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Re: [TowerTalk] Making an insulated base for 80 meter vertical from Rohn

Subject: Re: [TowerTalk] Making an insulated base for 80 meter vertical from Rohn 25
Date: Wed, 23 Dec 2009 11:29:59 EST
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Hi Guys,
I got a few emails asking where I got the insulated base. I made it. The  
insulated legs on the market are pretty expensive, and I didn't like that 
they  are in tension and compression when the tower moves with the wind and 
under  other external forces. It appeared to me, and I may be wrong, that the  
insulating material might not be as strong/durable as the original tower  
I bought a  1" thick 24" square HDPE cutting board from a commercial  
restaurant supply , about 18 dollars, and drilled it to fit over the  j-bolts 
a standard Rohn 3'x3'x4' concrete tower base. I put the Rohn  tilt base on 
top of the cutting board. There are several machine shops on ebay  that sell 
PTFE teflon machining end pieces, leftovers. I bought a couple of  short 1 
1/2" teflon rod pieces, 6 dollars, and drilled/turned them to fit  in the 
annular space between the bolt holes in the tilt base and the edges of  the 
j-bolts as insulating bolt sleeves. Then I took a short piece of 3" teflon  
rod, 3 dollars, and sawed 1/2" thick disks off of it. I drilled through the  
disks and made insulating washers for each of the base bolts.
This way all of the plastic parts are always in compression, at their  
strongest. I used teflon for all of the parts that are exposed to the sun to  
avoid UV breakdown of the insulators, also teflon is a superior insulating  
material for the thinner (3/16" thick) bolt sleeves. By using the tilt base, I 
 can lower the tower to make adjustments and repairs in the future ( not 
getting  any younger, hi hi).  I'm ready to install install the tower sections 
and  run the feed line as soon as the weather clears up.
Marty Haley AB5GU@ARRL.NET

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