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@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
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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