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Uni-directional brake

  1. Jun 10, 2009 #1
    Can someone direct me to the best way to accomplish uni-direction braking of a rotating disc. I want very little friction in the free spin direction of rotation, and when the driving force is stopped, I need instant hold from reverse direction spin. Like a ratchet but quiter and smoother.
  2. jcsd
  3. Jun 10, 2009 #2
    A well lubricated ratchet? :)

    The design of such a device could vary greatly depending on how little rolling friction you desire, the amount of backlash you can tolerate and how much reverse torque the device needs to withstand.
  4. Jun 10, 2009 #3
    Sorry, I should have specified that this must be mechanical, no magnets, electromagnets, solinoids etc. Want VERY little rolling friction, and zero to mimimum backlash. Reverse torque is in the range of 10 ft/lb.
  5. Jun 10, 2009 #4
    Instead of a set of teeth...why not apply a bearing?...or rubber bearings.
  6. Jun 10, 2009 #5


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    Last edited by a moderator: Apr 24, 2017
  7. Jun 10, 2009 #6


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    Something like a sprag clutch but it probably won't be silent. Nothing mechanical will be silent.
  8. Jun 10, 2009 #7
    What you want is a one-way bearing. I am very familiar with them as I use them in my RC helicopter for autorotation. They have very little friction and provide very smooth rotation in one direction but prevent any rotation in the other. They work very well when used properly but because of their complexity they can be very expensive (for nice ones) and can also be very prone to failure.

  9. Jun 10, 2009 #8
    Thanks to all for you input. Good stuff!
  10. Jun 11, 2009 #9


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    That bearing is actually a small version of a sprag clutch by the looks of it. I have never seen those. Who makes them?
  11. Jun 11, 2009 #10


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    This is a good place to start.


    If cash is a problem, go to some copier repair places, sometimes they will give the old ones away, the old behemoth copiers (and I guess the newer ones that do everything) are filled with different types of locking devices. A little work involved, but lots of interesting things can be pulled out.

  12. Jun 11, 2009 #11
    It basically is just a sprague except instead of having a ratchet like mechanism it just uses friction. The bearing is from an Avant Aurora RC heli, I'm not sure who makes it though. SKF maybe?
  13. Jun 12, 2009 #12
    After searching based on information on various posts to this forum, I have been able to locate exactly what I was looking for. It's called a Roller Ratchet. Available from www.omegatec.com I purchased one and it is fantastic. Thanks everyone, you are the best.
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