Saturday, April 12, 2014

Cable Clamp Safety

Some time back I added a couple of pulleys to my acorn table overhead frame to aid moving the electric hoist from one end of the track to the other.  After looking through my assortment of wire rope scrap I selected some small diameter pieces long enough to do the job.  No clamps were found so before I went to the hardware store I decided to check the internet and see if anything new was available.  It wasn’t surprised to find that the “U”-bolt-with-saddle still seemed to be the standard but I was surprised to find an illustration of how the the clamps should be fastened.  Apparently along the line I missed those instructions.

The terminal loop of the cable system is created by bending a loop and clamping the cable.   Apparently, if serious pulling force is to be applied two or three clamps are required.  Moreover, each must be oriented so that the “U” bolt side captures the short (dead) length of cable and the saddle captures the live (long) end and the minimum length of the turned back segment is specified.   Who would have thought?

I read on and learned more and more.  I seldom get myself into a predicament where I have to get out the chain or a come along and infrequent practice is probably the most dangerous state of preparation.  I didn’t know until a few years ago that the safety chains on the trailer tongue had to be crossed under the hitch.

I think this link offers about everything most of us will need to know about pulling on something safely.

Unfortunately, empirical proof is the only way to find out the ultimate strength of a system.  It also concurrently defines the weakest link in the system.  But breaking the system usually isn’t of practical value and instead we try to design in some safety factor and maybe even a fail-safe path.  Like most engineering it’s part science and part intuition or luck.  A fellow once said to me as we were ready to execute his plan, “If that’s not strong enough, I’ll always think it should have been.”

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