Crankcase Fretting - Rotax & Other Stuff

[Area-51]

Morse chain, hydraulic tensioner; backlash vibration and noise problems gone away...

[Moneybox]

6 minutes ago, onetrack said:

I don't see where the thrust problem couldn't be addressed with a bit of housing reinforcement, such as through-bolts close to the gears.

I'm sure you're right but you are tampering with a well proven design that in most cases has a good service life.

[Area-51]

5 hours ago, Moneybox said:

I'm sure you're right but you are tampering with a well proven design that in most cases has a good service life.

Agree... "just fly the plane" 👍

[Thruster88]

All the rotax 2 stroke gearboxes, B,C and E have helical gears, they still chatter if idled to low. Straight cut gears must be used for a reason in the 912. The big Continental GTSIO-520 producing 375hp has straight cut gears also. Probably the engineers choice rather than a cost of production thing.

[facthunter]

The same backlash can exist in either. Helicals can be quieter running  The  gear in question is doing a big job and  the clearances get worse as the ALLOY CASE expands and the gear has friction so will itself get hot and thin the oil on it.. . The prop is the ONLY flywheel and the four cyl configuration has the worst Piston momentum  set up of any Motor.. The Big Lycoming  Continental has Active (moving) Counterweights on the crankshaft that cut the torsional vibration  forces and the 6 cyl motors don't have the problem so much to start with . I would expect the gears to be ground to profile after the heat treatment to enable close running clearances in the Motors that Use Reduction gears which is only on certain Models. anyhow. Torsional vibration is a big problem anywhere it occurs and you can't feel it.  Nev