Engine with no cylinder head, no crankshaft, no camshaft, and no valves.

[turkeydance]

This is because the engine is an opposed-piston motor,
meaning that each piston's compression stroke is performed against a second piston
placed in the same cylinder bank rather than a static cylinder head.
It still only has four combustion chambers, though,
which means it sounds similar to a four-cylinder engine.

Company Builds Powerful 500cc 'One-Stroke' Engine, Immediately Installs It in a Miata

INNengine's half-liter opposed-piston engine makes 120 horsepower in an ultra-compact, super-efficient package.

www.thedrive.com

 

[Get Off My Lawn]

And now for something completely different…
That’s cool, I wonder how long it’ll run before replace /rebuild.
Technically, wouldn’t it be a 1/2 stroke engine?

 

[hp468]

I could see these getting big in power sports. No mention of rpm range and what not but if they can spin up like a 2 stroke I bet they’d work well in jet skis and small boats.

I’m curious about rebuild as well, the bottom of what I’ll call the connecting rod/roller looks like it has some interesting machining going on to keep the pistons moving.

 

[GymB]

I have a physics problem.

The pressure generated by combustion isn’t increased, and having 2 moving parts from the same pressure just means they move at half the velocity as 1 would. Doubling the parts does reduce efficiency through operating friction.

It might be smaller and lighter, maybe, but I don’t see it having more HP or higher fuel efficiency than a fixed-head ICE.

But that's just my first impression.

 

[John]

Opposed piston engines have been around a long time. Maybe Fairbanks Morse back in the 30's, and they were diesels, primarily for ships.

In those designs, the pistons were not in phase, ie tdc was at different points on the crank, or the center shaft in this case. The ports were at the bottom of the cylinder, much like a 2 stroke detroit. They seemed to work pretty well, but were heavy and expensive because of having two cranks, and a very large case.

The cam affair for the pistons is new sofar as I know. Not much mechanical advantage there, and keeping the rollers lubricated would be top priority!