Scarred for life?

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Following wholesale absence of period success, the Scarab seemed destined to be remembered as a poor racing car. But Julian Bronson’s machine has become one of the most successful historic Grand Prix cars presently competing. Why?

The writing for front-engined Grand Prix cars had long been on the wall. Stirling Moss broke the mould when he took his Cooper T43 to victory in the 1958 Argentine GP, while Jack Brabham followed up with back-to-back world titles in Cooper T51 and T53 over the following two seasons, the last for the 2½-litre regulations. A front-engined Ferrari 246 won the 1960 Italian GP, but only because the main British teams had chosen not to run on Monza’s bumpy high-speed banking.

F1’s traditional car configuration might have been consigned to the history books, but American constructor Scarab still opted to enter the arena with front-engined chassis when it made its championship debut at Monaco in 1960. Designed and built entirely in the USA, the cars were entered by Reventlow Automobiles Inc and driven by Lance Reventlow and Chuck Daigh. This was the first serious such American effort since Jimmy Murphy’s Duesenberg had won the 1921 French GP at Le Mans, but Daigh and Reventlow qualified only 21st and 23rd in Monaco, more than nine seconds slower than Stirling Moss’s pole position time of 1min 36.3sec. Moss agreed to try the Scarab, but Denis Jenkinson reported in Motor Sport that Moss could only muster a 1min 45sec – two seconds faster than Daigh, but still more than 7sec slower than he had managed in Rob Walker’s Lotus 18.

With only 16 cars permitted to start, the Scarabs did not qualify. Throughout the 1960 season they posted a depressing string of DNQs and DNFs, relieved only by Chuck Daigh’s 10th place in the US finale at Riverside. Even there the car was more than 8sec off the pace (Daigh had been ‘only’ 5sec off pole at Zandvoort, where the cars did not race because of a start money dispute).

MORE THAN 50 years later, Julian Bronson’s beautifully restored Scarab is a regular winner and consistent front-runner in HGPCA 2½-litre Historic Formula 1 races. It has twice taken pole position at the Goodwood Revival and in 2016 Julian won the Richmond Trophy, beating two Ferrari 246 Dinos. Even more significantly, Julian’s Scarab has lapped Goodwood within 2sec of the best Cooper T53 times.

So, let’s take a detailed look at the Scarab, then compare it with the Cooper T53 and the best front-engined F1 cars. Scarab sports cars performed well during the mid 1950s, funded by Woolworth heir Reventlow. Buoyed by this success, Reventlow launched the Scarab F1 project, intending that the car would be built entirely in America in time for the 1959 season. Lee Goossens, of Offenhauser and Meyer Drake fame, was contracted to design a new four-cylinder DOHC eight-valve engine with desmodromic valves (see sidebar), inspired by the 1954/55 Mercedes W196. Target power output was 280bhp at 8000rpm. Aside from the valve operation, engine design owed much to Offenhauser practice. Block and cylinder head were cast from aluminium, the engine was dry-sumped, used Hillborn fuel injection and a dual magneto system with two spark plugs per cylinder. The engine was laid on its side with the crankshaft to the left. This lowered the centre of gravity and allowed the driver to sit very low, with the propshaft passing on the left. A great deal of money was spent on the design and development of a continuously variable transmission, but this was eventually abandoned. A four-speed Borg Warner T10 was fitted and mated to a Halibrand crown wheel and pinion with limited-slip differential. Neat, small-diameter driveshafts with constant velocity joints transmitted drive to the rear wheels – a very advanced set-up for the time.

Aged just 23, Marshall Whitfield did the majority of the design and development work. The chassis is a simple, neat, well triangulated tubular spaceframe. Front and rear suspension is by dual unequal length wishbones, with concentric coil spring damper units and fabricated uprights. Anti-roll bars are fitted front and rear. The fuel tank is mounted in the tail and the aluminium bodywork appears to be influenced by late ’50s Indy roadster design. Drum brakes were originally specified, but Reventlow bowed to the inevitable and sourced discs from the UK. This was the only significant diversion from his ‘all-American’ policy. Goodyear tyres were specified.

The majority of the reliability problems during 1960 were engine-related – valve train and bearing failures caused by oil starvation. At the end of the season, the Scarab was rendered obsolete due to the change to a 1½-litre capacity limit for 1961. The Scarab engines were removed, near-standard Offenhausers fitted and the cars raced in the ‘rebel’ Intercontinental Formula. The programme ended when Daigh was injured in a crash at Silverstone.

In late 2012, Julian Bronson asked GSD RaceDyn to sort out his Scarab Offenhauser’s handling. Ridgeway Racing had rebuilt the engine and David and Paul from Julian’s own team had restored the car, with assistance from Mick Mobberley of Hitech Motorsport. Mick had improved the fuelling by using injectors with a better spray pattern. The magneto system did not provide a spark until engine speed reached 800rpm, making starting difficult. Power output was only 220bhp, about 50 short of the target.

GSD ran a very detailed analysis of suspension geometry and kinematics, spring rates, wheel rates, suspension frequencies and front and rear roll stiffness. It then ran stability analyses at turn-in, apex and under power in the corner exit phase, in second, third and fourth gears. It also analysed stability and pitch control under braking and conducted a critical damping analysis. In general the Scarab was assessed to be a very good basic design, but not fully developed.

Driver up, weight distribution was 47 per cent front, 53 rear – very good for a front-engined car. The tyre contact patch area ratio was well matched to weight distribution, which is good, but the following details were adversely affecting handling and performance: front springs 32 per cent softer than ideal; front anti-roll bar too soft by a factor of five; rear anti-roll bar ineffective and applying excessive localised loads to the rear wishbones; rear-mounted fuel tank causes substantial handling balance changes with fuel burn; ride heights too high by 35mm/40 mm front/rear, causing poor roll camber correction and a very high (97 mm) rear roll centre; the car (without driver) is 60-70kg heavier than the Cooper T53 – and has a relatively high polar moment of inertia.

GSD’s stability analysis showed that the Scarab would pitch too much under braking, followed by a lazy, unstable turn in with poor transient response. At the apex, excessive roll reduced tyre efficiency. Severe oversteer and poor traction reduced the ability to apply power in the corner exit phase.

At the front the solution was straightforward: 35mm lower ride height, 32 per cent stiffer front springs and a massively stiffer front anti-roll bar. Things were more difficult at the rear. Scarab had sensibly provided alternative rear pick-up points to accommodate varying tyre diameters. GSD was able to use some of these to correct the high roll centre. A revised anti-roll bar solved the wishbone loading problem and gave the required stiffness. Okay so far, but it was then found that the rear ride height couldn’t be lowered as much as was desired because of the angularity of the short left-hand driveshaft. Front and rear ride heights had thus to be slightly higher than was preferred. Despite this, it was possible to lower the car by more than 35mm, giving reasonable roll centres and roll camber correction. Finally, GSD ran its critical damping software and specified digressive damper force/velocity curves. The dampers were then revalved.

With the modifications completed, Julian reported that the car was much improved, giving a precise, stable turn-in and very good balance and traction.

He has since won many races.

NOW, LET’S compare the Scarab with the 1960 title-winning Cooper T53.

Designed by Owen Maddock, with input from Jack Brabham and Ron Tauranac, the T53 was a major step forward from 1959’s T51. The spaceframe chassis was lower and stiffer and the streamlined bodywork gave a lower frontal area and significantly less drag. The double wishbone suspension used concentric coil spring/damper units all round. The troublesome T51 transmission was replaced with Cooper’s own five-speed CS5 transaxle. The Coventry Climax FPF engine was improved with new cylinder heads. Power output was 235-240bhp and weight distribution 41.4 per cent front, 58.6 per cent rear – significantly better than the Scarab. The T53 was lighter, more powerful and had slightly less drag. The ‘laydown’ engine gave the Scarab a lower centre of gravity, but the Cooper had a lower (better) yaw moment of inertia and its central fuel tanks gave more consistent handling with varying fuel load. The Cooper’s five-speed ’box was better than the Scarab’s four, but the latter’s CV joints reduced transmission power loss.

The next stage was to run both cars through GSD’s lap simulation software, with the Scarab in its current ‘sorted’ form and both cars with an 80kg driver. This showed the Cooper to be 2.3sec and 1.84sec per lap faster at Goodwood and Monaco respectively. Just for interest, the Scarab was then ‘tested’ at Goodwood with its target power of 270bhp and was still 0.8sec per lap slower. It’s safe to conclude that, even with its engine and chassis sorted, the Scarab would not have won races in 1960. However, with a reliable 225bhp and the necessary mods, it could have been a consistent top-10 runner.

AND HOW does the Scarab compare with other front-engined cars of the period?

Introduced in 1955, the BRM P25 was initially uncompetitive but its performances improved to the point that Jo Bonnier used one to win the 1959 Dutch GP. The four-cylinder BRM engine delivered 260-plus bhp and the spaceframe chassis was sound. Compared with the Scarab, weaknesses are a high centre of gravity, larger frontal area, 50/50 weight distribution and less sophisticated suspension.

The Ferrari 246 won the 1959 French and German Grands Prix and has a very powerful V6 producing more than 270bhp. The twin oval tube chassis, leaf spring/De Dion rear suspension and Houdaille lever arm dampers are much less advanced than the Scarab.

The Lotus 16 is light and sophisticated but, like the Scarab, less powerful than the BRM or the Ferrari. It had two significant disadvantages, the troublesome five-speed sequential transmission and the Chapman strut rear suspension – very good in principle, though it applies bending loads to the damper shaft on the 16, causing excessive friction.

The TecMec combined the excellent 265bhp Maserati 250 engine and transmission with a lightweight spaceframe chassis and wishbone suspension. The car is light and powerful, but disadvantages are a high centre of gravity, narrow track and poor rear suspension.

GSD has analysed the Scarab, P25, Lotus 16 and TecMec Maserati, but not the 246. With its low centre of gravity, low frontal area, sophisticated chassis and suspension, the Scarab is probably the best chassis of the five, but the T10 transmission is heavy and the engine is less powerful than those of its rivals. In both simulation and on track, however, these five cars deliver very similar lap times in historic racing. This has led to wonderfully close competition between Julian’s Scarab, Tony Wood’s TecMec Maserati, Gary Pearson’s BRM P25, Philip Walker’s Lotus 16 and, occasionally, Rob Hall and Andrew Willis in Ferrari 246 Dinos – all very capable drivers in fabulous cars.

To summarise, the Scarab was basically a very good design, hobbled by poor engine reliability and consequent lack of suspension development. It arrived a couple of years too late and, even if reliable and properly developed, would never have beaten the Cooper T53. It did, however, have the potential to be the best front-engined F1 car of its day.

Nigel Rees is founder of GSD RaceDyn – a vehicle dynamics analysis firm. GSD has analysed more than 560 cars, many notching up victories and championship titles in historic racing.