Page 1 of 4 1234 LastLast
Results 1 to 10 of 31

Thread: Vibrations

  1. #1
    Junior Member
    Join Date
    May 2017
    Location
    Georgetown, TX
    Posts
    10

    Default Vibrations

    2007 Sport Cub, 300 hrs.: Has anyone experienced the vibrations described as follows.

    In the air or on the ground, as the RPM is increased from approx. 1,600 RPM to approx. 2,200 RPM, or the reverse, a noticeable vibration is felt - strongest at approx. 1,900 rpm. Have tried switching to one mag. Have tried varying mixture. None of this altered the vibration.

    Prop Sensenich Wood with about 200 hrs. Was removed from plane and stored for 4 years, then reinstalled 2 yrs ago. Prior owner dynamically balanced it about 1-1/2 years ago. Vibration status prior to balancing, not known.

    Has anyone had this problem or even heard of it.

    Thanks for your patience. LBlack

  2. #2
    Senior Member Pete D's Avatar
    Join Date
    Jan 2010
    Location
    Yakima, WA
    Posts
    938

    Default Re: Vibrations

    Take a look at the engine mount rubbers, they may be worn and the engine mount bolt(s) may be near the case.

    Also look at the spinner for wobble. Have someone stand a couple of wing spans to the side, inline with the prop and watch the spinner as it runs.
    Pete Dougherty
    R & D Shop Manager
    Cub Crafters Inc

  3. #3
    Junior Member
    Join Date
    May 2017
    Location
    Georgetown, TX
    Posts
    10

    Default Re: Vibrations

    Quote Originally Posted by Pete D View Post
    Take a look at the engine mount rubbers, they may be worn and the engine mount bolt(s) may be near the case.

    Also look at the spinner for wobble. Have someone stand a couple of wing spans to the side, inline with the prop and watch the spinner as it runs.
    -----------------------
    Thanks, Pete. I'll add these to my list of things to check. A couple of questions. First one is a stupid one: Which case are you referring to? Next, do you know of a way to strengthen the spinner bulkhead? It seems a bit too flexible.

  4. #4
    Senior Member Pete D's Avatar
    Join Date
    Jan 2010
    Location
    Yakima, WA
    Posts
    938

    Default Re: Vibrations

    The engine case. If the orange rubber part that is in the engine case that the 4 engine-to-engine mount bolts go through wear far enough the can contact the case of the engine.

    The orange part is the visco-elastomeric attenuator referenced in this old SA, there is a good photo of the bolt/spacer and a hose that was replaced by the orange visco-elastomeric attenuator.

    http://legacy.cubcrafters.com/techni...ations/50/view

    If you look at the engine mount bolt from the side, they should be reasonably centered in the case holes. If there is a lot of sag you may need to replace the visco-elastomeric attenuators and the black rubber parts on the ends.


    Re the spinner bulkhead, they tend to be flexible because of the cut outs in the flange for the prop blades. In the early days we used to put a bead of silicone around the prop where it contacts the backing plate. You want to make sure it fully sets before starting the engine though, as it will sling out and splatter all over the airplane back to the rudder! Big mess! I would let it dry for several days at least in a heated hanger with the spinner off...
    Pete Dougherty
    R & D Shop Manager
    Cub Crafters Inc

  5. #5
    Senior Member
    Join Date
    Nov 2013
    Location
    Upstate NY
    Posts
    372

    Default Re: Vibrations

    Do you leave the wood prop horizontal when you leave it in the hangar? Moisture in one blade more then the other might be your problem if you park it with the prop vertical?

    Glenn

  6. #6
    Junior Member
    Join Date
    May 2017
    Location
    Georgetown, TX
    Posts
    10

    Default Re: Vibrations

    Quote Originally Posted by Pete D View Post
    The engine case. If the orange rubber part that is in the engine case that the 4 engine-to-engine mount bolts go through wear far enough the can contact the case of the engine.

    The orange part is the visco-elastomeric attenuator referenced in this old SA, there is a good photo of the bolt/spacer and a hose that was replaced by the orange visco-elastomeric attenuator.

    http://legacy.cubcrafters.com/techni...ations/50/view

    If you look at the engine mount bolt from the side, they should be reasonably centered in the case holes. If there is a lot of sag you may need to replace the visco-elastomeric attenuators and the black rubber parts on the ends.


    Re the spinner bulkhead, they tend to be flexible because of the cut outs in the flange for the prop blades. In the early days we used to put a bead of silicone around the prop where it contacts the backing plate. You want to make sure it fully sets before starting the engine though, as it will sling out and splatter all over the airplane back to the rudder! Big mess! I would let it dry for several days at least in a heated hanger with the spinner off...
    Very helpful, Pete, thank you for your time.

  7. #7
    Junior Member
    Join Date
    May 2017
    Location
    Georgetown, TX
    Posts
    10

    Default Re: Vibrations

    Quote Originally Posted by Cubdriver2 View Post
    Do you leave the wood prop horizontal when you leave it in the hangar? Moisture in one blade more then the other might be your problem if you park it with the prop vertical?

    Glenn

    Glenn, yes, that is our objective, but oft times we fail.

    Thanks for the suggestion.

  8. #8
    Senior Member Mark Keneston's Avatar
    Join Date
    Dec 2016
    Location
    Saratoga Springs, NY
    Posts
    416

    Default Re: Vibrations

    Quote Originally Posted by LBlack View Post
    Glenn, yes, that is our objective, but oft times we fail.

    Thanks for the suggestion.
    What mags are on the plane? Did it ever swing a metal ground adjustable sensinich? Heard of mag problems in aps like that.

    MK
    Cub Crafters
    Factory Direct New & Used Aircraft Sales
    NorthEast & Great Lakes Region
    518.410.9404

  9. #9
    Senior Member
    Join Date
    Nov 2013
    Location
    Upstate NY
    Posts
    372

    Default Re: Vibrations

    Quote Originally Posted by Mark Keneston View Post
    What mags are on the plane? Did it ever swing a metal ground adjustable sensinich? Heard of mag problems in aps like that.

    MK
    Sensenich doesn't make a metal ground adjustable prop, but I understand what your trying to say

    Glenn

  10. #10
    Senior Member
    Join Date
    Nov 2013
    Location
    Upstate NY
    Posts
    372

    Default Re: Vibrations

    Quote Originally Posted by LBlack View Post
    Glenn, yes, that is our objective, but oft times we fail.

    Thanks for the suggestion.
    Not a normal habit to index it horizontal, most like it more vertical after they have walked into it horizontal a few times.

    Glenn

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •