[TowerTalk] Hand cranking the MA770

[Dick Green]

> Currently I am hand cranking this thing up and down and it
> cranks fairly easily up until about 45 feet and then it gets real
> difficult to crank.

Terry,

This doesn't sound right to me. My MA-770 is motorized and goes up and down
quite smoothly. Sometimes there's a bit of squealing from the sections
rubbing together if the wind is blowing, but no apparent binding. The load
on the motor appears to be constant all the way up. If there was as much
resistance as you describe, I think the motor belt would start slipping.
I've got a TH-7 on top, which weighs close to 100 lbs, so the load is about
the same as yours.

I'm no mechanical engineer, but I thought the hand-winch was designed to
give you enough mechanical advantage that you shouldn't feel any strain when
cranking. Yeah, you should get tired from the number of revolutions, but not
the force required. I know that when I use the tiltover winch it takes very
little force and a lot of cranking.

The first thing that comes to mind is that perhaps your antenna load is very
unbalanced and that's causing the sections to get out of alignment as the
tower is raised. But I'm sort of skeptical about that since mine goes up and
down OK when the wind is blowing. Do you hear any metal-on-metal squealing
when raising or lowering the tower? If not, then perhaps the cable is
binding up somehow inside one of the tubes or perhaps some debris managed to
get into one of the tubes and is interfering with smooth nesting.

If I were you, I'd call U.S. Tower and describe the problem. They should be
able to help. I agree that you shouldn't put the motor on until you get to
the bottom of the cause. I don't know the motor installation procedure, but
would guess that it involves replacing the main cable. If so, then you'll
have to take the tower apart and should be able to determine what's going on
inside.

Hope this helps.

73, Dick WC1M


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