ProSoundWeb Community

Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Lighting Forum => Topic started by: Ken Nelson on February 14, 2011, 04:54:39 pm

Title: Lightweight Truss / Crossbar System
Post by: Ken Nelson on February 14, 2011, 04:54:39 pm
So, we are thinking of running about 30 lbs of fixtures each on stage left and right, the length of the depth of the stage (front to back). This will allow us to sidefill and do some other effects.

We are running things like high powered Edison LED RGBA wall washers, around 8lbs per fixture, 3-4 per side. No moving heads. The bottom of the fixtures are going to be about 3 feet off the ground, no one underneath.

Running actual truss would be insane on both a cost/benefit and needs basis. I am also a photographer and have access to portable backdrop hangers, something like this:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=360338322884&ssPageName=STRK:MEWAX:IT

It has gotten me thinking about using alternative, lighter weight hardware to hang these fixtures. I like the idea of two tripod stands with ten feet of mounting ability between them, keeps the stage cleaner. Heck, we could probably double up on heavy duty zip ties to attach the fixtures to one of these background hangers in about 30 seconds and be done with it.

Anyone doing similar, or using something non-standard, and thus clever, in a similar use? We want an expandable span so that we can adjust the positioning based on the depth of the individual stage. Looking to not spend a fortune buying too much mounting hardware, so I can spend it on the fixtures instead. :)
Title: Re: Lightweight Truss / Crossbar System
Post by: Craig Leerman on February 15, 2011, 12:23:48 am
So, we are thinking of running about 30 lbs of fixtures each on stage left and right, the length of the depth of the stage (front to back). This will allow us to sidefill and do some other effects.

We are running things like high powered Edison LED RGBA wall washers, around 8lbs per fixture, 3-4 per side. No moving heads. The bottom of the fixtures are going to be about 3 feet off the ground, no one underneath.

Running actual truss would be insane on both a cost/benefit and needs basis. I am also a photographer and have access to portable backdrop hangers, something like this:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=360338322884&ssPageName=STRK:MEWAX:IT

It has gotten me thinking about using alternative, lighter weight hardware to hang these fixtures. I like the idea of two tripod stands with ten feet of mounting ability between them, keeps the stage cleaner. Heck, we could probably double up on heavy duty zip ties to attach the fixtures to one of these background hangers in about 30 seconds and be done with it.

Anyone doing similar, or using something non-standard, and thus clever, in a similar use? We want an expandable span so that we can adjust the positioning based on the depth of the individual stage. Looking to not spend a fortune buying too much mounting hardware, so I can spend it on the fixtures instead. :)


Using Zip Ties, even if there will be nobody under the fixtures is UNSAFE. While the good zip ties do have some breaking strength info on them, they are not considered  rated hardware and should never be used  to support the weight of a fixture.

Use only standard lighting clamps to attach a fixture to a bar, and then use a wire safety cable as a backup for all fixtures that are flown in the air (even ones only 3 feet off the deck!).

For your application I would get four pipe bases, 4 sections of 3' (or taller)  pipe uprights, four 90 degree coupler clamps or 90 deg cheeseboroughs (AKA Cheeseburgers clamps) and  two sections of 10' pipe to use as the crossbars.  The bases will cost you a little, but the pipes (standard metal black plumbing pipe) can be bought and threaded for the bases at any plumbing supply house or big box home improvement store for very little.

The 90 degree coupler clamps can be bought from any theatrical supply or lighting house, or the "cheeseburger" style can be bought from any scaffolding supply. Standard lighting clamps and safety cables are available everywhere stage lights are sold.

While the horizontal bars will not telescope for different depth stages, it will be safe and sturdy, and you can always use different length pipes for different depth stages.

Again, do not use zip ties for any rigging!

Craig
Title: Re: Lightweight Truss / Crossbar System
Post by: Ken Nelson on February 15, 2011, 01:43:16 pm
Good thoughts.

The zip ties comment was more a commentary of the weight on some of these fixtures. 8 lbs is high, we have several that are less than five pounds. On a practical basis, a couple of good mil-spec zips *would* hold this weight on a static basis for a couple of hours, on a liability basis, not a good idea.

Good idea on the pipe. Gonna put something together that does what I need.
Title: Re: Lightweight Truss / Crossbar System
Post by: Ken Nelson on February 15, 2011, 02:11:09 pm
Just a quick follow up.

For anyone looking to do a lightweight fixture setup, I did some research on the pipe solution that Craig mentioned. It is indeed an excellent robust solution and there are even online articles for DIY. One is here:

http://www.ehow.com/list_6640098_ideas-making-stands-stage-lights.html

Our only issue is transport/space considerations. Adding in some cash to put a pipe system in a proper transport system is going to make it more expensive.

Because we're going with about 30 lbs of fixtures total, I found this system rated at 55 lbs. They also make a 75 lb system at the bottom. You can get the 55 lb (JTL B-1012) for ~$135 on Amazon. Then add the rated clamps and such and I think we're good.

http://www.jtl-lighting.com/backdrop-stands-background.html

PS - We are NOT using moving heads. Anything like that and I'd be looking at real truss.
Title: Re: Lightweight Truss / Crossbar System
Post by: Richard McLawhorn on February 16, 2011, 08:38:15 pm
I use 1.5" schedule 80 steel pipe for similar applications. 

Like Craig said, get pipe bases that can be mounted to the floor with vertical pipes of whatever your desired height is, then use 90 degree elbows to mount the horizontal pipe.  Depending on the span length, then you may be able to get away with schedule 40 pipe at the weight that you are talking about hanging.

You can put a good amount of weight on these pipes when properly supported.  Most theaters use sched 40 on 8-10 foot supports for everything.  You can also be mount lights on the vertical pipes.  Remember that the pipe bases need to be securely attached (through bolts, not screws) to a wide and stable base.  If you are bolting to a stage floor a backing plate under the floor is recommended if possible.
Sched 40 vs 80:
http://www.mts.net/~william5/library/pipe.htm

Allowable batten loads based on span of support:
http://www.jrclancy.com/Downloads/Batten%20Load.pdf






Title: Re: Lightweight Truss / Crossbar System
Post by: Rob Spence on February 21, 2011, 03:43:28 pm

Because we're going with about 30 lbs of fixtures total, I found this system rated at 55 lbs. They also make a 75 lb system at the bottom. You can get the 55 lb (JTL B-1012) for ~$135 on Amazon. Then add the rated clamps and such and I think we're good.

http://www.jtl-lighting.com/backdrop-stands-background.html

I can't tell from looking at these what the exact diameters of the poles are. If they are aluminum then you really can't use normal lighting clamps as they will dent it. And, unless the diameters are just right, many of the cheesburgers may not grip well enough.
Just something to check on...
Title: Re: Lightweight Truss / Crossbar System
Post by: Royce Covington on February 21, 2011, 03:59:12 pm
If they are aluminum then you really can't use normal lighting clamps as they will dent it.

really???

just what material do you think most light truss, light trees and light stands are made of?

to prevent damage, simply do NOT over-tighten the clamps...

R~
Title: Re: Lightweight Truss / Crossbar System
Post by: Rob Spence on February 27, 2011, 11:11:03 am
My experience is that truss is a much heavier (that is, thicker walled) tube than most telescoping stands. If you tighten traditional "C" clamp lighting to thin wall aluminum, you will dent it before you get enough force to hold the instrument safely. I use "O-Clamps" on my thin wall tee bars and such to avoid the problem.
Title: Re: Lightweight Truss / Crossbar System
Post by: Nate Armstrong on March 09, 2011, 11:42:36 am
I purchased a backdrop stand almost identical to what you have posted.  I purchased it to hang Scrim from for laser animations.

I definitely would not get this to hold lighting even light weight LED pars.  The span for the tri pod basses have small foot print, and the tensil strength of the piping is very low.  IF you were to use this in a outdoor setting i could see the wind blowing it down.

you would be much better off getting a cheapy 10 ft aluminum truss for about $100  but I highly recommend going with a homemade schedule 80  or at least get a crank up aluminum stand.

after you use the non crank stand. you will realize you just wasted your money and should of went homemade or get a crank version.

http://accessories.musiciansfriend.com/product/American-DJ-Crank-II-Mobile-Trussing-System-for-Stage-Lights?sku=801152

http://accessories.musiciansfriend.com/product/Odyssey-LTP8PRO-Crank-Truss-Stand?sku=451010
Title: Re: Lightweight Truss / Crossbar System
Post by: Len Woelfel on March 10, 2011, 08:36:32 am
Using pipe booms seems to overengineer a solution.  Altman or SSRC bases are 50# each.  Who wants to slug those around for 30# of LED products when height isn't a concern?  Not me.  I'd really consider a tripod and t-bar if at all possible.  Another possibility is Matthews stands.  http://www.bhphotovideo.com/c/product/690971-REG/Matthews_B756020_C_Stand_with_Sliding.html More  expensive, but very low profile and very portable.