# Torque on a "draw bridge"?

• solarblast
In summary, the technician is working on a control system to automate the movement of the shutter and dome. The work is scheduled to be done by Monday.f

#### solarblast

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?.

How much torque
Presumably you mean "tension" rather than "torque." Have you done the calculations? Are you asking how to do the calculations?

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.

#### Attachments

• torque.jpg
60.6 KB · Views: 406
• clutch1.jpg
65.3 KB · Views: 419
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.

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.

I was going to suggest you'd be happier working with someone more at home in the building trades, or observatory dome trade.

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.

Bystander