Gearbox overhaul

by Edgar Teruel in General Tech Discussion 13 years ago

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Re: Gearbox overhaul

by Roger Lee » 13 years ago

Roger Lee

127 5.22k 4.83k

Hi Harri,

Technically the fuel pump gasket should be changed. That said if you haven't damaged it and it wasn't leaking before it will most likely be fine. If it does leak when you put it back on it's easy to replace. The bearing you have pointed to in your picture is fine and just leave it alone. The washer on the crank shaft with the gear can be left alone. If you want that box to last another 1000 hrs. then replace the shaft bearing, oil seal, Bellville washers. The split washer up on top of the prop shaft that holds everything in place should be changed. If you have been using 100LL then the slipper clutch (is you have one) should be sent in for cleaning. The shims may be different with new Bellville washers.

Last, but not least is yes you will need a few special tools and it would be better to let someone do the work that has done one before. You need a hydraulic press, and a couple of special tools to get the shaft in and out.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Thank you said by: Harri Lumme

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Re: Gearbox overhaul

by Harri Lumme » 13 years ago

Harri Lumme

3 18 3

Hi Roger,

Thanks again for your help. It was good that this topic was started. Otherwise I would probably not have had the gearbox inspection done since the line maintenance checklist does not directly mandate it for my engine (912 UL with overload clutch). I will definitely not attempt to dismantle the gearbox myself without the needed tools and skills. Anyway it is good to know which parts should be replaced in order to maximize longevity since the parts are not that expensive per flight hour and different service centres seem to have slightly different opinions as to what should be changed. The engine has run just under 30% of the time on 100LL so it is good to have the overload clutch cleaned and tested too. I measured the friction torque before removing the propeller and it was 60Nm which according to the maintenance manual is an "as new" value so I am optimistic that the lead has not done any harm.

Thanks and regards,
Harri

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Re: Gearbox overhaul

by Harri Lumme » 13 years ago

Harri Lumme

3 18 3

One more thing: what is the correct part number for the Belleveille washers and the shims (if they need to be changed together with the Belleville washers). In the IPC I found p/n 838215 Disk Spring B80 80x41x3. Is that the Belleville washer? I could not figure out what the shims are and how many are needed.

Thanks,
Harri

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Re: Gearbox overhaul

by Mike Goodrich » 13 years ago

Mike Goodrich

8 123 0

A disc spring is a belleville washer (Belleville invented them and the name stuck). Rotax use disc springs in accordance with DIN 2093.
Mike G

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Re: Gearbox overhaul

by Harri Lumme » 13 years ago

Harri Lumme

3 18 3

Thanks Mike,

You learn something new everyday, even on a Sunday :-) I did find the shims in the IPC after all. I suppose they are used as needed to adjust the friction torque to the top of the allowable range, ie. around 60Nm.

Harri

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Gearbox overhaul

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