By William Pearce

In 1935, Englishman George Edward Thomas Eyston traveled for the first time to the Bonneville Salt Flats in Utah, United States. At Bonneville on 3 September 1935, Eyston was able to witness Malcolm Campbell setting a Land Speed Record (LSR) in the last of his Blue Bird cars at 301.473 mph (485.174 km/h) covering one km (.6 mi) and 301.129 mph (484.620 km/h) covering one mile (1.6 km). In August, Eyston set a number of endurance records in his car, Speed of the Wind, which had been specially designed and built by Eyston and his partner, Ernest Arthur Douglas Eldridge. Eyston and Speed of the Wind set more records in 1936 and intended to return to Bonneville in 1937.

In early 1937, Eyston and Eldridge began the design of an LSR car to break Campbell’s record and achieve a speed greater than 350 mph (565 km/h). Campbell’s last Blue Bird car was powered by a Rolls-Royce R engine and was supported by six wheels. It was quickly decided that the new LSR car would use two engines. After consulting with Dunlop, it was determined that the car’s weight necessitated the use of eight wheels. The car was primarily designed by Eyston. Eldridge contracted pneumonia returning from Bonneville after Speed of the Wind’s successful runs in 1936. Eldridge passed away on 27 October 1937, one day before the new LSR car was first run at Bonneville.

The new vehicle’s design progressed quickly, and Eyston and Eldridge were able to use their many contacts to obtain the parts needed for the car. However, major sponsors for their effort were in short supply. Eyston had become acquainted with many people at Rolls-Royce while he was building the Kestrel-powered Speed of the Wind. Eyston was able to acquire two Rolls-Royce R engines, the same type that Campbell had used to set several LSRs and had been used to set water and air speed records. Some sources state that Eyston wanted Merlin engines. However, since the Merlin was in an early production stage at the time and only produced around 1,030 hp (768 kW), this seems unlikely. Although heavier, the R engine had proven its reliability and produced twice the power of the then-current Merlin. With the power plant decided, serious work began on the new LSR car, which was later named Thunderbolt.

Thunderbolt was built to be strong and heavy. Two frame rails, 18 in (457 mm) tall at their maximum, ran the entire length of the car and supported all major components. A radiator was positioned at the front of the car and had an elongated, eight-sided opening. Behind the radiator was a splitter that directed air that had passed through the radiator either up above the car or below it. Both upper and lower air exits were positioned between the front-most wheels, which did not have brakes. Another set of front wheels with a slightly wider track were positioned behind the first set. This configuration allowed for a more streamlined nose and ensured the second set of front wheels would not ride in the ruts created by the first set of wheels. Drive shafts connected to the second set of wheels were equipped with hydraulically actuated disc brakes at their inner ends, which were supported by the main frame rails. This arrangement provided friction braking for the front of the car. All four front wheels were used to steer the Thunderbolt and featured independent suspension actuated by transverse leaf springs.

Behind the second set of front wheels was the cockpit. While the cockpit was open, the driver sat behind a windscreen. A headrest extended behind the cockpit and was faired into the car’s body. The main frame rails ran on both sides of the cockpit. The Rolls-Royce R engines were positioned behind the cockpit and outside of the main frame rails. A supporting frame extended outward from each of the main frame rails and cradled the engines. The placement of the engines added weight on the rear axle and helped improve adhesion to prevent wheel spin.

A header water tank was positioned in front of each engine, above the supercharger and alongside the cockpit. The intake scoops for the engines protruded above the car’s body and were located just forward of the cockpit. The intake duct ran under the header tank and to the supercharger. For the outer cylinder banks, individual exhaust stacks protruded from the car’s sides. Exhaust from each inner cylinder bank was collected by a manifold and directed out the upper-center of the car with the outlets protruding above the car’s body. Between the engines and the main frame rails was a 22 US gal (18 Imp gal / 82 L) oil tank and a 48 US gal (40 Imp gal / 182 L) fuel tank.

The output shaft of each engine was coupled to the three-speed transmission through friction plate clutches. However, the final drive gear was locked in using dog clutches to prevent slip. To accommodate the two engines, the transmission was 5 ft 6 in (1.68 m) wide and located on the Thunderbolt’s centerline. The transmission alone was 2,469 lb (1,120 kg) and contained 54 US gallons (45 Imp gal / 205 L) of gear oil, which was water cooled. It was connected to the drive wheels via a bevel gear. Two wheels were mounted to the drive axle on each side of the car, and each side used independent transverse leaf spring suspension. The drive shaft extended behind the rear axle and supported a hydraulically actuated disc brake, providing friction braking for the rear of the car. Behind the rear wheels were hydraulically controlled air brakes.

A light metal frame surrounded the car and served to secure Thunderbolt’s aluminum body panels. The body was designed by French aerodynamicist Jean Andreau. The body panels were made by Birmal Boat, Ltd and covered the car except for the radiator and cockpit openings. The panel fitment to the frame was so tight that bulges were needed to provide clearance for each wheel and for the valve covers of the engines’ outer cylinder banks. Most of the panels were designed to be quickly removed, especially those covering the wheels and engines. The Thunderbolt’s body tapered back behind the rear wheels, and a vertical tail was fixed at the extreme rear.

Thunderbolt was 30 ft 5 in (9.27 m) long, 7 ft 2 in (2.18 m) wide, and weighed 13,900 lb (6,305 kg). All eight tires were made by Dunlop and were 7.75 in (197 mm) wide and 44 in (1,118 mm) tall. The tires were mounted on wheels that were 7 in (178 mm) wide and 31 in (787 mm) tall and had a steel center and an aluminum rim. Each tire and wheel weighed around 210 lb (95 kg). At speed, the tires rotated 45 times each second and became 1.5 in (38 mm) taller. Reportedly, the R engines used in Thunderbolt had been derated for reliability and produced around 2,000 hp (1,491 kW). At power, the engines consumed 9.6 US gallons (8 imp gal / 36.4 L) of fuel each minute. Engines R25 and R27 were used in Thunderbolt. R25 was previously used in the Supermarine S.6B S1596 to set an absolute speed record of 379.05 mph (610.02 km/h) on 13 September 1931. Engine R27 had previously powered S.6B S1595 to set a new absolute speed record of 407.5 mph (655.1 km/h) on 29 September 1931. Additionally, Campbell had loaned one of his spare engines, R17, to Eyston.

Design and construction of Thunderbolt took about seven months, but the actual assembly of the car took only around six weeks. The car was built by Bean Industries, Ltd in Tipton, England. Reportedly, as the car was nearing completion, a public relations representative from Castrol wanted a name for the car. Eyston said to name it whatever he liked, and the representative from Castrol decided on Thunderbolt. Eyston, Speed of the Wind, and the untested Thunderbolt left for Bonneville in late August 1937 and arrived on 3 October. Upon arrival, the weather was poor, and the Salt Flats were in a sorry state. Time was needed for everything to improve, and that was time Eyston needed to finalize Thunderbolt.

Before getting behind the wheel of Thunderbolt, the fastest Eyston had ever driven was around 170 mph (275 km/h). On 28 October 1937, Eyston made his first test of Thunderbolt and decided to push the car. The run north was clocked at 309.6 mph (498.3 km/h), about eight mph (13 km/h) above the existing record set by Campbell. On the southbound return, the dog clutches were damaged by the engines running out of sync.

While Thunderbolt was being repaired, Eyston turned his attention to Speed of the Wind. On 3 November 1937, Eyston and co-driver Albert W. Denly set a new 12-hour record at 163.68 mph (263.42 km/h) and covered 2,000 miles (3,219 km) at an average speed of 163.75 mph (263.35 km/h). On 6 November 1937, Eyston made another run in Thunderbolt. Hoping to spare the clutches, Eyston utilized another vehicle to push start Thunderbolt and averaged 310.69 mph (500.01 km/h) on the northbound run. However, the dog clutches again failed on the southbound return.

The clutch system underwent a modest redesign, and new parts were made. Some of the clutch redesign and new parts were made by Leo Goossen and Fred Offenhauser in Los Angeles, California. Eyston and the repaired Thunderbolt made another record run on 19 November 1937, with bad weather soon to close in. On the run north, Eyston shifted into second at 100 mph (161 km/h) and third at 200 mph 322 km/h). He covered the mile (1.6 km) at 305.34 mph (491.40 km/h) and the km (.6 mi) at 305.59 mph (491.80 km/h). It took just 16 minutes for Thunderbolt to be refueled and prepared for the return run with new tires. On the southbound leg, speed averages were 317.74 mph (511.35 km/h) for the mile (1.6 km) and 319.11 mph (513.56 km/h) for the km (.6 mi). Eyston’s goggles had gotten caught by the slipstream, and he had to grab them with one had while steering with the other at over 315 mph (507 km/h). All the effort had been enough—Eyston and the Thunderbolt set a new LSR of 311.42 mph (501.18 km/h) over the mile (1.6 km) and 312.20 mph (502.44 km/h) over the km (.6 mi).

In 1938, Thunderbolt was modified to improve its performance. The radiator inlet was extended slightly and rounded, with vanes added to help direct airflow. Shutters were added to the air exit to help regulate flow through the radiator. The engine intake scoops were enlarged, extended forward, and raised above the car’s body. The cockpit was enclosed by a rearward sliding canopy, and a respirator system was added. The respirator brought in fresh air from the front of the car. The headrest fairing was extended back to the center exhaust stacks. Exhaust manifolds replaced the individual stacks for the outer cylinder banks. New larger body panels without individual bulges over the wheels were installed. The vertical tail was decreased in size and modified so that it could be removed. The rear body of the car was extended for better streamlining. Coil springs replaced the heavy leaf springs used in the suspension. With all the modifications, Thunderbolt was lightened to about 12,000 lb (5,443 kg) and lengthened to about 35 ft (10.67 m).

Eyston faced a challenger in 1938 in the form of John Rhodes Cobb and his LSR machine, the Railton. The Railton was designed by Reid Railton, powered by two Napier Lion engines, and much smaller and lighter than Thunderbolt. Eyston had intended to make his LSR runs in July, before Cobb arrived at Bonneville. However, bad weather and water on the course delayed any attempts until late August, by which time Cobb had arrived. On a test run at about 270 mph (435 km/h), smoke filled the cockpit due to an issue with the friction brakes. Eyston could hardly see and struggled to keep the car on the course. He felt that the respirator prevented asphyxiation and probably saved his life. Eyston decided to rely on the air brakes until the Thunderbolt slowed to 180 mph (290 km/h).

On 24 August 1938, Eyston averaged a blistering speed of 347.16 mph (558.70 km/h) on the northbound run. The return run may have been even faster, but the timing equipment malfunctioned and did not record a speed. The camera failed to trigger, most likely due to the lack of contrast with the silver car, white salt, and bright background. On the run, salt spray from the damp course was flung off the drive wheels and damaged the aluminum body panels above the wheels.

Repairs were made, and the sides of Thunderbolt were hastily painted matte black for contrast. On 27 August 1938, Eyston made another northward run and averaged 347.49 mph (559.23 km/h) over the mile (1.6 km) and 346.80 mph (558.12 km/h) over the km (.6 mi). The return south covered the mile at 343.51 mph (552.83 km/h) and the km at 344.15 mph (533.86 km/h). With those speeds, Eyston had established a new LSR at 345.49 mph (556.01 km/h) for the mile (1.6 km) and 345.21 mph (555.56 km/h) for the km (.6 mi). However, not to be outdone, Cobb bettered those marks on 15 September 1938, averaging 350.20 mph (356.59 km/h) over the mile (1.6 km) and 350.10 mph (563.43 km/h) over the km (.6 mi).

Eyston had been preparing Thunderbolt for more speed in case Cobb took the record. The Thunderbolt’s radiator was replaced with a water tank. The radiator intake and air exit between the front tires were faired over. With the runs lasting mere seconds, the water would not completely boil over. Two small scoops, perhaps to cool the front brake, were added behind the new nose. Small bulges for the first set of front wheels were added to the body panels. The car’s vertical tail was removed. The black paint that had been hastily applied was removed, and a back high-contrast section that incorporated a yellow circle was painted on the panel covering the rear set of front wheels. On 16 September 1938, one day after Cobb took the record, Eyston and Thunderbolt made another attempt. Northward, the mile (1.6 km) was covered at 356.44 mph (573.63 km/h) and the km (.6 mi) at 355.06 mph (571.41 km/h). Traveling south, the speed was 358.57 mph (577.06 km/h) for the mile (1.6 km) and 359.64 mph (578.78 km/h) for the km (.6 mi). The runs established a new LSR at an average of 357.50 mph (575.34 km/h) for the mile (1.6 km) and 357.34 mph (575.08 km/h) for the km (.6 mi). Eyston reported no stability issues in the tailless car, but said that the lack of a radiator caused the cockpit to get quite hot on the return run as the water boiled off.

Wanting to break the 360-mph (580-km/h) mark and go faster than six miles (9.7 km) per minute, Eyston took Thunderbolt out again on 21 September 1938. Just entering the measured mile (1.6 km) on the run north at over 360 mph (580 km/h), the cover for the right rear wheels broke free. As the cover tore loose, it damaged the two right rear tires and caused them to destroy themselves. Unsure of the issues, Eyston kept the throttle down through the mile (1.6 km), which was only about 10 seconds. After the mile (1.6 km), Thunderbolt skidded to a stop three miles (5 km) short of the course’s end with its right rear corner dragging. The car was too damaged to be repaired at Bonneville. Despite the damage and extra resistance through the measured mile (1.6 km), the car’s average speed was recorded as 349.85 mph (563.03 km/h).

While Cobb returned to Bonneville in August 1939 and set new LSRs at 368.86 mph (593.62 km/h) for the mile (1.6 km) and 369.74 mph (595.04 km/h) for the km (.6 mi), Eyston decided to take some time off from LSRs. Thunderbolt had been repaired, and Eyston knew it was capable of more speed, but not much more. Rather than racing again, Thunderbolt went on a world tour and was displayed at the New York World Fair in mid-1939. The car was subsequently sent to New Zealand and displayed in the British Pavilion at the Centennial Exhibition. After the Exhibition ended in May 1940, Thunderbolt and some other exhibits were stored at the Exhibition site in Rongotai, near Wellington. The outbreak of World War II put other priorities ahead of the exhibits. Extra space at the Exhibition site was used to store wool and several aircraft and aircraft engines. On 25 September 1946, the wool spontaneously ignited, and the blaze spread quickly amongst the 27,000 bales of wool in storage. Everything in the building, including Thunderbolt, was consumed by the fire. Reportedly, the remains of Thunderbolt were still located near the site as late as December 1956. The engines had been removed before the car was on display and were preserved. Engines R25 and R27 are respectively on display at the Royal Air Force Museum at Hendon and the London Science Museum.

This article is part of an ongoing series detailing Absolute Land Speed Record Cars.

Sources:
– The Land Speed Record 1920-1929 by R. M. Clarke (2000)
– Fastest on Earth by Captain G. E. T. Eyston (1939)
– Reid Railton: Man of Speed by Karl Ludvigsen (2018)
– Land Speed Record by Cyril Posthumus and David Tremayne (1971/1985)
– The Fast Set by Charles Jennings (2004)
– Leap into Legend by Steve Holter (2003)
– “An Interview with Capt. G. E. T. Eyston” by William Boddy, Motor Sport (October 1974)
– “Thunderbolt Damaged in Speed Trail” San Pedro News Pilot (21 September 1938)
– http://www.beancarclub.org.uk/Thunderbolt/
– http://speedace.info/george_eyston.htm
– https://www.uniquecarsandparts.com.au/race_drivers_george_eyston
– http://www.stuff.co.nz/dominion-post/news/local-papers/the-wellingtonian/features/5664887/Spectacular-fire-remembered-65-years-on