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Thread: Vibrations

  1. #21
    Senior Member Clay Hammond's Avatar
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    Default Re: Vibrations

    Pull the prop and put it on a homemade prop balancer in your hangar or shop. (a round stick of sort or fashion laying across two sawhorses...etc.). If the prop favors one blade over the other there's the beginning of your troubles...and maybe all of it. Start eliminating your causes.

    If it is weighted one side versus the other, and it was balanced 1.5 years ago, and it is still on the same engine...then I would venture that prop was stored improperly. Nothing you can do but store it horizontal and wait. You can do that on the plane and just deal with the vibes until they hopefully go away. Or pull the prop and put another one on, store the wood prop in a horizontal position in a stable climate and let time do its thing.

    If the prop is balanced statically when not installed...then: When the prop was dynamically balanced 1.5 years ago how was the weight added? To the prop bolts or onto the spinner backing plate? I don't think they generally use the composite backing plates on the Cubcrafters spinners to mount balance weight because they are fairly light duty. If it IS on the backing plate though, are you 100% sure that the backing plate and prop were indexed correctly when reinstalling? If not then you gotta either experiment and fiddle with it to find that exact old position or do a re-balance. If the weight was on the bolts are there indexing marks as to which bolt with regard to the hub? And how was prop indexed to the engine. This ALL applies with a dynamic balance. The dynamic balance creates a harmonious condition with the rotating masses of the engine also. Everything has to be lined back up the same or you will not be in the same condition as it was previously. If this is not the case or you're not sure then you gotta re-balance.

    Short take: Make sure your prop is balanced by itself (and is tracking straight and true also), then make sure it is balancing with the engine just the same as it was before.

    Good luck.
    Last edited by Clay Hammond; 02-05-2018 at 07:44 AM.
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    Clay Hammond

  2. #22
    Junior Member
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    Default Re: Vibrations

    Thanks very much, Clay and Mark.

    The vibrations seem to be associated with a power reduction, specifically when passing through about 2,000 rpm in a rapid power reduction. Not so noticeable if the rpm is slowly decreased through 2,000. If fact, if during the reduction and the rpm is stopped at 2,000 - no vibrations. It seems to be a dynamic thing.

    Another idea offered is that it could be an induction air leak. As the throttle is closed, momentarily more outside air is pulled into the induction system, leaning the air/fuel during the throttle reduction. Comments?

    Thanks again.

  3. #23
    Senior Member Clay Hammond's Avatar
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    Default Re: Vibrations

    Both possibilities. Only way to run it down is to start eliminating possibilities. List them all out and then start picking them off one by one until the vibes are eliminated or start to mitigate. It might not be one single thing...that is always the bugaboo. Keep at it though and it will resolve. Only takes a combination of time, knowledge and/or money. Usually all of the above!
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  4. #24
    Senior Member Mark Keneston's Avatar
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    Default Re: Vibrations

    Quote Originally Posted by Clay Hammond View Post
    Both possibilities. Only way to run it down is to start eliminating possibilities. List them all out and then start picking them off one by one until the vibes are eliminated or start to mitigate. It might not be one single thing...that is always the bugaboo. Keep at it though and it will resolve. Only takes a combination of time, knowledge and/or money. Usually all of the above!
    Clay is right, hunt and peck. I feel like mags or prop damaged. MK
    Cub Crafters
    Factory Direct New & Used Aircraft Sales
    NorthEast & Great Lakes Region
    518.410.9404

  5. #25
    Junior Member
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    Default Re: Vibrations

    You guys are right. Thanks.

  6. #26
    Senior Member Springloaded's Avatar
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    Default Re: Vibrations

    Mine always had a slight buzz to it when I would pull the throttle back on it. I tryed everything balancing wise. Think I just got use to it. From what I remember the noise actually was coming from the jury strut I could reach out and touch the lift strut and make it quit. It had the ground adjustable prop. I put over 500hrs on it. I heard it had a mag problem around 800hrs. If that helps you any. If you go back thru the threads I think there something about this.
    I ended up hoisting up the fuel caps and rolling a Carbon Cub under them and it quit immediately😀(sorry couldn’t resist)
    Chuck Kinberger
    Southern Cubs
    Florida Cubcrafter Sales
    Jupiter Fl.
    Pa11890ck@gmail.com
    You can sit at home & hear the News or get out there & be the News

  7. #27
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    Default Re: Vibrations

    Chuck, appreciate your input. Do the Sport Cub's gas caps really fit the Carbon Cub? We might give that a try; it seems so easy.

  8. #28
    Senior Member ATXCubDriver's Avatar
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    Default Re: Vibrations

    I can make it happen!!

    Quote Originally Posted by LBlack View Post
    Chuck, appreciate your input. Do the Sport Cub's gas caps really fit the Carbon Cub? We might give that a try; it seems so easy.
    Mike Sasser
    Boomerang Air
    mike@boomerangair.net

    OK,AR,TX,LA
    www.cubcrafters.com




  9. #29
    Senior Member Springloaded's Avatar
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    Default Re: Vibrations

    Quote Originally Posted by LBlack View Post
    Chuck, appreciate your input. Do the Sport Cub's gas caps really fit the Carbon Cub? We might give that a try; it seems so easy.
    Absolutely easy as it gets and Mike will give you something to cover the S2 tanks for the new guy😀
    Glad to see you have a gd since of humor.
    Chuck
    Chuck Kinberger
    Southern Cubs
    Florida Cubcrafter Sales
    Jupiter Fl.
    Pa11890ck@gmail.com
    You can sit at home & hear the News or get out there & be the News

  10. #30
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    Default Re: Vibrations

    "Vibrations" (engine roughness a better description) - they have ended! Great A&P here in Georgetown got to the root of the problem. Turned out to be an induction air leak due to nuts becoming loose on a cylinder collar.

    Thanks for all your input.

    Happy ending!

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