# 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?


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## 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.


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## 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.


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## gafftapegreenia

MNicolai said:


> 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.


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## MNicolai

gafftapegreenia said:


> 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.


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## DuckJordan

gafftapegreenia said:


> 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...


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## gafftapegreenia

DuckJordan said:


> 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.


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## Footer

MNicolai said:


> 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.


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## 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.


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## 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.


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## MNicolai

kicknargel said:


> 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.


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## 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#.


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## gafftaper

MNicolai said:


> 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? 


DuckJordan said:


> 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.


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## MNicolai

gafftaper said:


> 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.


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## shiben

gafftaper said:


> 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


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## 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)?


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## shiben

Les said:


> 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...


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## erosing

gafftaper said:


> 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.


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## 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.


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## 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?


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## DuckJordan

you can't really mouse a quick link, and the weight is on the threads on the quick link. Where on a shackle the weight is on the bell and the pin not the threads, and the ability to mouse the shackle to never come loose is a big bonus.


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## kicknargel

I think the reason to use a quick link would be to fit into chain or other opening that a shackle won't get through.


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## BillConnerFASTC

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.


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## tprewitt

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.


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## DuckJordan

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.


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## BillConnerFASTC

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.


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## tprewitt

BillConnerASTC said:


> 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.


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## BillConnerFASTC

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.


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## techieman33

I'm posting this for BillConnerASTC
View attachment trim plate.pdf


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## kicknargel

The OP (me) was referring to (temporarily) attaching scenery to systems pipes rather than (permanently) attaching systems pipes to the system.


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## BillConnerFASTC

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.


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## Jackalope

coolsvens said:


> 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


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## MPowers

Jackalope said:


> 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.


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## rochem

Michael, I'm curious 

MPowers said:


> 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?


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## BillConnerFASTC

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.


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## Jackalope

MPowers said:


> 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?


----------



## Jackalope

Jackalope said:


> 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?


unless you only only go through the end links... that would work.


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## Jackalope

comments on the following welcome:
http://www.rosebrand.com/product173/Deck-Chain.aspx?cid=212&idx=2&tid=1&info=Chains+%26+Slings


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## derekleffew

Jackalope said:


> 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*):


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## Jackalope

i prefer the pictured bridal leg


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## BillConnerFASTC

Jackalope said:


> i prefer the pictured bridal leg


Me too. Could she pull that up just a little more?


----------



## derekleffew

BillConnerASTC said:


> ... "Could she pull that up just a little more?"


When I said that to the rigger, she slapped me.


----------



## AlexDonkle

As a curiosity, one thing I've yet to fully understand is why trim chains are even used in permanent install. What advantage do they have over batten terminations using pipe clamps with turnbuckles? Trim chain seems faster for temporary work, but I'm not entirely sure why it's common in permanent install as well.


----------



## MNicolai

Pretty sure Daft Punk had a song about trim chains. "Cheaper Better Faster Stronger", possibly?


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## BillConnerFASTC

adonkle said:


> As a curiosity, one thing I've yet to fully understand is why trim chains are even used in permanent install. What advantage do they have over batten terminations using pipe clamps with turnbuckles? Trim chain seems faster for temporary work, but I'm not entirely sure why it's common in permanent install as well.


I don't like the way turnbuckles project outward in a slack line condition, and catch things. But I don't disagree with your premise.


----------



## Euphroe

BillConnerASTC said:


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



Maybe people accept it because OSHA may not apply to certain lifts in audience view. Like a magician's "assistant" or a prop levitating on piano wire. Which is very different from the liftlines of a CW set. 

The more interesting question is this: is the SWL of a counterweight set always based on a fully-loaded arbor, no matter the "intended" load? Assume an 8' arbor is maxed, and the load is concentrated on one liftline; then 1/4" 7000lb wire rope makes sense, with matching hardware. 

How does this relate to the "intended" load? If two sets have 8' arbors, but one is "intended" for a cyc can you use smaller trim hardware than if the set is "intended" for an LX? 

Why should a 7-line set with an 8' arbor require the same hardware as a 4-line set with an 8' arbor? 

Now, how does this relate to a motorized set? Should the size of the wire rope and hardware be based on the winch capacity (as with hoist chain and hardware), or based on the "intended" load? If I only "intend" to fly 50lbs, can I install 500lb wire rope on a 1000lb winch? 

We seem to size counterweight components based on the max possible load.


----------



## MNicolai

Euphroe said:


> How does this relate to the "intended" load? If two sets have 8' arbors, but one is "intended" for a cyc can you use smaller trim hardware than if the set is "intended" for an LX?
> 
> We seem to size counterweight components based on the max possible load.



Theaters systems remain in use for sometimes upwards of 50 or 70 years. You cannot predict how someone will use those systems, nor do you want to limit how they _can_ use those systems. I've seen sets intended for cycs use to hang hard-covered scenery. I've seen shows where the audience is seated on stage and just about anything can become fair game for deviating from normal practices and uses. Designs for systems like rigging, lighting, audio, and video should not be looked at as designs for systems that will only be in place for 5-10 years. They are infrastructure for supporting the growing and changing needs of those venues over decades to come. While electronic equipment may be replaced more frequently, the other backbones of theaters (power and data distribution, rigging sets and points, lighting positions) will remain much longer and see far more different uses over the years.

As an example, at our design/install shop, we specifically pull spare network cables in our data conduits knowing if they won't use them right away, there's an excellent chance they'll be used in the future. We take into special consideration that installing those wires and conduits with in the first place so that the venue has room to grow is much more cost effective than later on if they have to hire an electrician to install those conduits and wires. Especially if installation would mean coring through concrete walls and floors, or trenching through concrete slabs. If we limit our design to the bare necessities on the first go 'round, when the venue does inevitably want to upgrade in 10-15 years, they can expect to pay a disproportionately higher cost than if they had put that infrastructure in place on Day One.


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## Euphroe

You're saying the design factor should be based on the potential force in the system. 

Since an 8' arbor could be fully loaded at some future date, the components should be sized for the capacity of the arbor, not the "intended" load. 

Say its a temporary installation and I'm using a 1T hoist, but only I only "intend" to fly 800lbs. Can I use an 880lb quick link to hang the 1T hoist to the beam? 

Or is it like the counterweight set where the components should be based on the potential force in the system (hoist capacity) and not the "intended load" (load weight)? 

If a balanced CW set strikes an adjacent pipe, the force is only what the rigger pulls. 

But if a hoisted load strikes an obstruction, the force is the capacity of the hoist and the quick link will break. 

So do we work from the "intended load", or from the potential force in the system? Because the two are not interchangeable.


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## MNicolai

I'd advocate for potential force, especially in extended use or permanent installations. Intent today and intent next month or next year can be drastically different. Temporary situations are different though in that you have more control over intent. That rigging used to hang a chandelier for a show on Monday is unlikely to be repurposed on Tuesday for hanging a line array. That's more of a "design for today's application" scenario than the "design for the future possibilities" scenario.

As for the the quick link, no you can't use it unless you find one that's rated for overhead lifting, and I only know one manufacturer in the world who makes those.


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## DuckJordan

On top of that Euphroe, most companies specify what kind of loading you can do using a single point on the system. The single point load on our battens with, I think, 6' arbors is 700lbs, thats as much as you can put on a single point. if spread out evenly accross the 6 lift lines the rating goes up to arbor max which is 2500lbs per line set.


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## BillConnerFASTC

I don't know what an "intended load" is. We design overhead lifting systems with safe working loads in mind, and have signage stating what that is. Loading on one line of a set, on a batten, and a combination of lines up to all of them in a set. This is in turn used to design the structural framing. And this applies to general purpose linesets on a stage that is not built for just one production. Electrics and shell sets have slightly different criteria, and we post that to.


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## Euphroe

MNicolai said:


> I'd advocate for potential force, especially in extended use or permanent installations. Intent today and intent next month or next year can be drastically different. Temporary situations are different though in that you have more control over intent.



DuckJordan: are those double arbors? 2500lbs would be 34lbs per inch. Either way, it seems trim chains are sized based on arbor capacity, not on intended load.

MNicolai and everybody else: Design factor is supposedly the minimum breaking strength over the "safe working load". Current standards seem to conflate SWL with "intended load". 

But what is the "safe working load"? It is whatever somebody decides can be flown on the hardware or the system. If the venue installs a 50,000lb winch with no wire rope on it, but tells the crew the "safe working load" is 100lbs, then it is a 100lb winch with a design factor of 500. 

But . . . then the crew decides to install 1000lb minimum breaking strength wire rope on the winch, based on the 100lb SWL of the system, and tells themselves the wire rope has a design factor of 10.

So we end up with a 1000lb wire rope on a 50,000lb winch. Have we followed the rules?


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## Euphroe

BillConnerASTC said:


> I don't know what an "intended load" is. We design overhead lifting systems with safe working loads in mind, and have signage stating what that is. Loading on one line of a set, on a batten, and a combination of lines up to all of them in a set. This is in turn used to design the structural framing. And this applies to general purpose linesets on a stage that is not built for just one production. Electrics and shell sets have slightly different criteria, and we post that to.




Hi Bill,

"intended load":

*1926.1431(g)(3)*Rigging hardware (including wire rope, shackles, rings, master links, and other rigging hardware) and hooks must be capable of supporting, without failure, at least five times the maximum *intended* load applied or transmitted to that component. Where rotation resistant rope is used, the slings must be capable of supporting without failure at least ten times the maximum intended load. (italics added)


Contrast the above with this:

1926.1414(b)(2)
Wire rope must be designed to have, *in relation to the equipment's rated 
capacity*, a sufficient minimum breaking force and design factor so that 
compliance with the applicable inspection provisions in § 1926.1413 will be 
an effective means of preventing sudden rope failure.

Design factor is MBS/SWL. But what is the SWL? It is MBS/design factor.

It is circular. The only non-relative term is MBS. 

We need another non-relative term. It should be the potential force in the system. NOT the "intended load". Because if you put a 1000lb wire rope on a 1000lb winch you are asking for trouble, even if the "intended load" is 100lbs. 

The reason I piggybacked this on the "trim chain" discussion is that we seem to intuitively accept that CW rigging components should be based on the potential load in the system, that is the arbor capacity. 

What happens if 1000lb counterweight lineset snags on the way out? The added force is the 40lbs or whatever the flyman applies. It's nothing, almost no risk of catastrophic failure. 

But what happens if a 1000lb winch snags when lifting a 100lb load? The "intended load" becomes irrelevant. What matters is the potential force in the system.


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## BillConnerFASTC

OSHA is very poorly written and I use the building codes and consensus standards as a basis, which follow generally accepted practices in the design and engineering trades. That fact that you find conflicts and/or circular references only reinforces my views.


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## DuckJordan

When did I say we ever max out our arbor with weight limit. We have never hit weight limit other than the arbors size limit. That motors load rating doesn't mean anything when its hung using 1000lb cable. Its wll is now 100lbs using a 10:1 ratio, that limit is not to be exceeded which is why we use safety factor. We don't load to breaking limit in case a snag or other issue occurs. I'm not sure what if any point you're trying to make is coming across.

Sent from my XT1060 using Tapatalk


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## Euphroe

Sent from my XT1060 using Tapatalk[/QUOTE

DuckJordan said:


> When did I say we ever max out our arbor with weight limit. We have never hit weight limit other than the arbors size limit. That motors load rating doesn't mean anything when its hung using 1000lb cable. Its wll is now 100lbs using a 10:1 ratio, that limit is not to be exceeded which is why we use safety factor. We don't load to breaking limit in case a snag or other issue occurs. I'm not sure what if any point you're trying to make is coming across.
> 
> Sent from my XT1060 using Tapatalk




No, winch capacity means everything. In case of DuckJordan's "snag or other issue", the tension in the line becomes the winch output, and an attempt to "de-rate" the winch by signage will prove only that winches can't read signs. 

The TD writes "SWL 200 lbs" on the wall next to a 2000lb winch. The show flies a performer at 10:1 design ratio, so the crew installs a 2000lb 1/8" wire rope on a 2000lb rated-capacity winch. 

Acceptable? or not acceptable? The wire rope has a 10:1 ratio to the SWL signage and to the performer's weight with an allowance for dynamic load. 

But it's a 1:1 ratio to the winch capacity, and that's a really dangerous game to play. In event of "snag or other issue" the winch will feed its 2000lbs tension into the line, the rope breaks and the load falls, because physics beats signage, every time.

Winch wire rope size should be based on concrete numbers, like this: 

MBS / (winch rated capacity) = 10 

5000lb winchline/ 500lb winch = 10 

(Also, most variable speed winches increase torque as they slow. A 2000lbs winch may be pushing close to 4000lbs at low speed. This is part of what a 10:1 based on winch capacity is supposed to cover, and why a 2000lb winch gets a 20,000lb+ wire rope.)


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## DuckJordan

Euphroe said:


> Sent from my XT1060 using Tapatalk[/QUOTE
> 
> 
> 
> No, winch capacity means everything. In case of DuckJordan's "snag or other issue", the tension in the line becomes the winch output, and an attempt to "de-rate" the winch by signage will prove only that winches can't read signs.
> 
> The TD writes "SWL 200 lbs" on the wall next to a 2000lb winch. The show flies a performer at 10:1 design ratio, so the crew installs a 2000lb 1/8" wire rope on a 2000lb rated-capacity winch.
> 
> Acceptable? or not acceptable? The wire rope has a 10:1 ratio to the SWL signage and to the performer's weight with an allowance for dynamic load.
> 
> But it's a 1:1 ratio to the winch capacity, and that's a really dangerous game to play. In event of "snag or other issue" the winch will feed its 2000lbs tension into the line, the rope breaks and the load falls, because physics beats signage, every time.
> 
> Winch wire rope size should be based on concrete numbers, like this:
> 
> MBS / (winch rated capacity) = 10
> 
> 5000lb winchline/ 500lb winch = 10
> 
> (Also, most variable speed winches increase torque as they slow. A 2000lbs winch may be pushing close to 4000lbs at low speed. This is part of what a 10:1 based on winch capacity is supposed to cover, and why a 2000lb winch gets a 20,000lb+ wire rope.)




So according to you we should never fly anything with less than half inch cables? Education is what matters if you have to always design for idiots there will always be better idiots.

Sent from my XT1060 using Tapatalk


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## Euphroe

Exactly. No matter how clearly you explain something, there will always be somebody who didn't get it.


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## BillConnerFASTC

1. Winches are used for pulling and hoists for lifting. I thought this was about hoists and lifting.
2. A motorized system designed for a swl of 200 pounds for overhead lifting should not be capable of lifting much more than 200 pounds. The hoisting capacity of the power train is usually not and should not be 8 or 10 times the swl.


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## Euphroe

BillConnerASTC said:


> 1. Winches are used for pulling and hoists for lifting. I thought this was about hoists and lifting.
> 2. A motorized system designed for a swl of 200 pounds for overhead lifting should not be capable of lifting much more than 200 pounds. The hoisting capacity of the power train is usually not and should not be 8 or 10 times the swl.




Bill, you use "SWL" twice in the above paragraph, as though SWL is separate from the rated capacity of the winch/hoist. 

Where does this "SWL" come from if not the winch capacity? 

From the "intended load"?

SWL = MBS/(design factor) My design factor is 10. My winch capacity is 700lbs. My intended load is 200lbs. 

What is my SWL?


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## DuckJordan

I'm going to make this easier to understand. A CM Lodestar 2 ton hoist is only capable of lifting 2 tons, after 2 tons it will not lift. There is a clutch that when it gets to the limit will keep the motor from taking chain. It will not fail at 2 tons its rated at 2 tons.

So using a 2 ton motor(in this case a CM Lodestar) you need to hang it using hardware rated at a SWL (Safe Working Load) of at least 2 tons. Since industry standard is a 7:1 ratio (although personally prefer 10:1) we would be looking for hardware with a minimum breaking point of 14 tons. This includes the shackle, the steel, and where it attaches to building steel (which should also be rated to work at 14tons on that point). Its very simple.


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## Euphroe

Well that explains that. Next time I rig "How To Train Your Dragon" or Lady Gaga I'll be able to understand why those shows didn't fall down the last time I rigged them. Still confused about the 3/4" shackles on the apex of the deuces but you can math that for me when I'm more advanced. 

Meanwhile I'm on the phone with an automation vendor who will wake up tomorrow being owned by Tait. 

Me: "What wire rope do I need to order for the 32 digitally controlled 290kg-rated acrobatic winches you're selling me?" 

Vendor: "Depends. What size groove do you want us to score on the drums?" 

Me: "Well I'm supposed to use rope that is 10x the SWL of the system. What is the SWL of the system you're selling me?" 

Vendor: "Depends. What wire rope do you plan on using?" 

Me: "I want to use the skinniest wire rope that is 10x the SWL. What is the SWL?"

Vendor: "Oh, the SWL is 1/10th the capacity of the rope you use, that's called the 'design factor'. What kind of rope do you want to use? We'll groove the drum for that." 

Me: "The artists probably weigh 120lbs - 160lbs or so. Is that my SWL?"

Vendor: "In that case, we'll score the drums for 1/8" wire rope. That'll leave a little extra for safety." 

Me: "Is that safe on a 290kg winch?"

Vendor: "It is if they don't hit anything."


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## DuckJordan

I guess I still don't get the point of this discussion, other than that Automation Vendor doesn't really understand what they are selling, at least not the way it seems from that conversation. Their winch also doesn't seem to have a fail safe built in, at least not one that will stop pulling when it reaches its calibrated limit. This brings up another point. Who is supposed to design the rig, the guy buying it or the guy selling it. To me If I were selling a winch capable of pulling 290kg I would spec minimum of 1/4" wire rope.


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## danTt

I think the point of discussion/question/theory, and it's something I've wondered about on an occasion or two, is that if you have a mechanical lifting device (and I'd guess you can catogirize them differently, and react differently, depending on if it's a wire rope hoist, or a chain motor, or something else entirely) 

With a 2000lb winch, is the 2000lbs a MBS or a SWL? Does it fail destructively at 2000lbs (just keeps going until something snaps), does it fail safely at 2000 lbs? (Clutched like a chain motor) does it fail at 2000lbs*some design factor? Just saying a 2000lbs winch leaves this ambiguous, and the answers become ambiguous. If it's a MBS of 2000 lbs, then I would say that you need to use equipment rated for a MBS of at least 2000lbs. If it's a SWL of 2000lbs, then you need to use equipment rated for 2000lbs * the design factor in use. At least that's how I'd interpret it. You can't logically say "The winch has a MBS of 2000lbs, so everything needs to have a SWL of 2000lbs" -- The weakest point is still the winch, and when that fails it doesn't matter how much the wire rope is weighted for--except that wire rope rated for 10x whats necessary will hurt a lot more when it hits you on the head


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## Jay Ashworth

Euphroe's (hopefully) notional automation vendor *entirely* doesn't understand what they're selling, no.

That was the best example of circular logic I've ever seen, I think, and if a vendor pulled that on *me* selling me gear to fly people, I wouldn't obscure their name when I posted the transcript here, lemme tellya.

That said, danTt, I think the point of the latter part of this thread is that any number without a label doesn't mean anything useful to anyone, and if you can't get a label to go with the measurement, even knowing what you're talking about isn't going to help you much.


----------



## LavaASU

Euphroe said:


> Well that explains that. Next time I rig "How To Train Your Dragon" or Lady Gaga I'll be able to understand why those shows didn't fall down the last time I rigged them. Still confused about the 3/4" shackles on the apex of the deuces but you can math that for me when I'm more advanced.
> 
> Meanwhile I'm on the phone with an automation vendor who will wake up tomorrow being owned by Tait.
> 
> Me: "What wire rope do I need to order for the 32 digitally controlled 290kg-rated acrobatic winches you're selling me?"
> 
> Vendor: "Depends. What size groove do you want us to score on the drums?"
> 
> Me: "Well I'm supposed to use rope that is 10x the SWL of the system. What is the SWL of the system you're selling me?"
> 
> Vendor: "Depends. What wire rope do you plan on using?"
> 
> Me: "I want to use the skinniest wire rope that is 10x the SWL. What is the SWL?"
> 
> Vendor: "Oh, the SWL is 1/10th the capacity of the rope you use, that's called the 'design factor'. What kind of rope do you want to use? We'll groove the drum for that."
> 
> Me: "The artists probably weigh 120lbs - 160lbs or so. Is that my SWL?"
> 
> Vendor: "In that case, we'll score the drums for 1/8" wire rope. That'll leave a little extra for safety."
> 
> Me: "Is that safe on a 290kg winch?"
> 
> Vendor: "It is if they don't hit anything."



Erm, so if this is an actual conversation going on for a system that will actually be built to fly people, please please please get a real rigger with experience on automation and flying people involved. This sounds like no one really knows what they're doing, and thats REALLY bad when peoples lives are at stake. People flying puts dynamic forces into play. They can be many times the load and sometimes mean you need greater than a 10:1 safety factor on the static load. Their has been two major incidents involving performer flying in the last year (both at major companies)-- one resulted in a death and the other resulted in several serious injuries. This is not a place to mess around.


----------



## Euphroe

DuckJordan said:


> This brings up another point. Who is supposed to design the rig, the guy buying it or the guy selling it. To me If I were selling a winch capable of pulling 290kg I would spec minimum of 1/4" wire rope.



Bingo. DuckJordan gets it. 

The guy buying the winch designs the rig, but the winch vendor is under market pressure to supply what the buyer wants. 

After the accident, the winch vendor blames the buyer who designed the rig with too-small wire rope, and the buyer blames the winch vendor for selling a winch with too-small grooves. If anybody asks the "standard", they will be told "design factor of ten times the SWL", but the standard does not define SWL except by circular reference to an undetermined MBS. If the winch was fitted with 2000lb MBS wire rope because somebody preferred the way it looked, the defendants will cleverly say "then the SWL was 200lbs, and since the load was less than 200lbs we complied with the standard." Never mind it's a 650lb winch. 

And DuckJordan is exactly right about the solution. A winch vendor selling a 290kg winch should groove the drum for 1/4" wire rope minimum and tell the client to work with that. Even then, ropes of that size vary from 5400lbs to 8500lbs. 

danTt: 

Winch components are engineered for various percentages of the rated load. The rigging designer does not need to know the failure load of the gearbox secondary shaft or the woodruff key -- that's the winch vendor's turf. The winch doesn't have a "minimum breaking strength". It has a rated load, generallly specced at its max speed. A 290 kg winch is about 650lbs at top speed, and maybe 1200lbs at lower speed. Beyond that it stalls. 

The wire rope is a critical component, it should be strong enough to stall the winch. The winch is not supposed to pull the rope apart if the load snags -- the rope is not a fuse link, it is a critical component. So generally the SWL is the same as the winch capacity. All components downstream of the winch should have an MBS 10x the winch capacity. If they have an MBS of 5x the winch capacity, you're operating at a design factor of 5. That might be okay, but remember the winch ultimate capacity could be twice the rated capacity.


----------



## danTt

Euphroe, let's approach this a different way. Your concern at the moment seems to be that if something is hung from a hoist, and catches on something it flys out, the wire rope should not fail before the winch does. I can understand this, but then I start wondering--why? Do you really want whatever the object is caught on to be subjected to 2000lbs of force? Might this not be more dangerous than having something fail quicker? 

Similarly, and to play devils advocate a little--All we are talking about at this point has been the rigging materials. If you are flying a broadway flat from a winch with a rating of 2000lbs, would you suggest that the flat needs to be constructed to withstand 2000lbs of force? If a wooden flat catches as it flys out, and is subjected to 2000lbs of force, the scenery is going to fall apart. Is this an area of safety that people should be concerned with? This becomes important to think about with motorized fly systems especially. I'd suggest some sort of load cell monitoring on hoists installed in these spaces to detect if the load changes dramatically while moving, and warn/stop under such circumstances.


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## LavaASU

danTt said:


> Euphroe, let's approach this a different way. Your concern at the moment seems to be that if something is hung from a hoist, and catches on something it flys out, the wire rope should not fail before the winch does. I can understand this, but then I start wondering--why? Do you really want whatever the object is caught on to be subjected to 2000lbs of force? Might this not be more dangerous than having something fail quicker?
> 
> Similarly, and to play devils advocate a little--All we are talking about at this point has been the rigging materials. If you are flying a broadway flat from a winch with a rating of 2000lbs, would you suggest that the flat needs to be constructed to withstand 2000lbs of force? If a wooden flat catches as it flys out, and is subjected to 2000lbs of force, the scenery is going to fall apart. Is this an area of safety that people should be concerned with? This becomes important to think about with motorized fly systems especially. I'd suggest some sort of load cell monitoring on hoists installed in these spaces to detect if the load changes dramatically while moving, and warn/stop under such circumstances.



Also if you are talking about people there comes a point (as far as force) where if they were to hit something the rope breaking would be the better option... someone might survive the fall, they will not survive being torn into pieces. That said, in a performer flying system, this should not be a problem (it should not be possible for them to get caught!).


----------



## cmckeeman

Euphroe said:


> Well that explains that. Next time I rig "How To Train Your Dragon" or Lady Gaga I'll be able to understand why those shows didn't fall down the last time I rigged them. Still confused about the 3/4" shackles on the apex of the deuces but you can math that for me when I'm more advanced.



The reason for the size shackles is not about SWL, but about fitting the eyes into the bell of the shackle. Crosby rates 1/2 in shackles for 2 tons but we use 5/8 for 1 tons. the other reason is that a 3/4'' shackle won't be able to rotate through the eye of the wire rope and potentially become cross loaded which is why i personally like using them everywhere except the free shackle...


----------



## Euphroe

danTt said:


> Euphroe, let's approach this a different way. Your concern at the moment seems to be that if something is hung from a hoist, and catches on something it flys out, the wire rope should not fail before the winch does. I can understand this, but then I start wondering--why?



Because it's all relative, but it's my job to make sure the rope does not break. The flat might disintegrate without hitting anything, the girl might fall off the cloud swing because she has the flu etc., but the rope is never supposed to break. Nobody should spec a winch system where the wire rope becomes the weak link because the design factor was too low.



LavaASU said:


> That said, in a performer flying system, this should not be a problem (it should not be possible for them to get caught!).



No, it is common. You have to design for it. You design for the worst-case foreseeable loading condition, which is that the load/rope is stopped against something and the winch is still pulling.


LavaASU said:


> Erm, so if this is an actual conversation going on for a system that will actually be built to fly people, please please please get a real rigger with experience on automation and flying people involved. This sounds like no one really knows what they're doing, . . .



No, it's me characterizing what goes on at the highest levels of the business, riggers with vast aerial experience working with the highest-end vendors. It's not that they don't know what they're doing. It's that the door is open for them to hedge the numbers because there's no clear standard. People at this level are not infallible, and not always as responsible as they should be. The winch buyer wants to cut the margins with a different rope, and the winch vendor goes along with it. The buyer tells himself it must be okay or the vendor wouldn't have agreed. The vendor tells himself that the buyer must know what he's doing and anyway it's his responsibility.

Call them on it and they will stonewall because there is no unambiguous standard that says the rope must be 10x the winch rated capacity, especially after deducting for the end attachments. And I've VERY often seen end attachments with a book efficiency of 60%. Whether they actually operate that low is an open question.


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## soundman

Euphroe said:


> No, it's me characterizing what goes on at the highest levels of the business, riggers with vast aerial experience working with the highest-end vendors. It's not that they don't know what they're doing. It's that the door is open for them to hedge the numbers because there's no clear standard. People at this level are not infallible, and not always as responsible as they should be. The winch buyer wants to cut the margins with a different rope, and the winch vendor goes along with it. The buyer tells himself it must be okay or the vendor wouldn't have agreed. The vendor tells himself that the buyer must know what he's doing and anyway it's his responsibility.
> 
> Call them on it and they will stonewall because there is no unambiguous standard that says the rope must be 10x the winch rated capacity, especially after deducting for the end attachments. And I've VERY often seen end attachments with a book efficiency of 60%. Whether they actually operate that low is an open question.



PlASA is working on it. BSR E1.43 - 201x, Entertainment Technology -- Live Performer Flying Systems is open for review until June 3rd.

4.8.4
Strength design factors
Lifting media shall be sized to meet the following design factors:
4.8.4.1
Flexible lifting media
Flexible lifting media (e.g., rope, chain, band, webbing) shall be designed with a minimum design factor of 10X WLL, 6X characteristic load and 3X peak load.

Peak load is defined as The maximum force applied to the performer flying system resulting from abnormal conditions, or irregular operation (e.g., effects of emergency stops, uncontrolled stops, drive electronics or power failure, stalling of the actuation equipment, extreme environmental conditions)

If you are worried about a load getting caught and the rope breaking then as I read the standard you peak load is the maximum amount of force the winch can exert at any speed. 3X to meet 4.8.4.1 and see where that leaves you.


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## BillConnerFASTC

I'm discussinng multi-purpose installed hoist systems and not a system designed for one show where knowing who will use and how it will be used has an impact on design choices.

If I have a motorized hoist system designed to lift 700 pounds and use a design factor of 10, then everything in the load path should be designed to hold 7000 pounds. That's hold, not lift.

PS Sorry, I missed there was a page 4 and this is a response to a much earlier post. Its the problem of spending a weekend in the woods with Scouts and not having cell service. Hope if interested you all can connect this.


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## Euphroe

soundman said:


> PlASA is working on it. BSR E1.43 - 201x, Entertainment Technology -- Live Performer Flying Systems is open for review until June 3rd.
> 
> 4.8.4
> Strength design factors
> Lifting media shall be sized to meet the following design factors:
> 4.8.4.1
> Flexible lifting media
> Flexible lifting media (e.g., rope, chain, band, webbing) shall be designed with a minimum design factor of 10X WLL, 6X characteristic load and 3X peak load.
> 
> Peak load is defined as The maximum force applied to the performer flying system resulting from abnormal conditions, or irregular operation (e.g., effects of emergency stops, uncontrolled stops, drive electronics or power failure, stalling of the actuation equipment, extreme environmental conditions)
> 
> If you are worried about a load getting caught and the rope breaking then as I read the standard you peak load is the maximum amount of force the winch can exert at any speed. 3X to meet 4.8.4.1 and see where that leaves you.




PLASA defines WLL by reference to MBS, and MBS by reference to WLL. The formula is circular until you define one or the other. PLASA does not say that WLL = winch rated capacity.

"Characteristic load"? "Peak load"? More variables.

Here's what happens in the real world:

Client orders winches rated at 650lbs at max speed, grooved for 1/4" wire rope. Vendor sells the entire automation system without asking any further questions about the lifting media, because nobody makes it his responsibility and the client is always right. 

Client typically installs 1/4" 19x7 rotation-resistant at 5400lbs. Then installs swivels on the 19x7, contrary to the Wire Rope User's Manual and wire rope manufacturer's warnings/advisories. The swivels reduce the breaking strength of that wire rope by about 40%, and cause birdcaging.

So is it now 3240lb wire rope? Would you take a 20% deduct for wire rope clips used as directed? But not take a 40% deduct for swivels used against warnings? 

At any rate, you now have a 5400lb - 3240lb wire rope on a 650lb winch. If the WLL = rated capacity, you do not have a 10:1. The winch maxes out at 1200lbs. If the payload hits an obstruction, you might or might not have a 3:1 depending on whether you account for the swivel in your math. Since you are not supposed to be using the swivel anyway (per the wire rope industry), you bury your head in the sand and call it a 5400lb wire rope.

That is literally how the pros do it. 

Oh and the recommended D/d for 19x7 is 34. Are they using 8.25" sheaves? (Ignore it, because the swivel will cause a birdcage long before the bending causes broken wires).

There is a 1/4" 8500lb wire rope that is 100% efficient with a swivel and approved for human lifts, recommended for D/d of 20. It costs about twice as much, lasts at least 4 times as long, and doesn't birdcage. I know two shows that use it, to their complete satisfaction, and past shows also. I've used it. Why don't you see it everywhere? 

* Neither the client nor vendor are responsible for treating the winch/rope combination as a single engineered system. There are OEM tires for a Hyundai, OEM chain for a hoist, but no OEM wire rope for a human-lift winch. Anthing goes. Install 7x19 from Home Depot and nobody will notice or care. 

* Wire rope is treated like an expendable, interchangeable product like gaff tape, rather than a special component like hoist chain. 

*PLASA won't address the Wire Rope User's Manual or manufacturer's warnings about swivels, because that would be like giving a monopoly to the one company that produces a wire rope for this application.

* Human lifts aren't important enough yet. One show flys people on 8500lb wire rope and changes the rope 4x per year. Another show from the same company flies people on 5400lb wire rope that has to be changed monthly. Both use the same model winches. Why? No reason, they just do. 

*Politics/pride. Riggers do not like being told they could be doing a better job, or that their math is off. Offer them an improvement and instead of being grateful, they feel accused and think about how it will look if they switch.

If I were a winch vendor, I would spec an OEM rope for my winches based on the output and without regard to what the client intends, 8 months before opening, to do with that winch. If the client wants to deviate after receiving the winch that's his responsibility.


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## soundman

Euphroe said:


> PLASA defines WLL by reference to MBS, and MBS by reference to WLL. The formula is circular until you define one or the other. PLASA does not say that WLL = winch rated capacity.
> 
> "Characteristic load"? "Peak load"? More variables.


I don't think the standard refers to MBS. 

> 2.40 working load limit (WLL):
> The maximum weight as defined by the Flying System Designer that a User is allowed to apply to a lifting medium in the performer flying system.




Euphroe said:


> That is literally how the pros do it.


That doesn't mean its the best way or even right. As more companies are getting into the winch building game I think having a defined process for specing hardware is going to become very important to clear up confusion. Perhaps one day it will by similar to hanging a chain motor where there is standard hardware sizing, but its not there yet.


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