Home-grown drag racer Alec Coe does a burn-out before each methanol-fuelled rail drag car race in the UK’s Supercharged Outlaws class, because it’s essential to leave a layer of rubber on the racetrack that gives the dragster grip as it rockets away from the start line, he tells Sharon Ann Holgate.
How do you do the burn-out? ‘You drive your rear wheels into what they call the burn-out box, which is a section of track with water laid down on it, then just floor the accelerator. The water allows the wheels to spin freely, reducing the load on the gearbox and back axle. The wheel speed is around 200 mph (321 kp/h), and the tyres actually grow by 4 to 6 inches (10.2 to 15.2 cm) in height because they are so flexible. The dragster gradually comes out of the water and when it gets on to the dry tarmac, the tyres really smoke. You can’t touch the tyres after— they’re so hot they’d blister your hands.’
Hang on, your tyres grow? ‘The tyres are really, really soft to give them grip, and because they need to expand once you’ve picked up speed. The bigger the tyre gets, the quicker you’re going to run. If my tyres are 33 inches (83.8 cm) high and 15 inches (38.1 cm) wide, when they expand they will go up to probably 38 inches (96.5 cm) high.’
But how does that actually help you to go faster? Dr James Brighton, head of the Centre for Automotive Technology at Cranfield University explains: ‘As the tyres revolve faster and faster they grow due to centrifugal force because their side walls are very flexible. This increase in tyre radius makes for a quick run because it acts like an automatic gearbox, without the weight and efficiency penalty, but still keeps the dragster engine operating at the optimum rpm (revolutions per minute) to give maximum power throughout the run.’
Does the burn-out do anything else to your tyres? ‘Yes, it cleans the tyres. The hot, soft tyres pick up every bit of stone and dust. If you left the line with dirty tyres, one could be dirtier than the other and lose traction. The back axle has a locked differential, which means both rear wheels rotate at the same speed, so if one wheel loses traction the car is going to turn, and you need the car going dead straight. You need to pump the tyres up identically. About half a pound difference in pressure from one side to the other could mean half an inch difference in tyre height, which could turn you left or right.’
Top Fuel Dragster
- Runs on a 90% nitromethane 10% methanol fuel mixture.
- Custom-built V8 engine produces 8000 bhp.
- Burns 1.3 gallons of fuel a second during a race.
- Pulls 6g from the start line.
- Accelerates faster than a NASA rocket launch.
- Each rear tyre costs $700.
- Top speed over 300 mph (482 kp/h).
Start Your Engines
Seasoned drag racer Lee Gallimore races methanol-fuel adapted drag cars at the Shakespeare County Raceway in Warwickshire. Here he tells Sharon Ann Holgate how it feels to race a drag car.
What does the acceleration of a drag car feel like? ‘My car will go from standing still at the lights to 18.3 m down the racetrack in 1.04 seconds. The acceleration is very, very fierce. We’re pulling around 3.5 to 4 g from the start line. It took me six years to get comfortable with that.’
How do you get a fast start in a race? ‘You have to slow your breathing to bring your heart rate down so it will control the adrenaline, and the blood pressure in your brain. As soon as the four amber lights flash on, that’s when I’ll leave, so I’m just going over the line as the lights change. It takes about 0.2 or 0.3 of a second from your eyes focusing on that light for your brain to react and tell your foot to press the accelerator. What we try to do is beat the brain function by anticipating the light before it has actually gone green.’
Do you feel the acceleration for the whole run? ‘There is constant pressure of g force from the minute the accelerator goes to the floor to when the car rolls to a stop. At the top end of the run, when it’s stopping with the parachute, you can pull more than during the acceleration and it snatches you forward into the safety harness.’
Many drag racers have lost their lives since the 1950s—doesn’t that scare you? ‘It’s a very dangerous sport. But we know what the dangers are and do everything we can before we get in that race car to make sure it is safe. Every nut, bolt, and bracket is checked, as are the brakes and parachute. You never, ever take the car for granted. We also have a safety harness, helmets, neck restraints, a fireproof suit, and a roll cage.’
© IET. Reproduced with permission.