In a message dated 3/25/02 8:36:08 PM Pacific Standard Time,
alwilliams@olywa.net writes:
> I am currently trying to decide how much of a 20' mast to have inside the
> tower when the top of the mast will have a Force12 mag 2/2 (185# and
> about 14 sq ft antenna wind load. My concern is the lateral pressure
> on the Orion M2. Should there be a thrust bearing just above the
> rotator?
The manufacturer wants all of the vertical weight to be on the rotator so
what's above it holding the mast isn't so important. I imagine you're got
some sort of hole at the top of the tower for the mast to poke through.
That's really all you need.
Another fixture between the top of the rotator and the top of the tower
is helpful when you need to hold the mast vertically whilst swapping
rotators. Just another rotator shelf is plenty. If you don't have one you can
always field fabricates something to hold it out of angle iron and U-bolts.
If you're worried about lateral forces against the base of the rotator,
there's not much you can do about them. But I have never encountered this
kind of failure before so I wouldn't worry about it.
As far as how much mast to have in the tower, it's almost more of a
function of how much mast is available and what antenna spacing you need but
if you had 1/3 of it in the tower that should suffice.
Cheers,
Steve K7LXC
TOWER TECH -
Professional tower services for amateurs
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