Hi i have an os 46 la and need to know how to modify it to run backwards for my twin. I was told i need to modify the crankshaft. Does anyone know this info? Thanks

A whole new reverse rotation crank would be needed, and I doubt that you would find one as the LA series were an affordable, no frills, basic engine. Now if you can find an OS46 FSR with the two piece crankcase, that can be modified to clockwise rotation very easily by rotating the front portion 90 degrees.

In my experience, unless you were going to Scalemasters or Top Gun with a P-38, reverse rotation is not necessary, and creates its own set of problems and does not offer any additional security or safety. If an engine fails, the asymmetric thrust is the greatest force at work and will happen no matter which engine fails, or which direction it is (or was) turning. All that counter rotating engines do is move the P-force vector to the inboard side of each wing on a conventional twin. It is relevant on a full size twin engine aircraft, but the effect is negligible on the size of models that we fly..

Thanks Wayne, The help is appriciated and your right about the asymetric thrust being our greatest issue on one engine.

Reverse rotation engines is the first thing folks want when they are going to try multi's for the first time and generally its a dead end. While its true it does eliminate a 'critical engine' at high deck angles (the left is critical with normal rotation engines) But the complications is not worth it.

The biggest complication that is a real pain is finding and stocking for this airplane a reversed prop (P) or pusher type in most manufactures labeling, for the opposite side.

Actually what is more helpful and this always sparks contraversy is out thurst on both sides. It is very usefull on many airplanes and I have one that is fully adjustable from zero degrees to eight degrees out both sides. This I use to taylor to the individuals skills when helping someone in the multi engine transition and learning to fly sustained flights on one engine.

John

John, did you know that on the P-38 they made both engines critical after test flights showed buffetting with the normal twin rotation?

And only a handful of general aviation twins have C/R engines. The difference in Vmc is only 5-6 knots, at most. Russ Farris

Yes I was aware of that but it was not done because of any consideration given to reducing VMC on one engine but to eliminate the aerodynamic problems of the buffeting casued by the unusual configuration of the twin booms with a stbilizer tieing them together When inward rotating CR engines were used. The single XP-38 was inward rotating but all subsiquient marks were changed to outward rotating

I am not aware of any other CR aircraft that are not inward rotating.

Maxpower that is true they are rare but one example is the very last production version of the Twin Commanche, the PA-39CR

But when it comes to RC its really a dead end not worth the added problems.

John