Using Elliptical trammel for opposed cylinder engine

[The tin man]

Question I'm sure theirs a reason this hasn't been done but why couldn't you use an elliptical trammel as a design for an opposed combustion engine where 2 cylinders are vertical and 2 horizontal and have the cylinders combust in separate loops wouldn't that technically do the same thing in principle as long as the pressure fed in a loop

 

[Baluncore]

Welcome to PF.
You could use an elliptical trammel in a four piston engine.

The reason it is not done is probably because of bearing lubrication problems, due to high surface velocity.

The engine would be more compact if it was built as a flat boxer, with a quadrature crankshaft for the two journals.

Maybe a diagram of your idea would help find references to that style of engine.

 

[jack action]

I think balancing the assembly at high speed might be difficult as the two cylinders would need to be offset (and the crankshaft as well). Or you would need multiple two-cylinder trammels to balance each other?

Otherwise, it would look a lot like a radial engine with fewer pins needed. In the following animation, the link with the 5 pins would be the rod between the two pistons; The middle of that rod being connected to the crank pin.

(original animated GIF)
​

I also found this but I have no clue what the engine looks like.

 

[Baluncore]

Without a closely coupled flywheel, the four piston engine would need to be of two-stroke design.

Four-stroke radial engines need an odd number of cylinders, usually greater than six.