Posted 13 April 2012 - 22:58
I have noted many of the questions and answers on this bulletin board about the Bugatti
Type 57 Tanks. If the following about the Type 57G 1936-37 is of interest, I shall be happy
to continue covering the 1939 Le Mans winning car, the 1937 T57S45 Tank, as well as
other T57Gʼs.
Part 1: Type 57G 1936-37
There are several books available about the successes of the T57G Grand Prix sports
cars, yet there are massive gaps in the story of their evolution. I have had a passionate
interest for the furious beauty of the Bugatti ʻTanksʼ since 1971 and have developed my
knowledge of them along with strong convictions about their development. Some of the
following opinions do not necessarily agree with more formal Bugatti historians or their
publications. Nevertheless, this is my interpretation of the Type 57Gʼs known data, history
and development, along with observations and a little analysis of Bugattiʼs 1934-35
competition record which lead to these cars. For a technical overview of the racing T57G,
it is important to recognize its origins as well as to understand its siblings.
The T57 touring model was the progenitor, with a wheelbase of 3.3 metres and a track of
1.35 metres. The T57S was a lowered and shorter sports car version of the T57, with a
wheelbase of 2.98 metres and track of 1.35 metres. Its low slung chassis frame was
characterized with deep sections at the rear, permitting its rear axle to pass right through it.
Its competition sibling, the T59 was a Grand Prix racing car with a wheelbase of 2.6
metres and track of 1.25 metres. The T57 and T59 were designed concurrently from 1932,
and the T57S in 1935. They shared a clearly common engine design architecture, yet each
version is different in many details and materials. The T57 engine has a wet sump
lubrication system, whereas the T59 and T57S a dry-sump version for improved
performance. Now we come to the origin of some confusion.
In all Bugatti publicity material the ʻTankʼ Grand Prix sports cars of 1936-37 were always
known as T57S, whilst their factory designation in documents and records was T57G. The
ʻGʼ was originally ʻGPʼ for Grand Prix. That is to say, this particular T57S was the Type 57
Grand Prix racing version of it, sharing its lowered chassis on a wheelbase of 2.98 metres.
It used the T57S hollow front axle which was specially adapted to accept GP T59 wheels
and brakes, where likewise, the T57S rear axle was also modified to accept the GP T59
wheels and brakes. My personal opinion regarding all Bugatti Type numbers, is that they
should be considered as project numbers. Thus, ʻT57GPʼ almost certainly began as a
racing engine project linked to the T57S project, where its ʻGPʼ designation in the drawing
office could embrace any additional parts specially required for its marriage to the standard
T57S chassis and T57S engine, such as special material valve seat, or an increased
capacity radiator etc. The ʻSʼ in T57S probably meant ʻsurbaisseʼ - ʻspecially loweredʼ,
although some believe it stands for ʻsportʼ. On the other hand, in 1937, Bugatti ran a T59-
framed, T59/57G-powered car with a chassis number 57248. This car was formally
designated as a T57 ʻSportʼ, so it seems unlikely that the ʻSʼ of the longer wheelbase T57S
was intended to be ʻSportʼ. The T57 and T59ʼs respective engines however, although
originally being different in capacity, firing order and component materials, had a generally
identical design pattern. As a result, there was always an inherent potential for some
degree of crossover of individual parts between them, even though the chassis design of
the three was distinctly different, as too their respective crankcases; wet or dry sump. I
strongly believe that Jean Bugatti - director of design during the creation and development
of the T57, T59 and T57S - considered all three cars as ʻT57ʼ variants.
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A historical overview is also important to consider. During 1934, it was apparent that the
performance of Bugattiʼs T59 Grand Prix cars was no match for the technically superior
state-sponsored German racing machinery. This recognition and frustrating acceptance
got to a point where Bugatti disbanded the racing team with conspicuous publicity at the
end of the year, including selling off four of the nine, now clearly redundant, Type 59 racing
cars already built. For 1935, Jean Bugatti decided to concentrate his limited resources on
the development of a super sports car to replace the outdated Type 55. The outcome was
the creation of a short wheelbase and technically refined version of his 3.3 litre Type 57
touring car; - the Type 57S model. Traditionally, the House of Bugatti would always ensure
there was a more competitive version of their road-going sports cars; hence the T57G.
Consequently, the ʻGʼ engine was a ʻGrand Prixʼ version of the T57S power unit, where its
refinement evolved as a hybrid, combining the very best characteristics of the T57 and
newly redundant Grand Prix T59 engines; albeit on an extremely limited budget.
The prototype T59 began in 1932 with a 2.6 litre power unit, given a bore and stroke of 68
x 88mm, but for production this was altered to 2.9 litre using the T57 engine block with its
bore of 72mm along with the 88mm crank. In 1933 however, the T59 crankcase was
cleverly redesigned, simply by tilting the previously vertical oil pump and drive outwards to
provide clearance for a 100mm stroke crank throw. This modification needed only the
minimum of change to the original wooden engine block and sump patterns. By now, the
3.3 litre capacity of the T59 engine was effectively the maximum the design would ever
permit, where realistically, increased power could only ever come from higher engine
revolutions. Unfortunately, as engine speeds increased, racing mechanicsʼ note books
record crank and block breakages, and subsequent replacements. Retrospectively, the
reason is relatively straight forward. The T59 crankshaft utilized a 4-4 array whereas the
T57 used a 2-4-2 version; both having distinctly different firing orders, yet the 2-4-2 was
much smoother running. The 4-4 crank layout originated from Ettore Bugattiʼs first
successful straight-eight, by coupling together two of his Type 13 four-cylinder engines in
1912, placing each crank plane of four at 90 degrees to each other. This arrangement
worked extremely successfully at the relatively modest engine speeds used during the
1920ʼs, but as speeds began to exceed 4,000 rpm for prolonged periods, a secondary fore
and aft rocking couple placed increasingly excessive stress on crankshafts and engine
blocks; draining power too. The mechanicʼs note books indicate breakages in areas
consistent with extreme fore and aft rocking couple forces. These mainly take the form of
near-centre journal crank breakages, and/or cracking of engine block casings by twisting,
as well as sometimes breaking the camshaft drive tower lower flange.
For Jean Bugatti, technically more sensitive to modern developments than his father, the
smoother running of the 2-4-2 crank of the T57 was an obvious improvement which would
enable higher engine speeds. It seems that rebuilding them using specially lightened T57
pattern crankshafts along with high-lift profile T57 camshafts, prevented further breakage
problems. It is possible that the first prototype T59 engine to be fitted with a 100mm stroke
crank was modified using 2-4-2 T57 specification components, and so became an
example found capable of revving higher with reliability. Significantly, it is apparent that as
early as mid-1934, lightened Type 57 pattern crankshafts were being successfully fitted as
replacements into some of the Type 59 racing engine crankcases. We may see therefore,
that the original T59 racing power unit had incrementally evolved into a T57 specification
engine within a T59 dry-sump crankcase. Effectively, by the end of 1934, the embryonic
T57S and G engines had almost arrived in the latest form of T59 engine. As an aside, the
2-4-2 crank array of the T57 was so smooth running and reliable at high speeds that Rolls-
Royce chose the 2-4-2 arrangement for their own straight-eights in the Post-War period.
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Interestingly, during 1935 and having officially abandoned racing, Bugatti entered just one
or two of his cars in numerous competition events throughout the year. Externally, these
were either GP T59 or T57 Grand Raid types. The latter version was a long-wheelbase
T57 with a tuned engine, having its radiator and bonnet line lowered by 80mm, and its
steering column dropped down correspondingly. A version of the GR included the Ulster
TT entries, although for the Brooklands BRDC 500 Mile Race for normally aspirated cars,
a T59/57 (G prototype?) powered GP T59 appeared. Whilst looking just like a Grand Prix
T59, it was formally entered as an unblown Type 57, so we can justifiably assume it had a
chassis number to comply with British import regulations. A T59-framed car exists with the
chassis number 57248, this being a T59/57G hybrid, known as the T57 ʻSportʼ or ʻKing
Leopold Carʼ. In addition to cylinder head and manifold refinement, we find special material
billets for crankshafts and camshafts, as well as high strength steel connecting rods, and
Rolls-Royce specification alloy aluminium components. Over a period of twelve months,
these competition engines had altered significantly in their material parts; far more suitable
for higher revolutions.
That these engines and associated components were being systematically modified during
1935 can be assumed from Bugattiʼs employment of the talented development engineer,
Piero Taruffi to drive in several races. By now the increased speeds and power demanded
a refinement of the standard T59 magneto, which was previously driven from the left-hand
camshaft. The result was a revised camshaft drive tower where the magneto drive came
from a sprocket in the cleavage between the camshafts; being directly powered from the
intermediate camshaft drive gear. This meant that the magneto would now run at engine
speed, being twice that of the original, providing a much more powerful spark. Also, being
closer to the rotational stability of the flywheel, it was less susceptible to torsional vibration
at higher revolutions. This special modification enabled precision with increased ignition
flux, more suitable for developing greater power through higher engine revolutions. With
greater power came increased engine heat, so a bolted steel top plate was fitted to the
cylinder head to ensure free passage of coolant around the valves and combustion
chambers, as well as increased coolant capacity above them. Some T59 engine photos
show seven-branch coolant risers; a modification which could only be achieved with a
bolted top plate. Additionally, an increased capacity oil cooler also helped to maintain a
reliable engine lubrication temperature. By the beginning of 1936, Bugatti had evolved a
reliable racing version of the Type 57S dry-sump engine - the T57G - which even in
unblown form, matched the road-going performance of the original supercharged T59!
The T57G super-streamlined ʻTankʼ made its maiden appearance at Montlhery for
functional and performance testing on the 8th and 9th June 1936. By the end of these two
days of successful exhibition, officials and observers were totally astounded by the carʼs
performance and reliability, prompting motoring writersʼ praise and surprise that its
development had been such a well-kept secret! However, I believe that during the evening
of the 9th, as everyone was packing up to leave, the prototype left the road at Virage de la
Ferme and crashed. This is the first acute bend at the end of the long straight returning to
the Autodrome after passing the water tower. The wrecked prototype is illustrated on page
60 of Bernhard Simon and Julius Krutaʼs book, ʻThe Bugatti Type 57Sʼ. The damage to its
alloy bodywork was such that the car could never have been repaired in time for the ACF
three weeks later. Consequently, it is my view that four cars were originally constructed,
where only three were ever seen at the ACF, and then later the Marne GP. Affirmation that
four cars were originally constructed may be established from the observation in
photographs, that the racing pit counter at the ACF show four bays allocated, along with
four race number headings. These being, 82, 84, 86 and 88, although only numbers 82,
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84 and 86 were actually used by the three ʻTanksʼ seen. Surely Bugatti was not so
extravagant as to finance four bays and numbers for just three cars? Undoubtedly, the
fourth Tank was written off, so that when the factory accountant, Pracht, allocated three
chassis numbers the day before the ACF, only three ʻTanksʼ really existed. The observant
will note that of the three Tanks, each is slightly different in detail, so can be individually
identified from some angles. Most obvious, is that Wimilleʼs car has high front wheel
cooling air intakes, whereas the other two have low ones. Additionally, each has a different
bonnet shape where it meets its fasteners, and the fastener position varies too between
them. It may also be noted that the two-tone blue ʻflashʼ is slightly different at the front of
the cars as well. From these little details, it is possible to establish that in the ACF, car
number 82 was race number 14 in the Marne Grand Prix. Car number 84 in the ACF was
race number 12 in the Marne, and car number 86 in the ACF was race number 44.
The three cars were weighed-in by officials at the Marne, but curiously, each had a unique
weight. It is known that the surviving car, which is the Le Mans winner of 1937, also seems
to be car number 12 in the Marne, and race number 84 at the ACF. Moreover, when
stripped for refurbishment in the early Sixties, it was seen to have a chassis lightened with
holes and utilized light-alloy cross-members. However, at the Marne GP, this car was
originally the heaviest at 1265 kg. The lightest car was Benoistʼs, being number 82 at the
ACF and number 14 at the Marne, weighing 1225 kg. Car number 86 at the ACF and
number 44 at the Marne weighed-in at 1245 kg. Each car was different by around 20 kg,
so the range between the heaviest and lightest was a considerable 40 kg. This range of
weight is conducive with the difference between a standard T57S chassis and a drilled
one, as well as conducive with the difference between one with a drilled chassis and one
with a drilled chassis and alloy cross-members. Additionally, there would be further slight
values between cars using standard T57S components, and those enjoying the benefit of
magnesium castings. Overall, given that the crashed prototype and Wimilleʼs car are
essentially similar in appearance, it seems probable to me, that these two Tanks were the
first ones constructed using early T57S components, and the other two with low tyre
ventilators, were constructed later; one with a drilled chassis, and the other with a drilled
chassis and alloy cross-members, with some magnesium castings. Inexplicably however,
Benoistʼs lightest car disappeared after the 1936 Paris Salon and was never seen again.
The two cars seen at Le Mans a year later, now greatly modified, have body details which
suggest that the winning Wimille/Benoist car number 2, was previously 84 at the ACF and
number 12 at the Marne in 1936. Likewise, the Veyron/Labric car, number 1, was
previously number 86 at the ACF and 44 at the Marne. The modifications included a new
fuel tank and spare wheel stowage, clearly necessitating that the cars be completely
dismantled and rebuilt. Given that the successful Wimille car had originally been the
heaviest in 1936, and has ended up with an extensively lightened chassis frame, alloy
cross-member and several magnesium castings, and given that we justifiably suppose it to
have originally been an early version using many standard T57S components, then it
follows that the lightest Benoist car which disappeared completely after October 1936, was
extensively utilized in the rebuild, leaving just the Wimille Tank body to be added to it. This
would make sense of the historical photographic evidence, and would be an appropriate
amalgamation for a car to satisfy both its drivers, Wimille and Benoist. This left only one
car, the Veyron/Labric one, to modify to similar standards. This scenario might also
reconcile the otherwise irrational rumour that the 1936 Wimille ʻTankʼ was rebuilt as a T57S
Works demonstrator! If the original Wimille car had an essentially unmodified standard
T57S chassis frame and running gear, then of the three cars, it was ideally placed to be
returned to the production line or rebuilt as a demonstrator.
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External body details changed during the Tanksʼ racing period. The original streamlined
prototype seen at Montlhery on the 8th and 9th of June 1936 had a pristine body shape. It
had only one central fuel filler, smooth rear wheel covers without louvres, no rear wing
ventilators, no rear jacking beams, no driverʼs flyscreen, and no leather bonnet straps. The
engine oil filler cap was located below a small access cover. By the ACF on the 28th June,
all three cars had acquired two fuel fillers, ventilated rear wheel covers, rear wing ventilator
exits, external rear jacking beams, a driverʼs flyscreen, a small flip-up cover above the
radiator filler cap, and leather straps to additionally secure the bonnet. Also, there were
long vertical ventilators each side to help cool the cockpit footwell, as well as small
ventilators each side of the scuttle, probably ducted to cool the magneto. For the Marne
Grand Prix a week later, an additional long louvre was cut into each side of the bodywork
just ahead of the rear tyres to aid cooling of the rear wheels and brakes. For the World
Record attempts at Montlhery between September and November later in the year, the
Wimille car had the long rear louvre welded back up, was fitted with larger diameter
headlamps, a higher and narrower driverʼs cowl, a wider passengerʼs seat cover to narrow
the cockpit, as well as special lockable covers for the fuel fillers. Additionally, the car
acquired a second rev-counter and other gauges, the radiator was moved about 100mm to
the left (as you sit in the car) to allow cool air to reach the carburetor; the small radiator
cap cover being correspondingly widened. Small baffle plates were added across the
radiator and oil cooler to maintain engine temperature during prolonged runs in these
cooler months. Rear wheel covers were fitted on some runs and omitted on others, as well
as the occasional fitting of larger diameter rear wheels to increase speeds. For the Le
Mans 24 Hour Race regulations, doors were cut into each side, the rear wheel was stowed
on the tail; the fuel tank being re-designed to suit. Also, an external engine oil filler cap
made access easier, a large central headlamp was fitted into the radiator intake tunnel,
and the radiator opening was increased in height to compensate for this restriction to flow.
In addition, the rear jacking beams were modified with ʻmushroomʼ heads to prevent the
car slipping off the jack, a large lamp was fitted into the right hand side of the body, and
the Wimille car acquired yet another revised dashboard layout.
I hope this information helps to clarify things for the 1936-37 T57G Tanks; especially for
model makers. Now to work on part 2.
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