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Hi All,

I seek your comments on an opinion recently made to me:-

# It is pointless to try and dynamically balance a propeller mounted to a Rotax (all geared aircraft piston engines) as the gearbox has a 'scavenge" (?) gear which causes the balance to continually change. When I questioned this, it was explained that as a dynamic balance, effectively takes the whole installation (engine/gearbox/prop) in to consideration, the scavenge gear continually changed the balance making a dynamic balance useless.

This comment would seem to be contrary to my propeller manufacturers (Airmaster) advice and to my own opinion, that has been guided by many years of "playing" with light aircraft.

 

What think you????

 

  • Re: Dynamic Propeller Balancing

    by » 2 weeks ago


    It is a must on both mine. i can feel the difference  but I  to do it  a couple times a year and after changing the pitch.  The balancer sometimes reads .20 or higner before and  .02  after


  • Re: Dynamic Propeller Balancing

    by » 2 weeks ago


    I would recommend you do a dynamic balance on the prop. It doesn't sit there and constantly change.


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


    Thank you said by: Sean Griffin

  • Re: Dynamic Propeller Balancing

    by » 2 weeks ago


    Hi Roger,

    I am with you all the way.

    What do you think a "scavenge" gear might be ?

    Does a Rotax 9 have one ?

    Does such a thing exist?


  • Re: Dynamic Propeller Balancing

    by » 2 weeks ago


    Sean,

    Typically the term scavenge, when used in reference to engine parts, means that a particular part scavenges oil. In other words, it picks up oil in a sump and distributes it, often by rotational force. Some automotive engines use thin disks, rotating on the end of the crankshaft to lubricate the cam timing chain in this way. These are referred to as oil slingers, or scavengers.  For the rotax gearbox, the OP must be referring to the fact that the driven gear (prop shaft gear) also conveys oil, and as such its balance is constantly being changed by the mass of the oil as it moves around the gear and is being flung off.  I have no idea how consequential this is to the prop balance. 


  • Re: Dynamic Propeller Balancing

    by » 2 weeks ago


    Fred,

    In your comment, "Both of mine", is referring to two propellers on the same plane, or two different planes & propellers?

    I agree that dynamic balancing is a good idea, as I have bought a used Kitfox with a cracked engine mount on the 912 ULS engine mount that came with my Skystar Kitfox Model 5 Vixen (tri-gear).  The total engine time of that configuration was somewhere between 1200-1500 hours, and I assume the propeller (Ivo Ultralight three blade ground adjustable) had not been balanced.

    Skot Weidemann

    N24V

     

     


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