Bottom bearings

[rattmann]

Gary wrote:
>Really appreciate your observations on how to stabilize the bottom section
>of the mast  (edit)...
 it would solve a problem that I have
>always had.... that is stabilizing the mast and yagi christmas tree when I
>am swapping out rotors. What I have done is torque down the top thrust
>bearing (obviously) which is set to take the vertical load off the rotor. My
>rotor just turns, it supports no weight. I then use a rope to tie-off the
>mast laterally inside of the tower to keep the mast vertical when I remove
>the rotor. The second thrust bearing would be a nice addition and remove any
>"white knuckling" left in my procedure. 

K6NA writes:
Yes, removing a rotator from underneath a top-heavy "christmas tree" stack
can be a thriller... your rope method for keeping the lower part of the mast
vertical is better than nothing but, as we all have found out, is a bit
spooky.  With an intermediate plate above the rotator, the instability goes
away... and one person can do just about everything with just a come-along
and a movable mast-clamp to act as a lifting/tie-point.

There is another benefit I failed to mention in my earlier post on this
subject. Let's say the intermediate plate is about 4 feet above the rotator.
If you are using a come-along in this area to lower the mast into the
rotator, you can also reach up onto the top of the extra plate, and tighten
a clamp (even one or two muffler clamps works fine) to bear on the plate (or
its thrust bearing, if in place).  This takes the load in case you need to
reposition the come-along, or whatever, and you don't need to climb all the
way back to the tower top to reach the clamp up there. In other words, you
can reach the clamps on the plate, and handle the come-along, at the same
time. After you lower the mast to "bottom out" into the rotator, you want to
nudge the mast back up a quarter-inch or so with the come-long in order to
remove all the vertical load from the rotator.  At this point you can reach
up and quickly tighten the clamp(s) above the intermediate bearing plate.
Remove the come-along, and at your leisure tighten the rotator clamps to the
mast.

73!  Glenn K6NA
rattmann@cts.com


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