Trim Chains

[kicknargel]

It would seem to be very standard practice in theatrical applications to use 1/4" grade 30 proof-coil chain for trim chains to connect flown hard scenery to battens. I imagine this is because it is readily available, not too expensive, and will accept a shackle. However, this chain is always labeled "not for overhead lifting." Is it because we tend to have about a 20x safety factor on the breaking strength of the chain that we feel OK about it? Does anyone have something they prefer? Spansets or webbing are good, but not adjustable and would burn in a fire. Does anyone use the (very expensive) grade 80 deck chains specially made to accept a shackle that are available from Fehr?

 

[Footer]

For me, if it goes overhead, its grade 8.... thats all that really need to be said. If you can't afford to use the proper chain, don't fly anything. That being said, I have seen people use simple slings to secure lift lines and stuff like that... that tends to work rather well.

 

[MNicolai]

It depends on how you use the chain. Grade 30 is used for trim chains frequently because it does not constitute overhead lifting. "Overhead lifting," as defined by the NACM (National Association of Chain Manufacturers) is a very specific definition:

Overhead lifting: that process of lifting that would elevate a freely suspended load to such a position that dropping the load would present a possibility of bodily injury or property damage.

The very key term used above is "freely suspended," to which JR Clancy does not consider a batten "freely suspended" because is always more than one lift line and the chain is not allowed to freely twist should the load spin around.

Here is a white paper from JR Clancy that goes further in-depth on this topic.

Personally, when I rig stuff I use G80 chain for the top chain that wraps around the batten, either in 24" or 36" lengths, with a quick link at that connects between the chain and wire rope, then I use wire rope for the majority of the distance, followed by a G30 trim chain on the bottom.

Because rated components such as shackles and quick links will not fit between the internal links of a G80 chain -- they will only connect to each end-link of a G80 chain, G80 is not suitable for the "trimming" function of a trim chain, unless you use a turnbuckle, whereas with G30 chain you can leave extra links hanging out of the quick link or shackle and take them in and out as is necessary for the sake of modifying the height of the trim.

Another finding of JR Clancy's was that when G30 chain had a properly spec'ed design factor for the application, the wire rope always failed before the chain did.

When you think G80 chain, think how chain motors are frequently used for things like hanging line arrays -- the failure of a single lift line can bring the entire speaker array crashing to the ground. When used for multi-point loads where the chain is more of a static device and is not passing through any kind of chain fall or hoist, properly rated G30 is appropriate -- the application does not fit the bill as "overhead lifting" by NACM's definition.

 

[gafftapegreenia]

Because rated components such as shackles and quick linkswill not fit between the internal links of a G80 chain -- they will only connect to each end-link of a G80 chain,

So you quick links are actually stamped with a rating? I mean if you''re actually buying rated quick links then I applaud you.

 

[MNicolai]

So you quick links are actually stamped with a rating? I mean if you''re actually buying rated quick links then I applaud you.

You betcha. 880lbs, purchased from Sapsis Rigging for $0.30 or so a pop. Unbelievably cheaper than if bought from a hardware store.

All of our permanent stuff is rigged with moused shackles, but we use quick links, G80 top chains, G30 bottom chains, and 1/8" wire rope cable for assembling lift lines for temporary stuff. The SWL of the wire rope makes it always the first component to fail, but its SWL is more than satisfactory for what we use it for.

I have a diagram I'd be willing to share via PM that shows our typical use-case, but I don't want it to be confused with a How-To guide for assembling your own rigging equipment.

Our last show install had about 500' of wire rope and 70 quick links in the air in addition to our permanent rigging. I keep about 100 of these 880lbs quick links on hand for general purpose use. They cost almost nothing and are easier to setup for temporary stuff than moused shackles. Also easier to strike.

 

[DuckJordan]

So you quick links are actually stamped with a rating? I mean if you''re actually buying rated quick links then I applaud you.

You mean people don't buy rated equipment?

Btw quick note on quick links... They only hold that weight when they are closed. Open they are maybe 1/36 of that strength if that...

 

[gafftapegreenia]

You mean people don't buy rated equipment?

Btw quick note on quick links... They only hold that weight when they are closed. Open they are maybe 1/36" of that strength if that...

Yes there are MANY people out there who either do not know or do not care about ratings.

 

[Footer]

It depends on how you use the chain. Grade 30 is used for trim chains frequently because it does not constitute overhead lifting. "Overhead lifting," as defined by the NACM (National Association of Chain Manufacturers) is a very specific definition:



The very key term used above is "freely suspended," to which JR Clancy does not consider a batten "freely suspended" because is always more than one lift line and the chain is not allowed to freely twist should the load spin around.

Here is a white paper from JR Clancy that goes further in-depth on this topic.

Personally, when I rig stuff I use G80 chain for the top chain that wraps around the batten, either in 24" or 36" lengths, with a quick link at that connects between the chain and wire rope, then I use wire rope for the majority of the distance, followed by a G30 trim chain on the bottom.

Because rated components such as shackles and quick links will not fit between the internal links of a G80 chain -- they will only connect to each end-link of a G80 chain, G80 is not suitable for the "trimming" function of a trim chain, unless you use a turnbuckle, whereas with G30 chain you can leave extra links hanging out of the quick link or shackle and take them in and out as is necessary for the sake of modifying the height of the trim.

Another finding of JR Clancy's was that when G30 chain had a properly spec'ed design factor for the application, the wire rope always failed before the chain did.

When you think G80 chain, think how chain motors are frequently used for things like hanging line arrays -- the failure of a single lift line can bring the entire speaker array crashing to the ground. When used for multi-point loads where the chain is more of a static device and is not passing through any kind of chain fall or hoist, properly rated G30 is appropriate -- the application does not fit the bill as "overhead lifting" by NACM's definition.

The OP was not asking about attaching lift lines to battens, he was asking about attaching loads to that pipe. In that case, yes, grade 80 is required. Depending on how the piece is rigged, failure of one point can send it flying to the ground and cause damage. Most scenery is rigged with as few points as possible, so one point can easy cause enough issue for concern. Added to that, a standard rigging package for theatre always includes a turn buckle so trimming at the pipe is hardly ever done.

So, with that as well, if your buying trim chain you might as well buy trim chain that can be used in every situation. As with any hardware, you don't want to have both "good" and "not good" hardware laying around. Every theatre should have 50-100 trim chains laying around. Buy it once, buy it right, never buy it again. Very few rental sets will actually come with trim chains, so having them in stock is a good thing.

 

[MPowers]

As Mike Nicolai has so eloquently said, and provided specific source information to support his statements, as the rigging elephant in the house (JR Clancy) publishes, trim chain for battens and chain as a trim device on scenic units hung from battens does not fall into the OSHA, or BOCA or other regulatory agencies definition of "Overhead Lifting". In fact grade 30 Proof coil chain has a higher load rating than the lift line from which it is attached. 1/4" GAC, the heaviest commonly used rigging cable has a WWL of 875#, Grade 30, proof coil chain has a WWL of 1250# using the smallest load limit published by various manufacturers. As the standard use of trim chain is with 1-1/2 wraps around the batten and shackled back to the eye, the chain is actually only experiencing 1/2 the load. Which item is the weaker link? Grade 80 chain is inappropriate as stage rigging chain as it does not suit the purpose and cannot be used with the appropriate connecting components if adjustibility of height is a desired factor.

As for hanging scenic units from a batten, if you are hanging an object from a single point, and it is to be subjected to oscillating and side loading, or if the chain is to be reeved over a gear wheel used as a drive mechanism, then you meet the definition of "Overhead Lifting" and grade 30, Proof coil chain is not appropriate. If you are hanging from two or more points, it is not overhead lifting.

If chain is being used in a situation where greater strength is needed, there are two very good products, Clancy Alpha chain and SECOA STC chain. They are both a grade 63 chain manufactured so that standard rigging components such as shackles, J&J turn buckles etc. will fit in middle links as well as end links. Both have manufacturers ID stamped on every link and a date code on every 10th link so that lot and date of manufacture are traceable. Both cost several times the cost of Grade 30, 1/4" chain.

a standard rigging package for theatre always includes a turn buckle so trimming at the pipe is hardly ever done.

Actually this is not true. First there is no "Standard rigging package". All the rigging manufacturers, Clancy, Thern, H&H, Vortek, SECOA, ETC et. al. offer several batten attachment methods, turnbuckles are only about 1/3 of the available choices. ETC Prodigy rigging does not offer turnbuckles at all. Stage Electric battens, if hung from the brackets supplied by the raceway manufacturer, are usually hing with turnbuckles, this is an excellent use of the device.

If "trimming at the pipe is hardly ever done" means turnbuckles at the arbor, turnbuckles at the top of the arbor instead of at the batten is a poor choice of rigging practice. This places far too much hardware into a cramped, often inaccessible location. Properly mousing the turn buckles is a major PITA. In addition, the trim device is in a remote location from the device being trimmed, thus one person cannot trim the batten without at least one additional stagehand. If the batten trim mechanism is at the batten, a single stage hand can properly and accurately trim a batten in a few minutes.

 

[kicknargel]

Three cheers to Control Booth--thanks all for the thorough (and researched) answers. The JR Clancy white paper puts my mind at ease.

Disclaimer: This thread contains a pretty high-level discussion among experienced professionals. Do not take the narrow "overhead lifting" definition to mean that you can use all those "rigging" components from the Big Box/Hardware store. Grade 30 proof coil chain has still been subjected to testing and rating. I'm not even sure that the chain at Depot is actually proof coil.

 

[MNicolai]

Three cheers to Control Booth--thanks all for the thorough (and researched) answers. The JR Clancy white paper puts my mind at ease.

Disclaimer: This thread contains a pretty high-level discussion among experienced professionals. Do not take the narrow "overhead lifting" definition to mean that you can use all those "rigging" components from the Big Box/Hardware store. Grade 30 proof coil chain has still been subjected to testing and rating. I'm not even sure that the chain at Depot is actually proof coil.

Hardware stores frequently have G30 proof coil chain for sale among an assortment of other types of chain, but it should always be labeled Grade 30 and should always have a rated SWL. If you are unable to determine the load rating of chain, do not buy it or use it. This same policy goes for in-house stuff. When you have a growing inventory of assorted ropes, chains, and wire rope cables, always make certain that the safe working load limits are known and documented for each material. I have several ropes that I travel with which I've thrown labels on, and I've printed heat-shrink labels for all of my wire rope cables that I've made showing their load limits given an 8:1 design factor. For chain, we only stock one size of G80 and one size of G30, so it's pretty easy to keep track of the SWL's on those.

Regarding "overhead lifting," it's important to note that the strict definition that NACM uses to define overhead lifting as based on freely suspended objects is not the same definition used for establishing design factors. When determining the design factor for a theatrical rigging application, overhead lifting is more broadly considered to be things that hang above peoples' heads, which should have a design factor of 8:1. However, when you buy chain the safety factor to determine SWL is 4:1, which is an industry standard by NACM for defining what the SWL of chain is. This differs from rope which is usually sold with a minimum design factor of 5:1 (though it may differ).

Thus, when you are designing a rigging application, be very careful what you use for your SWL's, because though the chain you've purchased may have an SWL of 800lbs, for your application of hanging something above someone's head in theatre you should halve that to an SWL of 400lbs. So those quick links I have that are rated for 880lbs? Effectively I shouldn't load them to greater than 440lbs, and because they retain a MBS (minimum breaking strength) of ~3500lbs, there should never be a situation where one of them would fail and cause something heavy to drop onto someone's head.

 

[MPowers]

Well said Mr. Nicolai.

As Mike pointed out, a confusing thing about various rigging components is that manufacturers of various products have a different design factor for different products. For example, the industry standard design factor is different for chain vs: GAC.

Design factor is the multiplier between the tested breaking point of a product and the published Safe Working Load (SWL) or Working Load Limit (WWL). Example is 1/4" GAC with a breaking strength of 7000#, an 8-1 design factor gives a WLL of 875#.

 

[gafftaper]

You betcha. 880lbs, purchased from Sapsis Rigging for $0.30 or so a pop. Unbelievably cheaper than if bought from a hardware store.

Not to trash talk Uncle Bill, but do those quick links have a manufacturer name stamped in them? I was always taught that unless it has the name of a manufacturer stamped in it, the load limit stamp is worthless. Without a manufacturer's stamp who is certifying that load limit is true? Who is responsible if it fails?

You mean people don't buy rated equipment? Btw quick note on quick links... They only hold that weight when they are closed. Open they are maybe 1/36 of that strength if that...

It's traditionally been a lot harder than you think to find a properly made, rated, and manufacturer stamped quick link. The quick links that came with my theater are all rated 500lbs and they are made by the world's most popular manufacturer... China. Who are you going to sue if they break?

Unfortunately, the old reliable American manufacturers like Columbus Mckinnon, who do stamp their name into their products, don't make quick links. As far as I know the only quick link in the world that is rated and has the manufacturer's name stamped in it is from a french company called Maillon Rapide. They will cost you around $3-$4 each, but as far as I know it's the only quick link that ever can truly be considered fully rated.

 

[MNicolai]

Not to trash talk Uncle Bill, but do those quick links have a manufacturer name stamped in them?

One side says 1/4 China WLL 880LBS and the other side says R. I do not know the significance of the "R".

The way that SRI ships them out is they throw them in a bag without any product packaging. If I asked SRI, they could tell me who makes them, but it could get ugly in a court of law trying to prove that my quick links did in fact come from a certain manufacturer.

 

[shiben]

Not to trash talk Uncle Bill, but do those quick links have a manufacturer name stamped in them? I was always taught that unless it has the name of a manufacturer stamped in it, the load limit stamp is worthless. Without a manufacturer's stamp who is certifying that load limit is true? Who is responsible if it fails?



It's traditionally been a lot harder than you think to find a properly made, rated, and manufacturer stamped quick link. The quick links that came with my theater are all rated 500lbs and they are made by the world's most popular manufacturer... China. Who are you going to sue if they break?

Unfortunately, the old reliable American manufacturers like Columbus Mckinnon, who do stamp their name into their products, don't make quick links. As far as I know the only quick link in the world that is rated and has the manufacturer's name stamped in it is from a french company called Maillon Rapide. They will cost you around $3-$4 each, but as far as I know it's the only quick link that ever can truly be considered fully rated.

The rigging handbook has a manufacturer in it, dont remember the name

 

[Les]

Hopefully I don't derail this thread, but here's something I've been curious about.

Altman states that their permanent continuous striplights (such as the #528 and #520-pictured below) are to be suspended using "twisted bowtie chain", aka "dog chain". I've seen this in use, and that is, in fact, what it is.

This hardware, surely, isn't rated, but Altman says it's okay. Of course, there are multiple hanging points, but how is this okay? I do note some potential violations aside from the chain, such as the AC and control lines for the Da-Lite screen just going right through the drywall all willy-nilly.

I expanded the following picture on my computer and noticed that the traveler is hung using the same type of chain:

Yes, that is a yellow extension cord draped over the track, apparently feeding a fluorescent blacklight (added by the end-users, in this case, an elementary school staff). That's a whole other post, though.

If I were to hang similar striplights, what would I use (not counting hanging irons)?

 

[shiben]

Hopefully I don't derail this thread, but here's something I've been curious about.

Altman states that their permanent continuous striplights (such as the #528 and #520-pictured below) are to be suspended using "twisted bowtie chain", aka "dog chain". I've seen this in use, and that is, in fact, what it is.

This hardware, surely, isn't rated, but Altman says it's okay. Of course, there are multiple hanging points, but how is this okay? I do note some potential violations aside from the chain, such as the AC and control lines for the Da-Lite screen just going right through the drywall all willy-nilly.

I expanded the following picture on my computer and noticed that the traveler is hung using the same type of chain:

Yes, that is a yellow extension cord draped over the track, apparently feeding a fluorescent blacklight (added by the end-users, in this case, an elementary school staff). That's a whole other post, though.

If I were to hang similar striplights, what would I use (not counting hanging irons)?

All of our soft good tracks are held up by dog chain stuff. I figured it was considered ok because there are points every 7 feet to our grid and the goods are only 16' tall...

 

[erosing]

As far as I know the only quick link in the world that is rated and has the manufacturer's name stamped in it is from a french company called Maillon Rapide. They will cost you around $3-$4 each, but as far as I know it's the only quick link that ever can truly be considered fully rated.

Yep, Maillon Rapide is the only one still, as far as I know as well. I've got a number of them, and they are worth every penny. You can actually feel the difference in quality. I made the jump to them earlier last year, and I won't use anything else when it's my butt. Rosebrand is the only theatrical, or local for that matter (relatively speaking), source I know of to get them, off the top of my head. But yes, they aren't anywhere near as cheap as other quick links. But that piece of mind and track back capability is worth it, who else gives you a 5:1 design factor. Seriously check them out, Maillon Rapide, they've got a bunch of great products.

Rosebrand prices for comparison for those that are curious but don't want to click the link.
1/8"----$1.25
3/16"---$1.40
1/4"----$1.60
5/16"---$2.26
3/8"----$4.25
1/2"----$6.55

As long as we're on the topic, anyone see Crosby's new player, the Theatrical Shackle? Alright, it's not really on topic, but I was looking for something else on their website last night and stumbled upon it.

 

[MPowers]

If I were to hang similar strip-lights, what would I use (not counting hanging irons)?

3/16" grade 30 proof coil chain and 3/16" forged anchor shackles.

 

[coolsvens]

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?