I agree with your analysis.
Quoting Rex Lint <firstname.lastname@example.org>:
> The Teflon rod would spread the weight of the tower over 4 square inches or
> so: marty's would spread it over 40 or so, about a 10 to 1 difference. I'd
> think deformation of a sheet of Teflon would not have a safety issue,
> wouldn't you? The tower is guyed.
> He HAS, however, built a home-made capacitor to ground. Depending on the
> value of that capacitor, screwey things might arise regarding RF current to
> ground, but I 'spect it will work OK anyway.
> -----Original Message-----
> From: email@example.com
> [mailto:firstname.lastname@example.org] On Behalf Of email@example.com
> Sent: Wednesday, December 23, 2009 12:15 PM
> To: firstname.lastname@example.org
> Cc: email@example.com; firstname.lastname@example.org
> Subject: Re: [TowerTalk] Making an insulated base for 80 meter vertical from
> Rohn 25
> One comment on Teflon.
> It is SOFT and will deform rather easily under stress, whether expansion OR
> compression. Do some testing before you put a lot of force on it.
> My original idea was to use Teflon rod for my insulated tower bases, but
> changed that IMMEDIATELY upon discovering the deformation that occurred just
> with the weight of the base legs on the insulators in static position.
> Now using (as previously done) fiberglass rod which can be purchased in 6'
> lengths at a farm supply store, disguised as 'electric fence posts'. They
> are exactly the right size for my purpose, being 1.25"
> in diameter, and fit snugly within the tower leg supports.
> Good luck,
> Quoting email@example.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
>> 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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