[TowerTalk] base insulators

[George Dubovsky]

TT,

I tried to use a surplus HV line insulator on my 160 Rohn 25 vertical, but
I couldn't convince myself that I could keep it stable and loaded in column
(vertical). I finally made my own base insulator, and it's been in service
for four years now.

<
https://picasaweb.google.com/116677848251094111716/AntennaStuff?authkey=Gv1sRgCK3-i-O46I-6kgE#5771759616145127026
>

The insulator is 3" diameter and, while I originally thought of making it
out of HDPE (as shown in the pix), I finally came to my senses and machined
it out of fiberglass, painted for better resistance to the environment. The
base of the cup is 1/2" thick, and it fits over a pier pin. There is also a
recess in the bottom of the insulator to clear the pier pin.

73,

geo - n4ua

On Wed, Aug 1, 2012 at 12:51 PM, David Robbins <k1ttt at verizon.net> wrote:

> I agree with thicker plates if you are doing an insulator like that, the
> ones i got are probably 1/2" or so and well galvanized.  the standard roof
> or pier pin plates are meant to be supported on their whole surface not
> just in the middle.  If the commercial stuff is too expensive i would do
> something with a 2-3" thick piece of lexan or fiberglass big enough to
> support the whole base plate... then probably just epoxy it down to the
> concrete, or maybe put a couple of small bolts sticking up an inch or so
> from the concrete into pockets drilled in it, and a bolt in a pocket as a
> pier pin from the top... that would be lots stronger for side stresses than
> the porcelain like i have.  if i were doing the raised one again i would
> sandwich something like that between the plates i have and keep the leg
> braces for lateral support.
>
>
> Aug 1, 2012 12:02:55 PM, knowkode at verizon.net wrote:
>
> David,
>
> I have pondered using this style insulator but have had concerns as to how
> well they could survive the forces you experienced which led to failure.
> One option would be to fabricate a pier pin to bolt to the top of the
> insulator so that the tower base insulator behaves as a pier pin on which a
> tower pier pin base plate sits, or better yet, a tapered bottom section of
> tower. My other concern lies in the relatively small diameter of the
> insulator with respect to the tower diameter. I would be more comfortable
> with a wider insulator especially at its base and cap. I have seen 1/4"
> base plates bent because of the forces applied between anchor bolts and
> tower legs. The answer of course it to fabricate with thicker plate when
> the forces cannot be kept linear.
>
> 73,
> Jim W5QM
>
>
>
> ________________________________
> From: David Robbins
> To: towertalk at contesting.com
> Sent: Wednesday, August 1, 2012 8:08 AM
> Subject: Re: [TowerTalk] base insulators
>
>
> be careful with repurposing old insulators, or even in applying new
> insulators in cases that they haven't been designed for.
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