Washington  - The process of machining the fastest wheels in automotive history has begun. The aluminium discs will be fitted to the Bloodhound Supersonic Car, which will endeavour to break the world land speed record (763mph) later this year.
Castle Engineering near Glasgow is leading the industrial consortium that is preparing the wheels. These 90cm discs are a crucial element of the Bloodhound concept, and will have to endure huge loads as they spin at over 170 revolutions per second.
Calculations indicate that at peak speed, the wheels will be generating 50,000 radial g at their rim. That's 50,000 times the pull of gravity. ‘What does that mean? It means that a bag of sugar sitting on the wheel when it's stationary would weigh more than an articulated lorry when the wheel is turning at full speed,’ explained Conor La Grue, the components chief on the Bloodhound project.
‘There are parts of this car where if we have a problem, the driver Andy Green can simply shut them off and bring the vehicle to a stop. But if we have a problem with a wheel, Andy is going to crash. So the design and performance of the discs are absolutely mission-critical,’ he told BBC News. Bloodhound SSC will use a Eurofighter jet engine bolted to a rocket to take it through the sound barrier. The ultimate aim is to push the land speed record beyond 1,000mph (1,610km/h) in 2016. The attempts will be made on a specially prepared lake bed in South Africa.
In rotations per minute (rpm), the wheels will reach a staggering 10,500. An F1 car would ‘only’ do about 2,500rpm. Exactly how fast Bloodhound's wheels will actually turn, however, is something of an unknown. There will come a point when the vehicle is going so quickly that the discs will not be able to keep up. They will slide. ‘Rudders’ might be a good description of them at that stage. Finding a wheel that can cope with the stress of running at 1,000mph ‘was my first and hardest piece of homework on Bloodhound,’ says La Grue.
Not only do the 91kg discs have to maintain their integrity during rapid rotation, they must do so while being blasted by small pieces of grit. The ‘race track’ at Hakskeen Pan in the Northern Cape has been cleared of all stone debris larger than a pea, but, even so, the top dirt layer on the lake bed will kick up. Particles lifted by the front wheels will hit the back ones with the velocity of a bullet. If there are any imperfections, any cracks, in the discs - then this assault could trigger a catastrophic failure. Lockheed Martin UK and Innoval Technology led the early research and design work on the wheels.