[TowerTalk] Re: Thrust Bearing Usage

[Don Havlicek]

An easier way to service a rotor when there is only a top-mounted 
bearing is to make a bracket of angle with U-bolts that attaches inside 
the tower above the rotor and holds the mast securely.
The Hy-Gain boom-mast bracket mounted on a piece of 2"x2" angle works 
excellently in most towers.
Don
N8DE

David Robbins K1TTT wrote:
>>I've been monitoring this interesting thread. I haven't had the need
> 
> to
> 
>>replace a rotor (yet) and I only have one thrust bearing on the top
> 
> (flat)
> 
>>plate. The rotor is 4 feet down the tower with the rest of the 20 foot
> 
> C-M
> 
>>mast and two beams above. It seems to me that if you lift the mast out
> 
> of
> 
>>the rotor and clamp it above the bearing, it will very much want to
> 
> sway
> 
>>and
>>tilt with the better part of the weight above the tower. It seems you
>>would
>>have to do some sort of stabilization just above the rotor to have a
>>fighting chance - a sort of faux bearing. Am I reading this correctly
> 
> or
> 
>>is
>>my physics off ?
>>
> 
> 
> Your physics is fine, 16' above the bearing and 4' below with all the
> weight above will definitely want to tip over.  To keep it from tipping
> a real bearing does the job also.  You can rig it temporarily by tying a
> very tight wire or rope loop as low in the mast as you can around each
> tower leg.  3 separate tight loops do a decent job of holding it upright
> while the rotor is replaced.  Note, don't take a shortcut and just loop
> around a leg then loop around the next leg without tying it off on each
> one or vibration will cause it to work its way off to one side or
> another making it very hard to get back straight.
> 
> On my flat tops I always put a second bearing just for that purpose
> above the rotor.  To keep it from binding I leave it loose until needed
> to remove the rotor.  And I do let the top bearing carry the weight of
> the mast and antenna(s) and leave that 1/4" or so gap below the mast so
> its easy to remove the rotor when needed without jacking up the mast.
> 
> 
> David Robbins K1TTT
> e-mail: mailto:k1ttt at arrl.net
> web: http://www.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>  
> 
> 
> 
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> 
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