Hi Dave,
The big difference IMO is that you *use* yours. The really damaged ones
I've seen - and they are the ones I inherited to make my modified ones -
are from something like a TH-6 mounted on a Ham M or similar and, most
importantly, parked in one direction for 9 months of the year (or longer).
The rotator allows a few degrees of freedom in rotation - the brake doesn't
hold the mast perfectly still - and the wind just rocks the antenna back
and forth, back and forth, and the steel balls wear on the aluminum races
relentlessly, in the same place. Small divots develop in the races, divots
turn into pockets, and before long, it feels like you have 5 pounds of pea
gravel in there when you finally go to turn it... ;-)
It doesn't seem to affect TB-3s that are in more-or-less constant service,
although I've never done any tower work where the bearing was exposed to a
salt environment; others will have to comment on that.
73,
geo - n4ua
On Mon, Jun 2, 2014 at 1:12 PM, David Robbins <k1ttt@verizon.net> wrote:
> I have a tb-3 that has been in the air for almost 30 years now, has
> outlived several rotors, a bunch of antennas, and a set of guy wires... and
> I haven't looked at it since I put it up there... it just keeps on turning.
> I have several others on different towers that have been up there 15 to 20
> years that have never been touched either. just how old are these tb-3's
> that are requiring all this work??? have they been used in a salt spray
> environment?
>
>
> Jun 2, 2014 01:03:10 PM, charlie@thegallos.com wrote:
>
> Exactly what I'd do if I needed to rebuild a thrust bearing, unless I
> could get some free torlon or vespel (haha, I'm funny, those are crazy
> expensive and overkill)
>
> Low rotation rate, shock loaded, out in the weather, where they will
> receive little in the way of maintenance is the place where engineering
> plastics like nylatron gsm shine. Heck, I can't see why any tower thrust
> bearing mfg would do anything else except to market to folks who say "ball
> bearings have to be better than PLASTIC"
>
> --
> 73 de KG2V
> Charlie
>
> > On Jun 2, 2014, at 12:41 PM, George Dubovsky wrote:
> >
> > I think I've mentioned it before on this forum, but I converted my TB-3
> > thrust bearings over to thrust bushings by machining them to accept
> inserts
> > made from a dry lubricant-loaded composite, Nylatron GSM.
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