Tech Talk
Two wheels of separation
Putting bike engines to work in car chassis
By Peter Dallimore
(January 15, 2005) -- In the two-wheeled world, many engines available for road use are extremely closely related to racing machinery. Over on four wheels, several generations of low-cost racing car constructors, from pre-war to current day, have turned this fact to their advantage.

In the years leading up to the Second World War, power units from all manner of sources - from motorcycles to water pumps - were being levered into an eclectic variety of quirky, home-grown racing cars. As the eccentrics and garagistes responsible for these curiosities resurrected their projects after hostilities ended in 1945, several became switched-on to the availability of proper racing engines from 500cc speedway and TT bikes – at reasonable prices – towards the end of the 1940s. These were light, strong and certainly powerful enough to give an exciting drive; so long as the cars themselves were also light and nimble.

Colin Strang, who was based in Harrow in north west London, was one of the first post-war constructor-racers to apply this formula. He sited his car’s Vincent HRD engine behind the driver to sharpen the handling and reduce the frontal area. On the other side of London, in Surbiton, John Cooper was similarly building a light and agile racer around a rear-mounted bike engine. In Cooper’s case, this was a single-cylinder 500cc JAP speedway unit. Both vehicles used Fiat running gear, from the ubiquitous Toplolino model.

The Fiat Topolino benefited from independent front suspension, incorporating a transverse leaf spring. Cooper used the Fiat front suspension at both ends of his little rear-engined car, endowing it with independent suspension all round. According to Roy Hunt of today’s 500 Owners’ Association, whose members still own and run these cars, Cooper’s scheme probably had more to do with saving time and effort than any attempt at improving cornering. But improve cornering it did.

As new and professional constructors joined the fray, Cooper and Kieft became the dominant marques in 500cc Formula 3. This category of racing came to prominence in the 1950s as owner/drivers and aspiring young racers took to the tracks and hillclimbs to prove their engineering and driving abilities. Packed grids featured racers built by other commercial constructors including Arnott and Martin, as well as a host of one-offs and home-built specials. Most followed the Strang and Cooper rear engine layout, but a very few, such as Paul Emery’s Emeryson and Clive Lones’ Tiger Kitten, were front engined. Cooper’s independent suspension at both ends quickly proved itself superior, as did the single-cylinder Manx Norton 500cc engine of Isle of Man motorcycle TT fame.

As competition drove further rapid innovations, F3 paddocks came to define the cutting edge of racing car design. Welded tubular steel chassis, for instance, had barely made it into Formula One in the early ’50s, but were the construction of choice for the little 500s where light weight and nimble handling were of paramount importance.

Comparing a 1950s F3 Cooper with the Maserati 250F, the epitome of contemporary Grand Prix glamour, highlights the point. The front-engined Maserati used relatively heavy de Dion suspension at the rear. It also had a simple ladder-type chassis that offered little rigidity for its weight. In 1954 the engine provided some 240 BHP, but the car weighed 630 kg. And with its front engine layout, the 250F expended much of that power to make a large - although unquestionably elegant - Maserati-shaped hole in the air.

Now wheel-in the Cooper MK 9 of 1955, with its twin ohc Norton bike engine and chain final drive. Its tubular steel chassis boasts lightweight independent rear suspension, tubular lower wishbones and telescopic dampers – now built from custom-fabricated components, although still true to the principles of the early Fiat-derived layout. The MK 9 shows just how far the 500cc formula had evolved since 1946. It’s low, narrow, slippery; and a mere 240 kg dry.

Arguments raged throughout the 500cc era as to whether the lighter swing axle type of rear suspension, or universally jointed drive shafts, was superior. Cooper favoured universally jointed shafts, which allowed the outside wheels to adopt positive camber for that classical drift through fast curves. Other constructors, such as Ray Martin who penned the original Kieft and built a small number of eponymous rear-engine racers, preferred the swing axle, which gave negative camber to the outside wheel to generate greater grip for a tighter line. But, as Roy Hunt comments, the handling was less progressive; once it let go, you were off the track.

Despite, or perhaps because of, the ongoing conflicts of opinion, these humble budget-racers were several seasons ahead of their F1 contemporaries in technological terms. The Maserati 250F graduated to a tubular chassis for 1957 and Fangio used it to score his fifth driver’s title. But the configuration and suspension technology it embodied would soon be eclipsed as Cooper took its 500cc construction ideas into Formula One with Coventry Climax power at the dawn of the 1960s.

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Fast-forward three decades, and despite the numerous production-based series offering relatively low-cost racing, there is a demand for “proper” racing cars that do not cost the earth to buy and run. The motorcycle-engined approach again offers a practical solution.

The world is awash with relatively inexpensive multi-cylinder engines that offer virtually everything a racer could wish for; light weight, huge power output per litre, and superb reliability. And a sequential gearbox as standard. There is more than adequate performance for sealed-engine racing where tuning is proscribed to keep costs low. On the other hand, for those who can afford a little (or a lot of) tuning, there is no shortage of expertise and special parts.

Global GT Lights started life as a 600cc sealed-engine racing series, using the 100 BHP four cylinder engine from the Yamaha Thundercat. The cars are designed and built by Graham Hathaway at Essex-based Graham Hathaway Engineering Ltd. Hathaway polices the engine regime and also controls chassis and aero modifications to keep costs low and competition tight. However, changes in the super-sports bike market over the last few years have seen the top-dog class move up from 750cc to 1000cc. Hathaway has moved with that trend, slapping the carburettor version of Yamaha’s outrageous 155+ BHP YZF-R1 engine in the back of his car. It is almost a straight swap for the Thundercat unit, and required relatively few modifications – even the throttle and clutch cables are the same.

The rolling chassis is serious kit, with high quality Ohlins dampers all round, beefy anti-roll bars front and rear, front splitter and rear wing. Adrian Newey, no less, has had a good poke around the car and praised it as a piece of engineering and as a basis for learning about car setup. Yes, he has driven it, seeking to understand how McLaren’s star drivers relate to his own seven-figure creations.

The package is capable of worrying a topflight touring car, which will swallow over a hundred thousand pounds to complete a season’s competition. On a short circuit, the Global GT Lights can beat a Formula Ford single-seater. And all this from a pocket-sized Le Mans look-alike that will give a good three seasons’ trouble-free competition with either Thundercat or R1 engine.

Another formula recently graduated from 600cc to 1000c is Formula Jedi, previously called Formula Honda 600. Built by Jedi Racing Cars in Northampton, these open-wheel racers can probably claim to be today’s closest descendants of the half-litre machines that spawned Formula 3 in the ’50s. Even though F3 moved away from the original formula, enthusiasts continued racing and developing cars using whatever engines were available. In response, the first Jedi took to the track in 1991 and became popular with hillclimbers and club racers. A one-make circuit racing series has been running since 1996, and is currently managed by Jedi. This has launched drivers into F3, touring cars, Formula Renault and Formula Palmer Audi. Again, the goal is cost effective racing, but there is deliberately more scope to tune, optimise gear ratios and adjust suspension settings.

According to Jedi’s Frazer Corbyn, it’s an ideal step for young drivers who need to move on from karts. It’s basically an open series; the Honda CBR600 engine can be tuned, balanced, blueprinted, and also upgraded to larger carburettors. Flatslide carbs, as preferred by many bike racers, are also permitted. But Corbyn draws the line at bored and stroked motors; that’s the start of chequebook racing, and is not what the series is about. Optional open or limited slip differentials are chain driven from the bike gearbox’s final drive. Jedi supplies multiple gear ratios, allowing drivers to dial the car into each track on the calendar, and the rod-ended suspension can also be set up to meet the driver’s preference. The latest model uses high-nose aerodynamics, and a variety of wing profiles are available to the drivers.

With the extra tuning opportunities, these cars are even faster than the Global GT Lights. Top Jedi qualifying times are typically on a par with a Formula Palmer Audi race lap. So this bike engined racing game gives little away in terms of performance or excitement to far more exotic and expensive machinery.

OK, so 155 BHP is enough to make a 400kg car move quite swiftly for a relatively small outlay. But what would it take to convince the die hard car devotees that bike engines are a serious source of motive power for 4-wheeled racers? A hyper-sports bike like the Suzuki GSX1300R Hayabusa might just prove the point.

In standard tune, the Hayabusa’s 1300cc engine pumps out 180 BHP at a screeching 9800 rpm. There is also plenty of torque, which often compromises lower capacity sports bike engines when dropped into car chassis. But the ’Busa is different: few road-going bike engines have threatened so much tyre-shredding potential direct from the production line. Specialist car builders Westfield and Radical have been quick to register this fact.

Richard Smith, of Birmingham-based Westfield, says his front-engined Megabusa is lighter and more nimble than its stablemates built using car engines; mainly because the entire Hayabusa engine and integrated gearbox weighs only about as much as a conventional 5-speed car ’box. The Megabusa follows the layout and styling cues of the company’s traditional minimalist sports cars. A pair of prop shafts either side of a reverse gear mechanism transmit the ’Busa unit’s ample power to a Quaife limited slip differential at the rear.

One step up from the Megabusa, the Westfield XTR2 mounts the ’Busa engine amidships, and also adds ground effect aerodynamics for extra roadholding. Westfield converts all its bike engines to dry sump lubrication in-house to boost reliability. Power tuning is also on offer, but that standard Suzuki engine is built to take a hammering. Westfield’s test hack covered 17,000 miles before the engine was whipped out, topped and tailed, and put straight back in to carry on its business.

Not very far away, in Peterborough, Radical co-founder Mick Hyde enthuses about the work of his chief designer, Nick Walford. It was Walford who penned Radical’s patented “Nik” rising rate suspension system that delivers single-seater cornering performance but also allows a smooth and low nose-line, free of the bulges of inboard suspension mountings. According to Hyde, Radical shuns exotic and - consequently - expensive materials and techniques, in favour of ingenuity and sound workmanship. Many components are made in-house, including uprights, wishbones and hubs, simply because Hyde was not satisfied with the quality available elsewhere.

Radical builds a family of cars powered by the Hayabusa, or the equally strong Kawasaki ZZR1100 unit, and organises its own series of endurance championships. Its in-house tuning business, Powertec, has been modifying bike power units for 4-wheel applications for over ten years, and lists upgrades to the clutch, gearbox and oiling system as essential for endurance racing.

The final drive also comes in for special attention. Bike-derived chain drive, still the most power-efficient way to connect to the driven wheels, comes with an ingenious engine-driven reverse gear courtesy of Nick Walford’s fertile mind. For those who don’t believe chain drive and 250 BHP will build a long-term relationship, there is a more car-like differential with a torque balancing system developed in conjunction with transmission gurus Quaife.

Bikers revel in the Hayabusa’s standard 180 BHP, but Radical tuning options take this up to a storming 252 BHP. But there is more: a Hayabusa-inspired 2.0 litre V8 built to Radical’s own design now puts 350 BHP, at a musical 12,000 rpm, in the back of a car weighing a gnat’s over 500kg!

A trackday version of the Radical SR3, one of Radical’s family of 2-seater circuit racers, has taken the outright circuit record at the Nürburgring. There is also a road legal example capable of seriously upsetting any supercar drivers still clinging to the belief that they rule Her Majesty’s highways.

But with all this power - and the transmission to handle it – coupled with that Atkins-diet weight figure, top-spec cars are now beating expensive GTs and prototypes in world-class racing. Radical SR3s claimed the top five places at the 400 km of Magny Cours in 2003. And it’s a very small step from there to the level of a Class 2 sports prototype. Just as in the fifties, these relatively inexpensive racers are employing cutting edge technology and showing the exotica where the action is.

Those who fancy a bit of radical racing action could find themselves lining up alongside some famous names. Damon Hill is an SR3 owner. Belgian Le Mans veteran Marc Goossens really rates it too. Martin Donnelly is impressed with the Radical as an alternative to the crowded single-seater scene. And when Colin McRae tested the turbo version, he rated it the best car he’d driven all year.

The opinions of these accomplished drivers really sum up just how far the idea of bike engines in cars has evolved. In fact, it’s reached the stage where the origin of the species is no longer the issue. Ex-F1, ex Le Mans, ex-WRC; no-one blinks. To them, it makes for extremely competent four-wheeled racing machinery.

With thanks to:

Roy Hunt of the 500 Owners Association ( www.500race.org ) for pictures of the Martin Special at Mallory Park

Graham Hathaway Engineering Ltd ( www.globalgt.net ) (GlobalGT Lights racing at Anglesey circuit, UK)

Jedi Racing Cars Ltd ( www.formulajedi.com ) (Jedi MK 6, and racing at Oulton Park, UK)

Westfield Sportscars Ltd ( www.westfield-sportscars.co.uk )

Radical Sportscars Ltd ( www.radicalsportscars.com )