Most pipe is quite strong. I've used quite a few things over the years.
The worst I've seen are the masts that you get at Radio Shack or similar
products. The Tubing is far too small, thin and light weight to be useful
for anything more than a UHF TV antenna.
Muffler pipe works well and is cheap. But it does rust quickly and will
leave stains on a building. But if you're in the middle of no where it's
quick and easy and effective.
Water pipe is heavy but comes in 21' sticks. And it can be screwed together
if need be. I'm on a tower that a farm company built back in the '70's
sometime. It's double strength water pipe, about 6" in diameter. The main
part is about 40' long and is guyed at about 3', yes I said 3', from the
tower. Into that is a 5 or 5.5" hunk of pipe about 30' long, that's been
welded into the outer pipe. I don't think the entire base is any more than
6' on a side. The tower is made to lay over (thought I'm told they had so
much trouble getting it up no one has taken it down). It's been there for
all of these years and we've seen winds of 70 to 80 mph (winds, not gusts)
since I've been on the tower.
Lately I've been using fence top rail for many projects. It comes in 8 or
10' hunks at the local hardware store. I'm sure I could get longer ones at
a fence supply store. It's pretty cheap, strong and galvanized.
If you're going to use pipe for a mast, the most important thing in my
opinion is to make sure that it's of sufficient diameter to insure that
you've got the strength that you need for your project. Smaller pipe is
much easier to work with, but the diameter is where the strong part comes
from. It's usually pretty easy to attach a short piece of smaller pipe to a
bigger stronger one.
Hope that helps,
marlon
----- Original Message -----
From: "jimlux" <jimlux@earthlink.net>
To: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
Cc: "Tower Talk List" <towertalk@contesting.com>; "Jim Brown"
<jim@audiosystemsgroup.com>
Sent: Friday, June 05, 2009 4:00 PM
Subject: Re: [TowerTalk] Rigid Steel Conduit as Mast?
> Roger (K8RI) wrote:
>>
>> Jim Brown wrote:
>>> I asked a colleague who builds a lot of commercial two-way
>>> installations where I could find 2-inch hot-dipped galvanized mast
>>> material locally. He suggested that I use 1.5-inch rigid steel
>>> conduit.
>> There are two types of rigid steel conduit. The one is like schedule 40
>> pipe and the other (EMT) is thin wall.
>> The heavy conduit like we used in industry is soft like water pipe, but
>> still fairly strong. Then there is thin wall or EMT which would
>> probably work IF the antenna is mounted right at the top of the tower. I
>> would not want to mount the antenna any distance above the top of the
>> tower due to the leverage or angular moment generated particularly due
>> to wind load.
>>
>> 73
>>
>> Roger (K8RI)
>
>
> I've used EMT as a (poor but expedient) structural material for things
> like tents and geodesic domes..
> here's my observations:
> a) It's crummy quality steel and highly variable in material properties
> to boot.
> b) It has a very obvious weld, which protrudes variably into the middle
> c) It bends once or twice, if properly jigged and supported (after all,
> this is what it's made to do)
> d) it cracks along the weld, or the ends, etc. Don't expect to be
> hammering the end flat to make a flange you can bolt through. Or, at
> least, don't expect that flat end to be pretty and not cracked.
> e) it's quite malleable.. not at all springy, so if you load it, it
> bends, and stays bent.
>
> On the other hand, it's incredibly cheap. So for a field expedient mast
> or something like that, I'd use it again. Just don't expect it to be
> rugged and long lived. You could throw up 30-40 feet of 3/4" or 1" EMT
> with some lightweight rope guys for a few bucks.
> _______________________________________________
>
>
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