CFD key to British-designed bike's world record attempt

A British design engineer is developing a unique design of motorcycle in an attempt to break the current world land speed record on two wheels. Dean Palmer reports

A British design engineer is developing a unique design of motorcycle in an attempt to break the current world land speed record on two wheels. Dean Palmer reports

A UK engineer is planning to smash the 15-year old world land speed record on two wheels on a novel, 400mph, jet-powered motorcycle.

The developer is Ben Kerrell-Vaughan, project design engineer at British motorcycle manufacturer Triumph Motorcycles based in Leicestershire. He told Eureka: "I'm developing the machine for an attempt on the world record in 2008. The outright land speed record for bikes stands at 322.15mph, set in 1990 by American Dave Campos' Harley-powered EasyRider streamliner. My target is 400mph."

While Kerrell-Vaughan conceded that Campos' record is around as fast as a wheel-driven motorcycle can hope to travel, he believes his jet-powered design, or Cyclone, is capable of reaching, even surpassing, the 400mph mark.

His design utilises a General Electric J85 turbojet taken from a US military Northrop T38 Talon fighter trainer aircraft. The turbojet will give the bike more than 2,450 lb of thrust. In theory, this thrust would accelerate Cyclone at 2g from standstill to beyond 630mph. But getting any vehicle to travel this fast is unrealistic. As Kerrell-Vaughan explained: "Our target speed is 400mph. In order to reach this, the bike will need to be stable and controllable. So I'm developing a stiff ladder-shaped frame that connects two swing-arms. The front wheel will have one as well as the rear, to help keep the bike's long, low profile."

Even though the motorcycle is designed purely for straight lines, hub centre steering is being incorporated to enable course adjustments. Each wheel has just 50mm of suspension travel to cope with any imperfections on the dry lake bed on which Cyclone will attempt its record run.

There's also a full roll cage made from steel, into which the rider (Kerrell-Vaughan himself) is strapped to give much-needed protection should the record attempt go wrong.

Aerodynamics is also key. Drag coefficient will be around 0.15 or below with a fully enclosed bike body. The body shape, which is currently a 'teardrop' design, will provide around 220N of downforce on each wheel at around 300mph. This, said Kerrell-Vaughan, has been proven to work well in other streamliners and is sufficient to keep the vehicle safely on the ground. Overall length of the bike is 4.65m with a wheelbase of 2.93m.

But the most crucial engineering challenge to overcome at such high speeds will be traction. As Kerrell-Vaughan explained: "Rear tyre slip during acceleration and at very high speeds limits the amount of power that can be put down onto the road. So increasing engine power doesn't necessarily result in higher speeds. Jet propulsion removes this obstacle and allows the boundaries to be redefined, so speeds in excess of 400mph are a real possibility."

Basically, the effect of a jet turbine accelerating and spinning at 16,500rpm produces a variety of forces, which will need to be countered if the rider is to remain in control. And this is where specialists from the University of Hertfordshire's aerospace, automotive design and engineering department are helping Kerrell-Vaughan develop systems that will neutralise the effects of the engine rotation. In particular, this work will look at the most suitable method of integrating the jet engine and chassis.

"A decision has yet to be made on whether we should run the bike on profiled aluminium rims or specially constructed tyres," said Kerrell-Vaughan. "Current land speed racing tyres are only rated at around 350mph. Some tyres have reached 400mph but only on four-wheeled vehicles. Basically, if tyre manufacturers can develop a tyre capable of running reliably at 400mph, we'll go with that. If not, we'll use profiled aluminium rims."
Kerrell-Vaughan is experienced when it comes to aerodynamics and traction of motorcycle designs. He worked as a chassis engineer at Triumph and was involved in the development of the front and rear suspension systems on Triumph's Daytona 1300 model back in 2003. Whilst this model had to overcome 4% wheel slip at 180mph on a tarmac surface, Cyclone will have to cope with 8-10% wheel slip on the Salt Flats in the US.

Particular areas of investigation for the University of Hertfordshire will include the type of air intake design. The options are to use twin fuselage intakes either side of the front wheel for the jet engine, or a single intake with an aerodynamically sound front wheel fairing within the intake.

The exhaust system will also need to be assessed. A divided exhaust system with twin jet pipes and nozzles is one option. Another is to have a single jet pipe system with a temperature, pressure and aerodynamically sound wheel fairing within the jet pipe. A single offset jet pipe system is also an option here.

Neutralising the gyroscopic effects of the rotating jet turbine presents another potential problem area for Cyclone. A mechanical system will be required to remove both axial torque reaction during engine speed changes and gyroscopic precession during axial pitching of the bike, such as during parachute deployment at high speed.

The University of Hertfordshire will also undertake studies into the best overall form given aerodynamic requirements for lift optimisation, flow stability, centre of pressure position and aerodynamic stability (particularly during cross-wind conditions), given the nature of two-wheeled vehicle dynamics. This work will include looking at the use of retractable air brakes for emergency stop assistance in the case of parachute failure.

As well as help from Hertfordshire University, Kerrell-Vaughan will also have the support of two further British companies. Triumph itself has offered its test and inspection facilities at its Hinckley site. The other company, Engenuity, will work closely with Kerrell-Vaughan and the University of Hertfordshire to optimise the shape of the chassis, using its expertise in structural analysis, motion modelling and computational fluid dynamics (CFD).

Engenuity, which has extensive experience in Formula One and motorsport vehicle dynamics, will create motion models of the bike's dynamics, including the jet engine, suspension, parachutes and brakes, in order to understand vehicle behaviour during transient engine/chassis manoeuvres, the structural analysis of the vehicle frame and the overall aerodynamics of the vehicle to simulate and assess vehicle drag and lift.

Apart from Cyclone, there are three other competing bike designs, which will challenge the world speed record over the next few years. However, Cyclone is unique in that it is the only design where the rider sits in the familiar forward position. This, said Kerrell-Vaughan, "gives the rider a more familiar, natural feel, which is important when travelling at such high speeds". The other three designs use the familiar 'lie back' position.

Currently, Cyclone exists only as a concept and to take the idea to market Kerrell-Vaughan requires sponsorship, around £150k in total, to purchase components and materials for the bike and to actually start manufacturing a prototype. Any interested parties can find more information from the Cyclone website, www.motorcylespeedrecord.co.uk

Author
Tom Shelley

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