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Throttle springs with less tension.

in General Tech Discussion 14 years ago

  • Re: Throttle springs with less tension.

    by » 14 years ago

    Since throttle controls are supplied by the aircraft manufacturer as opposed to Rotax they are of differing quality. The one fitted to my Evektor Eurostar in the UK is not great and it can certainly creep. It is of the plumger type using a compressed rubber washer to provide the friction.

    The one fitted to the CZAW Sportcruiser is far superior. That is of the quadrant type with a very nice friction pad that you lift away when the throttle is operated. There is no creep on that design.

    I like the locking style mixture control used on old Cessnas, I wonder whether that would make a more successful throttle as it has positive locking. It also has the benefit that it can be rotated to adjust the throttle precisely. The only problem with ones I have seen for sale is that they are only single cable for use on single carb engines.
      
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  • Re: Throttle springs with less tension.

    by » 13 years ago

    On my RANS S6S I don't seem to have much problem with throttle creep as long as I mildly adjust the friction. My throttle system may have more internal friction than some.

    My concern with the strong springs is that they tend to wear at the bottom attachment and will actually wear through the bracket on the carburetor. In my neighborhood we have three Rans S6's: one actually wore through the bracket, one was almost worn through and mine was about 1/3 worn through. The spring goes through a plastic "top hat" but it will wear through that and then wear on the metal bracket.
    Placing a drop of oil on that bottom attach point periodically seems to help the wear problem. A better attach mechanism from Rotax or Bing would be nice. A weaker spring(if your system internal friction is low enough) might also help this problem.

    Thanks --- Lynn
      
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  • Re: Throttle springs with less tension.

    by » 13 years ago

    Hi Lynn,

    I have never seen a throttle spring from Rotax ever wear through the anchor point bracket. The anchor point bracket is pretty hard steel. I wonder if Rans has replaced that spring with something they supplied? Something's different here.

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

      
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  • Re: Throttle springs with less tension.

    by » 13 years ago

    Roger,

    I do not know the answer to whether RANS replaced the spring. It all looks original to me compared to the 912s I have seen . It would really surprise me if the throttle brackets or springs on the three engines I spoke of in my neighborhood had any modifications on them. One guy ordered his replacement spring and bracket from Lockwood(I think) and the other ordered his replacements from Bing. The replacement parts looked just like the originals. The one that had worn through had about 100 hours on it and the other two had about 350 hours on them. All of these three engines were produced in 2006.

    Another guy in our neighborhood has a lot of hours, years and knowledge on 912s and when we asked him about it he did not hesitate to reply "oh yeah, just put a drop of oil on it everytime you change your oil". He had seen this problem before.

    It appears to be just the lower connection. The upper one seemed to be okay. Running the "cups" under the carburetors makes this difficult to see. I suggest using a flashlight to carefully inspect this area when doing a conditional inspection.

    Thanks --- Lynn
      
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  • Re: Throttle springs with less tension.

    by » 13 years ago

    I have a 2006 with 760 hrs. and my springs look fine and no wear. I have friends with between 1000-2000 hrs and they have never had any issues. I think I would find out why those engines must be vibrating so much and get them smoothed out. It could be poorly synced carbs, poor engine mounts, prop not balanced. Something must be causing enough vibration to cause this wear that the majority of 912 owners don't have.

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

      
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