Unsafe safety cables

I am looking to see if any agrees with me about safety cables not really being safe? With a standard electrician coming in and hanging a light they will place a safety cable straight through the yoke and around the batten. This place it in the weakest part of the light with two standard 1/4" bolts that hold the yoke to the light that combined have a sheer strength of less then 800 pounds. The design of a c clamp causes the forces to be pushed against a piece of metal that is almost an inch thick. Basically meaning your pipe will fail before you break a clamp. And on top of all that a light should in theory 3 times before any performance should occur under it, once while hanging, once while focusing, and once by the lead electrician. I find that people use them a cheap insurance meaning they are putting their trust in a piece of hardware that is not rated or designed for hanging over head. I can find OSHA rules on not using the clip on safetys as well. I have a hard time believing that they are as safety as some people say and might even call them unsafe to use. Does anyone agree or is you all just going to call be dumb?
 
Welcome to CB! Feel free to introduce yourself in the New Members Forum!

Safety cables are "safe" in a sense that if the clamp fails (which is more common then you'd think with the force some people tighten them with), the fixture won't fall on anything expensive or alive below. I see your point though. But, adding a safety doesn't mean the light is any more likely to fall or something is more likely to fail. There is some other discussion on here about safeties, and one thing is that most fixtures have an attachment point beyond the yoke that you "should" be using to safety your fixtures.

We put faith in the rated equipment, and then something else as a precaution. But, when you see a fixture hanging from a safety during a channel check, are you going to just let it hang? Or are you going to go find out why something failed.

My $.02.
 
I've never seen a pipe fail but I have seen 3 or 4 clamps fail from over tightening/being dropped causing fractures. For one, Source 4 fixtures actually have a point molded into the body that you can run a safety cable through seen here in the bottom left of the photo.
proxy.php

other lights have similar features. That being said once a light is tethered to the batten were it to fall it only would drop about 6 inches before the cable goes taut. It's pretty unlikely that you'd hit that 800 pound sheer strength of those bolts. Sure it is still possible that a bolt could fail or something won't be tightened down right.

I don't really see how they could be considered unsafe to use however. It is another failsafe device that keeps a light in the air. You still shouldn't use those crappy keyring carabiners on them because they obviously aren't rated. Also I apparently didn't read Chase's post clearly enough when I started typing this and therefore mentioned the same attachment point.
 
The overtightening should be an issue that a head electriancain should be check for as they are inspecting their plot. I know about the ring on the source 4 but find that most people don't use them. If a light is drop from really any sort of height more then 3 feet I have it inspected for before it will go back into service looking for stress cracks or anything like that. I have seen clamps fail but the dead give away that is was going to fail was the huge dent in the pipe where the clamp was from being tighten down. I guess it was not correct wording to say unsafe, what I am trying to find is others who agree that there are issues with them
 
The overtightening should be an issue that a head electriancain should be check for as they are inspecting their plot. I know about the ring on the source 4 but find that most people don't use them. If a light is drop from really any sort of height more then 3 feet I have it inspected for before it will go back into service looking for stress cracks or anything like that. I have seen clamps fail but the dead give away that is was going to fail was the huge dent in the pipe where the clamp was from being tighten down. I guess it was not correct wording to say unsafe, what I am trying to find is others who agree that there are issues with them

C-Clamps are cast products. In the casting process, defects are pretty much the norm. These defects mean that the clamp can fail for any reason... at any time. As the casting wears, it weakens. The clamps will literally blow apart. Hince the reason for safety cables. Also, in an earthquake, its just one more thing to keep that light from falling.

Also, there is no reason for a "head electrician" to check every fixture before it leaves the deck. They got better things to be doing then going back and checking other peoples work. In academia, do it, however in the real world you should be able to trust a stagehand to hang a light correctly. If they can't, get them off the call. Added to that, there is no visual way to see if someone over-tightened a clamp short of bending the pipe.
 
EDIT Kyle beat me too it.

In general the weak link is always going to be the iron c-clamp that uses steel bolts, that can break due to over tightening of the clamp bolt. I have never heard of nor seen dual failures on the steel 1/4 inch bolts that hold the yoke to the fixture. These tend to not get over tightened to a failure point and when they they do, something else gives, be it the aluminum body of the fixture (Altman 360Q design) or the plastic handle the bolt threads into. And while I've seen one of these occur, I've never seen BOTH occur AT THE SAME TIME. And that's important

Thus the safety cable is protecting against c-clamp failure.

Possibly the fixture can be hit by moving scenery, but again, the weak link is going to be the iron c-clamp.

Do I inspect every light that gets hung to ascertain if the c-clamps have been over tightened ?. No, I have to rely on the skills of the electricians to tighten the clamp correctly and the only way to check if the bolt is too tight is to loosen it and re-do it.

When I have somebody new I observe their work methods and when I see something being done incorrectly, I educate the technician as to the correct method.
 
Agreed, not my job to check every light, nor can I due to time constraints, especially when it is a grid and not fly system. If it is a smaller hang I will go down the line to double check that the instruments are at least tightened down versus only finger tight or simply sitting there, but there are still far too many positions and instruments for me to check each fixture individually.

This is one of those really stupid discussions that people, especially those with too much time on their brain or whom are relative neophytes, bring up entirely too often rather than just doing it. It is simply one more way to prevent or reduce the impact of a disaster. I had an intern this summer attempt to argue with me that pinching the loop to push it through the attachment point on S4's destroyed the integrity of the safety. Again, the force and mass that they can hold, even with some derating, is much greater than will be generated by any common failure, and placing them through the attachment point reduces the number of points of possible failure by two (considering the entire system on each side attaching the instrument to the yoke).

Are there other ways in which we could "safety" the instrument"? Yes, but none of them really make sense in the world we are operating in.
 
The reality is that a safety cable is the last ditch effort to prevent an injury (or other damage). You are definitely observant that the spring clip used on the majority of safety cables is not intended for overhead rigging, which is why we need to make sure that they are not used in that manner. As with any equipment, it must be used for its intended purpose and in the proper manner. This is one reason why, even on the permanent installed show that I work on, we continually inspect all of the fixtures to make sure that the safety cables are still installed correctly (since you never know if someone had to replace an instrument, move the cable because of something else that was installed or moved, or general aging of the equipment, etc.).

The longer that you work in this environment, the more accidents you will see, even from seasoned professionals. Yes, all accidents should be preventable, but they do happen. So we add that extra measure of safety just in case the inevitable happens (something didn't get double/triple checked and happens to fail). Sometimes the crew is running behind and something gets missed. It happens.

As to how effective they are for actually securing a light should it fall, this also has many variables. I recommend that nobody uses home made safeties unless you are a qualified rigger. There are many different outlets where you can purchase them at a reasonable cost. We should ensure that they are used properly by attaching them to the light appropriately and around an appropriate point to support the light should it fall (which I find wrong often). Obviously, as you stated, proper installation is preferrable for every light, but please continue to use these as they are an insurance policy for oversight.
 
I find the safety factor that I'm far more concerned about isn't the safety cable, but the clamp itself. As many others have mentioned, they often get over stressed. However, most of those cast c clamps are not load rated in any official sense. I've specifically asked ETC about this, not any other manufacturers. They pass the "well, it worked last time, so it should work next time," but don't stand up to any rigorous testing.
 
...I've specifically asked ETC about this, not any other manufacturers. They pass the "well, it worked last time, so it should work next time," but don't stand up to any rigorous testing.
Back to topic: Official word from one manufacturer, (guess which one:)), here.

http://www.controlbooth.com/forums/...ixtures-integral-safety-attachment-point.html
http://www.controlbooth.com/forums/lighting-electrics/11934-safety-cables.html
 
Last edited:
I also concur that the most common point of failure on fixture is the c-clamp. They have nothing going for them, unrated, cast iron, and very odd force vectors. I have seen multiple c-clamps fail while putting fixtures on a pipe and the person tightening the clamp didn't even feel any strain, the clamp just shattered. It is actually for this reason that I teach anyone who works for me to put the light on the pipe, finger tighten the clamp, attach the safety, and then finish tightening. Why? Because the most common time for clamp failure is when you are tightening it (also why you never should tighten a c-clamp more than 1/4 to 1/2 turn past finger tight).

Another interesting note, on most newer fixtures, the source four included, the yoke is not actually pivoting on the bolts. The yoke actually pivots on a hub and the bolt just retains the yoke. I believe that the factory yoke retaining bolts on a source four are actually grade 5 rated. Due to this attachment method for the yoke, you would have to actually break the casting of the fixture before you broke the bolt (or the yoke itself would have to fail) for the yoke to come off the fixture.

As far as having the head elec check every unit, that will never happen. Even on a show with a small plot, it would just take too much time. We do general maintenance each year and check for problems as we go, but I can't supervise and direct a full crew and check every unit during each hang. I have to trust that I have taught my crew to spot problems and not create new ones.

All in all, if you are hanging a light over someone's head, it should have a safety. I have unfortunately seen situations where they were needed.
 
The safety cable saved my butt when a defective clamp snapped while I was tightening it. It was a cheap clamp and there was an air bubble in the casting where it snapped.
 

Attachments

  • BrokenClamp.JPG
    BrokenClamp.JPG
    153 KB · Views: 616
Shattering clamps like that is exactly why we don't use any of the cast iron clamps on any of our fixtures. Go out and find yourself a rated clamp. We use the Megaclamps, and those are specifically load rated.
 
I have only seen one situation where a Safety cable saved a lamp from falling. The fixture was being focused at the time, and the 3\8 inch bolt attaching the fixture to the clamp broke. It was a Kliegl Clamp. The fixture was a 10 inch Fresnel.

I was the person messing with that light at the time. Was very glad that the safety was there since I was the person directly under the light, and on top of a 25 foot ladder.
 
Last edited:
I find the safety factor that I'm far more concerned about isn't the safety cable, but the clamp itself. As many others have mentioned, they often get over stressed. However, most of those cast c clamps are not load rated in any official sense. I've specifically asked ETC about this, not any other manufacturers. They pass the "well, it worked last time, so it should work next time," but don't stand up to any rigorous testing.

You just gave me a great idea. I should start traveling around and offering safety consultant services. I can put my NDT cert to good use again and start doing mag particle testing on clamps.
Oh Well, It was just another useless thought of mine trying to make a buck...
 
Has anyone ever had a cast ETC clamp with its reenforcing "backbone" fail? Or are they usually Altman/generic c clamps?

Anyway, arguing against safety cables is stupid. Aside from the fact that I could imagine a home brew safety cable being less safe, in general, safety cables are ALWAYS a good idea.

So, how long before Sapsis or Clancy tells us we have to throw away our spring clips and start using shackles on our safety cables? (Anyone want to start making rated dog clips and spring clips?)
 
I have only seen one situation where a Safety cable saved a lamp from falling. The fixture was being focused at the time, and the 3\8 inch bolt attaching the fixture to the clamp broke. It was a Kliegl Clamp. The fixture was a 10 inch Fresnel.

I was the person messing with that light at the time. Was very glad that the safety was there since I was the person directly under the light, and on top of a 25 foot ladder.
I really hate Kliegl clamps. Someone donated some Kligel fixtures, the first thing I did was to throw the clamps away.
 
So we use a slightly different clamp design down here. That's not entirely relevant here.

I've been under a fixture that the safety cable caught. Fixture wa in the grid for an outdoor stage. Had been up a couple of days and then we hear this clink clink. That was the nut and washer hitting the deck. Looked up to see the light just hanging there...
Especially in outdoor grids, vibration will happen. Vibration will loosen fixings. When they get too loose they fall out...
 
I haven't broken a c-clamp (yet), but I have found some that were so loose they were ready to fall off the batten. I don't know if they weren't tightened sufficiently when they were hung or if they loosened up over time, but still, I'm glad they had safety cables just in case they had fallen. Many of our lights are hung for the rep plot and aren't touched except to change lamps on occasion, so they could loosen. Still, it never hurts to use safety cables.
 

Users who are viewing this thread

Back