Ultimate MotorCycling Exclusive – Meet the Duke Axial Piston Engine

Forget everything you ever thought about the piston engine in your motorcycle. Imagine that instead of a single, V-twin, V-four, flat-opposed twin, parallel twin, triple or inline four-cylinder engine, your next superbike has a five-cylinder engine, with the cylinders arranged like the chambers of a revolver handgun.

Next, imagine that it can work without cam shafts, pushrods, rocker arms, valves and springs. Image that it displaces 1000cc in an engine package that is about 9.5-inches wide, 9.5-inches high, 16.7-inches long (excluding external components) and delivers about 1 horsepower per pound with total power output of 125 horsepower and 87.7 ft/lbs of torque.

These are some of the statistics on the Duke five-cylinder axial piston engine for motorcycles, which is now in concept form.

But first, some info on the Duke axial piston engine that has evolved over the years.

The Duke axial piston engine has been under development in New Zealand since 1993. It has a proof-of-concept prototype construct and has been run-tested at the University of Auckland in 1996.

By 1999, the V1-version engine was installed in a car for in-use testing. In 2004, a 993cc prototype was endurance tested at 6500 rpm for 30 hours. In 2006, the 3.0L 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 and a co-development arrangement was achieved with Mahle Powertrain in the U.S.

Duke Engines points out that the axial piston concept offers a number of important advantages compared to conventional piston engines of like displacement; The axial piston concept:

  • is about 20 percent lighter
  • has fewer moving parts due to no valve train being required
  • has greater power output per pound
  • features inherent balance, eliminating the need for counterbalancers
  • is multi-fuel capable

How smooth is the Duke axial piston engine? The company’s website shows a Duke engine being revved up on a test stand with a coin balancing on edge atop the engine and not falling over, despite the engine being revved up repeatedly.

The engine is built around some unexpected and innovative design concepts. For example, 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. Intake and exhaust four-stroke porting and valve function were achieved using sliding seals between 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. This likens the intake and exhaust system to 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.

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, or hydrogen with modifications. Work on diesel versions is also underway.

John Garvey, co-founder of Duke Engines, Ltd. in New Zealand, tells Ultimate MotorCycling, “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 40 and around 450 horsepower. Above that, Duke technology would be applied to a compression ignition version.”

Among the applications being considered are light aircraft, unmanned aerial vehicles, generators, hybrid vehicle range extenders, marine applications, defense and special purpose applications.

But the potential application of interest here is to motorcycle design.

Duke provided Ultimate MotorCycling with insight into its concept motorcycle engine package. The specifications are impressive and could set the stage for an entirely new range of high performance sport and sport touring motorcycles.

The concept package is a five-cylinder, axial piston engine with a bore of 67mm and stroke of 56mm, displacing approximately 1000cc, producing 125 horsepower and 87.7 ft/lbs of torque.

Crankshaft output speed would be 7,500 RPM with reciprocating speed of 9000 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 lbs. The bare engine width and height would be about 9.5 inches (242mm) and length 16.7 inches (424mm).

Further development and manufacturing/licensing agreements are still under development, but the motorcycle market would seem to be a promising opportunity for a new engine concept that is mechanically simpler, lighter, cheaper to manufacture and capable of delivering substantial power running on a wide range of fuels.

Stay clicked to Ultimate MotorCycling for more on this story as it develops. For additional information on the Duke axial piston engine, click here.