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Thread: Tandem One-Way-Bearings

  1. #1
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    Tandem One-Way-Bearings

    Hello,
    I am new to the forum, but I can't seem to find the answer I am looking for using the good ol' google (or previous posts).

    I have a simple pulley with some chord on it that drives a friction device (workout equipment) with a one-way bearing. My system is working well and smooth but to achieve the pull force on the chord (about 75lbs), I am failing the bearing. I know that up sizing the bearing to a stronger one will solve this problem, but this causes the cost to increase too much for other components that mate with it. The only costly solution I can think of is using two of the same clutches in tandem with each other so each takes half the load. In theory this should work, but I am left wondering; will one clutch grab before the other, taking the full load and fail, then the other bearing fails? I might be fine and handle it okay, I just wanted to get some other thoughts before taking this idea to the factory level.

    Thank you,
    Nick

  2. #2
    Technical Fellow jboggs's Avatar
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    Your theory of failure is correct. Two bearings will help and should increase operating life, but one of them will always engage slightly before the other one does, and therefore will be carrying the great majority, if not all, of the load.

  3. #3
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    @jboggs
    To throw some numbers at it. The one-way bearing can take about 10.5 ft*lbs before failure, and the machine produces about 11.5 ft*lbs. So two bearings would give me about a FOS of almost 2.

    Without any testing yet, my gut says this should work... does you agree?

  4. #4
    Technical Fellow jboggs's Avatar
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    Depends on your definition of success. Its not a real FOS of 2 because one of the two bearings will always be carrying the majority (90% or more in my opinion) of the load. Two bearings will last longer than one, but will eventually fail. If that eventual failure is outside your requirements or definition of "success" you're good. Only real world testing will answer your question more reliably.

  5. #5
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    @jboggs
    Thank you taking the time to reply, I really do appreciate it. It helps out a lot having someone back my thinking to prove I'm not crazy! Well, at least not 100% crazy...

    Thanks again.

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