Duke Engine: Innovative Axial Piston Engine
Back in October 2014, we broke the story about a radical innovation in engine design—the Duke axial piston engine.
The Duke engine is very compact, has fewer moving parts and is lighter than conventional internal combustion piston engines. The Duke is a five-cylinder engine, with the cylinders arranged like the chambers in the cylinder of a revolver.
The cylinder group rotates counter to the crankshaft, at about 20 percent of crankshaft rotational speed. The counter-rotating design allows the engine to partially quash torque reaction and cancel vibration. In operation, the engine is so smooth, no counterbalancer is required.
Intake and exhaust 4-stroke porting and valve function is achieved using sliding seals between the low-speed rotating cylinder group and monoplane ported surface, which eliminates the need for the conventional valve train of tappets, rockers, springs, cams and even the intake and exhaust valves themselves. In this respect, the intake and exhaust system resembles a piston-port two-stroke but in a four-stroke engine.
The five cylinder engine requires only three fuel injectors and three spark plugs. The absence of exhaust valves reduces the potential for pre-ignition or spark knock when operating on low-octane pump gas. A normal operating cycle provides three ignition events per crankshaft revolution—the same as a conventional six cylinder four-stroke engine.
This degree of simplicity facilitates an engine that displaces 1000cc, is about 9.5 inches wide, 9.5 inches high, 16.7 inches long (excluding external engine components) and delivers about 1hp/lb. with total power output of 125 horsepower and 87.7 ft/lbs of torque. It was that compact form and power output that got us interested in covering the Duke engine as a potential new powerplant option for motorcycles.
The Duke axial piston engine has been under development in New Zealand since 1993, with a proof-of-concept prototype constructed and run-tested at the University of Auckland in 1996. In 1999, the V1 version engine underwent in-use testing in an automobile.
Then, a 993cc prototype ran an endurance test on a stand at 6,500 rpm for 30 continuous hours in 2004. In 2006, the 3.0L Version 3 (V3) prototype engine was dyno tested at the University of Auckland. In 2010, the V3 engine was test run on JetA1/Kerosene fuel and spark-ignited heavy fuel on the dyno at the University of Auckland. By 2012, the next generation V3i engine was run successfully on JetA1 fuel and pump gas.
The range of fuels that the engine can run on without modifications include low and high-octane gasoline, kerosene/jet A1/A5/A8, and LPG, CNG, hydrogen with modifications. Work on diesel versions is also underway.
In our 2014 coverage, John Garvey, co-founder of Duke Engines, Ltd. in New Zealand said, “Duke has developed an axial piston internal combustion engine, capable of very high power-densities in a lightweight and small package and capable of running on light and heavy fuels.”
“Duke has huge further development potential and is already achieving 1.25 KW/kg with expected potential for up to 3.0 KW/kg. Super and turbo charging and many enhancements applied to conventional engines can be applied to Duke technology. Duke spark ignition technology is technically attractive between 40hp and around 450hp. Above that, Duke technology would be applied to a compression ignition version,” Garvey explained as he described the current and future performance profile of the axial piston engine.
Potential applications for the Duke engine include light aircraft, unmanned aerial vehicles, generators, hybrid vehicle range extenders, marine applications, defense and special purpose applications. The potential application to motorcycle design is what sparked our interest.
The motorcycle concept package is a five-cylinder, axial piston engine with a bore of 67mm and stroke of 56mm, displacing approximately 1,000cc, producing 125 hp and 87.7 foot/lb. of torque. Crankshaft output speed would be 7,500 RPM with reciprocating speed of 9,000 RPM.
Fueling would be by direct electronic fuel injection; lubrication would be a dry sump system. The installed engine including all the necessary external intake, cooling and exhaust components is estimated to weigh 110 lb. The bare engine width and height would be about 9.5” (242mm) and length 16.7” (424mm).
These specifications could set the stage for the Duke engine to be a fascinating powerplant option for high performance sport and sport touring motorcycles.
We recently contacted John Garvey to follow up on our original story and found that work has continued on Duke engine technology development and that the company is available as an investment.
Garvey indicated that potential sale structure of the company would consist of “patents, intellectual property and know-how and some existing historic prototypes. They will then contract the key Duke employees and propose running a design office in New Zealand. The prototype work will likely, but not necessarily, be undertaken in the USA by Mahle Powertrain in conjunction with the ex-Duke team who will be employed by the purchaser.”
Garvey indicated interest in the company has been expressed already, but that at this point there have been no commitments made, so the opportunity is still open.