Good question. Static control UHMW has carbon black as a filler so it
is probably a bad choice. Black virgin UHMW that I bought is FDA and
USDA approved, so I think it is unlikely that the coloring agent will
cause a problem. As an element insulator block or insert it should work
fine since the voltage stress is low. However, note that it has a low
creep resistance so don't use it as a boom plate.
It is easy to cut with saws, but I find it unpleasant for machining
since it is so slippery, gummy, and springy. It's very hard to hold any
close tolerances. Acetal/Delrin, ABS, and nylon are much easier to work
with. A twist drill needs to have the edged stoned flat a bit or it
augers in, badly on UHMW but also for brass and some other plastics.
Some white UHMW thrust+radial mast bearings for 3" mast came with some
beams I purchased. After 7 years exposure they did show deep crazing
but were still solid. That is why I am going with black.
There is always the stick it in the microwave and see how fast it melts
test, although a bit of overkill for HF.
Grant KZ1W
On 8/15/2014 3:47 PM, Chuck Smallhouse wrote:
The idea of using a chunk of black UHMW bored out for a bearing sounds
interesting. I fell in love with UHMW, when I HB'd a full coverage
skid plate for my UTV, of the stuff. It was very easy to work with
(cut with a band or sabre saw), tough as nails and didn't dent or take
a permanent set. I understand that they use it to line the beds of
garbage trucks ?
My question is the black version at all conductive ? I'm considering
using scrap pieces of it, cut into plates, to mount yagi elements to
their boom ? Someone mentioned that the white variety can
deteriorate, when exposed to UV ?
BTW, the use of a basketball hoop attached to a gin pole, to be of an
aid in raising tall items, like a pole vertical to the top of a
tower, or even small tower sections such as Rohn 25, is a terrific
idea. This is now added to my R & C notebook (Research & Copy) ! I
need to start visiting garage sales to find a used one.
Chuck, W7CS
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