Torque on a "draw bridge"?

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  • #1
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Suppose I have a four foot high rectangular slab that weighs 100 pounds, and is hinged at the bottom. The slab is essentially a draw bridge. It is anchored at the by two chains on either side. A winch can lower and raise it. Suppose the slab is at 45 degree angle. How much torque is there in the chain? How about if it is at 60 degrees?.
 

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  • #2
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How much torque
Presumably you mean "tension" rather than "torque." Have you done the calculations? Are you asking how to do the calculations?
 
  • #3
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This is a practical application that I'm facing. It's been a long time since I did any physics. It would be interesting to know what the calculations are. I don't think it's tension. Torque is measured by force times lever arm.

OK, here's the application. See the image file. The clutch is rated at so much torque. Something like 70-110. If the torque produced by the slab is too great the clutch will slip, causing the slab to fall. The device on the floor will be mounted on a shutter of in an observatory. Actually, not on the shutter, but next to the shutter near the top.
 

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  • #4
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Whole buncha questions:
1) shutter opens inward, or outward;
2) chain/cable/whatever is pulling from frame to shutter where;
3) what sort of wind speeds are typical when opening/closing.

Torque on your winch motor is immaterial; you change sheave diameter to apply whatever you need.
 
  • #5
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1. outward
2. lowers and raises with winch, just like a drawbridge.
3. not used when there are strong winds.

I was wrong about where winch, motor, clutch. It is at the bottom.

Thanks for the interest. The technician I'm working with resolved issues I had.
 
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I was going to suggest you'd be happier working with someone more at home in the building trades, or observatory dome trade.
 
  • #7
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Believe me this is really a challenging project. I'm putting in a control system that will automate the movement of the shutter, and dome rotation. I was lucky to find someone who has the knowledge to do it. As far as I know there are only two people in the contiguous 48 states that can do it. I know of another guy in Hawaii who can do it. The work will probably be done by mid-Monday--a four day effort.
 

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