When using a long mast (say 20 ft) in a flat top section of 45G where a
thrust bearing is installed on the flat top and the rotor is mounted about 5
feet down inside the tower.... what is the preferred method of
supporting/guiding the mast between the rotor and the top of the tower:
(1) Do nothing?
(2) Fab up a tube/sleeve slightly larger I.D. than the mast O.D. and pass
the mast through it? If this is your preference how do you design the sleeve
support... weld it on the bottom of a Rohn accessory shlef? What do you use
for sleeve?
(3) Install an intermediate thrust bearing? How do you mount... on a Rohn
accessory shelf? I see in the Texas Tower's catalog that rotor plates are
not designed to substitute for a flat top (rotor plates flex).... but is
this a problem on an intermediate bearing?
I would think some sort of support is needed inside the tower at least on a
temporary basis if one plans to use a tram to raise an antenna and the tram
is attached to the mast. Without such a support all the pull is on the top
bearing and it would seem the bottom of the mast would go all over the place
(and bearing would seem to be under undue stress). Other ideas for tramming
if (1), (2) or (3) not used?
Larry WI5A
Friendswood, TX
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