Interesting engine concept

Pretty wild concept

I see a lot of major problems, the first of which is that all of the power is transmitted through relatively small bearings, mounted on little cantilevered shafts which experience fully reversing bending loads in both planes.

I would not expect this solution to be very durable.

While the number of moving parts is small, as claimed, the parts which do move are extremely intricate and would be difficult to make using conventional techniques; using additive manufacturing to produce them maybe gets you there after some expensive machining.

This guy never should have gotten a patent. His root claim ("[a dual piston engine], wherein each of the pistons drives a reciprocating crankshaft that protrudes through a cylinder wall and cooperatively rotate a pair of rotors by engaging substantially sinusoidal cam tracks in the rotors.") as there are a number of axial cam driven engines in prior art. The oldest is likely the Laage Axial Cam aero Engine of 1923:



The infamous Dyna-Cam engine of the early 1940's is quite similar as well:



The patent language from the first paragraph above is so broad it also encompasses the Michel Engine of 1921:


The advantage of a cam driven engine is that it allows precise and somewhat arbitrary piston movement (within the bounds of material stresses and friction), a capability particularly valuable in port timing of two stroke engines. A cam driven engine can also have multiple strokes per rotation which can be exploited to mechanize a reduction gear, a capability particularly useful in aircraft engines as propeller efficiency is greatest near 3,000 RPM. These advantages come at the expense of cam loading and friction, and no engine I'm aware of has been able to overcome these problems.

I address the cam issues in my design by using a large number of small lightweight pistons, far smaller than conventional wisdom dictates, to minimize loads due to centrifugal forces. I also employ a very rapid expansion phase to keep the cam contact angles in the most efficient region. Finally, I employ a reduction gear in the cam design in order to keep radial surface speeds down. In spite of these measures, the cams remain at the very top of my risk list, and my first hardware experiments will explore their operation (I plan to construct the cam system first and run it on a motoring dyno to get accurate FMEP measurements which I will then incorporate into my thermodynamic models to see if the engine is worth pursuing further.


P.S. Anyone proposing a new engine should carefully review the catalog of old engines at

RodRico I think his design is substantially different in having two contra-rotating cams performing the opposing displacements.

je suis charlie

gruntguru, where did you see contra-rotating cams mentioned? I see no mention of them in the patent claims. I don't recall seeing contra-rotating cams in any engine other than Retevec's ( and I'm skeptical whether they provide enough benefit to offset their cost and complexity... they serve primarily to eliminate side loads on the piston, but the same result can be attained using a radial slot in the cylinder wall that takes the side load produced by a single cam.

It seems like a lot of those funky piston engine designs would work better as a pump for a compressor than as an engine, visually looking at it, they seem to have more advantage driving the pistons than the pistons would have driving the system. And is why the old crankshaft is not easy to replace as a reciprocating motion to rotary motion converter.

enginesrus,

Yep. Cams have attractive features that keep luring folks (including me) into using them, but the simple fact is that reciprocating motion is a natural fit to a crankshaft and it's very hard to beat in that role!

Rod

Cams are interesting, it's easy to want to play around with cam ideas just for the fascination factor, but it often comes back to the traditional crank