It seems that the opposed piston engine has some benefits. Double the acceleration away from TDC means less time at high pressure/temp which may reduce NOx emissions. It also means a more adiabatic expansion. Achates has been working on one for some time. They have some contracts and a partnership with Cummins.

The 2-stroke design may have some benefits as well. I installed some kits from Clean Cams Technology Systems in the past. They took the exhaust cam from a 71 series Detroit Diesel, ground most of the lift off of it, and added a turbocharger to restore the airflow. In theory it was the equivalent of in-cylinder EGR. It was certified to US EPA Tier 2 emissions standards on a fully mechanical injected engine which was quite remarkable.

You know they're not serious about taking it into production when you see the open K&N air filter on it.

That reminds me of the engine that Rodrico developed here a few years back without the extra compression/expansion stage.

Hopefully this is the fruit of his labor.

Nothing pulling the pistons back is shown. I also question the reliability of a roller running on a spinning disk.

*Nothing pulling the pistons back . . .* LionelHutz

- Yes, noticed this too. The thing might self destruct unless it’s intended for one way; torpedoes or such. Found this design by Duke engines that uses rotating swashplate but restrained conrod https://www.dukeengines.com/advantages/low-vibrati...

If it runs on a 2-stroke cycle you don't need to pull the piston back down. I have operated some EMD 2-stroke diesel engines in the past. The piston attaches to the carrier with just a snap ring and that's a big piston at 9-1/8 inches diameter.

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If it runs on a 2-stroke cycle you don't need to pull the piston back down.

Right...but how do you start it?

Quote (LionelHutz)

Nothing pulling the pistons back is shown. I also question the reliability of a roller running on a spinning disk.

If you look at their exploded views, each piston assembly has two bearings which ride on the lower plate. The inner bearing closest to the shaft also appears to ride on an inner plate, which looks to be smaller diameter and is fully within the inner diameter of the piston group. So the piston 'return' loads would pass through only one bearing. Maybe not an issue if they are low enough during starting.

I definitely agree regarding the durability questions. Lots of very careful material and treatment choices would be required to give that contact interface any sort of chance. I don't love using roller element bearings either.