Improperly swaged wirerope/ aircraft cables

[RonHebbard]

Typically today it's a 30" or so length of grade 30 or for those that agree with the chain manufactures, like I do "Grade 63 hardened alloy chain meeting OSHA requirements for sling usage OSHA 1910.184(e)(5)" with one end captive on the thimble at end of lift line and other end anchored to the thimble with a shackle. Double load path.

Appreciated and understood in the case of finessing and securing system pipes to their supporting cables.
In the two theatres I spoke of previously, their trim chains were supplied and stored loose and used for attaching loads other than soft goods to system pipes.
Toodleoo!
Ron Hebbard

 

[BillConnerFASTC]

From the ANSI standard for rigging:

2.63 Trim chain: A system employing a length of chain and fittings used to connect a lift line to a batten (or other load) and adjust its level relative to the other lift lines along the batten.

 

[josh88]

The first trim chains I met were lengths of welded link chain with a rated snap hook on only one end which was intended to snap back into the chain.

We had Tiffin Scenic in and redid a bunch of our rigging this summer, they (including one of their inspectors) were still fine with the rated snap hooks on trim chains and a safety bolt connecting the two legs of the chains. Wenger's engineers however didn't like them and replaced the snap hook with another shackle into the thimble (which matches the other end of the chain), and removed the safety bolt entirely. It was an interesting conversation.

 

[gafftapegreenia]

We had Tiffin Scenic in and redid a bunch of our rigging this summer, they (including one of their inspectors) were still fine with the rated snap hooks on trim chains and a safety bolt connecting the two legs of the chains. Wenger's engineers however didn't like them and replaced the snap hook with another shackle into the thimble (which matches the other end of the chain), and removed the safety bolt entirely. It was an interesting conversation.

I don't think I've seen a "rated snap hook". Got a link?

 

[BillConnerFASTC]

The safety bolts add no safety and can only cause problems.

Rated snap hooks are available but I find ones rated equal to the chain are large and expensive.

But the debate will continue with strong opinions both ways. Like grade 30 or 63 - depends if you want to comply with OSHS.

 

[josh88]

I don't think I've seen a "rated snap hook". Got a link?

I dont, ours are 20 years old and I believe are brass, but are stamped with a rating.

The safety bolts add no safety and can only cause problems.
Rated snap hooks are available but I find ones rated equal to the chain are large and expensive.
But the debate will continue with strong opinions both ways. Like grade 30 or 63 - depends if you want to comply with OSHS.

Tiffin still specs the snap hooks and bolts in current installs apparently. Wenger's stance is that they don't spec the safety bolts anymore because its not worth it but feel there is still a minimal benefit as long as they are rated bolts. It was interesting because we had them in a week apart and the Wenger installer was surprised to see them and they wanted them changed before we hung any of their pieces from them. But then also just shackled up to the thimble on both sides which negated any leveling or trimming we had done and raised everything by 3-5 chain links.

 

[Tom Strong]

For example 1/8" wire rope with 1 sleeve and 1 crimp

Several years ago I took a rigging class that involved making up some small slings and then taking them to a machine to have them broken. Most of the ones made correctly seemed to break around +/- 10% or so of the rated breaking strength, but I was curious what would happen if one wasn't done correctly. Going by memory, a single crimp on a single sleeve came in around 60-70% of the rated breaking strength of the cable, and it failed by slipping out of the sleeve. This was a very non-scientific test (we didn't repeat it, and I didn't even think to write down the results at the time) but it seems like the majority of the strength comes from the first crimp. It's not enough to be safe, and obviously you should never use it that way, but I'd be interested in seeing some real numbers on what happens when you don't terminate cables correctly. I would guess that the percentage of the strength you'd get from a single crimp would decrease as the cable gets larger too.

Does anyone have access to a more scientific study of it?