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  • bobdxcool
    bobdxcool

    Member • Oct 21, 2016

    One way bearing usage

    I am developing a motorized cable reel. I am using a geared DC motor to drive central cable drum on which the cable rests. This cable reel is only used to automatically retract the cable back once the cable is pulled out. The cable is pulled out manually by hand from the cable reel.

    I am using a one way bearing coupled to my DC motor shaft to make it easy to pull out the cable manually. The one way bearing housing is in turn connected to a small sprocket. The small sprocket is connected to the bigger sprocket (attached to the cable drum) via a chain.

    Now, the problem that I am facing is that the whenever I power on the motor, the entire assembly rotates in the direction that the one way bearing moves. But what I need is the assembly needs to rotate in the direction opposite to which the bearing moves. On the side where the bearing rotates freely , I pull the cable out manually (as the bearing makes it easy to pull cable out), and I dont turn on the motor in this case. In the other direction where the bearing doesn't move, I need the entire assembly to rotate in order to pull the cable in, but what happens is that just the motor shaft rotates, the bearing, bearing housing, sprocket, etc dont move.

    What modifications should I make to achieve my goal or any other alternatives for this ? I cannot use an electromagnetic clutch here.

    Also, below is the link to a video where I explain the problem I am facing. #-Link-Snipped-#

    Also, the one way bearing is connected to the motor shaft via a keyway slot on the bearing and a key on the shaft. I am trying to use the same cycle chain and sprocket concept here and I am trying to understand where I am going wrong here.
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Replies

  • Ramani Aswath

    Member • Oct 22, 2016

    The relative movement between the shaft and the reel both when you are unreeling the cable and trying to rewind is the same, which is why it does not work.
    Why do you need a one way bearing at all?

    Let the motor shaft rotate in the opposite direction during unreeling. It is not powered then and there is no harm. When you want to rewind switch on the motor to turn in the reverse direction pulling in the cable.
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  • Kamlesh Vora

    Member • Nov 11, 2016

    u don't really need one directional bearing, use simple or needle bearing if possible.
    second for one direction movement you can observe ur bicycle rear wheel. It has a gear inside its hub which is also called freewheel. It moves when u pedal ur bicycle in forward direction and it doesn't work when u pedal reverse. It can be available easily.
    if u decide to go with freewheel u can use it at reel side which is actual load.
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  • Ramani Aswath

    Member • Nov 11, 2016

    Kamlesh Vora
    if u decide to go with freewheel u can use it at reel side which is actual load.
    Not really. In a bicycle the tension is in the top section of the chain when pedalling and in the bottom section when freewheeling. The ratchet concept works. In the proposed application whether one is unreeling manually or power rewinding the tension is the same. There's no need of anything. Just switch off the power when unreeling. The motor shaft will rotate freely. Use power for rewinding.
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  • Kamlesh Vora

    Member • Nov 11, 2016

    A.V.Ramani
    Not really. In a bicycle the tension is in the top section of the chain when pedalling and in the bottom section when freewheeling. The ratchet concept works. In the proposed application whether one is unreeling manually or power rewinding the tension is the same. There's no need of anything. Just switch off the power when unreeling. The motor shaft will rotate freely. Use power for rewinding.
    agree there is no need of any more mechanism. But bicycle ratchet can also be work or he can try.
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  • Ramani Aswath

    Member • Nov 11, 2016

    The issue is the direction of the torque. In both cases it is the same, which is why the concept won't work.
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