[TowerTalk] Re: Thrust Bearing Usage

[Tower (K8RI)]

On the old tower I used a 2 X 4 U-bolted to the tower legs with another 
U-bold holding the mast centered.  It served no purpose other than to keep 
the mast centered and take any bending moment off the top plate.  It didn't 
even have to be real tight.  Just tight enough to keep things from flopping 
around.  With some masts I can see where it'd either be necessary to mount 
the 2 X 4 on one side or the other of the two legs and sometimes use a wood 
shim to get a snug fit against the mast.

Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com


> 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
>>  _______________________________________________
>>
>> 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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>>
>
>
> _______________________________________________
>
> 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
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> http://lists.contesting.com/mailman/listinfo/towertalk
>