CVT - continuously variable transmission I have designed 2 of them for small vehicle applications at my last job, and worked on 2 others that someone else designed. I will tell you that though in theory they are simple, in practice they are full of gremlins. I wouldn't go as far as to say you can't do it, but I don't think would be worth the development effort. It won't be lighter than a standard gear reduction for sure.
That said - I guess I'm missing the benefit. With a "constant speed" prop, you (well, the prop gov.) vary the prop pitch to control engine and prop rpm, and thus load on the engine dependent on a throttle setting. Driving a fixed pitch prop at one rpm while varying the engine rpm doesn't get you anything except a prop that spins 2400 rpm from idle (or tries before killing the motor) to somewhere in the power-band. Even if you made the output (prop) rpm adjustable, there's no gain because FP props are most effecient at a small range of rpm while (hopefully the powerband of the engine) in a specified airspeed range. The only thing you might get out of it is the ability to tune the engine to a specific prop/airframe, which we do already (but in reverse) by playing with prop diameter, pitch, blade profile, etc... It works great in a ground vehicle because you can tune the engine to max efficiency, or max power, and the cvt can change gear ratios as wheel rpm (speed) increases to keep the engine at the same rpm. It doesn't work like that in an airplane. You need to be able to vary the pitch of the prop most importantly to get efficiency at different airspeed while keeping the engine at a speed it likes to make power in (or run more efficient in). The prop is the actual transmission. So in effect, the hyd/electric prop govs. are akin to CVT's. In reality, I'd love to be able to vary diameter too! And telescope the wings ;-) If I'm off on my thinking here, please elaborate. It sounds like you want/need a gearbox with an oil system so that you can run a const. speed prop :-) Matt E. On 7/12/2012 6:03 PM, John wrote: > I was wondering if anybody has heard of anybody doing a CVT type setup > instead > of the PSRU? (Constant Velocity Transmission) search youtube for CVT. > seems to me that it could weigh about the same and keep the prop at say > 2400 rpm > while the engine rpm varies. > From what I've seen they're all set up to let drive wheel rpm vary > while engine stays > in "best power" - >
