912 ULS Checking of propeller gearbox

Re: 912 ULS Checking of propeller gearbox

by Rob Seaton » 10 years ago

Rob Seaton

3 1.32k 251

Agreed, we always bench test them. But if I owned a busy flying school I would make a jig like this to perform the test on-aircraft. With the support bar in place it should not damage the engine mount:

clutchbreakawayon-aircraft.jpg (You do not have access to download this file.)

Re: 912 ULS Checking of propeller gearbox

by Conrad Beale » 10 years ago

Conrad Beale

3 66 22

Rob,
Never really understood that picture. Is the red arm bolted to the side of gearbox housing in some way & then fixed to the floor?
Would the two M8 bolt holes that normally hold the auxiliary generator on be sufficient to mount the (red) arm or is there some other place to secure to?

Re: 912 ULS Checking of propeller gearbox

by Rob Seaton » 10 years ago

Rob Seaton

3 1.32k 251

The idea is to go around the propshaft flange so the load is taken up at the same place it is being applied. It would take some considerable fabrication to make this jig.

Re: 912 ULS Checking of propeller gearbox

by Conrad Beale » 10 years ago

Conrad Beale

3 66 22

Rob,
I dont get it.
I thought the crankshaft needed to be locked (using the crank locking pin). Now referring to the screen shot of the manual you uploaded. The propshaft needs to be turned by the green lever to determine the force at which the clutch breaks at. I'm assuming the red lever is to steady the engine to prevent the engine mount taking the torque load.
What I really cant work out is where do Rotax intend the red lever to be fastened to an how the load path to the floor works as shown in the manual.

Maybe we should continue this offline as I'm clearly being stupid.

Re: 912 ULS Checking of propeller gearbox

by Rob Seaton » 10 years ago

Rob Seaton

3 1.32k 251

no, not stupid at all.
picture the red support as a large bearing around the propshaft.
you would need to build a jig that goes around the propshaft and a inner piece that picks up propshaft holes and attaches to the torque bar (I don't like the idea of a torque multiplier; we have a very good Snap-on unit and it says right on it to allow a 25% error. We use a 8 foot bar so no error)