[TowerTalk] [Bulk] Re: Top Bearing Plate for 55G vs Rotor Plate

[Don]

THAT is a good idea, the UHMW bored block. Zerk fittings and the plain old 
typical steel inlanders use go quickly here. Living on the OR coast next to 
the ocean you learn quickly that putting antennas together and mounting them 
requires 'different' approaches to keeping them in a low maintenance mode.

I also use the Lear compound, CorrosionBlock, on anything that turns, 
slides, screws or moves. Won't wash out and has no metals, RF neutral. Put 
onto this by the fleet folks up in Newport who apply it to all their 
electrical connections, AC, DC and RF. I've easily taken elements apart 
where the salt spray has literally 'grown' on the element exterior. It is 
lightly colored so it is easy to see where you are putting it. See 
http://www.learchem.com/userfiles/Industrial%20Strength%20Protection.pdf for 
some information.

Don W7WLL

-----Original Message----- 
From: Grant Saviers
Sent: Tuesday, August 12, 2014 9:52 AM
To: towertalk at contesting.com ; rthorne at rthorne.net
Subject: Re: [TowerTalk] [Bulk] Re: Top Bearing Plate for 55G vs Rotor Plate

I agree with Steve that a middle bearing is not a good idea as aligning
3 bearings is very difficult and a middle bearing serves no purpose at
rotator rpms.

However, a middle support plate with a removable u-bolt or clamp, that
can constrain the mast when you want to raise it to remove the rotator
for service is a big help.  Then the mast stays in column and doesn't
overload/twist the top bearing.

I also dislike the commercial "thrust" bearings.  A block of black UHMW
3" thick bored for the mast od will never need servicing.  Or stack up
some HDPE kitchen cutting boards bored to fit, but they will need a coat
of paint to protect them from UV.  A rotator sized for a 4L full size
40m beam bearings can easily handle a 500lb thrust load.  btw, my 40m 3L
full size OWA weighs 350# plus 150# for the 3" x 0.25" wall alloy mast
(a must for that size antenna).

Grant KZ1W


On 8/12/2014 8:04 AM, K7LXC--- via TowerTalk wrote:
>>   I'm working on getting the parts together for a Rohn 55g  tower.
> ?  The Rohn 55g Bearing plate sure is expensive.  I see  two other
> possibilities.
>
>>   1 - Use the less expensive beacon  plate and drill a hole for the
> mast/bearing.
>>   2 - Use a rotor  plate for the same purpose.
>
>>   I plan on having a top bearing, an intermediate bearing  then the 
>> rotor.
>   I have no idea what the thickness of the Rohn bearing  plate is as
> compared to a beacon or rotor plate.  I'm hoping to put up  a full size 4
> element 40m beam some day, so the system will need to handle a  good
> 300+lbs.
>
>
> Hiya, Rich --
>   The beacon plate is FB if you don't mind  drilling it.
>   As for an intermediate bearing, I'd  discourage it. The plates are not
> precision items and you'll just introduce bind  into the system. Since all
> you're trying to do is capture the mast, put the  rotator plate in the 
> middle
> and skip the bearing - cheaper too. And the upper TB  carries all the
> weight anyway so a middle bearing doesn't provide any structural  help.
>   Cheers & GL,
> Steve     K7LXC
> TOWER TECH
>
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