The Bluebird-Proteus CN7 is a gas turbine-powered vehicle that was driven by Donald Campbell and achieved the world land speed record on Lake Eyre in Australia on 17 July 1964. The vehicle set the FIA world record for the flying mile at .
Design and construction
In 1956, Campbell began planning a car to break the land speed record, which then stood at set by John Cobb in the Railton Mobil Special. The Norris brothers, who had designed Campbell's highly successful Bluebird K7 hydroplane, designed Bluebird-Proteus CN7 with in mind.
The CN7 (Campbell–Norris 7) was constructed by Motor Panels in Coventry, supervised by Donald Stevens of Norris Bros & Maurice Britton of Motor Panels with Ken and Lew Norris as co-chief designers and was completed by the spring of 1960.
Bluebird CN7 was the first land speed record vehicle to be powered by a gas turbine engine. The Bristol-Siddeley Proteus was the Bristol Aeroplane Company's first successful gas turbine engine design, and delivered with no thrust allowed by FIA, exhaust was limited to fill in aerodynamic disturbance at the rear. The Proteus was a two spool, reverse flow free-turbine turboshaft, because the turbine stages of the inner spool drove no compressor stages, but only a power shaft. The engine, a Proteus 705, was specially modified by Norris Bros to have a power shaft at each end of the engine. These shafts are connected directly to final drive assemblies with differentials and fixed ratios of 3.6:1 providing power to all four wheels via half-shafts.
The car weighs 4 tons and was built with an advanced aluminum honeycomb sandwich of immense strength, with a fully independent double wishbone suspension. The split-rim design wheels and diameter tyres were manufactured by Dunlop. The tyre inflation specification was set by Dunlop at greater than . When the car ran at Goodwood they were set to and for record attempts was used. Bluebird has a frontal area of and a drag coefficient of 0.16, giving it a Drag area of .
Brakes consist of Girling disc brakes, inboard mounted (to reduce unsprung mass) at all four wheels. The brakes are hydraulically controlled with a back up pneumatic system operated from compressed air reservoirs. The brake discs measured in diameter and are capable of operating up to a maximum temperature of . Additional braking was provided by hydraulically powered air brakes that extended out from the rear of the vehicle. The turbine engine also provided approximately 500 hp of engine braking when the throttle was closed at , but this diminished as speed decreased.
Goodwood, 1960
Campbell demonstrated his Bluebird CN7 Land Speed Record car at Goodwood Circuit in July 1960, at its initial public launch and again in July 1962. The laps of Goodwood were effectively at 'tick-over' speed, because the car had only 4 degrees of steering lock, with a maximum of 100 mph on the straight on one lap. Its shakedown was actually at RAF Tangmere on the main runway in 1962. The press release photos were taken at Goodwood
Bonneville, 1960
Following the low-speed tests conducted at Goodwood, the CN7 was taken to the Bonneville Salt Flats in Utah, USA, scene of Campbell's father's last LSR triumph in 1935. In early September, CN7 accelerated from a standing start to just under in 24 seconds covering 1.5 miles, using approximately 80 per cent of the engine's full power. The LSR attempt however, which was heavily sponsored by BP, Dunlop, and other British motor component companies, was unsuccessful and CN7 was severely damaged during a high-speed crash on 16 September. Campbell suffered a fracture to his lower skull, a broken ear drum, and cuts and bruises. He convalesced in California until November 1960. Meanwhile, plans had been put in motion to rebuild CN7 for a further attempt.
His confidence was severely shaken, he was suffering mild panic attacks, and for some time he doubted whether he would ever return to record breaking. As part of his recuperation he learned to fly light aircraft and this boost to his confidence was an important factor in his recovery. By 1961 he was on the road to recovery and planning the rebuild of CN7.