There have been a number of axial engines designed over the years with some similarities between them, but these examples from Duke Engines of New Zealand show a very impressive and well developed prototype. Arthur, one of our readers, spotted the engine on display at the recent EAA Airventure in Oshkosh, Wisconsin and thought you might be interested. The engine has 5 cylinders, 3 injectors and zero valves.

The pistons are all attached by their connecting rods to a reciprocator which rotates as a result of the movement of the pistons and is itself attached to the crankshaft which rotates in the opposite direction. As the pistons move through their strokes, they also move past the ports, injectors and spark plugs, eliminating the need for valves. It’s a very ingenious arrangement.

The axial engine has a number of interesting features:

The counter rotating components generate very low vibration

Only 3 injectors and plugs for 5 cylinders plus no valve train reduces the parts count

It is designed to run on a wide variety of fuels

Lighter and more compact than similar displacement conventional engines

Watch the videos to see the internals in motion and how it works and also note the balanced coin on the running engine as it is repeatedly revved. It’s a natural for aircraft which explains the Oshkosh display, but this type of compact, low vibration engine could easily find its way into a number of applications. I like it.

Thanks for the tip, Arthur!

Link: Duke Engines

UPDATE: I added this link in a comment below but figured some of you might miss it so here it is. It’s a whole series of old axial engines of various designs. Pretty neat. check ’em out

Videos below: