Thunderbolt (car)

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Thunderbolt
Manufacturer	Bean of Tipton
Production	one-off
Body style(s)	land speed record car
Layout	twin steering front axles, single driven rear axle with twin-wheels
Engine(s)	Twin Rolls-Royce R-type V-12 aero engines
Transmission(s)	Coupled gearbox and single final drive
Curb weight	7 tons

A British Land Speed Record holder of the 1930s, driven by Captain George E.T. Eyston

Records held

Between 1937 and 1939, the competition for the Land Speed Record was between two Englishmen: Captain Eyston and John Cobb. Thunderbolt's first record was set at 312.00 mph on 19th November 1937 on the Bonneville Salt Flats. Within a year Thunderbolt returned with improved aerodynamics and raised its record to 345.50 mph on 27th August 1938. ^[1]

This record only stood for a matter of weeks before John Cobb's Reid-Railton broke the 350 mph barrier and raised it to 353.30 mph on the 15th September 1938, as Eyston watched. This inspired him to take Thunderbolt to a new record of 357.50 mph. Cobb had held the record for less than 24 hours.

Eyston and Thunderbolt held the record for almost a year, until Cobb took it again at a speed of 369.70 mph on 23rd August 1939. This was the last record attempt before WW2. Although Cobb returned after the war and further developed his car to exceed 400 mph, Thunderbolt never attempted the record again.

The car itself

The leading Land Speed Record cars of the period had taken two approaches to obtaining power: either using the latest and most sophisticated aero-engines available, or combining multiple engines together. Thunderbolt simply used both techniques, to produce an unprecedentedly powerful car. In its day, terms like "leviathan" and "behemoth" were commonly used to describe the 7 ton car, over twice the weight of its competitors.

The engines were a pair of Rolls-Royce R-type V-12 aero engines, as previously used singly in Malcolm Campbell's Bluebird of 1933. Indeed one of Eyston's spare engines for the record attempts was on loan from Campbell. There were so few of these engines built (around 20) that many of them had illustrious careers over several different records. One of Thunderbolt's had already powered the Schneider Trophy winner. Each engine was of 36.5 litres capacity, supercharged, and had an individual output power of 2,350 bhp. Handling all this power through a single driven axle required great innovation in metallurgy and in manufacturing the geartrain, as well as water-cooling the completed transmission.

The chassis and bodyshell were built at the Bean works in Tipton. ^[2] There were three axles and eight tyres. The two leading axles steered and were of varying track, so that each tyre ran on a clean surface rather than following a rut. The driven rear axle used twin tyres to reduce the load on them, a technique already used by Bluebird. Separate panels of polished silver Birmabright, a new aluminium alloy, clad the chassis. The body never had the aerodynamic refinement of the Railton Special and was distinctly blocky in appearance. At the rear was a large triangular tailfin, flanked by a pair of hydraulically-activated air brakes. ^[3]

When first built there was a large eight-sided cooling air intake at the front, replaced by a smaller oval intake for the 1938 season. Another improvement for this second attempt was to paint a matt black arrow onto the side of the car. During the first attempts, the new photo-electric timing equipment had failed to detect the polished aluminium car body against the brilliant white salt.

For the 1939 attempts, the streamlining was increased further. A rounded nose filled the open radiator air intake and the stabilising fin was removed, all leading to an appearance more like Cobb's Railton.

Thunderbolt today

Thunderbolt toured New Zealand during WW2, but was destroyed by a fire. Engine remains can be seen in the Museum of Transport and Technology, Western Springs, Auckland, NZ.

Another surviving engine can be seen in the Science Museum in London.