[TowerTalk] Re: Thrust bearing

[Keith Dutson]

I have not seen any specs posted about the Rohn TB-3 or TB-4.  I use the
TB-3 (for 2 inch mast) and these "set screws" are actually bolts.  I recall
they are 9/16 or larger.  The bearing appears to have races on side and
bottom.  Does anyone know the rated weight for this bearing, or vertical
load rating on the bolts?

Keith 

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Jerry Keller
Sent: Thursday, July 22, 2004 3:55 PM
To: (Reflector) TowerTalk; Chuck Lewis
Subject: Re: [TowerTalk] Re: Thrust bearing

Chuck, I'm no engineer (I just play at being one) but it seems obvious that,
like any other part of the system,  a TB needs to be rated for the loads
placed on it, both vertical and horizontal loads I would think. All I do is
spread the vertical load over the surface where the double-saddled muffler
clamp meets the TB, rather than hanging all that weight on the dents 3 or 4
little set-screws make in the mast.  Properly centered (or even close) the
mast probably doesn't put much load on the TB horizontally, but a word of
caution....I'm no expert, I just pay attention here on towertalk and the
smart guys here make things pretty clear without having to understand the
math :-)

73,  Jerry K3BZ
  ----- Original Message -----
  From: Chuck Lewis
  To: Jerry Keller
  Sent: Thursday, July 22, 2004 4:21 PM
  Subject: Re: [TowerTalk] Re: Thrust bearing



  ----- Original Message ----- 

   I figure the less weight that bears on the rotator, the longer it will
  last.... and TB's are cheaper than rotators!

  N4NM comment:

      I have always been taught that ball and roller bearings must be
properly
  preloaded to prolong life. Granted, these rotor bearings are running at
  really slow speed, so it's not the same issue as a wheel bearing on a race
  car, but intuition tells me that axial loading (within manufacturer's
specs)
  is beneficial in maintaining bearing alignment and reacting against
lateral
  (shear) loads through the plane of the bearing. I seem to remember seeing
  that corroborated by a rotor manufacturer, but I can't quote the
specifics.
  Can anyone with some credentials weigh in here? Having a "thrust" bearing
to
  take the vertical load is like Mom and Apple Pie. If it's a misconception,
  we need to refute it, but if the "thrust" bearing tradition is correct, I
  need to crawl into my hole and shut up.

  73,
  Chuck, N4NM




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