Trim Chains

Well, this is an interesting 2 year plus look back. I'll have to see if I joined CB after the initial thread but I take exception to several comments here.

First, trim chains - like on a normal theatre manual counterweight lineset with 5 or 6 or 7 lift line or similar definitely is a overhead lifting application according to NACM. I have spoke to every member of the committee responsible for the NACN standard and shown the photos and diagrams and there is no doubt in my mind that the basic trim chain is chain used for overhead lifting. It all arose out of an incident that had multiple points of suspension - like a lineset. Freely suspended basically means not other forces, like restraints. The example the chair gave was lifting an atlas missile from a silo and the suction created.

Why anyone accepts the OSHA does not apply is beyond me. If you a an employee and you're under the lineset, OSHA applies.

You'll note that the PLASA standard (at least first edition - I haven't looked at any changes) required "Trim chain assemblies shall be fabricated of chain approved by the manufacturer for the application." While some rigging contractors have made "letters" available from chain manufacturers, the manufacturers do not say that grade 30 - or any non-alloy chain like grade 80 - is suitable for overhead lifting applications.

Finally, both SECOA and Clancy developed an alloy chain that overcame the problems of grade 80 - a concession if there ever was one.

Is grade 30 a problem? Not one that I loose sleep over knowing that I use to specify it - but if there ever is a problem - related to the chain or not - I count on it coming back.

While not specifically advocating immediately changing out all existing grade 30 trim chains, as if it were asbestos, I don't see any reason not to use the alloy alternatives available now in all new installs. The cost is insignificant in terms of the whole line set and less than the cost of coffee breaks for an entire whole new building. (Clancy list price of $25 for black alloy 1/4" with 1/4" fitting vs $15 for mil finish grade 30 similarly outfitted - $70 per 7 lineset at list.)

Somebody has to be the dog turd in the swimming pool.
 
Wow, Bill made this pool so attractive......but my mind has always been similar. G30 isn't necessarily dangerous IMO. At a minimum there is a question over the standards. We have better solutions that have minimal added cost. We might as well utilize them if we can.

Trim chains bother me far more over the fact they slide so easily than any fear of them breaking. Heck, the old unrated ones with dog clips, the dog clips would break, but never heard of the chain breaking. What I do see all the time is trim chains that have been slid out of place. I've also seen pipes hung on 2 or 3 points get fouled and slide out.

As a wise lawyer said, the goal is not to get into a lawsuit you can win. The goal, is not to get into a lawsuit. Whether G30 trim chains meet the applicable standards or not, in most situations batten clamps are just safer.
 
Not to muddy the waters at all but what about double wrapped trim chains that create almost a choke on the batten? We ear them fairly regularly in our space and was wondering how okay they are.
 
I have used clamps in the past - ones with a trim plate rather than turnbuckles which I can't fault but don't like - but prefer the alloy chain. I do have battens marked to show home position and I don't find with the double wrap that they slide very easily. No problem with the RACA that ETC includes with Prodigy.
 
I have used clamps in the past - ones with a trim plate rather than turnbuckles which I can't fault but don't like - but prefer the alloy chain.

What is it about the trim chains you prefer? Or is it just an annoyance with the clamps? I'm not familiar with the trim plate variety.

I agree. The paint marks make a big difference.
 
It's not clamps I don't like - it's the turnbuckle - vertical. I don't like the way the line "folds" if it slacks at all, and the possibility for the end of the turnbuckle to catch something. I'm ok with a turn buckle with double clamps - one to anchor the turnbuckle and one with a turning wheel, so turnbuckle is horizontal - thought admittedly this is a lot of obstruction on the batten.

I have never figured out how to post a jpeg here or I would show you the trimming clamp. When I click upload files, nothing happens. Likewise attachments. What happened to cut and paste? Send me an email and I'll send you the image I clipped.
 
My apologies. A long time ago, I use to specify scenery chains - which I see Mutual Hardware calls a Trimming Chain. Scenery Chain gets some of the most unexpected google results I have seen - and none relevant.
 
I really enjoyed the intelligent discussion on trim chain. I just wanted to find out the reasoning behind using a rated quick link vs. a rated shackle that would be strong. Is it price point, ease of use, load rating difference (3/16 shackle would be similiar I guesS), ability to fit through G30 chain?

I really hate to resurrect an old post, but this last question was exactly the info I was digging for. Is shackle or the highly rated quick link mentioned above the preferred connector for connecting trim chain to the eye of the wire rope when attaching scenery to a batten
 
I really hate to resurrect an old post, but this last question was exactly the info I was digging for. Is shackle or the highly rated quick link mentioned above the preferred connector for connecting trim chain to the eye of the wire rope when attaching scenery to a batten
OK, you've asked two very different questions here.
First, attachment of the trim chain to the lift line ..."eye of the wire rope".
Second, "attaching scenery to a batten."

Attaching the trim chain to the lift line eye should NOT use a shackle OR a quick link. The lift line eye MUST be formed around/through the end link of the trim chain. The chain is then wrapped 1 1/2 times around the batten and a shackle is used to attach a link of the chain back to the lift line eye, NEVER to a link of the chain. I do not approve of using a quick link, even if it is rated, for terminating trim chains.

Attaching scenery to the batten can be done in any number of ways, depending on what the unit is, how it is constructed, how much it weighs, how many lift points are practical, etc. I personally do not approve of using quick links because there is (to my knowledge) only one truly load rated brand and it is a European make not widely available n the US. Of course there are also many unrated shackles available through big box stores and name brand hardware stores.

The quote you cited listed 3/16" shackle, this is NOT an acceptable size for trim chain termination. Trim chains should be attached with a 1/4" minimum shackle in conjunction with minimum G30 proof coil chain. If using STC or Alpha G63 chain, one should use a minimum 5/16" shackle. 3/16" shackle is an acceptable size for attaching scenic units using 3/16" or smaller cable or 3/16" or smaller proof coil chain. NOTE: DO NOT use any non welded chain to rig scenery or objects overhead.

Hope this helps.
 
Michael, I'm curious
The lift line eye MUST be formed around/through the end link of the trim chain....

Not to take this too far off topic, but I'm curious about this. While most of the installed systems I've seen do have this, and it's obviously a good idea for an installed system, can you elaborate on why it "MUST" be this way? I've built a number of temporary linesets, and/or had to rerun AC through loft blocks, where we terminated the lift line with an empty thimble, then shackled the trim chain in later (being sure to orient the shackle pin up). I can't see any structural reason why the chain would need to be permanently locked into the thimble, as the failure of the shackle in either instance would still have the same result. Is this one of those things that's just done to future-proof an install against losing chain and replacing it with Home Depot hardware, or is there a structural and/or code related reason that I'm not seeing?
 
I have same question for Michael Powers as rochem Michael. Why would shackles at both ends of trim chain be wrong?

I agree on quick links and in particular because inspection is harder compared to a moused shackle.

I obviously object to grade 30 since no manufacturer of grade 30 will say the application is acceptable, but read elsewhere.
 
OK, you've asked two very different questions here.
First, attachment of the trim chain to the lift line ..."eye of the wire rope".
Second, "attaching scenery to a batten."

Attaching the trim chain to the lift line eye should NOT use a shackle OR a quick link. The lift line eye MUST be formed around/through the end link of the trim chain. The chain is then wrapped 1 1/2 times around the batten and a shackle is used to attach a link of the chain back to the lift line eye, NEVER to a link of the chain. I do not approve of using a quick link, even if it is rated, for terminating trim chains.

Attaching scenery to the batten can be done in any number of ways, depending on what the unit is, how it is constructed, how much it weighs, how many lift points are practical, etc. I personally do not approve of using quick links because there is (to my knowledge) only one truly load rated brand and it is a European make not widely available n the US. Of course there are also many unrated shackles available through big box stores and name brand hardware stores.

The quote you cited listed 3/16" shackle, this is NOT an acceptable size for trim chain termination. Trim chains should be attached with a 1/4" minimum shackle in conjunction with minimum G30 proof coil chain. If using STC or Alpha G63 chain, one should use a minimum 5/16" shackle. 3/16" shackle is an acceptable size for attaching scenic units using 3/16" or smaller cable or 3/16" or smaller proof coil chain. NOTE: DO NOT use any non welded chain to rig scenery or objects overhead.

Hope this helps.

Sorry, I can clearly see my misuse of terminology (and the fact that I missed that there was a second page of discussion) muddled my question. Our theater was recently built in 09 - The permanent installation is lift line formed around end link of trim chain than other end links of trim chain shackled to a batten clamp. My real question had to do with the temporary rigging of stage scenery to the batten. We tend to fly broadway style flats. We use bottom hanging irons and keeper plates and 1/8" wire rope which we shackle (and mouse) to the bottom hanging irons with rated 1/4" shackles. The scenery is than hung to G30 chain which is wrapped 1.5 times around the batten. because we can't get the chain to fit into the shackle, we have been using a larger 5/16" or 8mm quick link.
I feel comfortable with the hardware at the scenery end as it is rated and made for the exact purpose we are using it for. The chain and connector at the batten end is where I am less confident. As we are buying some new hardware for flying scenery---I want to get the right stuff. I.e it sounds like we should be getting the new chain from SECOA and Clancy mentioned above.

How do you connect the eye to the chain wrapped around the batten? i.e the 1/4" shackle doesn't fit more than one link. Do you use a different shackle size?
 
comments on the following welcome: ...
My comment:
The Rose Brand product is wonderful, but in no universe is a deck chain synonymous with, or even similar to, a trim chain. Note the size: "Our deck chains are made of extra long (1/2" x 4") links of grade 80 alloy chain." Don't try wrapping that around a batten. In fact, don't even try wrapping that around a beam. Its intended use is to allow for adjusting the length of a bridle leg.
(Which, by the way, is different than a bridal leg):
proxy.php

:eek:
 

Users who are viewing this thread

Back