# Schedule 40 Pipe Inverted Tees



## jametcalf (Jan 5, 2011)

I'm looking to build some inverted tees with 1-1/2" or 2" schedule 40 pipes and a cheeseborough clamp. These will be hung from the structure above and will be used to hold a Martin Mac 600 off of the 2' cross piece and 3-4 conventional fixtures off of the 10' vertical piece. What is the best way to safety the pipe and fixtures.


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## Footer (Jan 5, 2011)

You could have rings welded in to tie off to, but that does not cover you in case of the cheeseborough fails. It I were you and I was looking to secure the safeties to something, run a piece of rated chain with the tail down and clip off to that.


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## Traitor800 (Jan 6, 2011)

When I've done tail downs with pipe I usually make a safety with appropriate aircraft cable that I run down the center of the tail down pipe and around the grid or batten that the tail down is coming off of. as far as individual fixtures Ive seen the LX guys wrap the safety around my tail down safety and ive also seen them place a spare clamp on the tail down above the fixture and then safety the light off to that. This works for conventionals but I wouldn't do that for the movers.


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## mstaylor (Jan 8, 2011)

I like Footer's solution with the rated chain. I would suggest using 1 1/2 pipe.


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## disc2slick (Jan 10, 2011)

My first thought is that sounds like a lot of weight to be on a single cheeseboro mounted vertically. Also, whenever I am building a position like that, I like to lock down a c-clamp on the vertical pipe directly above the cheesboro to keep it from slipping.

-Dan


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## Van (Jan 10, 2011)

mstaylor said:


> I like Footer's solution with the rated chain. I would suggest using 1 1/2 pipe.


 
Just as a clarification. 1 1/2" Sched 40 pipe has an outside diameter of 1.90 inches. Unfortunately a lot of folks confuse the outside diameter for the measurement of the pipe. Sched 40 pipe is measured by the interior. So to the OP a 2" pipe would have an outside diameter of approx. 2.38 inches, and it would be too big for most light fixture clamps. 1.5" is a standard that *most* venues use.


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## MPowers (Jan 19, 2011)

Make your tail downs like a capitol "I" instead of a "T". use 2 or 4 double CB's or Mega Swivel Clamps Swivel Coupler to attach to the batten. Being able to fasten hard at two locations would make for a much stiffer connection when the mover twists at speed. While the redundancy of the clamps would almost make a safety cable redundant, if you have a "T" at the top as well, then a standard safety cable, choked around the drop down stem and clipped around the batten would be easy to rig. Do a shock load calculation to see if more than one cable would be needed for your situation.


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## bishopthomas (Jan 23, 2011)

I don't know if this helps you, but something I'm looking at picking up next week to do what you're talking about: Mega-Coupler Pipe Adapter


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## skienblack (Jan 23, 2011)

I may be wrong but I was always under the imrpression using threadeds for weight bearing applications would greatly reduce its capacity.


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## MPowers (Jan 25, 2011)

You are correct, threaded couplings are designed to make fluid (gas or liquid) tight connections. The original design was conceived with the intention of supporting the connection, the pipe and the contents of the pipe with a reasonable safety factor and not leaking. They were never intended to be structural fastenings carrying lateral and vertical loads as a part of a load bearing structure. IMHO, the only acceptable way of using a threaded coupling under load, is in direct compression such as a pipe light boom threaded into a 50# boom base, and with lateral and diagonal bracing as needed. Other acceptable uses of threaded couplings are as a positioning device, such as a wall flange to keep a pipe from swaying when it is supported by other means. They are OK for decorative structures that are not load bearing and for light weight furniture. Even in those cases, the structure needs to be designed and built to minimize points where a threaded portion of the pipe is carrying load in a shear or lateral bending condition. 

Threaded couplings in compression loading, strongest condition. In straight tension, second strongest, not to be used for overhead lifting. Any condition where the coupling supports more than the weight of the pipe and any contents in a shear or bending condition, to be avoided at all costs. HTH.


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## TheatrePros (Feb 1, 2011)

I have had great success using welding rings to weld to Schedule 40 and then tie off with Wire rope (aircraft cable) back to where your original pipe is hanging from. If you dont trust your welds, I have also drilled into the pipe and use forged eye bolts in place of welding.


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## rsmentele (Jul 19, 2013)

Reviving and old thread here.... I understand the concern with using threaded couplings for a inverted T intended to be used as a light hanging structure. Would it make any difference if you welded the fittings to the pipe once it was assembled? Do you feel that would suffice as taking the shear load off the threads and help to make the apparatus safer for use, or make you more comfortable with hanging lights off of them?

I have made a few of these using the mega coupler adapters and clamps, and only intend on hanging one or two fixtures from the bottom 'T' but I want to make them as safe as possible.

Let me know your thoughts either way....


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## 65535 (Jul 19, 2013)

Doing some very rough calculations under working pressure of 1700psi a threaded joint in 1.5" sch40 black pipe could have upwards of 12,000lb-f of tension. I would think The Light Source's threaded adapters would be well capable of most tail down applications and that their rating of 1100lbs even cut down to a 50% safety factor at 550lbs would make me feel comfortable working with them, especially with a chain safety attached to the top of the pipe with a through hole and bolt.


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## DuckJordan (Jul 20, 2013)

You know when hanging above peoples heads industry standard is between 1:5 and 1:10 so between 20% and 10%


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## 65535 (Jul 20, 2013)

I believe The Light Source quoting a SWL of 1100# represents the safety factor, possibly 1:10.


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