[TowerTalk] mechanical construction of 80m vertical

[Eric Scace K3NA]

Chris --

   I think you were originally looking to do a 20m high vertical (i.e., quarter-wave on 80m).  My observations about your ideas:

   Electrical conduit is a relatively soft steel not designed for structural purposes over a significant distance.  It's cheaper
than high strength steels because it doesn't have to be structurally strong over distance.

   Welding steel with galvanizing requires removal of the galvanizing (it forms a poisonous vapor otherwise).  The piece, after
welding, will have to be completely regalvanized.  That means transporting a 20m piece of material to a facility with a 20m+ etching
and hot-dip galvanizing bath.  This will be expensive.  If one just paints the welds, the interior will be unpainted and will rust
from the inside out.  It's condition will not be inspectable and failure will be sudden.  (This is why tower parts come in
sections.)

   A steel vertical will be enormously heavy and require additional care to erect from a horizontal to vertical position.  Raising a
vertical (while it is usually without guys) typically is one of the most stressful operations that can easily cause the tube to kink
and collapse.

   To get adequate structural strength, a steel vertical will look like a tower.  A single pipe will be more expensive for the same
strength as a tower section and, because it is a custom piece of work, much more expensive than tower sections.

   Plastic pipe is not welded but glued.  The glue will not be the weak point in a chain of plastic pipe.  Again, a great deal of
care will be required in lifting a plastic vertical as it will be very flimsy and likely to crack.  Plastic pipe is not designed to
be a structural material over great distances.  One could envision a "plastic tower" that might have structural strength, but the
material costs will exceed those of a normal steel tower.

   People use aluminum tubing because:
   a) it is both strong and fairly stiff compared to its weight and cost, especially if appropriate types of aluminum mix are
chosen.
   b) it is relatively easy to work with.
   c) it holds up well to the environment with relatively little maintenance.
   d) it has a very low electrical skin resistance, helping to keep losses to a minimum.

   All of the alternative materials that you have mentioned fall short against (a) through (d) in one or more ways.

-- Eric K3NA

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com]On Behalf Of Chris BONDE
Sent: 2003 March 21 Friday 18:43
To: Jim Hill
Cc: towertalk at contesting.com
Subject: RE: [TowerTalk] mechanical construction of 80m vertical


I have been unable to find a supplier of irrigation tubing within a
reasonable distance.

The other metal tubing that I have been trying to find out more about, and,
in some cases have found that they are good but expensive, are;  electrical
conduit used for the stack, ie that part above the roof line ($$$$$),
industrial grade top rails for chainlink fencing, looks good but shipping
the problem for me 20ft lengthas about CA$30 a length, the last was custom
automobile exhaust tubing, comes in various sizes, can be welded together
or flared.  Should be galvo on the inside as well.

The other one that took my notice was the new plastic electric
conduit.  Have to use the large diameter to obtain wall thickness and donot
use the coupling, use a length of the main pipe as a splice or spint over
the joint.  I was wondering about plastic welding, is that as strong as the
main pipe as it is in steel pipe welding?

Chris opr VE7HCB


At 02:45 PM 2003-03-21 -0800, Jim Hill wrote:
>Finding tubing isn't easy.  I've stopped at a number of businesses in
>farming areas with little luck. plastic tubing seems to be currently used.
>However, the following store in Bakersfield CA  is a good choice:
>
>The Irrigation Store, 4001 State Road, Bakersfield, CA 93303  661-4421 or
>800-742-7246. Their web site is: http://www.rainforrent.com/  Their web
>site shows tubing with end connections, but I thought I saw just plain
>pipe when I visited them.  The web site also shows stores at other locations.
>
>73's Jim
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with
>any questions and ask for Sherman, W2FLA.
>
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_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free,
1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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