Dennis Schaefer wrote:
> I needed a piece of steel mast. I am using a Hazer and need about 2 feet
> out of the Hazer to clear the top of the tower and about 3 more feet to get
> the KT-34A a respectable height above the tower. A few more feet above the
> beam could hold a 2 meter antenna or something light. I'm not going to try
> to stack very much on the Hazer. I thought surely I could find an
> acceptable piece of steel tubing locally.
> The first thing I did was go back through Towertalk archives. I found that
> "Schedule 40, etc" did not seem to be acceptable, and was sometimes
> referred to as "water pipe". I saw messages about the MARC program and
> realized that I should have ordered it a long time ago. I decided that for
> my application, chrome-moly was not necessary if I could find a good grade
> of structural tubing. This led to some surprising conversations.
> First, I went to a local steel distributor. I had never been there, and
> was surprised to find a large firm that appeared to employ almost 100
> people. The sales rep. told me that they mainly fabricate things, and
> they do business all over the U.S. He would be glad to sell me a piece of
> tubing (pipe) though. I showed him an ad from Texas Towers (2", high
> carbon steel, 79,000 psi yield) and told him that was what I wanted. "Oh,
> what you need is Schedule 40", he said. I asked him if they didn't have
> anything better, and he assured me that Schedule 40 and Schedule 80 were
> all they used, and their structures carried extremely heavy loads, as well
> as human beings. I asked about the psi yield rating, and he waffled a
> little. "We are only concerned about downward pressure, dead weight
> capacity. We don't really have a spec for the wind loading stuff you are
> talking about".
> Anyway, I was surprised to hear that Schedule 40 was considered by some to
> be structural material, even if the specs I wanted were not available.
> He gave me the exact dimensions for the Schedule 40 and 80 pipe, and I
> left. I looked in the Glen Martin (Hazer) catalog, and saw they had mast
> tubing at a very attractive price. I also noticed that the dimensions
> looked strangely familiar. I called them and, yes, it was Schedule 40!
> They said I could probably get it locally and save the shipping charges.
> They also told me that UPS could ship up to 9 feet lengths. I thought the
> limit was 7 feet. If Texas Towers has a 9 foot mast, maybe I'll just order
> one. Or maybe the truck freight charges on a 10 footer won't be more than
> I am willing to pay. (Or - TT is only a 6 hr drive - and I could also visit
> some computer stores!) Maybe K5RC has some input for me, also.
> I don't think I am presenting any new information here, or really asking
> any questions, but it was an interesting afternoon.
The definition of schedule 40 or schedule 80 is only the dimensions
of the tubing to meet a standard size. IT'S THE MATERIAL THAT
DETERMINS YEILD STRENGTH ETC.....
Galvanized water pipe is not the same as 4140 or 4145 or other
grades of steel
I prefer 2" or 2.5" Schedule 80 seamless Aluminum Tubing for masting
much lighter but more expensive.
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