Exactly what I mentioned in some comments here a few years ago. The rotary could be optimized to run at a set RPM driving a generator for a battery, thus making the most of its power/weight ratio .

It would be interesting to know if your comment on CR4 played a role in this design decision. I doubt your comment inspired the approach but it might have been part of the corroborating chorus.

I thought this was a rotary engine . . . .

Ya call THAT a rotary engine?

THIS is a rotary engine:

That's a radial engine actually. I know, I know many in the aeronautic field call that a rotary engine but the combustion chamber doesn't rotate unless the plane rotates.

That actually is a rotary engine. The crankshaft is affixed to the airframe and the rest of the engine rotates around the fixed crankshaft. The way you can tell a rotary engine from a radial engine is that the rotary engine has the intakes coming out of the crankcase. Rotatry engines also have total loss lubrication systems. In the Second World War, the radial engine was used on many aircraft like bombers and the Thunderbolt among others.

So that's from a WWI Fokker. They were the only ones I knew of that used such an atypical approach of spinning the engine block. I always wondered how the fuel could possibly get to the engine without leaking all over the place at some rotating seal. The gyroscopic twist to the plane must have been something fierce. With the moment of inertia being so high the throttling of propeller speed must have been slow, too.

Does that go in one of these?

https://cr4.globalspec.com/blogentry/29088/Rising-Star-The-Rotary-Engine-of-the-Thomas-Morse-S-4

Sure looks like a good match to me, but in truth, I'm not exactly sure.

I stand corrected. (Well actually I usually sit at my computer.) Many of the WWI aircraft used rotary engines. The Wankel rotary engine rotates the combustion chamber but without spinning the exterior of the engine compartment.

Radial = round

Rotary = goes round

In 1971 I bought my first car, an RX2, USA sales then being only in Texas, California, and Washington. Quietest, smoothest-running, and quickest acceleration of any car I have owned since. Since then I have never seen any car with so much space under the hood, and such a compact engine. Always felt that the engine could be designed/tuned for operation at a constant speed/load, with substantial results in increased fuel economy and emissions reductions. The use in a hybrid is well worth pursuing.

--John M.