First diesel military motorcycle to hit the road

A unique technology partnership between Cranfield University and California-based Hayes Diversified Technologies (HDT) has created the world’s first production diesel military motorbike – and the first bike of any kind with a purpose-designed diesel power unit.

An initial order for 522 diesel motorcycles has already been placed by the US Marines. Delivery is due to commence in early 2005. In addition, keen interest is being shown by the US Army, the UK Ministry of Defence and other NATO forces. John Crocker worked alongside project leader Dr Stuart McGuigan of the Engineering Systems Department, Cranfield University at Shrivenham, Oxfordshire to design the diesel power unit.

The challenge was to come up with a low technical risk design that was sufficiently light and powerful, and with an engine speed (RPM) range wide enough to give the level of performance required for use as a tactical vehicle. John said: “The motorcycle also had to meet strict NATO requirements for all armed forces to operate their entire inventory of vehicles and powered equipment on either diesel fuel or aviation grade kerosene. “This capability has major logistic advantages in obviating the need to carry other fuels to battle. And their lower flammability, in comparison with petrol, also greatly reduces fire hazards.”

This is a ‘world first’, in that the team was able to design and develop a motorcycle engine powerful enough to be used on the battlefield for reconnaissance, policing and courier duties as well as for on-road and off-road performance.And so powerful is the motorcycle that in September 2004 it set the world’s first land speed record for a diesel fuelled motorcycle.

Fred Hayes, founder of HDT, who was in the saddle at the world famous Bonneville Salt Flats, Utah, said: “The event was marred by rain the previous week and by poor track conditions, which limited the top speeds due to soft, wet salt. The normally aspirated bike was officially timed by the AMA at 85.466mph, against our calculated top speed of 86mph with production gearing. The calculated speed was at sea level (4350ft) on hard pavement. We’re delighted with the result. If we’d had an option for gearing and more track time, we may have broken the 90mph barrier.”

The production motorcycle is based on the running gear of a Kawasaki KLR650 petrol-engine trail bike. The engine of the diesel motorcycle is a liquid cooled, single cylinder four- stroke which displaces 584 cm³ and currently produces some 21 kw (28 bhp). It is a double overhead camshaft design, with a four-valve cylinder head. A multi-cylinder engine was rejected as unnecessary because of the increased weight and because diesel engines work less efficiently in small cylinder sizes.

Cranfield University and HDT beat off stiff competition for the US Marines contract, including European manufacturers as well as the well established Harley Davidson that had teamed up with Lockheed. Fred does not rule out that the motorcycle may be made available for the consumer market. “Although the motorcycle is about 20-30% more expensive than a comparative conventional motorcycle, there would be cost savings for riders and environmental benefits in that the diesel motorcycle can do 110 miles per gallon – a little over twice the range of a conventional motorcycle,” said Fred.