The 1986 Brabham BT55 – Analysis Of A Failure

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Principal sponsor Olivetti unveiled the BT55 on January 20, 1986 claiming that it had taken 732 working drawings, 117,000 man-hours and an investment of 6.8m to produce.

In retrospect, everyone involved with the project agrees that the radical car had arrived too late. For example, the winter build phase had rushed ahead of transmission development; this, according to American gearbox expert Pete Weismann, was due to late delivery of an engine mock up, and he anticipated early transmission headaches. For his part, Paul Rosche recalls: “everything was too late – the gearbox was very late. We wanted to run earlier but it wasn’t possible – the gearbox wasn’t ready”. The greatest worry during the design phase concerned the driving position: if the drivers couldn’t adapt to the car the entire concept would have been wasted. Thankfully, the first, short test at an icy Donington confirmed that the drivers could cope, as Piquet had predicted. A second, more extensive but largely washed out test at Estoril confirmed impressive cornering power but Rosche recalls: “the gearbox kept breaking and the only thing we could see was that the oil and water temperatures were very high…”

Rio confirmed the worst. Roche got an oil temperature reading of 128 degrees – the top of his scale. He suspects it might have gone as high as 150 degrees. Water temperature and charge temperature were also too high. The car was designed to to engine bay vented but the vacuum in it’s wake was insufficient to extract all the hot air. The entire cooling system had to be revised: engine bay venting was supplemented by side venting, reducing downforce, and the oil and charge coolers had to be moved forward, compromising the weight distribution. There was also an undependable transmission to contend with, and the Brazilian Grand Prix was only a week or so away…..

As a race car, the BT55 was a failure. Throughout the season it suffered a fundamental lack of acceleration. Properly sorted, it would corner quickly and would eventually reach a high top speed, but it wouldn’t pull strongly from low to high speed. Rosche’s abiding memory is of “lots of wheelspin”. Murray says :”it came out of corners and just stopped!” He adds that the BT54 had pulled from 2.0 to 5.0 bar in around 3 seconds, while early in the season the BT55 took almost three times as long. With longer inlet trumpets and a revised exhaust system, that was improved, but Murray insists: “the engine never picked up properly out of corners”. The Rio test modifications lengthened already long charge plumbing and Murray reflects that, “in later tests, we found it had made no difference to response – the basic engine response was so poor!”. Lack of traction was certainly a failing of the BT55, and was down to the dynamics of it’s weight distribution. The Rio test modifications had taken 2% off the rear, leaving the car with a 41 – 59 static distribution, and that caused a traction problem, given a very long wheelbase and a low centre of gravity, both of which discourage weight transfer. The lack of weight transfer provided “great braking”, Murray explains, “with all four wheels sharing the load”. But as little weight went forward under braking, so little weight went backwards under acceleration and traction was poor. Additionally, Murray believes the engine suffered poor pick up due to a scavenging problem.

Murray reckons the lay-down engine didn’t scavenge properly on right hand corners, the oil in the crankcase mounting to a level in which the crank was thrashing around in it to the detriment of power output. He says “The car generated 30 – 50% higher oil temperature than the BT54 all year – we could never explain that. It needed a huge amount of oil cooling”. He points to an earlier engine he experienced which had a scavenge problem and ran hot. Rosche, however, says: “We made many tests to see if there was a scavenging problem, and never found one. I don’t think there was a problem”.

Murray reflects: “There were a lot of unsolved mysteries with the BT55”. He points to the engine’s poor pick up, and to the fact that it wouldn’t run as high qualifying boost as the upright engine. The BT55 worked well at the Osterreichring, for example, Patrese fastest through the speed trap and fourth on the grid; his best position of the season. But the upright engined, similarly Pirelli shod BMW – Benetton was only a fraction slower through the trap, and sat on the front row. Murray reckons the BT55 was cornering faster but was only running 4.9 bar boost whereas the B186 was accelerating faster and was pumping 5.3 bar. Rosche admits that boost had been constricted by the charge pipe incorporated in the engine cradle prior to Hungary. However, thereafter the integral pipe was by-passed and with the same turbo the BT55 should have enjoyed the same boost……

Both Murray and Rosche agree that the project lacked development time. Murray reflects: “In retrospect, given the resources we had, it was too big a step in the time available. We needed six months development prior to the first race”.

Steady progress was made from the shambolic Rio test to the point at which Patrese was able to qualify 6th for Monaco. From Estoril the car ran the longer (street circuit standard) inlet trumpets for better torque and response which, Murray says: “made the car more drivable and only upset the aerodynamics a little”. Monaco brought the revised exhaust: “That improved pick up a lot, it had been a disaster before…..” The Principality also saw certain elements repositioned to put more weight on the rear, to the benefit of traction.

Immediately after the encouragement of Monaco came tragedy at Paul Ricard. As de Angelis took the flat out Verrerie esses his car got out of control and, having vaulted the armco, it came to rest upside down, trapping it’s driver. Although, thanks to the inherent strength of the chassis, de Angelis’ injuries were light, fire starved him of oxygen. The Brabham team took his death very hard and Murray opted to miss the following race at Spa.

Over the summer the BT55 development programme lost momentum as the team found itself torn by internal strife. Technical decisions became political battles. For example, Murray wanted a shorter transaxle case between engine and differential to push weight back – perfectly feasible given the possibility of rolling the pinion shaft up around the parallel transverse sister shaft. Instead, the team shortened the wheelbase experimentally by cutting a section from the tank. Murray could see no logic in taking length out of the chassis right at the centre of gravity, and the experiment was not a success.

Brabham had taken on an over-ambitious project, and the team did not have the resources to cope with it’s difficult season. According to Murray, the project deteriorated amidst: ” Bad Politics, so many people putting there noses in and nothing logical being done. Energy was being put into the wrong things. The way the team had operated for the last 15 years broke down…” He often had to take a back seat as others meddled in his domain. By the end of the season he had left, and he went on to replace Barnard as Technical Director at McLaren International.

After Monaco the BT55 did not appear in the top six qualifiers once more until the Osterreichring. Warwick had the second drive from Montreal and generally it was a struggle to make the grid top 10. Warwick re-joined his former race engineer John Gentry, who had moved from the now defunct Renault team towards the the end of ’85. He was the sole BT55 runner at Brands Hatch, an old BT54 sitting in the next pit. Patrese suffered a mysterious lack of straight-line speed from the dusted off upright engined car yet lap times were equal. Murray asserts: “The underlying problem was an engine problem – the lay down engine never approached the upright engine. The BT54 was cornering slower, but accelerating faster….” Motorsport was not prepared to furnish an upright engine supply, so the experiment could not be repeated. Throughout the the year lay-down engine reliability was poor; there were a dozen failures from 29 starts. And the BT55 only scored points twice, Patrese running home sixth on each occasion. In contrast, Benetton won the Mexican Grand Prix…..

During the course of the troubled season, BMW looked seriously at running it’s own, in house team using a chassis produced by old partner March and possibly designed by Barnard. However, as March boss Robin Herd studied a proposal in June, the marque announced that it was to quit Formula One from the end of the year. Nevertheless, Ecclestone held BMW to his supply contract for ’87. However, his attempt to revert to upright engines was rebuffed – the stock was sold to Megatron.

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