Originally Posted by
Concentric
Turboshafts
A redesign as you suggest with a stiff casing could, to describe it in a term you will understand better than most, result in a 'schlimmbesserung'. Not only would the stiffness increase be counter to load sharing among planet gears but by containing fragments in a space designed only for gears' running clearances you could jam up the gearbox with equally catastrophic consequences.
You are getting there, recognising the need to secure the bottom of the mast after epicyclic failure, but there are more practical ways of achieving this than an array of up to 10 suspension bars.
I can think of 2 practical solutions, one of which is particularly elegant. It would not surprise me if AH are already working on one, or even both.
It is probably too late for the offshore market but it can be made safe again. Probably in a similar timescale to the bevel gear shaft redesign and replacement.
I am clearly not an expert in the field of helicopter gearboxes,
but the same problems is apparent in all automatic gearboxes.
They do not have the same amount of planetary gears,
but they do have "stiff" housings. The same accounts for automotive differentials.
I will go back in citate the Nasa conical housing test that I referred to.
Yes I agree there could probably be more solutions to this that is smarter than my suggestions, I was not trying to come up with a final solution, but rather to prove my point. And I realize as well, making the mast completely stiff to the AC would probably allow for much more frequent ground resonance problems as long as the AC has stiff landing gears and not a flexible undercarriage.
Riff_raff
If the planet carrier is unloaded, what is actually
contributing to the load-sharing? Only the input torque?
I donīt agree to that the splines are not a rigid fit.
it is probably a very rigid fit. otherwise it may suffer from
severe failure due to the nature of the vibrations acting directly on the shaft.
loose fit, normally leads to small spot weldings on the shaft and finally overheating. in this case the splines are running completely in oil.
but to say that the splines are a loose fit that unloads the ring carrier I have problems to understand. How are they preloaded? How do you see that the lower bearing is tapered? In any case i would say that the bearing of this size would not be able to take any axial load at all. given the size of it