The world's first production diesel military motorbike has been created by a partnership between Britain's Cranfield University and California-based Hayes Diversified Technologies (HDT). Although several bikes, particularly the Royal Enfield, have been fitted with standard commercial diesel engines, this is the first bike of any kind with a purpose-designed diesel unit.
An initial order for 522 of the bikes has been placed by the US Marines and delivery will start early next year. Keen interest is being shown by the US army, the British Ministry of Defence and other NATO forces.
The engine was designed by John Crocker, who worked alongside project leader Dr Stuart McGuigan of Cranfield's engineering systems department at Shrivenham, Oxfordshire. The challenge was to come up with a low technical risk design which was sufficiently light and powerful - and with a rpm-range wide enough to give the performance required for a tactical vehicle.
"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," said Crocker. "This capability has major logistic advantages in obviating the need to carry other fuels to battle. The lower flammability of diesel, in comparison with petrol, also greatly reduces fire hazards."
This is a "world first". The team was able to develop a motorcycle engine powerful enough for battlefield use for reconnaissance, policing and courier duties, with good on-road and off-road performance. So powerful is the machine that in September it set the world's first land speed record for a diesel motorcycle.
Fred Hayes, founder of HDT, was in the saddle at the world famous Bonneville Salt Flats in Utah. "The event was marred by rain the previous week and by poor track conditions," said Hayes. "This limited top speeds due to soft, wet salt. The normally aspirated bike was officially timed by the American Motorcycle Association at 85.466mph (138km/h), against our calculated top speed of 86mph with production gearing. We're delighted - if we'd had an option for gearing and more track time, we may have broken the 90mph (145km/h) barrier."
The production bike is based on the running gear of a Kawasaki KLR650 petrol-engine trail bike. The diesel engine is a liquid-cooled, single cylinder four-stroke which displaces 584cc and currently produces some 21 kw (28 bhp). It's 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 and HDT beat off stiff competition for the US Marines contract. European manufacturers were in there, as well as Harley-Davidson which had teamed up with Lockheed.
Hayes doesn't rule out the possibility that the bike may be made available for the consumer market. "Although it's 20 to 30 per cent 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."
In developing countries where motorcycles are still widely used for everyday transport rather than as leisure vehicles, the improved fuel economy of a diesel bike, perhaps with somewhat lower performance than the current military unit, would bring major economic advantages and conserve scarce fuel resources. The engine could also be run on kerosene or bio-diesel.
The use of light four-wheeled ATV quad bikes in agriculture, horticulture, forestry and prospecting is expanding rapidly in many countries. This motorcycle engine would be ideal for adaptation to ATVs and would allow the use of a common fuel for tractors, other vehicles and implements. Work in this area is already underway.
The power unit would also be an ideal basis for a light industrial diesel engine for pumps, generators and similar portable equipment. Such a unit would offer a power-to-weight ratio around twice as good as current small industrial diesels.
A twin, or multi-cylinder, diesel engine based on the design principles of the power unit would be attractive for small aero engines. Though heavier than the two-stroke petrol engines currently used in this field, the superior fuel consumption would reduce the fuel load. The engine's high reliability and the absence of a high-tension electrical system would be additional advantages.