At 04:00 PM 7/30/2005, you wrote:
>Didn't know to what you referred so did a search:
>http://www.ticona.com/index/products/uhmw-pe.htm
>
>This site does not mention outdoor use where degradation
>from intense and sustained sunlight destroys many synthetics.
>
>WDYT about UHMW bearing up under west central Florida weather?
>
>Where does one acquire chunks of UHMW?
>
>Just wondering ... doc
There are types of UHMW that are specifically resistant to UV, but
white has held up well in the CO sunshine (300 days per year of sun
and high altitudes).
BUT a PROPERLY designed bearing would not even expose the
UHMW to sunlight. Especially easy to do if you are making a
bearing that will also handle the vertical load.
Any decent plastics house will have it. I bought mine years ago
from Boulder Plastics (now Colorado Plastics), but here is the
best-price, on-line source I have seen. (But you can do an eBay
search for UHMW and find sheet, although it will be mostly rods.
http://www.professionalplastics.com
Assuming 3,000 lbs. psi and a one inch thick block, and a 2 inch mast
(total of 2 inches of projected area) you will have a bearing that is rated
at 6,000 pounds of horizontal force. Should be good enough for single
Yagis, if you plan on a long mast with stacks of Yagis you will need to
do your homework.
A one square foot piece of one inch thick UHMW will set you back $20.
You only need a 6x6 inch piece for a bearing, so each bearing will cost
you $5 for UHMW. You can get a bunch of cutting boards (not all are
UHMW, some are only HMW PE) and stack them up and make a bearing.
Just use enough layers to handle the side load you need.
--John W0UN
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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