Guys, I've used PVC for this same application (A3-A4 and similar beams DE
In one case, in a pinch, I bought a solid block of PVC from a local plastics
supplier (cost about $5), gave them a drawing of what I needed. They put it
into a multi-axle CNC machining center and about ten minutes later I had a
custom made PVC center insulator for $25. Took them more time to clamp the
block into a fixture than it did for the actual machining.
A lot of plastics shops can do this. PVC is really strong, not bad for the
application. This was the "black" stuff, UV tolerance seems pretty good --
the beam's been up for years with no sign of deterioration.
From: K8RI on TowerTalk [mailto:K8RI-on-TowerTalk@tm.net]
Sent: Thursday, August 31, 2006 3:50 PM
Subject: [BULK] - Re: [TowerTalk] Cushcraft A3 center insulator
>>I had a new one kicking around in my garage, and finally
>>threw it out, I think. But if I still have it, it's in the same
>>storage tub as my rotor and coaxes. I'll check. You can have
>>it for postage. Wl msg you privately, in 24 hours, if so.
>>But...why not just order what you need from Cushcraft? Crash parts
>>for these things aren't all that expensive, and then you know you have
>>the right stuff. Reinventing the wheel usually isn't a productive
> Just got my Inquirey back from Cushcraft, this is why.
> The fiberglass insulator fo the Driven El. on A3S is 122096, and is $34.70
> Its a 10 in. piece of fibreglass for heavens sake.
The earlier ones were phenolic. I have an ATB-34 out in the shop that just
uses a phenolic tube about 8 or 10" long. The elements fit into it. It is
drilled and tapped, 1/4-20. They use a SS round head screw plus a double
nut to hold the crip on connector that goes to one side of the coax or the
other. The insulator is held to the boom using an Aluminum plate and a pair
To make one of these would only take drilling out a phenolic rod of the
proper size. The same could be done with a fiberglass rod of a large enough
diameter. I used the phrase "only take". It'd only take a lathe to do it the
easiest way and keeping things centered. OTOH the resin in fiberglass is
sensitive to UV light and will not last near as long as those old phenolic
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com (Use return address from home page)
> Scotty W7PSK
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