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Posted (edited)

I agree with you Nev....smoothness introduced through a dynamic balance is just that and nothing more, smoothness contributes to ongoing wellness but if something was unwell to begin with then your simply masking it until the next degradation occurs....and it will

Edited by AndysAtCoffs
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Posted
45 minutes ago, AndysAtCoffs said:

the other issue with an extension shaft is that generally, in the ones I've seen, there are 2 flat plates that are bolted together with the engine/gearbox output flange with 6-8 bolts around the circumference, and the prop at the other end. They are supposed to be made so that the plate on the engine end, and the other are at a perfect 90 degrees to the shaft (and so perfectly in parallel to each other so that when everything is bolted up and you look for run out by spinning the gearbox/engine and measure at the haft as far away from the engine/gearbox as possible you don't see any/very little  which means the surface was at that exact 90 angle all around. If there is any introduced runout because of a manufacturing defect or the uneven bolt tensions have pulled the shaft away from its center position then no matter how good the static balance the shaft at speed will introduce a vibration because its center of mass is no longer in line with the output shaft of the gearbox/engine. If the runout cant be Zero'd with bolt tension variations/adjustments, then a dynamic balance can help counter the vibration but to me that's a bit lipstick on a pig..... swap out the pig....

 

At least thats what Id do....YMMV

The engine prop setup to look at with your device / method would be the Savannah S as they have a very long spacer between the engine flange and the prop hub.

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Posted

Eprop balance the whole assembly inc the spacer no matter what length at the factory before delivery and each part is marked so it goes together exactly how it should be. All customers report that they have never flown behind a prop that is so smooth and finely balanced. I suspect that they use a 2 plane balancer at the factory because the balance of every prop is outstanding. There are balancing weights inside the spacer and also the spinner

 

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