[Towertalk] Plumbing a tower??

[Ray Benny]

I'm new to the list, I hope someone can help with my problem.

I have a 4 section, 71 ft motorized tower. It has 6 - 8 inch skids at
the top and bottom of each section (not rollers) for the sections to
slide as the tower is raised or lowered. I grease the sections once in a
while with a non hardening grease.  Its been up for 20 years.

I have had a bit of a problem over the past year or so, I think it is
caused by the tower not being perfectly straight. As I lower the tower,
the sections bind causing the tower to descent in jerks. This jerking
resonates and causes the tower to start shaking violently. I, of course,
stop the motor and let the tower settle down. When I start the descent
again, it starts this jerking / shaking again. Only until the tower is
about half way down does the jerking stop. The same thing happens while
the tower is being raised, but not near as bad.

I do notice that there is some scaring on some of the tower skids, as
well as the tower legs where the skids slide. I come to conclude that my
tower is not truly straight. It is not visibly leaning, so it can't be
off much.

This tower has four bolts per leg and can easily and safely adjusted in
the lowered position. I want to be able to measure, or relate the
direction the tower is off. I also think that the torque of raising
cable on pulleys can cause the sections to turn or twist somewhat, I may
have to compensate for this as well.

Any comments or ideas as to how to accurately straighten a tower? Anyone
else have this problem?

Ray, N6VR