train pipe. Without this the brake would remain applied whilst either the vacuum or air reservoirs remain charged.

These reservoirs provide the energy source which operates the brakes.

5. Safety valve 6. Pressure switch 7. Auto-drain valve 8. Non-return valve

powered locomotive.

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Air brake pipe

9. Pressure regulator 10. Driver’s brake valve 11. Release valve

NEXT TIME We discover how we can create a vacuum.

>> 675

Martin Gearing presents an ideal beginner’s project with great potential for the more experienced builder.

Continued from p.621 M.E.4716 May 5

Grasshopper Beam Engine

PART 20

Fig 69

=

=

1. Setting of Valve CAM Position crank at top dead centre Adjust cam peaks to be equal below top face of cam follower, then secure

Sectioned view showing spool in valve block

2. Setting of Valve SPOOL Position crank at 90° Adjust spool to be flush with lower face of top port

Sectioned view showing spool in valve block

3. Double checking Valve SPOOL setting Position crank at 270° Check spool to be flush with upper face of lower port

Valve setting.

676

Model Engineer 19 May 2023

GRASSHOPPER Valve setting

Having satisfied yourself that the assembled parts all move freely with one another the last ob is to set the valve timing (fig 69). This is done in two stages.

144

145

Setting the cam

Note that because of the mechanism of the beam, the centre of the clevis in the connecting rod will N T be in line with the shaft and pin of the crank at 0 degrees to the base – so do not bother to try and position all three centres in a straight line Turn the crankshaft until the crankpin is at its highest point in relation to the base.

Another way to look at this statement is that the centres of the crankshaft and crankpin need to lie on a line at 0 degrees to the base. hen that position has been achieved turn the cam so that the two e ual peaks on the profile are exactly the same amount distance below the face of the top surface of the cam follower. The cam should now be secured by tightening the M x 10 grub screw (photo 144).

Setting the valve spool

Tighten the clamp screw in the valve lever cam.

Turn the crankshaft until the crankpin centre is at 0 degrees on from T C, and on the same hori ontal centre as the crankshaft.

Coincidentally this is the same centreline as the cam follower shafts 52.5 above the base (photo 145). ith the crankshaft in this position, carefully rotate the spool valve lever on the cross shaft until the upper face of the spool is exactly flush with the lower face of the ports in the top of the cylinder block. Nip up’ the clamp screw. otate the engine at least a full turn and bring the crankpin back to the 0 degree position.

Check to see the spool is still in the correct position, resetting if necessary. hen this is the case tighten the clamp screw (photo 146).

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Setting the cam.

Setting the valve spool.

146

147

Valve spool clamp screw.

fi g spool setting

otate the crankshaft until the crankpin centre is at 270 degrees from T C, and on the same hori ontal centre as the crankshaft and cam follower shafts (photo 147). ith the crankshaft in this position, without moving the crankshaft, turn the engine on its cylinder block end until you can see into the end of the valve block.

The end of the spool should be exactly flush with the upper face of the lower port in the cylinder block. If not, slacken the clamp bolt and ad ust until the spool faces are in exactly e ual positions in relation to the ports at both 0 and 270 degree crankpin positions. etighten the clamp bolt (photo 148).

First test run

For the least amount of noise it is a great help if the vacuum cleaner you use as a power source has a variable speed, or at least high and low speeds, which should be set to the lowest - otherwise ust accept the noise

onfirming the valve spool setting.

148

Valve spool clamp bolt. ush the control valve handle so the top is fully over towards the cylinder block.

Connect your chosen cleaner hose to the inlet port of the control valve and switch the cleaner on. ou should now hear the sound of the vacuum being drawn through the Spill’ port in the control valve base, as the supply of vacuum to the engine valve block is closed.

Slowly rotate the control valve turning the flywheel away from either of the dead centres if it doesn’t start to rotate. ou should find the engine speed

responds to the rotation of the control valve.

Hopefully you have arrived at this point with an engine that responds to the position of the control valve and most importantly will run slowly, so that the mechanism’s movement may be observed. ou will have experienced a pleasure that is becoming increasingly rare. The skills experienced are transferable to most forms of mechanical engineering, sadly once commonplace.

ME 677

Basic Oscillator Steam Engine in CAD PART 2

Fig 22 Luis Trincão takes us through the CAD process step by step.

Continued from p.625 M.E.4716 May 5

Crankshaft.

Fig 23

Crankshaft

The next part is the crankshaft.

It is an easy part to draw and is represented in fig in

its basic form. Perform the following operations: Step C1 – Create a Part studio and make the sketch of fig 3. Select the Top plane. Use the Dimension tool to define the position and diameter of the circles.

Step C2 – Make a 4mm Extrude-New of the 16mm circle in the positive Z direction – fig .

Step C3 – ExtrudeAdd 14mm of crankpin circumference in the same direction. You need 14mm to compensate for the 4mm of the part made in Step C2 and get the final 10mm crankpin dimension.

Step C4 – Extrude-Add 18mm from the 3mm centre circumference to create the Axle. This extrude is made in the opposite direction to the crankpin.

Step C5 – Change the default part name to Crankshaft and assign the colour and material.

In my case I selected cast iron.

See fig . In the Properties option you can see that this part will weigh 6.99g.

Fig 24

Crankshaft sketch.

678

Crankshaft extrude.

Model Engineer 19 May 2023

CAD

Fig 25

Fig 27

Crankshaft rename.

Fig 26

Flywheel.

Fig 28

New crankshaft.

Now I propose the challenge of transforming the crankshaft made to the one in g . I won’t describe in detail how it’s done, just saying that one option is to create a new sketch on one of the crankweb faces, draw the part to be removed and make an Extrude-Remove of these parts. Of course, you could have done it in step C1, drawing the intended shape instead of using the circumference. At any time, you can edit a previous sketch but there can be negative consequences. There may be incorrect extrusions or other later actions that relied on sections removed from the original sketch. Usually, a fix in other actions can solve the problem.

g

Flywheel sketch.

Flywheel and set screw are the next parts to be created. Note that all parts of this engine could have been generated in the same Part Studio. I chose to create several Part Studios to facilitate the explanation.

I suggest you watch a tutorial reading QR Code 5. You can also search on the Internet for ‘Onshape patterns’.

QR Code 5 - www.youtube.com/ watch?v=BFURYp4Rgck

The dimensions of these parts are shown in fig .

Step F1 - Create a Part studio where you will make the sketch for the Flywheel – fig . Use Top Plane. Draw from the rigin point. The 0 degree

angle is set to allow placing the set screw in line between hole 1 and hole 6. Draw hole 1, leaving the remaining holes to be created with the Circular patterns tool.

You may have noticed that the circles are not fully constrained because they are in blue. That is no problem if you do not move them. Not wanting to complicate things at this stage, there are ways to make the drawing fully constrained, turning all the lines black.

Step F2 – Create a plane parallel to the right pane with an offset of 12mm. It will be tangent do the Flywheel between holes 1 and 6. This plan will be used to set the hole centre for the grub-screw – fig .

Fig 29

Grub screw plane.

>> 679

Fig 30

Fig 32

xtrude ywheel.

Fig 31 Set screw hole.

Fig 33

Set screw hole centre.

Fig 34

Set screw sketch.

Set screw chamfer.

Fig 35

Set screw.

80

Step F3 – Extrude-New your sketch, leaving out the circumferences of the holes and axis – fig 3 . Use Symmetric Extrude option as shown.

Step F4 – You will now make a sketch just to mark the centre of the set screw hole aligned with the centre of the drawing – fig 31.

Step F5 – Drill a counterbore hole – details in fig 3 . It could be also a straight hole.

You can thread the set screw hole or leave it as is.

Now let’s create the set screw in the same part studio.

Step G1 – Create the sketch – fig 33. Use the polygon tool to draw the hex hole.

Step G2 – Extrude-New a 6mm high cylinder. Include the polygonal part.

Step G3 – Extrude-remove the

polygon with a height of 2mm.

Step G4 – Use the Chamfer tool to obtain the result of fig 3 on the opposite face of the hex hole.

Step G5 – Thread set screw as explained for the ports on the Base part using the ‘Thread Creator’ custom feature. You will achieve result from fig 3 .

Step G6 – Name your parts, set the material and colour.

I could avoid creating the Grub Screw, Nut and Washer because there is a library with these and other standard parts.

This library is accessible in the model assembly under the “Insert-Standard content” option. For pedagogical reasons I decided to explain the creation of these components.

To be continued.

Model Engineer 19 May 2023