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Belt, Gearbox, Clutch


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There's always been the big discussion of which is best and why. Conclusion is always personal choice.

I want to explore the idea of a new style drive.

Gearbox but without clutch and without double spring starter. It would work and feel like a direct reduction belt drive.

Why? I'm not a clutch fan, but not against gearbox reduction.

Are there any pilots who would welcome a design like this?

No belt wear, no clutch wear.

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The idea makes some sense for sure. :-)

The good thing about belts and clutches as that if you do have tumble on take off, there is normally enough give in either the belt or the clutch to avoid snapping your crank.


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You could but I have 2 belt drive machines. Lol.

I'm more seeking advice on pit falls or if it's just not wanted.

SW has a good point about impact, the a clutch or belt even engaged would slip a bit during an accident. Replacing a prop is bad enough, replacing a prop and mechanical parts would be worse. A safeguard would need to be built in.

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  • 2 weeks later...

Apologies in advance if I'm pointing out the bleedin' obvious:

A possible concern would be the oscillating loads on the gearbox at low rpm.

The propeller is a large flywheel. The engine makes all its power during the combustion cycle, and accelerates the crank for that part of its rotation. During the rest of the rotation, the crank slows. Thus the engine exhibits 'torsional vibration'. This is most noticeable at low RPM.

A centrifuge clutch provides torque transmission proportional to rpm, so it can disengage or slip at low rpm (when the engine rotation contains significant torsional vibration) and prevent the load reversals which would be seen at the gearbox in a rigid drive setup.

A torsional shock absorber between the crankshaft and the gearbox would reduce the effect.

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