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Re: [TowerTalk] Rigid Steel Conduit as Mast?

To: "Roger (K8RI)" <>
Subject: Re: [TowerTalk] Rigid Steel Conduit as Mast?
From: jimlux <>
Date: Fri, 05 Jun 2009 16:00:11 -0700
List-post: <">>
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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