I haven't read all of the replies yet, but Teflon is a poor structural
material. If under compression or expansion it will move. It "cold
flows" substantially, like an extremely thick taffy. I used it for the
base insulator on a mobile antenna. In less than 20 miles the antenna
was swinging around at almost a 45 degree angle. I had to stop and guy
it into the car through the windows using heavy fishing line.
Delrin, or the strongest ...fiberglass painted with a UV protecterant
should work fine.
73
Roger (K8RI)
brahmangou@aol.com wrote:
> 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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>
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