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how weak is threads when using on tower pipe?
By picmacmillan, Section Homebrewed Electricity Posted on Sun Apr 10, 2005 at 03:10:37 PM MST
does anyone know how easily the threads will tear on black pipe?

i have a quantity of black pipe, various sizes, that i am going to use for a tower...nothing too tall(maybe 25-30')..the thread on the pipe is national course..2" i.d...i do remember from tool and die days that the threading on the pipe makes it very weak at this point...has anyone used this pipe with the threads on it?...i was hoping just to use the connectors and add additional pipe via the thread, but if it is too weak(which could very well be),i will cut the thread and weld the lengths of pipe together?..i am going to guy wire this tower at the 10, and 20' levels...i am too lazy to go look it up, as i cant even remember where to find my answers.....how deep is the thread into the wall of the pipe is what i am asking,...it is schedule 40 pipe?...thanks...pickster

how weak is threads when using on tower pipe? | 6 comments (6 topical)

Re: how weak is threads when using on tower pipe? (3.00 / 0) (#1)
by electrondady1 on Sun Apr 10, 2005 at 09:39:44 AM MST

if i can remember, from school. the shear strengh of mild steel is 45,ooo lbs per sq. inch . put you have too figure out the cross sectional area of the roots of all the threads that a whole lot of math pic.

Re: how weak is threads when using on tower pipe? (3.00 / 0) (#2)
by DanB on Sun Apr 10, 2005 at 09:48:50 AM MST

its very much a weak spot - I'd not thread anything together on your tower. Better - if you dont want to weld, is to make slip couplings and pin, or bolt things together.

Re: how weak is threads when using on tower pipe? (3.00 / 0) (#3)
by BruceDownunder on Sun Apr 10, 2005 at 03:42:14 PM MST

Hello, I used to make radio masts when rigging for a communications Co. The pipe was 4 inch and we used to couple them by threading . Thats big pipe.
Your smaller pipe would be ok if you are using only a couple of lengths. Try to guy the mast at the thread area.
But really , you should try for a bit bigger pipe down low and sleeve and couple the next smaller size pipe for the upper section.

Bruce

Re: how weak is threads when using on tower pipe? (3.00 / 0) (#4)
by Joseph Turrisi on Sun Apr 10, 2005 at 04:27:29 PM MST

Don't use the threads to make connections on your tower I try the same thing for a flag ploe and the top 10' section broke off at the treads. I only use 1" pipe but if that won't hold the stress of a flag I don't think 2" will take the stress of a wind generator.

Re: how weak is threads when using on tower pipe? (3.00 / 0) (#5)
by TERRYWGIPE on Sun Apr 10, 2005 at 11:51:49 PM MST

Our antenna masts in the military are either crank-up or of the sleeve type. The army dont use threaded lengths do to the stresses, so I wouldn't try it either
Terry

Re: how weak is threads when using on tower pipe? (3.00 / 0) (#6)
by picmacmillan on Mon Apr 11, 2005 at 06:42:26 AM MST

thanks all for the comments...i knew that was the case, but thought i better ask..because the threads are cut into the pipe, they create ridges which are more prone to a weak yield strength but couple that with making the wall of the pipe that much more thinner, ...a radius is much stronger than a sharp corner...also on pipe you are never supposed to exceed a hole in it more than 50% of its diameter...with aboviously a smaller hole being more optimum.....i just didnt remember the stats on that, but i do thank everyone for their post...i always like to ask....seems the more people you include on your project, the better chance you have at success...thanks again..pickster
http://www.frecklefarmloghomes.com

how weak is threads when using on tower pipe? | 6 comments (6 topical)

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