I do a similar thing, but I have a suggestion that may make it simpler
and cheaper for you.
Drill holes in one face of an 18 inch length of angle iron spaced to
accept the bolts from a saddle-type muffler clamp (available from Pep
Boys for a few dollars), and use that homebrew assembly instead of a
second thrust bearing on the lower bearing plate. I use angle iron that
is about 1.5 inches on each face, but you could use 2 inch angle iron
and have room for two muffler clamps if you want the additional safety
of redundancy. The muffler clamps will work fine to keep the mast from
sliding down while you remove the rotor, and the other end of the angle
iron can easily be secured to the bearing plate with a C-Clamp to
prevent the mast and antennas from pinwheeling in the wind. If my
description here is poor, let me know and I'll send you a picture of mine.
Another advantage of using the angle iron and muffler clamp idea is that
you should be able to get a crow bar between the muffler clamp and
bearing plate to recover any minor slippage that might occur in the
process of removing the rotor. I doubt you'd be able to do that with a
normal thrust bearing since they sit flush on the plate.
You won't want to leave the thing on the tower when you aren't using it,
though, since the muffler clamps and bolts can rust rather quickly.
73,
Dave AB7E
On 5/25/2010 8:32 AM, Mark Robinson wrote:
> I am thinking about possible rotor maintenance on my new tower. I will be
> lifting a 22 foot mast and antenna stack onto the tower with a crane and
> nesting it 4 feet or so into my Rohn 45 tower. I will have a thrust bearing
> on the top and an Orion 2800 rotor 4 feet below the top thrust bearing.
>
> I am thinking of setting a second bearing plate just above the rotor which
> will be about 4 feet below the top thrust bearing. I will have a TB3 bearing
> on it. I may well lift this bearing off the plate and clamp it to the mast a
> few inches above the plate so that I don't have alignment issues. The
> bearing just sits in the air above the plate. When I want to remove the
> rotor I should be able to lower the bearing, bolt it to the plate and add a
> clamp to the mast so that the mast rests on this bearing or will the bearing
> stop the mast sliding down. Some sort of u
> bolt or a saddle clamp should work. The stack and mast will weight about 220
> pounds.. I should be able to remove the rotor
> then with the mast held in place. Yes it's more money but it makes it
> possible to remove the rotor and repair it without dealing with the stack.
>
>
> I am still thinking this out but I want all the pieces fabricated and
> checked out with the tower on the ground first
>
>
> Mark N1UK
>
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