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Crankcase Bearings!

in 912 / 914 Technical Questions 11 years ago
Hi!

I am new to this group and I have some questions!

I have just bhought an Rotax 912ULS engine which has been involved in an accident. The wing of the airplane came of and I bhought some parts from the remaining airplane including the engine.

The engine is from 2003 and it has run about 4h. Since the propeller stroke water during the crah I decided to take the engine apart and go trough and check al part .

My question is:
what is the recomended tolerance for the crankcase beraings? I cant find this information anywhere.

I have gone trough amoust al parts now and everything seems to be in order.


Best Regards,
Razvan

  • Re: Crankcase Bearings!

    by » 11 years ago

    Do you have training, experience, documentation and equipment to perform such work?
    - Will you be making a logbook entry for this aviation product you are working on?
    -There are many pitfalls and “gotchas” in the overhaul/splitting the crankcase. You are taking a big risk if you do not have the experience/tools necessary to perform the work to an aviation standard.
    I am not just protecting my own livelihood of overhauling Rotax engines but I am also concerned about your safety and others as well. What will happen if you sell the engine after making unapproved repairs and someone dies in the aircraft?
    I also am concerned about the good name of Rotax aircraft engines. It is not correct to do this type of work without the proper experience, tools and equipment. That is why Rotax does not allow un-authorized overhauls or splitting of the crankcase.
    I am finished my rant now,
    Rob
      
    Report

  • Re: Crankcase Bearings!

    by » 11 years ago

    Hello!

    Thank for your answer!

    First I want to say that I understand your concern.

    I can't say that I am an expert but I am no beginner either.
    I have worked with engines for a while now and I feel safe in my way of working and my knowledge of engines.

    For the moment I work as an engine repair man so I have all the equipment I need to do a great job. I have previously
    worked as a CNC
    operator and programmer of lathe and milling mashins for Atlas Copco.

    The aircraft I have built I did it only by using the drawings, didn't by any kit.

    I am to concerned of my own safety and life so therfore I am not taking any shortcuts since this engine
    Is for me and my family.

    Everything I do is well documented with pictures, videos and written information.

    Anyway, One more time, thank you for your answer.



    Razvan
      
    Report

  • Re: Crankcase Bearings!

    by » 11 years ago

    Razvan,

    Go to chapter 72-00-00, section 3.18 of the heavy maintenance manual. It will give you the crankshaft tolerances you need to check without removing the crankshaft. If you have access to micrometers and runout gauges, you can check all the tolerances necessary to determine whether or not the crankshaft has to be removed.

    The heavy maintenance manual can be downloaded from the support tab at the top of this website.

    If the crank is out of allowable tolerances, there is not much you can do about it. conrods cannot be removed without pressing the crank apart. There are no journal caps. Because of the way the counterbalances are built onto the crank, the journal surfaces cannot be reground or replaced without pressing the crank completely apart. Because of this, rebuilding the crank takes some highly specialized equipment.

    Rotax does have an OVERHAUL manual but it is only available to certified Rotax service centers. By the time you have checked everything that is explained in detail in the HEAVY MAINTENANCE manual, you are down to two pieces. The crankcase and the crank.

    If the engine was underwater, you may have a whole new set of crankshaft problems to deal with.

    If you have the necessary measuring equipment and the engine was not submerged, I would check the tolerances. The crank may be OK. If it is not, take Rob's advice and find a service center.

    Bill.
      
    Report
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