[TowerTalk] RE: Tower Talk Digest V3 #480

[Dick Green]

> I have a new MA-770 Steel Tower.
>
> Now that the freezing weather is upon us, it seems that the tower freezes
> at the point where it is surrounded by the support collar (up about 6 feet
> from base).
>
> Is there a product that I can use during the Winter to prevent freezing of
> connecting steel tower components?
>
> Tnx/73
>
> Rick
> WA7ND

Rick,

I assume you have the rotating base, or you wouldn't be asking this
question. Is the tower actually freezing (i.e., ice forming between the
collar and tower), or is the tower seizing (turning partway, then jamming)?

There is one thing you should do that will help either problem -- coat the
inner surface of the support ring with a thick layer of automotive grease.
Low-temp grease would be fine, too, but I use plain-old automotive grease
here in NH. This is required for the tower to rotate properly and to prevent
the bare metal ring from abrading the rotating base tube. I got this
straight from Bruce, the president of U.S. Tower. Of course, this should be
in the instructions, but there are no instructions...

If you have the tiltover fixture, use it to hold the tower while you open
the support collar jaws. You may need to tilt the tower slightly forward to
get at the inside of the ring (don't forget to remove the pin bolts in the
tilt hing!) When I don't feel like tilting the tower, I just shove grease in
the space between the tower and ring with a popsicle stick. I rotate the
tower a few times to open up different gaps where I can put the grease, and
to spread the grease. Grease should be applied about every 6 months or when
it looks dry.

If the tower is seizing, and the grease does not fix the problem, the most
likely cause is incorrect vertical positioning of the rotor (i.e., it's too
high.) The rotation system depends on the short (8") pipe stub that connects
the tower drive shaft to the rotor jaws. The stub acts as a poor-man's
U-joint or flex coupling. Since the tower rocks slightly when it turns, and
the bottom tube cannot be made perfectly round, the tower and rotor cannot
always be perfectly aligned. The stub allows some flexibility in the
coupling to compensate for this. If you push the rotor up too high on the
stub, the stub will not be able to swing back and forth. If you tighten the
bolt/nut on the stub too much, the same thing happens. When the stub can't
move, the tower will likely seize at some point in its rotation. There
should be at least an inch or two between the top of the rotor jaws and the
bolt that holds the stub to the drive shaft. The aircraft nut should be
tightened only enough for it to contact the surface of the pipe, but not so
far that it would prevent the pipe from moving.

It took me days of great frustration to figure this out, with a few hints
from Bruce. The problem was compounded by the fact that my tower base had
been built about 2" shorter than spec, which prevented me from lowering the
rotor (a Tailtwister) enough. I had to cut off the tops of the base bolts to
be able to lower the rotor plate sufficiently (recommended by Bruce to solve
the problem.)

Hope this helps. If you have any other question, just ask.

73, Dick WC1M


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