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@ARRL.NET
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