[TowerTalk] Choice of material for Mast

[npalex@aol.com]

The question was asked about the differences in Aluminum tubing and aluminum 
pipe. The answers that followed in some cases indirectly answered the 
question and in other cases also illuminated other differences between "tubing" 
and "pipe", two things that are often confused by many. 

With respect to the original question, Tubing may be extruded and essentially 
seamless, or it may also be rolled and have a welded seam. Pipe is almost 
always rolled and welded. The bright shiney aluminum tubing used in many 
antennas is run through a die twice to get that mirror finish (also makes it 
more expensive then "mill finish material"). 

Next is dimensional considerations - Tubing is measured OD, and various wall 
thicknesses reduce the diamater accordingly. Pipe is dimensioned nominally on 
the ID as it is used to compute fluid flow characteristics. There are various 
wall thicknesses that impact the inside diameter, but not the Outside diameter 
as that must be held to a standard so as to interface with thread dies, and 
associated fittings. A schedule 40, 2" pipe will have a ID of about 2.060 
(nice slip fit for 2" TUBING) and an OD of 2.375".ÂÂÂ An often used 
substitute for a 2" mast is 1-1/2" PIPE whose OD is around 1.9" making it a 
sloppy fit inside of a 2" thrust bearing, but that can be shimmed to 
compensate. 

When choosing a material for MAST applications there are many other factors to 
be considered then just Pipe or Tubing. Probably to most important is what is 
the Wind load of the antennas to be attached? From that info and how much 
exposed mast (distance above the top bearing) there is, the stress can be 
calculated which leads to the strength of materials, diameter and wall 
thickness computations. Selection of materal (aluminum or steel), diameter 
(2" for tubing, 1.90" for pipe), wall thickness (lots of choices in tubing, 
schd 40 or 80 for pipe). The "strength of material number" will vary over a 
wide range depending on the type choosen.

But back to what most hams do, and thatÂis find the cheapest or most 
available. If it bends in the first wind storm then that becomes the time of 
regret in your choice. Depending on where it bent, you will likely cut it 
there and reuse what is left only now not as long. Ten or twenty-one foot 
lengths of galvanized "PIPE" are readily available at home improvement stores 
or local plumbing outlet. Aluminum pipe may be available at a large 
electrical supply house as it is often used as rigid conduit (pipe sizes) and 
10 ft lengths. Or you can find both steel and aluminum tubing at a metals 
distributor, who may or may not supply to a retail market. Or you can buy 
super quality chromaloy masts from various tower and ham supply outlets. 

I would stick to tubing for a mast application, and choose the appropriate 
material (steel or aluminum), andÂwall thickness to achieve the necessary 
strengh needed.Â

Norm W4QN

------------------------------
Message: 8
Date: Thu, 31 May 2007 20:35:06 -0500
From: <jacobsen_5@msn.com>
Subject: [TowerTalk] tubing vs pipe
To: "towertalk" <towertalk@contesting.com>
Message-ID: <BAY111-DAV1597E7095AC1E110413AD7B22C0@phx.gbl>
Content-Type: text/plain;ÂÂ charset="iso-8859-1"

Hello all. I've tried to check the archives but don't seem to find an answer. 
Just what is the difference between aluminum TUBING and aluminum PIPE. 
My 
"gut" (and poor memory) says tubing is extruded and pipe has a welded seam. 
TIA

73
K9WNÂ Jake

------------------------------

Message: 9
Date: Thu, 31 May 2007 20:39:34 -0500
From: "Clint Talmadge" <unclebudd@bellsouth.net>
Firstly:
Pipe is measured inside and tubing is measured outside.
Secondly:
Pipe is meant to carry pressure on the inside and tubing caries stress on the 
outside.

Clint - W5CPT
 ------------------------------

Message: 10
Date: Thu, 31 May 2007 19:08:26 -0700
From: "Richard (Rick) Karlquist" <richard@karlquist.com>

Correction:

Pipe is also measured outside. For example, all
so-called "2 inch" (Iron Pipe Size) pipe is 2 3/8 inch O.D.,
regardless of wall thickness. The I.D. varies
from below 2 inches to above 2 inches, depending
on wall thickness. It also varies depending on the material
the pipe is made out of.

Rick N6RK

------------------------------

Message: 11
Date: Thu, 31 May 2007 22:55:04 -0400
From: "Bert Almemo" <balmemo@sympatico.ca>
Subject: Re: [TowerTalk] tubing vs pipe
To: "'Richard (Rick) Karlquist'" <richard@karlquist.com>,ÂÂ "'Clint
ÂÂÂ Talmadge'" <unclebudd@bellsouth.net>, <jacobsen_5@msn.com>,
ÂÂ 
This is the first time I've heard anything to be defined the way you measure
it!! The difference between pipe and tube is how it's made - not how you
measure it or what you use it for.

Pipe is made of cast iron or other metal and tube is made of sheet metal
that's folded and welded or drawn from a blank through a die, cold or hot.

73 Bert, VE3OBU

 -----Original Message-----
[mailto:towertalk-bounces@contesting.com] On Behalf Of Richard (Rick)
Karlquist
Sent: Thursday, May 31, 2007 10:08 PM
To: Clint Talmadge; jacobsen_5@msn.com; towertalk
Subject: Re: [TowerTalk] tubing vs pipe

Correction:

Pipe is also measured outside. For example, all so-called "2 inch" (Iron
Pipe Size) pipe is 2 3/8 inch O.D., regardless of wall thickness. The I.D.
varies from below 2 inches to above 2 inches, depending on wall thickness.
It also varies depending on the material the pipe is made out of.

Rick N6RK


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