Racecar Engineering Historic Racecar

A digital supplement from the publisher of

HISTORIC RACING Mercedes C11 The >> creation of

a legend

Bugatti Type 35

Climax engines

NDT Testing

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RACECAR ENGINEERING | HISTORIC SUPPLEMENT

CONTENTS 4 SAUBER MERCEDES C11 Restoring the prototype of an endurance racing legend 12 BUGATTI TYPE 35 Profiling possibly the most successful racecar ever 18 NDT TESTING Detailing the processes needed to keep cars safe 26 CLIMAX ENGINES Featherwight engines of the 1950s and 1960s

Bugatti’s Type 35 was a force to be reckoned with in the 1920s and 1930s on the circuits of Europe

T

he classic car market is rapidly changing. Prices have increased in recent years as in many cases investments are considered to be safer in older racing cars than in a bank. Due to the increased interest in historic racing, an industry is rapidly becoming more tuned towards the maintenance of these exceptional cars and their work is becoming ever-more critical. With more carbon chassis cars coming to the market, the variation in the quality and the differences in lay up styles over the past two decades has meant that they need to be checked by experts. One manufacturer sold some of its heritage having preserved the original spare parts in a lock up, only to find when they were delivered that they were not fit to run.

While that was a shock to them, it was also an eye-opening moment for the buyer who fortunately had selected one of the many companies in the UK that specialises in the maintenance of such cars to care for his investment, and the team there already knew the weak points of the car.

The issue with the carbon cars is that they were designed for a short period of competition and not with a legacy in mind.

With increasingly advanced design techniques, parts were

built for a singular purpose and lifed accordingly. For the companies that have been set up to cater for these machines, their technology has also had to improve in order to monitor cars such as these and ensure they are safe to run. Never before has there been so much opportunity to race these cars either.

In the pages of this supplement we talk to some of the companies that are involved in the upkeep of modern classics, look at the different technologies that can be used to ensure their safety, and also at some of the cars that are running in competition.

One of those is the development mule of the classic Mercedes C11 that won the World Sportscar Championship and Le Mans, while we also take a look at arguably the most successful racing car in motorsport history, the Bugatti Type 35.

We also profile one of the most prolific of engine manufacturers, Climax, which dominated the racing scene in the 1950s and 1960s with its lightweight concept. It is our own celebration of a British engine manufacturer that had such a diverse portfolio for its technology.

Parts were built for a singular purpose and lifed accordingly

Andrew Cotton, Editor Racecar Engineering • Historic Racing 3

Racecar Engineering • Historic Racing 3

MERCEDES C11

Class of 1990 Mercedes’ C11 is as robust today as it was when it took the 1990 World Sportscar Championship title

By Lawrence Butcher

T

he Mercedes C11 was a pivotal car in Mercedes’ modern motorsport history as in some respects it paved the way for the manufacturer to return to Formula 1. Through its young driver programme, it was also the car that provided Michael Schumacher with his only Le Mans start, sharing in 1991 with Karl Wendlinger and Fritz Kreuzpointner.

4 Historic Racing • Racecar Engineering

4 Historic Racing • Racecar Engineering

Swiss outfit Sauber first became involved with Mercedes in the early 1980s. Mercedes engineers provided some informal development work to help with Sauber’s C6 and C7 Group C cars. Unhappy with the performance of BMW’s straight-six engine it was using at the time, Peter Sauber had approached Mercedes for an engine supply, which initially came in the form of the 2-valve

M117 V8, and then following came the four-valve, 5-litre, M119 V8.

Officially, these engines were prepared by fellow Swiss Heine Mader but in fact the bulk of work was undertaken

by Mercedes at its engine facility in Untertürkheim, under the supervision of Hermann Hiereth. The Mercedes engined C8 arrived in 1985, and the company’s branding came the next year.

The monocoque dated back to 1982, designed by Leo Ress while he was between jobs at Mercedes and BMW

Mercedes’ C11 contested the FIA World Sportscar Championship in 1991 before it delivered the company its most recent win at Le Mans. The test mule has received an extensive make over at specialists BBM to allow it to run in modern classic events

The C7, 8 and 9 were all evolutions on a theme. The monocoque dated back to 1982, designed by Leo Ress while he was between jobs at Mercedes and BMW. Ress eventually joined Sauber full time in 1985. While not an entirely clean sheet design, the C11 was the first of Sauber’s cars to be built with full Mercedes backing and it benefited from the company’s resources that entailed,

hence the car featured a Mercedes Benz rather than Sauber designation.

The first car was chassis C11-89-00, which embodies a fascinating point in the mid-evolution between the alloy chassis C9 and the carbon-tubbed C11.

The car has been owned and run by Northamptonshire based BBM Sport for the past 12 years and as such, Technical Director Steve Briggs knows it inside out.

Although the first of its kind, chassis 00, which is pictured in this feature, is still actively campaigned in Historic Group C racing, having taken a number of high-profile wins and regularly running at the front of the pack. In fact, during one outing at Spa in 2011, its qualifying time of 2m05s would have put it in sixth place on the LMS grid running that same weekend.

Racecar Engineering • Historic Racing 5

Racecar Engineering • Historic Racing 5

MERCEDES C11 Briggs notes that there are a number carry over parts on chassis 00 from the C9. For example, the routing for the turbocharger air feeds is different between this car and those that went on to race in period. Similarly, it has an aluminium front crash structure, while the later cars were all carbon.

The most obvious difference at the front of the chassis is the suspension mounting structure. This is a fabricated aluminium construction, bolted to the carbon tub, while on the race versions it was carbon fibre and fully integrated with the rest of the chassis.

Home run The car was delivered to BBM directly from Sauber complete, but still in need of an extensive recommissioning before it could be raced. This entailed an engine and transmission rebuild, along with replacement of the coolers and other heat exchangers. At the same time, all of the suspension components were crack tested.

The car was ran successfully before a crash at Donington in 2012 led to the replacement of some suspension components. However, a fire at Monza in 2015 necessitated more extensive works. A fuel rail in the engine bay had split and set the rear alight. ‘It was an aluminium fuel rail that cracked,’ explains Briggs. ‘The engine had a vibration.

I think it had been over revved, and that caused a timing guide to fail.’

A failed valve spring bucket bush caused the car run on seven cylinders at the Le Mans Classic in 2018, although fortunately that did not result in a fire.

However Briggs remarks that so strong is the car as a package that the problem was not noticed immediately. ‘We think it went at the end of the first round at Barcelona,’ he says. ‘We did a test before Le Mans and the bush failed, sticking the valve open slightly. However, we didn’t spot this, took it to Brands Hatch for a shakedown before Le Mans, and it was fast there. The car went to Le Mans, where it qualified third, but then another driver got in and said it didn’t feel right. We did a leak down test and found it was down to seven cylinders.

It wasn’t a dramatic problem, but it was only running on seven. Now we leak down test after every event.’

Mercedes did consider a variety of options for engines when it began the Group C project, ranging from highly boosted I4s through to larger capacity 6 Historic Racing • Racecar Engineering

6 Historic Racing • Racecar Engineering

One of the anomolies for the car was the aluminium crash structure, replaced in race trim with carbon

Chassis 89-00 needed a rebuild before it was ready to run, including the engine and transmission

Many variations were considered before Mercedes opted for a turbocharged V8 layout for the C11

The test car was not even fitted with lights, so BBM took the opportunity to replace the looms as well

Jochen Mass hands the C11 to Mercedes young gun Karl Wendlinger at Spa in 1991

V12s in an attempt to strike the best balance for the fuel consumption rules then in play, set at 51 litres/100 km.

In the end, it settled on a capacity of 5-litres, with maximum boost pegged at 2Bar (absolute) with a 7500rpm limit and a target weight of 210kg.

Although it has some spare parts in stock, BBM does have to get some components made for the engines, the maintenance of which is undertaken

by Xtec engineering which specialises in Group C cars. ‘It probably gets rebuilt every two to three years,’ says Briggs. ‘We do have a check over every winter and anything that needs doing is dealt with.’

While it is possible to get parts produced, some can prove to be more problematic. For example, the car is currently running the last factory block.

If issues arise in the future, a production Racecar Engineering • Historic Racing 7

Racecar Engineering • Historic Racing 7

MERCEDES C11 car unit will need to be modified. ‘It’s based roughly around the production M119, so if you had a road block, you can weld it up, strengthen it and machine it to work if you really had to,’ says Briggs.

The original blocks are bespoke, with closed deck architecture although the crankshaft was a modified production unit. The race engines also used a simplex chain drive for the double overhead cams, rather than the duplex drive found on the road cars. Oiling is taken care of by a fivestage dry sump pump, with two stages dedicated to turbocharger lubrication.

The cooling system is of a parallel design, which theoretically provides almost identical temperatures across all cylinders.

One common problem on cars of this era is handling the original electronics systems. Electronic fuel injection systems were just starting to mature and in the case of the C11, all of the fuelling and ignition was taken care of by a Bosch Motronic MP 1.8 ECU. These are no longer supported by the German firm and finding computers on which to run the software can prove challenging.

This leads most who run cars such as the Sauber to update to a modern ECU setup, in this instance a Motec supplied system. The old Bosch ECU is a sizable beast and this has allowed for the new unit to be packaged within the original case, retaining an original appearance.

Data logging was present in period, and relied upon another standalone (and large) data logger sited within the cockpit, which prints out a ticker tape record at the end of each run, much like a till receipt. The Motec ECU now handles data duties, but Briggs says that some do still use the original systems. ‘It’s a white box with a few keys and it prints off a load of one and zeros to tell you what is happening. A few are still using them, but they are difficult to get and if they fail, there is only so much you can do.’

On the subject of wiring, when BBM acquired chassis 00, it needed a full rewire in order to be run, not least because being the test car, it was not fitted with equipment such as lights. ‘As the lights were never fitted, it required looms as well and as we were doing all of that, we replaced the whole vehicle loom,’ explains Briggs.

Another modification to ease running has been the replacement of the original wastegates and control systems with modern components. In period an air bleed system, controlled by the ECU and utilising Bosch fuel injectors as 8 Historic Racing • Racecar Engineering

8 Historic Racing • Racecar Engineering

Michael Schumacher conducted testing ahead of the Le Mans 24 hours in 1991 as part of Mercedes’ driver training programme

solenoids, regulated the opening pressure of the wastegates. This functionality is now handled by the Motec system and incorporated within the ECU housing.

There was nothing inherently wrong with the original system, but this approach is easier to manage.

Boxing clever The C11 transmission was an upgrade on the C9, with a Mercedes designed casing that houses mainly Hewland internals. However, it has some features that can complicate maintenance. The C9 ran a Hewland VGC box, which says Briggs, ‘was really the Achilles heel on the car.’ VGC internals are still available and there are companies that manufacture replacement parts.

The only real challenge is the crown and pinion gears, explains Briggs. ‘They use a palloid cut on the gears. The regular VGC has a pair of taper roller bearings, which are preloaded, and has Gleeson type gears with tapered teeth. The palloid cut gears are parallel cut, which allows for a degree of float and they run on angular contact bearings. But palloid cutting machines are very expensive, so most people use Gleesons. The palloid is better and can accommodate more wear.’

‘If you had a road block, you can weld it up, strengthen it and machine it to work if you really had to’ Steve Briggs

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MERCEDES C11 Unknowingly, BBM had a set of Gleeson type gears made, which without close inspection, look very similar. ‘We had special bearings made as well, because they are not available anymore, and they allowed a degree of float in the pinion,’ explains Briggs. ‘That end float, combined with the taper on the gears, meant the pinion acted like an axe. We went through about six sets in a year but still won the championship. We’d do a race, then qualifying and practice for the next race, then fit a new ring and pinion. We knew what the problem was but had to wait for new gears to be made in Germany.’

Briggs did source a cache of detailed transmission information from Beagle Engineering (originally called Staffs Silent Gears and whose subdivision Elite Racing transmission still produces motorsport gearboxes) that worked on the cars in period. Unfortunately, on the way to collect the information, which was in the form of faxes, it transpired that the company had filled two skips with gearbox internals a year earlier because they didn’t know of anyone running a C11.

Set up standard As noted, the C11 was considered a benign car in period, and as such, BBM tends to run the car as setup by Mercedes, based on existing notes they obtained. One of the main changes between the C9 to C11 was a switch to pushrod suspension at the rear, from a rocker system, with titanium coil springs and Sachs supplied dampers.

‘The dampers are original, we just get them serviced every year,’ says Briggs. ‘They only have six adjustments.

We have all of the testing information from the period, all of the setups, so we just used their base setups. Maybe we could do some work there, but it works well as it is, so why try and reinvent the wheel? Mercedes put 40 million Deutschmarks budget, so they are pretty well sorted. Why would we go away from what was worked out for some of the best drivers, by the best engineers in the world at the time?’

Compared to some of its contemporaries, the C11’s gutsy V8 also helps make it a very tractable machine to drive. Briggs observes that though there are no driver aids such as traction control or ABS, the low-down torque helps make it controllable. ‘There’s no put your foot down, wait, then bosh in you back,’ he says. ‘It’s similar to the AMR1 Aston in that respect. You can put it in gear, let your 10 Historic Racing • Racecar Engineering

10 Historic Racing • Racecar Engineering

The C11 moved to a pushrod rear suspension, and while handling is benign it is effective even today

foot off the clutch and just pull away.

You don’t have to rev it. With the C11, the turbos just help it along a bit. They don’t run much boost, around 0.5 bar.’ In this trim, the engine produces around 700-750 bhp. In full qualifying trim in period, the engine was capable of over 1000 bhp, but BBM is clear that at 0.8-0.9 bar boost the engine would not last.

The cars are relatively straightforward to run, says Briggs. ‘You have to remember with Le Mans machines, they were designed to be driven for 45 minutes, stopped, turned back on and driven off. It’s not like F1 where you need 15 people with laptops to start them and if they stop, you can’t restart them.’

History repeating It is inevitable that in competition damage will occur and as such, BBM has had moulds made for the key bodywork parts, taken directly from the existing body.

‘There are some differences between this car and the race ones,’ highlights Briggs.

‘For example, the front bodywork clips on from the top, while the race versions just used pins.’ For the engine cover, which was destroyed in the fire at Monza, a mould was taken from another C11.

The bodywork of Chassis 00 has other features that make it unique from later cars. For example, the trailing edge of the rear wheel arches are add-on items, riveted and bonded to the bodywork.

They differ from the C9 in hugging the contour of the wheel more closely and, once the profile was proven during testing, were incorporated as an integral part of the main body. For the last of the Mercedes Group C line, the C291, the curve of this section became even more

‘Although it might make sense to make moulds for all of the bodywork in anticipation of accident damage, this is not always the route customers take with their cars’ Steve Briggs pronounced. Originally, that section was just clear fibreglass, with a step to the bodywork where it was attached, but it has now been smoothed out.

Although it might make sense to make moulds for all of the bodywork in anticipation of accident damage, this is not always the route customers take with their cars. ‘You can guide the customer and advise them it is a good idea, but you can’t just go out an spend their money saying we’ll get a full set of moulds, because it’s not cheap,’ says Briggs. ‘They might regret it later, but generally, there is always a way around, some way to fix things.’

Despite representing the pinnacle of manufacturer-backed sportscar development in the 1980’s, the C11 is a straightforward car to operate and maintain. BBM looks after a stable of Peugeot’s 908 LM P1 cars, and although these are manageable, they cannot be rolled out, fired up and raced in the way old Group C machinery can.

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www.geoffpageracing.com Racecar Engineering • Historic Racing 1 31

BUGATTI TYPE 35

Bug’s life

By Lawrence Butcher

Ettore Bugatti created arguably the most successful racecar of all time with the Type 35

Ferdinand de Vizcaya whose father, Pierre, funded Bugatti to start his company, competed in the 1925 Targa Florio driving a Type 35. A similar example won overall

F

ew racing cars reach truly iconic status, and fewer still gain kudos beyond motorsport dilettantes.

The Ferrari 250 GTO and Ford GT40 are two such cars, but at the top of the pile sits the Bugatti Type 35 (and variants of ), its horseshoe grill and red emblem often eliciting recognition even in those unfamiliar with racing cars.

However, they are likely unaware that the Type 35 is arguably the most successful racing car of all time, eclipsing even the Porsche 911 if one considers the time span over which it competed. Between 1924 and 1930 the model secured more than 2000 race victories, and amassed 351 wins in the first two years alone.

However, the Type 35’s debut, at the 1924 Grand Prix de l’Automobile Club de France staged in Lyon, was less

12 Historic Racing • Racecar Engineering

12 Historic Racing • Racecar Engineering

than stellar. Thanks to Ettore Bugatti insisting on the use of an unproven tyre, developed by Dunlop to his own design to specifically work with the car’s novel, two-piece cast aluminium wheels, all five cars entered had trouble. One retired, one crashed and only two of the remaining three were classified in the 11 finishers, in seventh and eighth place.

Following a switch to conventional rubber supplied by Michelin, the car’s fortunes improved rapidly. Over the following five years, the Type 35 and its derivatives would claim a plethora of victories across Europe, in Grand Prix and hill climb events.

Overall, around 400 of the type were constructed, and a large proportion remain in existence today with a significant number still actively competing in historic racing. This despite

the fact the entry price for ownership of an original is well north of £1 million, with ‘good’ cars fetching in excess of £4 million. There are of course replicas, some of which are eligible to race but for the purposes of this article, we will concentrate on the factory-built cars.

Complexity of nature ‘They are complicated cars, there’s no doubt about it,’ says Ollie Crosthwaite of long time Bugatti specialists Crosthwaite and Gardiner. As a result, originality is highly prized. It was not uncommon for cars to be bastardised. If an engine broke, there was no guarantee it would be replaced with an original unit, or even one from Bugatti. This complexity also means their upkeep is not the work of a moment and some parts in particular require an in-depth understanding of the

Bugatti was a force to be reckoned with on the Targa Florio and in 1927 Emilio Materassi scored another win for the young car maker in the Type 35C

original design intention and considerable engineering capabilities, beyond the skills of the average restoration outfit.

Although Bugattis only account for a small percentage of C&G’s work these days, the company has decades of experience from which it can draw.

Founded in the 1960s by Bugatti racer

The Type 35 and its derivatives would claim a plethora of victories across Europe in Grand Prix and hill climb events

Dick Crosthwaite and toolmaker and restoration engineer John Gardiner, the company began as a specialist in Bugatti parts. Over the years it branched out into other marques and established an expertise in the restoration and recreation of components likely unmatched anywhere in the world.

Ollie, Dick’s son, took charge of day-today operation at the company in 2009. He had previously trained as a tool maker and worked as an aircraft mechanic, servicing the Crunchy Flying Circus’ aircraft, before returning to the family business via a stint on an historic race team.

In years gone by, the company held a considerable supply of new old stock parts, purchased from the Bugatti factory in Molsheim. ‘Dad used to go to the factory to buy parts in the 70’s,’ recalls Crosthwaite. ‘They’d wrap them up in

these big Bugatti train posters. They had a big stack of them on the floor in the stores.’ The posters in question feature a Bugatti Type 57 racing a Bugatti styled train, and now fetch well over £1000 each.

Alas, the days of picking up NOS parts are long gone and for decades, C&G has produced many components for Bugattis of all types, as well as those for other historic cars. The company can manufacture all-new Coventry Climax engines as well as rarities such as blocks for Ferrari and Alfa Romeo Grand Prix cars.

In the past this work was undertaken on manual machines, but the company sold off many of its specialist tools, such as crank production lathes and cam grinders.

It now relies on Haas CNC centres and a pair of Matsura five-axis machines, one of which can accommodate 850mm billets weighing up to 500kg.

Racecar Engineering • Historic Racing 13

Racecar Engineering • Historic Racing 13

BUGATTI TYPE 35

The Type 35B competed in Grands Prix in the 1920s and it remains the archetypal high performance car of the time

The attention to detail on parts they produce is impressive. Take for example a Bugatti light bracket. In period, these were forged or cast. Today, they are produced by CNC machining, but the surface finish replicates the original.

Material strain It is the Type 35’s engine that best illustrates the complexity of their construction. With the exception of the 4-cylinder equipped Type 37 (a development of the 35) all the cars featured a straight eight, with the majority of competition versions running roller bearing cranks. ‘If you bought a 35T, or 37, you got the boy’s model, with a 4-cylinder, solid front axle, and wire wheels,’ explains Crosthwaite. ‘They were expensive toys and if you had the money, it was hollow front axle, alloy wheels and the eightcylinder and a roller bearing crank.’

The construction of the crankshaft highlights the intricate nature of the engine. Constructed from eight sections, in two main halves, each throw is located by means of a taper and cotter pin.

‘The angle you grind on the cotter pin is how you line the sections up as you assemble it,’ points out Crosthwaite.

The two main crank sections are joined by a tapered fit and keyway.

14 Historic Racing • Racecar Engineering

14 Historic Racing • Racecar Engineering

When it comes to camshafts and rockers modern metallurgy makes new items more reliable than originals C&G manufactures new cranks, previously using its own forgings for each section but now simply starting from billet. In the past, production this entailed many different turning and milling operations on manual machines, made more complex by the fact the journals are case hardened. Now, the entire process can be completed on a single five-axis machining centre.

It takes the company around three weeks to build a crank from scratch.

The cylinder blocks are another case in point. Head gasket technology was far from advanced in the 1930s so, much like Miller with his Indy engines, Bugatti opted for a one-piece block and head.

Although metallurgy has moved on since the 20s, the casting process for new blocks is still challenging as it is very fine and with modern health and safety, some of what’s needed to get the metal to run well isn’t allowed. C&G doesn’t currently produce blocks as there is already a supplier in Germany and Crosthwaite notes there is not much point in two companies vying for what is a relatively small market. However, he does propose that in time, additive manufacturing may provide a viable alternative to casting.

When the blocks do fail, it tends to be between cylinders two and three;

liners can be fitted but Crosthwaite states emphatically, ‘if they go there, its dead.’

However, blocks were never numbered. ‘[Original] Bugatti parts are only really valuable when they’re numbered,’ says Crosthwaite. ‘The crankcase and sump have the chassis number and engine number, as does the cam box, but not the blocks. As the block is machined on every face, you’d be hard pressed to tell a new block from an old one.’

Advances in materials technology have also paid dividends when it comes to reliability of the valve train in the straight-8. The cam is gear driven with bevel gears and Crosthwaite says the drive is generally reliable as long as you keep an eye on wear, particularly on the skew gears.

When it comes to the camshaft and rockers, modern metallurgy and manufacturing techniques make new items far more reliable than the originals.

‘We can make the cams and rocker fingers last a lot longer now,’ says Crosthwaite. ‘We have better materials and heat treatments and we probably know a lot more about surface finishing than they did in the 20s.’

Beyond straight improvements in materials or manufacturing methods, there are areas where the performance of the engines can be subtly improved,

The Type 35B had its first Grand Prix victory at Monaco in 1929 in the hands of W Williams after a duel with Rudolph Caracciola’s Mercedes

for example the superchargers. C&G manufacturers completely new supercharger units that are slightly improved over the original parts.

The original blower rotors are a three-lobe design, but C&G’s use a two-lobe rotor, similar to those found on later Type 57 cars. ‘They didn’t quite get the profile right and there are parts where the clearance changes,’ explains Crosthwaite. ‘Ours have a different profile and a constant gap [between the rotor and housing].

They’re just a bit more efficient.’

Overall, the engines, if looked after, are generally reliable. ‘You want to take a look at the crank now and again, keep an eye on the rollers,’ notes Croswthwaite. ‘You also need to change the oil regularly. The oil is so much

‘It’s a crash box and if you put in a bad driver you are going to need a set of gears pretty quickly’ Ollie Crosthwaite

better these days, as long as you keep an eye on the methanol mixing with the oil and not letting it break down.’

Despite the inherent resilience of the originals, Crosthwaite says it is not uncommon for the company to supply entirely new engines, either fully built or in kit form. ‘A usual thing would be for a customer with a very original car that they still want to race,’ he says. ‘They may be due a rebuild and have an original engine with some new parts already fitted, but still have the original parts as well.

They will build up the old engine with all original parts, put it to one side, then race the new engine and not be scared of putting a rod through the crankcase.’

If an original motor has been damaged, there is still a case for repairing even catastrophic damage. However, as Crosthwaite explains, repairs can be more expensive than replacement. ‘They don’t call it restoration, these days it’s conservation and if you’re conserving an engine, it can get really expensive,’ he says.

The gearboxes are relatively conventional, a four-speed, crash unit, but gear wear is high. Again, C&G used to undertake the entire gear manufacturing process in house, but now it is more cost effective to subcontract out the cutting work, though they still produce

the blanks and heat treat them. There are some refinements possible to the gear profile and surface finish, but driver quality can make a difference. ‘It’s a crash box and if you put a bad driver in the car, you’re going to need a set of gears pretty quickly,’ says Crosthwaite bluntly.

A company called Brineton Engineering does offer for the Type 35 a dogbox conversion which is highly rated, though not commonly seen in competition, as a lot of Bugatti racing customers prefer to maintain authenticity.

Simplicity in frame By the standards of a modern racecar the Bugatti chassis is beautifully simple, but compared to its peers it was an advanced design. It features two stressed channel sections running its full length, with the rails arcing out from behind the engine compartment to accommodate the body.

Various cross members span between these main sections and at the front, the engine is rigidly mounted while two cross members behind the engine support the transmission. ‘You want to make sure before you build a car that you straighten the chassis on a jig, because most if not all of them have had an accident,’ says Crosthwaite.

‘They’ve just been around a long time Racecar Engineering • Historic Racing 15

Racecar Engineering • Historic Racing 15

BUGATTI TYPE 35

The Type 35 was built on a simple spaceframe with crossmembers that added stiffness although the bodywork was wired into place due to movement

and in their day were an expensive car to repair, so you certainly need to make sure the chassis is straight and square.’

A unique feature of the Type 35 is the front axle, a patented Bugatti design which is of hollow construction with the front leaf springs passing through two holes, forged through the case-hardened nickel chrome steel. The springs are located in place by upper and lower wedges, the top wedge being adjustable to allow for changes in castor angle.

Damping is somewhat rudimentary relying on a relatively complex friction shock absorber, featuring a steel shoe pressing against a liner within a bronze drum; keeping these working smoothly is a constant battle for racers.

When coupled with the semi-elliptical suspension springs, poorly adjusted dampers can lead to a jarring ride.

Innovative thinking One of the Type 35’s signature features are the spoke, cast alloy wheels, which also incorporate the brake drums. The wheels are a beaded edge design, with a detachable outer rim held in placed by 6mm, countersunk screws. The bead on the edge of the tyre fits into a ‘clincher’, which the tyre locks into when inflated.

The use of a combined brake drum and 16 Historic Racing • Racecar Engineering

16 Historic Racing • Racecar Engineering

rim not only reduced unsprung weight, but also allowed for (relatively) rapid changing of the brake shoes during a pitstop. The wheels are one of the most common parts C&G supplies. ‘The market for wheels is still very strong,’ observes Crosthwaite. ‘Wheels do crack and people are very conscious of [having] safe wheels.’

At the rear, the car features a twopiece, cast aluminium differential casing, with semi-floating halfshafts in steel axle tubes. The rear axle assembly is located by the springs to the rear and a pair of radius rods running forwards. A torque arm also bolts to the left side of the differential housing, fixed to one of the chassis cross members. Impressively, the axle tubes are machined from solid steel billets.

The bodywork is all aluminium, made in nine sections, with each section secured by screws. Bugatti knew that the chassis was flexible as he had designed it that way and as such, also recognised that the bodywork could not be rigidly attached. Instead, each screw sits in a brass ferrule, larger than the screw’s diameter, allowing for a degree of movement. To prevent the screws working their way out (they are not done up tight) each panel’s screws are wired together.

Bodywork is of course, the first casualty in any racing incident and here,

Bugatti knew that the chassis was flexible and that the bodywork could not be rigidly attached

Crosthwaite notes replacement is not entirely straight forward. ‘Getting the shape right can be quite hard, but even then, the hard bit is making sure the louvres are correct,’ he says. ‘That, and every body is different in its own way.’

Overall, though the Type 35 and its descendants may have acquired significant value over the years, they can be raced. Admittedly, their bespoke racecar pedigree can hold its challenges.

‘You don’t work on Bugattis without a lathe and a mill,’ points out Crosthwaite.

‘It’s different to, say, running a Jaguar E type, where you just need a big toolbox.

A guy with a Bugatti has a smaller toolbox and machine tools. It’s a different sort car.’

However, when it comes to running them, provided everything is within specs they are reliable and, in the right hands, as competitive now as in period.

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RACE PREPARATION

Bentley Motors

Two of Bentley’s 2003 EXP Speed 8s reside at Progressive Motorsport, one that completed much of the testing and ran at the Le Mans Test day, and this example that finished second overall

Crack testing Buying classic racing cars and spare parts is not a guarantee that they all work. Racecar Engineering looks at the pitfalls and solutions

By Lawrence Butcher 18 Historic Racing • Racecar Engineering

18 Historic Racing • Racecar Engineering

I

t may seem obvious, but historic racecars, as the name suggests, are old. Even the most recent machinery, found in series such as the Masters Endurance Legends, are well past their planned service lives, and they were never built with longevity in mind. So how can it be deduced if such cars are in a fit state to race? The answer is through a combination of meticulous preparation, preventative maintenance and NDT testing, the latter being the subject of this feature.

The simple fact is that a component may look fine on visual inspection but can hide potentially catastrophic flaws.

This can be true even for parts that are NOS, and those that have already been subjected to the heat of competition.

As Howden Haynes, former Audi Sport and Bentley Engineer, now technical director at specialists Progressive Motorsport points out; ‘new means it’s just been made, not something that has been sat in a box since 1982.’

Phil Cooper, of motorsport NDT specialists Comptech, flags up the example of a new wheel (illustrated) which failed on an installation lap, fresh out of its box. Occurrences like this serve to highlight the good sense in having safety critical, highly stressed components checked as a matter of course.

There are a variety of processes that can be employed for NDT assessment of historic cars, which can be generally broken down into methods for metal and those for composites. Which process is

Testing original parts can save money in the long run, if only in underpants

There are a variety of processes that can be employed for NDT assessment of historic cars, generally broken down into methods for metal and for composites Racecar Engineering • Historic Racing 19

Racecar Engineering • Historic Racing 19

RACE PREPARATION

Dye-penetrant testing is generally utilised on aluminium and magnesium components used depends on the part in question and the particular material, with composites requiring a more nuanced approach.

Air force Magnetic particle inspection (MPI), generally referred to as Magnafluxing, is well-known as a means of checking for cracks in ferrous metallic parts. The process relies on inducing a strong magnetic field around a part that is coated in a fluid containing ferrous particles in suspension. If there is a crack or void in the part, the magnetic field ‘leaks’ as air cannot support the same strength of field by volume as metal. Particles are attracted to these areas of flux leak, highlighting any flaws and are mixed with a pigment to make them fluoresce under UV light.

Magnafluxing is generally undertaken on a dedicated test bench that has an induction coil and a pair of magnetic heads. Whether the coil or heads are used depends on the geometry of the part being tested, owing to the orientation of the magnetic fields generated. For example, cracks running longitudinally along a shaft will not show up when placed in the coil, as the magnetic field of the coil runs perpendicular to coil windings.

For non-ferrous parts, dye-penetrant testing can be used for crack checking, so long as its limitations are acknowledged.

A part to be checked is coated in a luminescent fluid, then rinsed with the process relying on capillary action to draw fluid into any cracks. A developer is applied, which has the effect of drawing out dye that has settled in any cracks, highlighting their presence when inspected under UV light.

Dye-penetrant testing is generally utilised on aluminium and magnesium components. It can be very effective on clean parts that do not have any form of coating. However if there is a coating in place, for example paint or anodising, this can mask cracks as it blocks the penetrant.

In certain circumstances, the dye can leave a permanent stain on parts. That 20 Historic Racing • Racecar Engineering

20 Historic Racing • Racecar Engineering

Dyes can be used and under UV light show up cracks and potential failures in key components

Parts need to be inspected be they metallic or carbon and different processes are required for each of the materials, here eddy-current testing

is less of a problem if they are internal, but is less than desirable, particularly on a historic car where appearance can be important. Fortunately, there are other NDT processes that require greater operator skill. They can be very useful in the context of NDT testing for motorsport, for example, eddy-current inspection.

Eddy-current inspection A probe consisting of a wire coil that generates an oscillating magnetic field via an alternating current is connected to an oscilloscope. When the probe is held close

to a conductive material, for example aluminium or titanium, an eddy current will be induced in the material, generating its own magnetic field, which interacts with the magnetic field of the probe.

If there is a change in thickness, or a void is passed over, the eddy current will either change in amplitude (in the case of a thickness shift) or collapse.

These changes in the eddy current and its magnetic field are displayed on a monitor, and this is where the skill of the operator in interpreting the changes comes into play.

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RACE PREPARATION To the uninitiated, the fluctuations in the display would be hard to relate to the properties of a part being inspected. With the probe placed over a sound area of material, a dot is displayed on the screen, representing the magnetic field generated. As the probe is moved over the part and the material properties remain the same, the dot will remain almost static.

As the probe reaches the edge of the part or a hole, the dot will change into a loop, due to the magnetic field beginning to collapse. This also occurs when it passes over a crack and a skilled inspector will be able to interpret whether the signature loop is created by cracks while also determining the size and depth of a flaw.

Wheels are particularly bulky and hard to study, although potential weak points are well known

Bulk testing Eddy-current testing is particularly useful because it can see through coatings, meaning you can inspect under anodising, paint or plated finishes. It can effectively be used, for example, on components such as wheels which often have painted or anodised finishes prior to NDT testing. Paint could fill flaws that occur during manufacturing which would not be visible using a dye-penetrant test.

However, as eddy-current testing relies on inducing a magnetic field into a part, coatings or paint make no difference.

Wheels are also bulky, which can complicate testing using a dye, not simply in terms of fitting them in a tank to ensure proper coating, but because of the area covered by dye. If a whole wheel is covered in luminous dye, much of which is still present even after rinsing, it can be hard to differentiate cracks or flaws from the high level of overall luminosity when placed under UV light.

Generally, only small sections of wheels are checked using the eddy current method, as it is very time consuming. A tester will concentrate on highly stressed areas such as the inner and outer edges of the bead, the junctions of the spokes with the wheel centre and rim, and the areas around the bolt holes. Also, although a wheel is unlikely to crack in the main meat of the rim, several passes can also be made with the probe around the circumference of the rim and across its width to pick up potential issues.

Composite tracing When it comes to composite parts, NDT becomes more complicated.

Ultrasonic testing is the best method for in-depth inspection of composite 22  Historic Racing • Racecar Engineering

22 Historic Racing • Racecar Engineering

Composites have changed considerably over the last 20 years as the technology has improved. Testing for classic cars must recognise this point

Recommended updates for FIA inspection

T

he FIA’s list of recommended checks should be updated, say Comptech and Tour De Force Racing, who added a list of their own checks for the FIA. Modifications to the FIA specification highlighted in bold:

and type of construction of the component in question. Ideally, each metallic component should be clearly identified and be indelibly etched or marked, and the use of the original lifing numbers engraved (in a nonstressed area) on the part is preferred.

The following items of all cars must be checked for structural integrity and/or corrosion by a non-destructive test: • Steel suspension wishbones • Carbon fibre suspension wishbones, annual check or 1500 km, whichever is sooner • Flexures, if separate from wishbones or checked as part of wishbone check • Complete steering columns and steering arms regardless of material • Light-alloy steering components • Light-alloy wheels • Suspension rockers and linkages, regardless of material • Push/pullrods and bellcranks, regardless of material • Wheel hubs/spindles, wheel nuts • Suspension uprights, whether cast or fabricated • Suspension mounting brackets or plates, including complete rear impact structure where this constitutes a suspension mount • Front wing mounting points, hangers/pylons and attachment/bond to nose • Rear wing inserts for hangers or mounts and bond check, including the complete rear impact structure where this constitutes a rear wing mount • Rear wing endplates • Brake pedal • Brake pedal balance bar • Carbon chassis, specifically nose mounts points and nose pins (primary safety structure), suspension pick-up points, seat belt mounts/inserts, engine mounts? (suggest a 3000 km testing interval)

All composite parts must be presented for inspection with a part number and a part specific lot/serial number. It is strongly recommended that a transponder tag is also permanently bonded to the parts. These numbers should be referenced in the NDT certificate.

It is strongly recommended that similar inspections should be carried out on components that are vital to the integrity of the car but which may not be contained in the list above.

New parts that are not fabricated – that is, machined from billet where the billet is supplied with a certificate of conformity to an acceptable specification – are excluded until a year old. New parts that are fabricated – as in welded – must have penetration flaw detection performed as a minimum to test the integrity of welds.

All of the above components (including, to avoid doubt, spare parts) must be tested and certified using methods appropriate to the material

parts and relies on time-of-flight measurement of ultrasonic waves emitted through a component.

A probe is passed over the surface of a component, and if there is a delamination of the composite plies the return signal will be different from where the material is fully consolidated.

By characterising these signals, using

A report/log sheet of all carbon suspension should be kept. All defects should characterised and added to the log sheet showing position, shape and size. This report must be kept to monitor future growth of defects enabling a structural assessment.

The test certificate/manufacturer’s declaration must be available to scrutineers on circuit and should be dated no more than 12 months (one calendar year) previous to the date of presentation.

The tests must be carried out with reference to one or another of the following standards: Visual inspection BSEN 970:1997 (or current edition or equivalent standard recognised by the ASN of the applicant) Penetration flaw detection BSEN 571-1:1997 (or current edition or equivalent standard recognised by the ASN of the applicant) Magnetic particle flaw detection BS 6072:1981 (or current edition or equivalent standard recognised by the ASN of the applicant) X-ray flaw detection BSEN 1435:1997 (or current edition or equivalent standard recognised by the ASN of the applicant) Eddy-current Inspection Relevant BSEN Ultrasonic inspection As there are no agreed standards for motorsport composites, it is recommended that all ultrasonic inspection is carried out by a person who is competent and familiar with structural motorsport composites.

All defects should be characterised using a 2/5 mm flat-bottom hole reflector. A suitable technique and procedure will be made available for scrutiny as required.

reference material samples, a survey of a part’s make-up can be conducted.

A comprehensive grasp of both NDT procedures and also composite construction methods is required for an inspector to make an informed judgement on the condition of a part. Some composite layups can be exceptionally complex, for example

around sections of chassis where bulkheads meet. Only by having a proper understanding of these complexities can their soundness be assessed.

This is further complicated in the case of historic racers, owing to the fact that the construction of composite chassis and components has evolved over the years. The lay-up methods used for a car Racecar Engineering • Historic Racing 23

Racecar Engineering • Historic Racing 23

RACE PREPARATION

The Bentley steering rack

The lay-up methods used for a car built in the 1980s will be quite different from one constructed in the 2000s Flat out at Le Mans still means more than 200mph even in classics such as the Bentley Speed 8

built in the 1980s will be quite different from one constructed in the 2000s. In some cases, older composite cars can be much easier to inspect, as they used simpler layups which are easier to define, without the added complication of mixed composite materials and inserts.

Change culture The FIA’s Appendix K, the specific regulations for historic racing, covers inspection of structural parts (Appendix III) and the repair of composite parts. This recognises the fact that in the past the only checking of parts for competition use was a visual inspection by scrutineers.

While that would pick up any major defects, it would be impossible to spot problems such as fatigue cracks starting in safety-critical parts. As such, it specifies some basic items that must be subject to crack testing on a regular basis.

Cooper, who deals with a host of both historic and contemporary racing machinery along with one of his clients, Matt Faulks, MD at historic racing specialists Tour De Force Racing, both felt that Appendix K is somewhat ambiguous in terms of specifying what must be checked on a composite chassis car. For example, parts such as crash structures are not subject to compulsory testing.

However, they both recognise that having a blanket requirement to check every part, in the way a modern F1 team would, would price many racers out of the market, so a balance needs to be struck between cost and safety. With this in mind, they created an amended list of requirements and have supplied it to the FIA, though the sanctioning body has yet to provide a response (see box-out p23).

It remains a fact that NDT testing is not something that crosses many racers mind. However, with a greater quantity of modern machinery taking to the track once again, run by much smaller outfits than in period, its importance should 24 Historic Racing • Racecar Engineering

24 Historic Racing • Racecar Engineering

T

hese illustrations here are a prime example of why NDT testing can prove invaluable from a safety perspective. They show the steering rack from a 2003 Bentley Speed 8 LM P900, currently in the charge of Progressive Motorsport. Inspection of the parts immediately flagged up that failure was imminent due to cracks propagating at the roots of many of the teeth.

Howden Haynes, having worked on the cars in period, was aware this could be an area of concern.

‘We knew straight away that we had to check the racks, because it was an issue I knew of,’ he says.

‘It’s not a commercial thing for use, checking areas like this, it is because I’ve seen what happens when things fail.’ In the case of the Bentley, the solution was to produce new steering racks, although that was an expensive option. ‘For the owner, they’ve just spent a lot of money on the car and it’s a tough pill to swallow to have to have something like the steering rack re-engineered,’ he says.

With the Bentley tub, Progressive had them ultrasonic tested. ‘There wasn’t anything major,’ confirms Haynes. ‘Just some small areas of delamination, that sort of thing, and then it was a case of deciding the best way to repair it, for example, with a glue injection or localised repair to the carbon.’

not be underestimated. It is particularly important to note that the machines built in the era of computer-based finite element analysis, where more accurate stress calculations allowed for a lower safety factor on the sizing of parts, need to be treated with considerably more caution than their more substantial, older relatives. While NDT inspection may add unwanted cost to already stretched budgets, it could well represent the difference between nipping an issue in the bud, and a catastrophic accident.

Having a blanket requirement to check every part, in the way a modern F1 team would, would price many racers out of the market

Still a favourite among many Le Mans fans, the Bentley Speed 8 took victory at Le Mans in 2003

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Racecar Engineering • Historic Racing 25 3

CLIMAX ENGINES

Diversity rules Formed at the turn of the last century to cater for the needs of defence and the fire brigade, Coventry Climax accidentally arrived on the racing scene in the 1950s

By Lawrence Butcher

The Lotus 32B was powered by a Coventry Climax FPF 2.5 litre engine. Modern day versions of the same engine are probably more reliable and more powerful than in period

26 Historic Racing • Racecar Engineering

26 Historic Racing • Racecar Engineering

L

ong before Cosworth famously started to provide engines for customer and factory race cars, Coventry Climax was the go-to company for those needing a plug and play racing engine. From diminutive sub-1000cc units to screaming V8s, it produced a myriad of engines, but here we will concentrate on two of its 4-cylinder offerings, the FW series and the FPA, the two engines that helped the brand into motor racing lore.

That Coventry Climax became a byword for post-war racing engines may seem surprising given the history of the

company prior to the 1950s. Originally it was founded as Lee Stroyer in 1903, a joint venture between Horace Pelham Lee and Danish born Jens Stroyer. Following the departure of the Dane in 1905 it became Coventry Simplex under the ownership of Pelham Lee. The company manufactured a range of light car and tractor engines, including those used by Shackleton’s trans Antarctic Expedition of 1914.

In 1919, having spent the first war manufacturing generator sets for searchlights, Pelham Lee purchased another company, Johnson & Smith Ltd, and changed its name to Coventry Climax Engines. The old company would continue under separate management while the newly formed Coventry Climax went from strength to strength.

Through the 1920s, production of car engines continued, supplying firms such as Morgan, Crossley and Triumph, but the financial strains of the early 30s saw the company diversify into more industrial applications, including waterpumping equipment. It was this move that laid the surprising foundations for some of its best known racing engines.

Following the Second World War, the key personalities of Walter Hassan (Chief Engineer and Technical director) and Harry Mundy (chief designer) joined the company. One of their first projects was the ‘FW’ engine, FW standing for Feather Weight, which was developed in response to a government tender for a lightweight fire pump engine.

That tender was for a pump capable of delivering double the volume of water of the then current units, but weigh half as much. The engine Climax developed easily met the government requirement of producing 35 bhp at 3,500 rpm, in fact putting out 38 bhp, and the company was awarded the contract.

The FW was never intended for automotive use, never mind racing, but when it was displayed at the Earls Court Motor show in 1953 its high power to weight ratio attracted admiring glances from the racing fraternity. This was not surprising, the engine had an alloy block and head, OHC and even in industrial trim, a useful power output.

Climax didn’t have any racing plans for

the engine, and it was already involved in the development of a bespoke race engine, the FPE (see sidebar), but after some encouragement from constructors (including Cyril Keift, who bought a government surplus fire pump unit in 1953 for use in the Keift 1100 sportscar), Hassan, along with Leonard Lee (MD of Coventry Climax) saw there was potential for a move into the racing market.

The first FWA engine (Feather Weight Automotive) was under development by the end of 1953. Work was done on the porting and valve train, the capacity was upped to 1097cc (to suit the 1100cc racing class) and a pair of SU carburettors were fitted. The upgrades meant that the first FWA’s were good for 71 bhp at 6000 rpm and the first of four prototypes was used by Keift at Le Mans in 1954 (the car dropped out with a differential failure).

The engine went on to be developed through various iterations, with capacities up to 1.5 litres and as low as 750cc (for the class that ran to that capacity at Le Mans), culminating in the 1-litre FWG for Formula 2 which revved to 9000 rpm and made just shy of 100 bhp.

The FWE More FWEs were produced than any other, specifically for Lotus to use in its Elite. With a capacity of 1216 cc (though generally referred to as the 1220) in road going trim, the engine featured a single SU carburettor and produced 70 bhp at 6000 rpm. However, in racing tune it had considerably more pep. Chris Tolman, of Tolman Motorsport, has been working with FWs, and FWEs in particular for many years, and the company has developed the engine extensively in pursuit of both reliability and performance. ‘It actually all started with one client, who raced an Elite,’ says Tolman. ‘He was an engineer and had done extensive work on the engines in the past, including with Brian Hart. He approached us explaining how they had been handling the engines, explained why they would break and asked us what we would do to fix it.’

Going back to engineering first principles, Tolman and his engineers quickly realised one of the most pressing problems was the cylinder heads breaking

The first FWA’s were good for 71 bhp at 6000 rpm and the first of four prototypes was used by Keift at Le Mans in 1954 Racecar Engineering • Historic Racing 27

Racecar Engineering • Historic Racing 27

CLIMAX ENGINES where the dynamo attached. ‘The first thing we noticed was that there was a counterbore machining for studs, so we put a radius in there,’ notes Tolman.

‘Then we realised that nothing really lined up properly, so [put] everything [on a coordinate measuring machine] and made up new brackets that didn’t put any preload on any of the fasteners.’

Another perennial issue was oil leaks, which were cured by having all of the various fasteners remanufactured to much higher standards than the originals, curing these issues at a reasonable price.

Various traditional modifications to the engines also proved to be somewhat wide of the mark. ‘The blocks, being a post-war, aluminium casting, are not great, but that said, the main bearing

studs are actually fantastic,’ says Tolman.

‘Yet people were taking the existing bearing caps out and ‘strengthening’ the bottom end with a plate and cap head bolts. So instead of machining off the cast alloy caps and putting in a steel plate, we’ve remade the centre main caps in 7075 aluminium, which works in conjunction with a stress plate, and that makes for a really strong engine.’

Another area that has come in for Tolman’s attention is the cam carrier, and the company has produced its own fiver bearing aluminium production to replace the cast iron original. ‘That helps a lot with things like the stack height of the cam, because the cam chain tension is a function of where the cylinder head and cam carrier sit,’ says Tolman. ‘Over

The FIA spec engine stays faithful to the original design, but has been developed using modern understanding of efficiencies and materials 28 Historic Racing • Racecar Engineering

28 Historic Racing • Racecar Engineering

Tolman and his engineers quickly realised one of the most pressing problems was the cylinder heads breaking where the dynamo attached years of machining blocks and heads, you end up having to shim the cam carrier higher and higher under each of the bolts. I didn’t like the original cast iron [cam carrier] and it used to twist, so we have made an aluminium carrier, which is thicker than needed and which is then machined to the correct height during the build. That has also saved about 30% on friction, because it is aluminium with a steel bucket follower, rather than cast iron and cast iron.’

The company has developed three different piston versions: a replica of the original design, a variation with cutouts for larger valves and an intruder variant, the latter being intended specifically for race engines to allow fine tuning of compression ratio. ‘That also gives really good squish and a good burn,’ notes Tolman.

Tolman highlights that it has concocted an engine build specification to suit restrictive FIA historic racing regulations, which has great attention paid to areas such as the camshaft grind, and general finessing of the combustion process.

Due to the FIA demands regarding originality, he points out that these engines must also retain a completely mechanical distributor system. ‘We always run electronic ignition where we can, but with the FIA, it has to be clockwork, so we have done a lot of work to get that working well,’ explains Tolman.

One myth Tolman is keen to dispel is that FV engines were designed to be built with large tolerances, due to their original use as a fire pump. ‘The majority of owners think that, but having done the research, they have really tight clearances because its an aluminium engine, and it even says so in the fire pump build manuals from the era.’

He also notes that the real killer of these engines is the vibrations they produce, recounting, ‘the dyno we use is rated to take 2000 bhp drag racing engines, but we’ve done more damage

The FPE

C

The Lotus Elite featured the Climax FW engine and was one of the reasons the engine was so prolific

with a little 1200 Climax than any of the big engines. In that respect, it’s a pretty horrible engine and we’ve broken driveshafts on the dyno before.’

The FPF As noted in the sidebar, Coventry Climax was already working on a bespoke, V8 racing engine in 1952, but while development of that stalled, it spawned what would be one of the companies most successful racing products, the FPF inline-four. Designed by Harry Mundy (who actually left the company in 1955 having completed the design, only to return in 1963), it saw service in a host of Grand Prix and sportscar machinery through the late-50s and 1960s.

Originally utilising the cylinder head design of the FPE, it was a twincam, OHV, I4, again, all alloy in its construction. The engine started out with a 1.5 litre capacity for Formula 2 competition, before being enlarged to nearly two-litres for Formula One use, and then 2.2 litres. This was the limit of its original architecture (it was never

‘We always run electronic ignition where we can, but with the FIA, it has to be clockwork’ Chris Tolman

initially designed with larger capacities in mind) and in late 1958, a redesign was undertaken to create a 2.5 litre engine, which went on to considerable success with Jack Brabham winning that year’s world championship in a Cooper-Climax.

Though externally similar to the its smaller predecessors, the 2.5 was quite different internally, most notably due to the use of a four-bolt steel main cap design, rather than the cast aluminium, two-bolt system used on earlier engines. The result was an engine that produced 220 bhp in initial trim, rising to nearer 250 bhp in later variants.

The engine would be stretched to 2.7 litres for use by Brabham in a Cooper at Indianapolis while a 1.5 litre variant was developed when the Formula One rules switched to that capacity in 1961.

Specialists Crosthwaite and Gardiner, covered elsewhere in this issue for their work with Bugattis, has also carved a niche in the production of Coventry Climax FPF engines. According to owner Ollie Crosthwaite, it began working with the engines because ‘we had a customer in the US that liked good-quality parts for their Climax engines, and he suggested starting to make some new bits. Before we knew it, we had made almost everything.’

The company can now produce entirely new engines of various volumes.

‘We now do the 1.5, 2, 2.5 and 2.7 [litre] engines,’ says Crosthwaite. ‘We have also done one of the later cross-bolted 1.5 litre blocks, and a 2.2. We also do different levels of tune on them – a racy one, and a very racy one.’

oventry Climax decided to enter the race engine market in 1952 following approaches from HMW, Cooper and Connaught at that year’s Motor Show. It started development of the FPE, a 2.5 litre engine intended to suit upcoming rule changes for the 1954 Formula One season. Ultimately, however, the engine would never be used in anger.

Designed by Hassan and Mundy, the FPE was of all alloy construction, with twin overhead cams on each cylinder bank. An interesting feature was that it used the same casting pattern for the cylinder heads, with a ‘front’ cast at both ends of each head, the unused portion machined off later. The engine also had an impressive ‘zero backlash’ gear drive for the camshafts, where the gears were machined, hardened and then ground to very tight tolerances.

Unfortunately, reliability was elusive, with initial problems centering around the valve train, although a number of piston failures were also experienced.

It would not be until 1955 that the FPE was running reliably on the dyno, and it certainly made impressive power figures. However, by the time it was nearing being competition ready, the company’s four-cylinder engines were proving popular with racers and the project was sidelined. This was not the end though as in 1966, the development engine was purchased privately, bored out to 3.0 litres, fitted with a Tecalimit Jackson fuel injection system and raced at Silverstone housed in a converted Shannon Formula 3 chassis.

Hinting at the potency of the FPF engines, the 2019 Goodwood Revival featured the sight of the 2.0 litre C&G Climax-engined Lotus 15 of racer Roger Wills out-dragging a 2.5 litre Ferrari Dino down the straight. Crosthwaite explains that there is plenty that can be done to improve performance without falling foul of the regulations. ‘We keep on the legal side,’ he says. ‘The bore and stroke have to be the same [as original], as do the port diameter and valve sizes. But where we make all our power is on the port design and surface finish. Then it’s a case of incremental gains everywhere else.’

Remaking the FPF engines also gave the opportunity to improve areas of Racecar Engineering • Historic Racing 29

Racecar Engineering • Historic Racing 29

CLIMAX ENGINES The original 8-cylinder engine was redesigned to a fourcylinder and that was then developed throughout the 1960s in various categories of motor sport

the original that can present reliability issues. For example, Crosthwaite says the crankshafts are a particularly poor design.

‘They were really bad. They were not properly counterweighted and balanced for the weight of the rod and piston, particularly on the 2.5s.’ To address this issue, C&G’s new cranks have dense metal inserts in the counterweights. ‘We did the stress calculations, and the original design puts a load of around 2.5 tons through the centre main bearing. That is why the 2.5s always used to crack at the centre main. It is lots of little things like that which make the difference.’

For the cylinder head development, the company has leveraged computer simulation of the inlet and exhaust pulses to help optimise the port design and cam profiles. ‘It is pretty clever,’ Crosthwaite says. ‘We have run simulations on the cam designs, and everything we simulated we tested back to back on the dyno. It was close enough that our engine builder, who initially thought the simulation wasn’t going to work, had to admit it was pretty good.’

There are also gains to be made by simply making parts more accurately than they were in period. ‘That is a really big thing,’ Crosthwaite remarks. ‘It means things can be assembled more quickly.

With some of the parts, if you make them to the original drawings they just don’t fit together. I think it was what they [engineers in the past] called a fitter’s job. They would polish things to size, but 30 Historic Racing • Racecar Engineering

30 Historic Racing • Racecar Engineering

The engine was hard to balance and has even damaged dynos that are capable of managing drag racing engines capable of delivering more than 2000 bhp. Vibration is an engine killer

my view is to make things to the right size in the first place. It is a little more expensive to make something to a tighter tolerance, but they go together better.

If my customers get parts that won’t fit together, they just moan. It doesn’t matter if they are to factory specs!’

It is testament to the original designs that Coventry Climax engines are capable of producing impressive power even by current standards, and with a dose of modern refinement, they can be raced reliably in historic machinery around the globe.

‘With some of the parts, if you make them to the original drawings they just don’t fit together. I think it was what they called a fitter’s job’ Ollie Crosthwaite

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