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Vibration

in General Tech Discussion 9 years ago

  • Re: Vibration

    by » 9 years ago

    Hi Eugene,

    1/2 degree between blades is way too much. These need to be reset so they are as close to dead on as possible. 1/2 degree will cause a vibration. You should have no problem getting them to one tenth of a degree without any problem. I can do that with a bubble level and throw in a digital level and all the better.
    No use getting a dynamic balance until the blades are right.

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

    Thank you said by: Eugen Beutler
      
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  • Re: Vibration

    by » 9 years ago

    Bob from Light engine supply demonstrated a way of getting them perfect;
    he uses a jig to position a digital level at the exact same location on each blade (I used a piece of plywood and cut out the profile of the blade so it bottoms out at a station near the tip)
    1-loosen the hub bolts so the blades will just turn, with considerable hand force, but not loose.
    2- he checks the blade is perfectly horizontal (using the level)
    3-then, this is the trick, he uses a deadblow hammer with a towel taped onto the head to tap the blade into position. this technique prevents the "overshooting" you get when trying to turn the blade by hand.
    You should be able to get it exact with this method.
    Buy a digital level that has a magnetic base and use a piece of tin/sheet steel on top of the jig.



    Horzlevel.jpg (You do not have access to download this file.)
    bladeangle.jpg (You do not have access to download this file.)
    Thank you said by: Eugen Beutler
      
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  • Re: Vibration

    by » 9 years ago

    The problem with the Warp Drive prop is although they come as a matched pair or three or four, the blades can have different amounts of helical twist ( washout ).

    This means that if you set the tips of the blades at the same angle, by the time you get 6 inches in from the end they can be 1/2 degree or more difference between them.

    I have made a jig to test them and went through 5 brand new boxed sets of blades before I came across a set that I thought was acceptable.

    I use 3x spirit levels at the same time to set the blades. It ends up being very accurate.

    Mark
    Thank you said by: Eugen Beutler
      
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  • Re: Vibration

    by » 9 years ago

    Nasty, I did not expect they would be any difference. We do find they need a lot of weights to dynamically balance. Although I did one last week that needed no weights.
    Thank you said by: Eugen Beutler
      
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  • Re: Vibration

    by » 9 years ago

    You might look at the vibe spectra to determine the cause of the vibration. Check out the video.

    http://blog.rpxtech.com/dynavibe-blog/identifying-and-addressing-rotax-engine-vibration
      
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