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Roger,

I've looked at calculations till my brain is fuzzy. Please help. I'm trying to measure the friction torque of my slipper clutch with a set of scales that measures in lbs. If I measure out two feet on the prop and pull from that point with the scales, I calculate I should measure between 11 to 22 lbs on the scales. Does this sound right?

Bill.
  • Re: friction torque

    by » 11 years ago


    Hi Bill,

    You are correct. You can measure any where from 24 - 30 inches out from the center of the prop hub. Put your handy dandy fish scale on that mark and make a nice steady pull until the prop stops noting all the time what the lbs. reading on the scale as you pull. I usually do it 2-3 time to double check. The reason not to go lower than 24" for me is that the closer to the hub the harder it is to have a nice steady smooth pull. Once you get your lb. from the scale then multiply that by the number of inches you measured out from the prop center.

    Example.
    You measured 26" from the prop hub center.
    Your reading on the scale was 18 ft/lbs.

    26" X 18 ft/lbs = 468 in/lbs of slipper clutch torque. This should be done at every 100 hr. inspection and or the annual.

    The range is 264 in/lbs to 532 in/lbs and the higher the better. Normal seems to be anywhere from 420-480 in/lbs with 460 average.

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


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