Destructive testing.

egilson1

Senior Team
Senior Team
CB Mods
Premium Member
ETCP Certified Technicians
So here are some photos of a few items we tested today at the KCACTF region 1 conference. There is a video of the trim chain on the ERS Facebook page here https://www.facebook.com/198317007472453/posts/323129164991236/


11517649-6142-44C5-9110-CB07D0C610E4.jpeg 11BBDEB6-4EF7-4506-BEDD-D3CBB48D7C50.jpeg 3003D941-9BC4-4C71-90A5-87286FCB6B93.jpeg 782E0F6F-EA0F-458C-AA3E-139FA998FB98.jpeg 4AF2D3DF-4AAE-4065-AFD7-DDA1E65BDA26.jpeg

The shackle was 5/16” which broke at 7,945 pounds. Country of origin was China.

The chain was 1/4” grade 30 proof coil chain set up like a trim chain with the shackle connected back to a single chain link. It failed at 6,700 pounds. Also made in China.

Enjoy!
Ethan
 
Last edited:
Is that good?
 
A full comparison chart would help me seeing the results here. Item rating (WLL), item failure point (where it broke), difference between the 2. Because I work in metric systems where 5/8 shackle means nothing to me because different materials mean that something of a size may be stronger or weaker than another object.
Thanks
Geoff
 
Is there a number missing from before the comma? Or did it break at 555 lbs below the 'rated' working load?

Yes. I somehow deleted the 7 when I added the comma.

Corrected now.
 
i imagine @egilson1 may post full results at some point, but . . .

1/4" Grade 30 Proof Coil chain is usually rated with a Safe Working Load (SWL) of 1,250 or 1,300 pounds. In their test it failed at 6,700 pounds. That is 5.15 times greater than the SWL or a factor of over 5.
A 5/16" Shackle is usually rated to 3/4 of a ton or 1,500 pounds. If you strain your eyes you can see the one tested was marked WLL 3/4. 'WLL' means Working Load Limit, another way to say SWL. In their test it failed at 7,945 pounds. That is 5.3 times greater that the SWL.

A lot of people knock 'Chinese' stuff as inferior junk, but a 5:1 ratio of breaking point to SWL is pretty typical for the industry. We have an importer in our area who brings in one or two containers a week of chain, wire rope, etc and repackages onto smaller reels or buckets and sells nationwide. They test a sample from every spool of wire rope and vat of chain and randomly test connectors like shackles. They tell me their suppliers are almost always providing things that fail at over 5 times the SWL. And if something doesn't pass, there is a scrap metal dumpster out back and I've seen whole spools or wire rope in it.

The important part is to know who you're buying from and that they're a quality vendor. It's not hard to paint the pin of shackle red and try to pass it off as a genuine Crosby brand item.

And I don't mean to offend anyone or sound like a grumpy old man who is disappointed with the way some colleges are cranking out techs who don't know the basics, BUT if you don't know what the numbers on a shackle mean or where to find the SWL for chain or know the relationship between SWL and breaking point . . .
 
i imagine @egilson1 may post full results at some point, but . . .

1/4" Grade 30 Proof Coil chain is usually rated with a Safe Working Load (SWL) of 1,250 or 1,300 pounds. In their test it failed at 6,700 pounds. That is 5.15 times greater than the SWL or a factor of over 5.
A 5/16" Shackle is usually rated to 3/4 of a ton or 1,500 pounds. If you strain your eyes you can see the one tested was marked WLL 3/4. 'WLL' means Working Load Limit, another way to say SWL. In their test it failed at 7,945 pounds. That is 5.3 times greater that the SWL.

A lot of people knock 'Chinese' stuff as inferior junk, but a 5:1 ratio of breaking point to SWL is pretty typical for the industry. We have an importer in our area who brings in one or two containers a week of chain, wire rope, etc and repackages onto smaller reels or buckets and sells nationwide. They test a sample from every spool of wire rope and vat of chain and randomly test connectors like shackles. They tell me their suppliers are almost always providing things that fail at over 5 times the SWL. And if something doesn't pass, there is a scrap metal dumpster out back and I've seen whole spools or wire rope in it.

The important part is to know who you're buying from and that they're a quality vendor. It's not hard to paint the pin of shackle red and try to pass it off as a genuine Crosby brand item.

And I don't mean to offend anyone or sound like a grumpy old man who is disappointed with the way some colleges are cranking out techs who don't know the basics, BUT if you don't know what the numbers on a shackle mean or where to find the SWL for chain or know the relationship between SWL and breaking point . . .

Crosby 5/16" shackle rated for 1500bs with a 6:1 design factor. https://www.thecrosbygroup.com/prod.../crosby-209-carbon-screw-pin-anchor-shackles/

1/4" Grade 30 Proof coil is rated for 1300lbs with a 4:1 design factor https://www.cmworks.com/Rigging/Tra...ChainHooksComponents/CMProofCoilChain/Grade30

Based on these, the shackle would not have passed. The chain would have.

You speak of buying from a quality vendor--and I'd posit that that's what people specifically refer to when they talk of domestic vs. imported. There are certainly quality chinese manufacturers of rigging hardware, but the hardware you buy for a fraction of the price because your theater doesn't have a big budget is not going to be this, and I wouldn't limit this to any country of origin.

Given that so much of the hardware used in theatre is overkill for many applications, I think hardware failures due to overload are certainly worth considering, but not a show stopping point of conversation. My biggest gripe about imported shackles is that the threading tends to be much worse in the SPA shackles (fewer, less precise) which leads to needing to use a wrench to "break" them much more regularally on load outs, adding additional stress and also introducing the idea to inexperienced people that wrenches and shackles should commonly be used together.

Also-- Thanks @egilson1 for sharing this. I'm curious to hear where the discussion went after these tests.
 
FYI, ASME B30.26 requires a DF of 5:1 for shackles rated at 150 tons or less. So the Chinese shackle performed within this requirement. Remember that standards are a MINIMUM. You can, and sometimes should, go above and beyond the standard and both Crosby and CM (I’m sure others do too) offer shackles with a 6:1 DF if desired.

I have a few other Chinese shackles where the threads stripped as the point of failure showing that the tolerances in manufacturing may not be as tight as the domesticity made hardware.
 
FYI, ASME B30.26 requires a DF of 5:1 for shackles rated at 150 tons or less. So the Chinese shackle performed within this requirement. Remember that standards are a MINIMUM. You can, and sometimes should, go above and beyond the standard and both Crosby and CM (I’m sure others do too) offer shackles with a 6:1 DF if desired.

I have a few other Chinese shackles where the threads stripped as the point of failure showing that the tolerances in manufacturing may not be as tight as the domesticity made hardware.
Thanks for the information on the required DF.. thats a good number to have in my head.

I haven't ever had the reason to go down the rabbit hole until now, but it's interesting to me that Crosby and CM have significantly different WLL's for a 5/16" shackle (and with the same 6:1 DF as far as I can tell, this means that one is inherently stronger than the other? Or is one company just being more conservative than the other? Do manufacturers apply their own "DF" to the MBS before publishing the MBS?
 
Crosby and CM have significantly different WLL's for a 5/16" shackle (and with the same 6:1 DF as far as I can tell, this means that one is inherently stronger than the other? Or is one company just being more conservative than the other? Do manufacturers apply their own "DF" to the MBS before publishing the MBS?

The WLL is quoted as the same as the tested 5/16 shackle at 1500lbs but they have a higher safety factor.
Remember we must compare apples with apples WLL is the load that can safely be applied where as MBS is the mean breaking strain (average). PPE, Harnesses and lanyards and crabs are rates at MBS. Here in Australia a fall restraint system must withstand a 15kn/21kn (1 person/2 people) force and still hold up but it can fail at 0.0000001kn over that so there is no extra safety factor built in. This is in our OHS/WHS legislation (OHS Act 2004 and OHS regulations 2017)

There will always be people who push the limit of safety and we can only try to educate them the best we can and remember our duty of care that is you see something wrong then say something about it.
Regards
Geoff
 
The WLL is quoted as the same as the tested 5/16 shackle at 1500lbs but they have a higher safety factor.
Remember we must compare apples with apples WLL is the load that can safely be applied where as MBS is the mean breaking strain (average). PPE, Harnesses and lanyards and crabs are rates at MBS. Here in Australia a fall restraint system must withstand a 15kn/21kn (1 person/2 people) force and still hold up but it can fail at 0.0000001kn over that so there is no extra safety factor built in. This is in our OHS/WHS legislation (OHS Act 2004 and OHS regulations 2017)

There will always be people who push the limit of safety and we can only try to educate them the best we can and remember our duty of care that is you see something wrong then say something about it.
Regards
Geoff
Ah, but this isn't true:

Crosby 5/16" Shackle: 1650lb WLL, 6:1 DF
CM 5/16" Shackle: 2200lb WLL, 6:1 DF

A direct link to CM is a bit hard because of the website, but same information is buried in here: http://www.cm-et.com/Public/55138/Full Line Catalog CMETPC-0216.pdf
Similar for Crosby: https://www.thecrosbygroup.com/prod.../crosby-209-carbon-screw-pin-anchor-shackles/

These differences are fairly consistent across the board.-- See Page 4 of this pdf for a fancy table.

With this in mind, why buy Crosby shackles over CM?
 
Last edited:
MBS is the mean breaking strain (average).

Might be a difference of terminology on opposite sides on the pond, but for all the rigging I've dealt with (purchased in the US) MBS meant minimum breaking strength not mean. I always assumed this allowed the manufacture to apply their own design factor between the worst performing unit in their destructive testing and the rated MBS.
 
You'll have heard me say this before: regardless of where they're actually fabricated, I think the important difference is whether the hardware is stamped with a company's initials. Basically, is there someone to sue when it fails? Not so much because you want to sue, but because in assuming liability you have assurance that the company is going to great lengths in quality control.
 
Aint physics grand?

When asking a colleague for advice when bidding a very budget-conscious project the subject of imported rigging hardware was discussed. His advice was "take the WLL seriously, these (units we were looking at) aren't forgiving." We notified the architect and the engineer signed off on them.

Our video subcontractor bought C-M shackles for their rigging trunk. They're a pleasure to use.

Working as a stage hand I see most touring shows with Chicago Hardware shackles, at least in the 5/8 bin.
 
The QC in imported goods of any kind can be suspect. Independent factories, i.e. factories that are not managed by a single known manufacturer, can and do replace materials and processes as they see fit. An item that you spec and approve for build one day can be drastically different the next as they will change materials without your knowledge or consent. Without proper oversight and QC, you never know what you might get.

Thus the danger of using foreign goods
 
The QC in imported goods of any kind can be suspect. Independent factories, i.e. factories that are not managed by a single known manufacturer, can and do replace materials and processes as they see fit. An item that you spec and approve for build one day can be drastically different the next as they will change materials without your knowledge or consent. Without proper oversight and QC, you never know what you might get.

Thus the danger of using foreign goods


That’s pretty a pretty harsh blanket statement. Why would a company making thousands a pieces a day that supplies a good chunk of the world not conform to some standard even if they changed material. Not only does that jeopardize them but the people using it.

Foreign or independent. You don’t set up an operation that big and not QC.

Furthermore if you are being cheap and expect quality product well good luck.

But

Every good big or small factory will gladly answer your questions about material and QC. The ones that don’t well don’t buy from them.
 
Gotta say...

I learned more from this thread and 15 minutes of reading Crosby/CM data sheets and manuals than I ever did from trying to learn basic rigging on the job. I don’t imagine this post was intended to be entirely educational, but it was an education for me!

Learn all the terms! I feel... *inhales*
...smarter!
 
The QC in imported goods of any kind can be suspect. Independent factories, i.e. factories that are not managed by a single known manufacturer, can and do replace materials and processes as they see fit. An item that you spec and approve for build one day can be drastically different the next as they will change materials without your knowledge or consent. Without proper oversight and QC, you never know what you might get.

Thus the danger of using foreign goods

I've used rigging components made in the US, Europe, and Asia. As a general rule if you pay what it's worth you'll get what you expect. Things that seem be too good to be true usually are. If you don't think anyone outside the US can make a quality product consistently you'll severely limiting yourself to who you can purchase from and probably spending more money than necessary to do it.
 
Gotta say...

I learned more from this thread and 15 minutes of reading Crosby/CM data sheets and manuals than I ever did from trying to learn basic rigging on the job. I don’t imagine this post was intended to be entirely educational, but it was an education for me!

Learn all the terms! I feel... *inhales*
...smarter!

That’s the goal. Education.

Ethan
 

Users who are viewing this thread

Back