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Help balancing a tension system

  1. Feb 27, 2012 #1
    I have built a horizontal masking system that covers a projector screen. Basically amount to faric that is rolled onto a 1-1/2" shaft and is kept in tension to hold it tight by a haning weight attached to a pulley at the end of the shaft.

    With the system as it is it takes X amount for force to pull the fabric out and you have to physically lock it in place so way to keep if from retracting. I would like to add an equal constant force pulling the oppisite way on the fabric so that it would be balanced. Another words it would take almost no force to move the fabric and it would stay put when you stop.

    If I am correct the problem I see is that the force needed to keep is balnced is going to change with the amount of fabric that is rolled up on the shaft, chaging the diameter of the shaft. Also I could have the same problem with the cable rolled up on the pulley at the end of the shaft if I have more them one wrap of cable.

    Looking for thoughts or idea on how to get it to work and how to figure out how much weight it takes to offset what I have.

    Attached a drawing of what I have that might make it easier to understand.

    Attached Files:

  2. jcsd
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