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Rotax 912 A3 - use without governor?

in 912 / 914 Technical Questions 8 years ago

  • Re: Rotax 912 A3 - use without governor?

    by » 8 years ago

    I just got a bit of clarification: The local dealer says there is a big risk of an oil leak between the propeller flanche and propeller when it is not plugged. I did notice there is oil behind the protective plastic cap on the prop flange and wondered what would happen when I removed that cap and mounted the prop.

    In order to avoid this he suggests mounting a cover piece in the front of the propeller axle. It has to be glued with Loctite 648 and pressed in place, which is apparently difficult without opening the gear box.

    Then he suggests that it is a good idea to fully convert the engine from A3 to A4. This is the list of parts needed:

    244980 SEALING COVER
    430175 O-RING
    810306 OIL INLET COVER
    232241 ROLLER BEARING
    230150 SEALING RING
    641733 PLUG SCREW
    944222 BLINDING SHIM
    430060 O-RING

    I am not sure whether I can do this myself or I will have to get a certified Rotax mechanic to do it. I can find instructions on how to go from A4 to A3 (i.e. installing a governor), not vice versa.
      
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  • Re: Rotax 912 A3 - use without governor?

    by » 8 years ago

    I still don't think you'll have a problem.

    I would like to hear from Rob, but he is on a two week vacation. maybe Michael can chime in and or you can wait until Rob gets back and you can have everyone's experienced input.

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

      
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  • Re: Rotax 912 A3 - use without governor?

    by » 8 years ago

    OK, thanks. I will order the parts anyway, they are not that expensive.
    But if can postpone the change it would be great. Then I can start the engine and have the engine installation inspected as is, and fly the Rans to my local airport. It is currently a long driv eaway from where i live, and hard to find time to work on it there.
      
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  • Re: Rotax 912 A3 - use without governor?

    by » 8 years ago

    So, here is how it went:
    I did the conversion with the help of two skilled friends.
    The swedish Rotax dealer was out of the tools needed to get the gearbox front off, so I made my own:
    A piece of 6mm ply with two holes 78 mm apart to screw into the gearbox. A threaded rod attached to the plate with a piece of wood to knock against a nut at the end of the rod. Worked fine.

    Basically two pretty much identical operations needed to be done to cover the holes at back of the prop shaft and the governor drive shaft (above prop shaft).
    It was to remove the rollerbearings at the back of the shafts and install a cover plate, then reinstall the roller bearing to keep the plate in place.
    It makes alot of sense to do it this way, because it positively seals everything off so no oil al all can escape from the back of the gearbox.
    The only hard part was driving the prop shaft rollerbearing out, as it sits really tight. It took an hour of work using a home-made puller tool (a plate and two screws to tighten to slowly press it out).

    Lastly we inserted another blind plug into the prop shaft from the front. It just needed to be gently hammered into place with loctite 648. At first it seemed a little strange that no locking pin wowuld hold it in place, but I guess it has been proven to work. Anyway, I will keep an eye out for oil leaks behind the the prop hub.

    In conclusion I think it was the right thing to do converting the engine rather than just installing the transport-cover.
      
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  • Re: Rotax 912 A3 - use without governor?

    by » 8 years ago

    Too late now but for future reference you could have just used the cover plate. Basically you are converting to a -4 configuration by pressing in the 244980 "frost-plug" into the front of the propshaft and adding the 926231 cover plate. It has an oil passage to lubricate the bearings and brass flute. Rotax uses it to test run the engines and it will not harm the engine. I am using one on our 912iS until we can afford a constant speed prop.


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