Propeller/Gearbox Overload Clutch

by Bill Hertzel in 912iS Technical Questions 6 years ago

This question is directed at anyone with Direct Experience on the 912is engine.

The new section of the site that allows you to search the build configuration of your engine reports that my engine WAS built with a Propeller/Gearbox Overload Clutch.

I have always assumed that my engine did NOT have the Propeller/Gearbox Overload Clutch installed because there is absolutely no free play in the prop.

The 912ULS Line Maintenance Manual has a procedure to measure the 15-30° Free play of the Propeller and to measure the "Friction Torque" within that free play area.

The 912is Line Maintenance Manual is missing this procedure.

Is it True that the Propeller/Gearbox Overload Clutch that is installed in the 912is engines if different from the clutch installed in the 912ULS engines and they do NOT have any Free Play?

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

Re: Propeller/Gearbox Overload Clutch

by Richard Boslaugh » 6 years ago

Richard Boslaugh

9 122 84

I purchased an early 912iS engines. When the free kit came out to upgrade the engine to 912iS Sport I requested and received the upgrade kit. Included in the kit was a new clutch with a different part number than the one listed in the parts manual in use at that time. I sent the gear box, new clutch, and one or two associated parts to the west coasts Rotax warranty facility who,I assume, replaced the old clutch with the new one and re-shimmed to no play in the dog assembly. As a side note I have sent the gearbox back for vibration 4 times and last flight I think I noticed the start of vibration again. The engine has about 270 hrs.

There is some play when moving the prop due to the back lash tolerance in the bull gear and the prop shaft gear.

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Re: Propeller/Gearbox Overload Clutch

by BROTAX » 6 years ago

BROTAX

0 21 11

I think that this is a commonly misunderstood component of these engines. All 912IS engine come from the factory with an overload clutch. This clutch has a break away force of 600NM.

When we test the friction torque on a 912ULS we are not testing the clutch. This 30 degree movement that we measure is the force required to move the dog ears of the gear and dog hub. On the 912IS engines we do not have this 30 degree movement. Therefor we do not have a friction torque procedure for this engine series.

Hope this helps.

Thank you said by: Bill Hertzel, Patrick Cooley

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Re: Propeller/Gearbox Overload Clutch

by Bill Hertzel » 6 years ago

Bill Hertzel

13 1.95k 7.96k

Thanks, BRO!

That is what I was thinking.
The 30° soft spot in the rotations has always been an easy way to confirm that a clutch was installed.
The New clutch without the Freeplay removes the easy confirmation.

The build sheet and the part numbers on the gearbox are the new confirming evidence.
It is not as convenient but good to know.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Propeller/Gearbox Overload Clutch

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