Rulon and Vespel are terrific materials and fantastic choices for a slow
speed bearing, metal to plastic. No stick slip, lowest coefficient of
friction for rulon, thermally stable, no moisture absorption, high PV
ratings, yada yada.
HOWEVER, a Vespel bearing for a 2" mast might cost more than the tower,
rotator, mast, and antennas all together. It is fantastic stuff but
incredibly expensive. I understand the DuPont patents have run out so
there are knockoffs coming to market, but still quite expensive. Rulon
is somewhat cheaper but still has an impressive price.
How about Nylon MDS as a alternative - molybedenum disulfide filled
nylon has good wear and UV resistance and is inexpensive. I've bought
2" thick plate on ebay at very low prices e.g. $40/sq ft. It would make
a good radial bearing and maybe with some engineering a combined
radial/thrust bearing, which if the thrust load exceeds the rotator
capacity, what is needed. Otherwise, use the rotator for thrust and
have just a nylon MDS sleeve bearing to handle the top of tower radial
load. Bore a hole 0.025" or so oversize the mast od, drill a bolt
pattern to fit the top plate and install. Might be a good idea to
smooth up the galvanizing where it contacts the nylon.
Simple, cheap, no maintenance, no rust, no discussion of grease.
On 10/9/2011 7:55 PM, Charlie Gallo wrote:
> Hey Gang,
> Reading the Nth thread on lubing thrust bearings, and just had a thought -
> would it be a good idea to design a thrust bearing that works based upon an
> 'ultra high molecularly weight filled self lubricating plastic" (aka
> something like a filled teflon - or rulon or even vespel) - nothing to ever
> rust/lubricate, and they can take decades of low to medium speed
> rotation/sliding - heck, in theory, if your mast was truly round, you could
> just have 3 or 4 pressure blocks, and it just rides on that
> BTW, for that matter, if you could assure it stays WET (not dry, WET), I'd
> bet a lignum Vitae bearing would be about perfect for a tower thrust bearing
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