Anatomy of a Top Fuel Bike
Below is the anatomy of a typcial Top Fuel Bike, however all bikes vary.
According to the rules there can be no computer controlled functions on the bike at all but teams can log data such as exhaust temperatures, supercharger, fuel pump and injector pressures, fuel flow, clutch and gearbox slip and G force etc. to maximise the bikes potential and help tune the engine for the next run.
Approx 1000+ Horsepower.
0-60mph in 0.7 seconds.
0-100mph in 1.1 seconds.
1-220mph in under 6.3 seconds.
1. Tyres and Wheels
Side driver PM rear wheel shod with a 14" wide Mickey Thompson slick tyre. Lightweight Performance Machine front wheel shod with 3.5" wide Cooper Avon tyre. Tyre pressures typically between 5 and 7psi.
A hand crafted aluminium alloy or composite multiple piece body is attached to the chassis with quick release Dzus fasteners. On the faster bikes a rear 'wing' is fitted to provide down force hence optimal traction.
Delivery of fuel to the engine is provided by a timed enrichment system running in parallel with the clutch control system. The volume of fuel increases in the line with the increase of clutch pressure to keep the fuel to air ratio correct for the amount of power that the engine needs to produce at any given point during the run. Put simply, the engine does not need the same amount of fuel on the start line as it does 3 seconds into the run.
Sitting in front of the engine is a belt driven compressor that literally rams air at a colossal rate into the engine. A typical supercharger turning at 11,000rpm will displace 110,000 cubic inches of air per minute.
5. Fuel System
Delivery of fuel to the engine is provided by a timed enrichment system running in parallel with the clutch control system. The volume of fuel increases in line with the increase of clutch pressure to keep the fuel to air ratio correct for the amount of power that the engine needs to produce at any given point during the run. Put simply, the engine does not need the same amount of fuel on the start line as it does 3 seconds into the run.
Unlike the car the only braking system used for the Top Fuel Bikes are two 11" diameter PM cast iron brake rotors and 6 piston callipers at the front and an 11.5" PM cast iron rear disc and 6 piston calliper at the rear. The bikes have the most difficulty in slowing down from a high speed run as they do not have the benefit of the hugely effective parachutes used by the cars.
The power elixir that helps coax more than 1 horsepower from each of the engines cubic centimetres is the fuel - nitromethane. Nitromethane is produced by the nitration or propane; the end result is CH3NO2. Typically 85-90% is used with the remainder a dilutant of Methanol. The Nitro is fed to the engine by a fuel pump delivering between 10 and 20 gallons per minute and 4,000rpm. During warm up procedure, burn out and a quarter mile a Top Fuel Bike can gulp almost 5 gallons of fuel costing around £35 per gallon.
A Top Fuel Bike chassis is typically fabricated from approx. 20 metres of 4130 chrome moly tubing.
The big advance in performance in recent years has been due to more efficient magnetos. Modern magnetos are so powerful they have allowed greater amounts of fuel to be burnt efficiently, therefore increasing the power output of the engine. Coupled with this is the multiple advance and retard systems now available that allow the Crew Chief to change the timing of the ignition spark, either increasing of reducing power, to give optimum traction. The magnetos used on the fastest bikes are one and the same 44 Amp units used on the Top Fuel cars.
Power is transferred from the engine to the transmission by way of a huge Kevlar reinforced Gates Polychain rubber belt. To prevent a loss of traction a complex timer controlled hydro - pneumatic clutch system is used. Centrifugal force on the clutch arms creates pressure on the 3 friction and 2 steel 'floater' plates. The pressure is increased gradually in a series of minute stages. This involves a hydraulic and sometimes air over hydraulic ram or 'cannon', the speed of movement of which is controlled by a series of timed adjustable restrictors. The clutch will slip for approx two seconds into the run until complete lock up with the engine and transmission is achieved. After this point the rider selects second gear by way of a handlebar button applying over 250psi to a planetary two speed gearbox.
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