Brabham BT55

TheBrabham BT55was aFormula Oneracing car designed byGordon Murrayand David North for theBrabhamteam owned byBernie Ecclestone.It used aBMWfour-cylinder turbocharged engine tilted over on its side to allow a clear supply of air to the rear wing. The car competed during the1986 Formula One season.It was not successful and its introduction coincided with the end of Brabham's time as a competitive team.

Brabham BT55

Brabham BT55 (next to the bottom car) on display at the 2016Goodwood Festival of Speed
Category	Formula One
Constructor	Brabham
Designer(s)	Gordon Murray(Technical Director) David North (Chief Designer) Paul Rosche(Chief Engine Designer (BMW))
Predecessor	BT54
Successor	BT56
Technical specifications
Chassis	Carbon fibreandKevlarcompositemonocoque
Suspension (front)	Pullrods,Double wishbones
Suspension (rear)	Pushrods,Double wishbones
Axle track	Front: 1,778 mm (70.0 in) Rear: 1,675 mm (65.9 in)
Wheelbase	3,408 mm (134.2 in)
Engine	BMW M12/13,1,499 cc (91.5 cu in),Straight 4,turbo,mid-engine,longitudinally mounted
Transmission	Weismann Laydown Transverse 7 Speedmanual
Weight	555 kg (1,224 lb)
Fuel	Castrol
Tyres	Pirelli
Competition history
Notable entrants	Motor Racing Developments Ltd.
Notable drivers	7.Riccardo Patrese 8.Elio de Angelis 8.Derek Warwick
Debut	1986 Brazilian Grand Prix
Races Wins Poles F/Laps 15 0 0 0
Constructors' Championships	0
Drivers' Championships	0

Concept

By 1985, Brabham had reached the limit of aerodynamic development of theirBT52-BT53-BT54 series of cars. The 1985 car won only one race whenNelson Piquetwon inFrance,and Murray decided that a radical approach was needed. Withground effecthaving been banned a few years earlier, the rear wing of a Formula One car once again created much of its downforce, but its effectiveness is reduced by the bodywork in front of it disturbing the flow of air. Brabham's tall, relatively heavystraight-fourBMW M12engine was particularly difficult to package to allow a good flow of air to the rear wing. Designers in the 1950s had addressed the same problem of reducing the cars cross sectional area by tilting the engines around a vertical or longitudinal axis by a small amount. Examples include the 1950sKurtis-KraftandEpperlyChampionship CarsandColin Chapman's Formula OneLotus 16.

Both the Brabham team and their gearbox supplier Weismann lay claim to the idea of doing this with the tall BMW engine in order to create a car with very low bodywork that would allow a large supply of air to reach the rear wing undisturbed and create more downforce without harming the straight line potential with high drag. The driver was placed in a lying down position (approximately 30° according to Murray), as had been common in the 1960s, but had become rare by the 1980s. BMW designed a special version of their four-cylinder turbocharged engine with theengine blocktilted almost horizontally (18° from horizontal).

Chassis and suspension

The car was also Brabham's first fully composite monocoque. Although the team had been the first in Formula One to make use of carbon fibre composite panels in the structure of the car in 1978, Murray had been reluctant to design a fully composite car until he understood how it would perform in a crash: he eventually persuaded Ecclestone to finance a fully instrumentedcrash testof aBT49chassis.He was not happy to employ a two piece composite chassis, preferring to develop a technique which produced a seamless monocoque of carbon fibre/kevlar composite over anomexhoneycomb. This structure was reinforced, like his earlier designs, by machined aluminiumbulkheads.

Engine and transmission

At Murray's request, BMW designed a special version of their M12 inline four engine. Differences from the standard upright unit were few, mainly concerning the oil scavenging system and the cradle in which the unit was mounted. Like the upright version the unit was not a stressed component. Mounting the engine on its side meant that the power takeoff from the unit, previously at the bottom, was offset to one side. A special 7-speed 3-shaft gearbox from American gearbox specialists Weismann was produced to deal with this.

Racing history

At the end of 1985, Piquet left Brabham after seven seasons and two world championships, joining Williams which made him a much better salary offer.Marc Sureralso left the team.Riccardo Patresereturned to Brabham, and was joined byElio de Angelis.

The aerodynamic concept worked, in that the car produced plenty of downforce without increasing drag which allowed the cars to run less wing and be among the fastest in a straight line at the faster tracks likeHockenheim,Monzaand theÖsterreichring(where Warwick was actually the quickest through the speed trap at 344 km/h (214 mph) heading into the Bosch Kurve). However, the tilted over engine and specially designed gearbox also produced many reliability problems including oil surge and a lack of throttle response that only compounded the already poor response of the BMW turbo (four cylinder turbos generally suffered more 'turbo lag' as a result of only using a single turbocharger, whileV6andV8 enginesused twin turbos and suffered less lag). This saw the Brabhams off the pace on the slower circuits such asMonaco(where de Angelis qualified 20th and last for his final race, though amazingly Patrese managed to qualify 6th),Detroit,and the then new circuits ofJerezand theHungaroringwhere acceleration counted for more than outright speed. The team scored just two points all season, both by driverRiccardo Patresewith sixth placings inSan MarinoandDetroit.As in 1985, the Brabham's performance was severely hampered by inconsistent Pirelli race tyres.

While the car's problems were primarily engine and gearbox related, most of the media and those in the F1 paddock labeled the car as a 'lemon', choosing instead to claim that the lowline concept simply did not work.

Qualifying atImoladuring Round 2 of the season highlighted both the problems and advantage that the lowline Brabham BT55 had during 1986. Acceleration out of the Variante Bassa chicane before the start-finish line showed the Brabhams as among the slowest cars when they crossed the line. However, by the time they reached the speed trap just before the braking area at Tosa, they were among the quickest. The cars were slow out of the corners, but once they got up to speed the lowline aerodynamics and the 1,350 bhp (1,007 kW; 1,369 PS) BMW turbo did their job and with the reduced drag, from the high speed Tamburello curve both Patrese and de Angelis accelerated quicker than any other cars. At Imola, the Brabhams were almost 4 seconds off pole with Patrese qualifying 16th and de Angelis 19th. The Brabham-BMWs were in fact slower than both theBenettonsandArrowswhich used the conventional upright BMW engine.

Italian driver Elio de Angelis who had joined Brabham after six years with Lotus, was the first driver to die in a works Brabham when he was killed in an accident while testing at theCircuit Paul Ricardin France. The car survived the accident relatively intact and de Angelis had only minor injuries. However, there were very fewtrack marshalsat the circuit and he was trapped in the car and sufferedoxygen deprivationdue to a fire before they arrived, prompting a review of testing safety, with changes including more marshals as well as medical staff and a required medical evacuation helicopter. De Angelis died from smoke inhalation 29 hours after the crash at the hospital inMarseillewhere he had been taken. In theBelgian Grand Prixfollowing the death of de Angelis, Brabham only entered one car for Patrese. From the next race inCanada,British driverDerek Warwickjoined the team. According to team Boss Bernie Ecclestone, Warwick, a former factoryRenaultdriver who had been driving for theTWRJaguarWorld Sportscar Championshipteam in1986after having missed out on a seat atLotus,was reportedly the only top level driver without a current F1 drive who did not contact him in the days following de Angelis' death to ask about the drive.

During qualifying for theItalian Grand Prix,Warwick and Patrese were the 3rd and 4th fastest cars through the speed trap on Monza's long front straight (behind the similarly BMW poweredBenettonsofGerhard BergerandTeo Fabi). Warwick's top speed of 347 km/h (216 mph), only 5 km/h (3 mph) slower than Berger, again showed that while the car suffered from sluggish acceleration, the lowline concept worked as it created downforce but did not increase drag and hinder top speed.

Aftermath

Murray has since summarised the reasons for the car's failure: "...I was much too ambitious in how much we lowered it. The rather tall BMW [engine] had to lie down so far it produced a heavily offset crank needing a special gearbox and drivetrain, and what I did wrong was to try to do it in the time available.

Secondly, the engine never worked properly in the lay down position. The exhaust and turbo system was a nightmare and it had incurable oil surge and drain problems in corners. One way it was OK, but not the other.

The weight distribution gave dynamiccentre of gravitymovements that messed up the traction.

And then Bernie [Ecclestone, owner of the team] who is totally non-technical and had always left that side completely to me, started to get involved on the technical side. We had had 16 years with never a cross word until then, and things were changing with his deeper and deeper involvement in [theFormula One Constructors Association]. ThenMcLarenmade approaches to me and I just felt it was the end of the road at Brabham. "

Murray also stated in an interview towards the end of the 1986 season that despite the BT55's record, he still believed in the lowline concept pointing out that the cars problems were engine related. He said that the car would have worked better had the BMW been a more compactV6rather than a straight-4.

Murray left the team at the end of the year to join rivals McLaren where he replacedJohn Barnardas the team's Technical Director. The very successful1988McLaren MP4/4is usually said to have been based on the BT55 concept, but that has been disputed, and that it was primarily a development of its predecessor, theSteve NicholsdesignedMP4/3.

Brabham regrouped with the much more conventionalBT56,but had to re-use the tilted over BMW engine and a new, 5 "shorter, Weismann 6 speed gearbox as the German manufacturer, already reducing its involvement in Formula One, had sold the supply of conventional engines toMegatronfor use byArrows,and laterLigier.BMW pulled out of Formula One altogether at the end of 1987. Bernie Ecclestone sold the Brabham team to Alfa Romeo and the team missed the 1988 season.

Complete Formula One results

(key)

Year	Entrant	Engine	Tyres	Driver	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	WCC	Pts.
1986	Motor Racing Developments	BMW M12/13 S4tc	P		BRA	ESP	SMR	MON	BEL	CAN	DET	FRA	GBR	GER	HUN	AUT	ITA	POR	MEX	AUS	9th	2
				Riccardo Patrese	Ret	Ret	6	Ret	8	Ret	6	7		Ret	Ret	Ret	Ret	Ret	13	Ret
				Elio de Angelis	8	Ret	Ret	Ret
				Derek Warwick						Ret	10	9	8	7	Ret	DNS	Ret	Ret	Ret	Ret

References

Books

• Bamsey, Ian; Benzing, Enrico; Staniforth, Allan; Lawrence, Mike (1988).The 1000 BHP Grand Prix cars.G T Foulis & Co. Ltd.ISBN0-85429-617-4.
• Hodges, David (1998).A-Z of Formula Racing Cars 1945-1990.Bay View books.ISBN1-901432-17-3.
• Ramirez, Jo (2005).Memoirs of a Racing Man.Haynes Group.ISBN1-84425-238-8.
• Staniforth, Allan (1994) [1988].Competition Car Suspension.Haynes.ISBN0-85429-956-4.

Magazines

• Howard, Keith (June 2006). "Carbon fibre". Motorsport. p. 52.