Hello Everyone, I am a electrical/lighting engineer and we have a project that is very mechanical. It consists of a series of pulleys mounted in a row along a wall. On the other side of the room there is another series of pulleys. One motor is positioned to drive one continuous loop of stranded cable that weaves back and forth from one side of the room pulley to the other side of the room pulley and back around to the motor. (See attached image) We used 1" pulleys and 3/64 7x7 strand galvanized cable. We chose the galvanized so we could run power through it. We have light elements that mount onto the cable itself, so the cable loop never makes a complete rotation. The light elements basically go back and forth in the room and never pass around a pulley. The cable itself after running for an hour or so started to unwind and fray. Could this be an issue with the cable making right turns then left turns? Could the issue be pulley size related (This is actually our next step)? Could it be caused by the cable just going in one direction and then switching back in the other direction over and over, never making a complete loop? Any other suggestions? We need this to run nonstop for over a decade. Thank you in advance.

Jason

Check with you cable supplier to find out what the minimum bend radius is for that cable. 1/2" radius seems very small to me. Have you checked the maximum tension on the cable? In a horizontal application it is very easy to overload it even with a very small payload. Have you described the actual application to your cable supplier to get his recommendations? There are many variations of cable construction. Some are stronger, some are more flexible, etc.

Okay. The minimum bend radius for this wire is 1". So we need to remedy this. Our payload for the light fixture is almost negligible because it is a simple LED mounted on a thin circuit board that weighs approximately .2 oz. The breaking strength of the cable is 270 lbs, but we will only tighten it to the point of negligible sagging with emphasis on limited stress on the motor.

Is there any recommendations that chould alter our design to make it work better?
Is there any links that we should look into for a quality pulley source?
Should the wire rope on the motor sheave wrap 180 degrees? Less or more?
Is there any suggestions for tightening our cable that makes it work better? (ie. springs) Keep in mind we do not want any bounce happening to the cables. It should run smooth and straight.


Thank you!

A "rotation resistant" rope may assist.

Regards,
Lyle

"nonstop for over a decade"?
Not gonna happen.

Try consulting these folks for design assistance.
http://www.savacable.com/