Rotating top section(s)

[Robin E. Midgett]

        Greetings! I am interested in rotating a section (no more than 2) of
Rohn 25 on top of my Rohn 45 (130'). The top section of the 45 has the
flat-top plate, bored for a 2.5" mast (I believe that dimension is correct)
with a 4 bolt pattern for a thrust bearing, which I currently have in use
with an aluminum mast holding a Telrex 5 element tri-bander & a Cushcraft
17B2. I woul like to replace this current arrangement with a rotating
section of 25. I plan to use a prop-pitch which I already have. I am
interested in hearing from folks who have designed/built/installed rotating
top sections. 
        The top of my 45 is 9' above the last set of guys. The last set is
connected to a TA45 torque arm at the joint of the 'next to last/last
section'; so I don't anticipate a problem with torquing the tower when all
is said & done. I have been in touch with Dick Weber of RTS & discussed
preliminary plans; am interested in hearing other solutions as to how to
acheive the goal. I have in mind, basically speaking, a large "Lazy Susan"
device, using SS balls in a machined track between two heavy pieces of plate
steel, with flanged cam followers on the perimeter to hold things together
both laterally & vertically. I am investigating glavanizing the metal
against the elements, & hard chroming the machined grooves for duribility.
Other suggestions concering bearing solutions are welcomed; ready made
thrust bearings large enough are VERY expensive ($800-$1000). I expect the
plates for the Lazy Susan will end up being app. 16-18" diameter. Thanks!