[TowerTalk] Making an insulated base for 80 meter vertical from Rohn 25

[brahmangou at aol.com]

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  
legs.
 
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 in 
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 at ARRL.NET