I guess it depends on the individual rotor manufacturer and their theories
....... I quote from the instruction manual for the Create Model RC5A-3
>>>
" A bearing or similar item is usually installed at the top of an antenna
tower to prevent the antenna from swaying. Such a bearing must be used only
for this purpose. Using it to support any of the weight of the antenna or
antenna mast would have an adverse effect on the rotor. This is not only
because the rotor is more thrust-effective than the bearing, but also
because eccentricity arising from structural imprecision cannot be absorbed
at the top of the tower and so the resultant waste force would work on the
bearing and rotor. "
I, consequently, let the weight of the antenna and mast rest on the rotator,
while the TB just provides lateral support. Works fine -- the antenna / mast
weigh about 225 lbs. on tower # 3.
On the other two towers I don' t use thrust bearings at all and the weight
rests entirely on the rotor. No failures in 10 years of doing it this way;
the rotators are a Ham IV, a Tailtwister, and the RC5A-3.
I won' t attempt to say what's " right or wrong " - I just know what works
for me...
73,
Kent - K4MK
I
----- Original Message -----
From: "Chuck Lewis" <clewis@knology.net>
To: <towertalk@contesting.com>
Sent: Thursday, July 22, 2004 4:26 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
>
>
>
> _______________________________________________
>
> 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.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
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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