[TowerTalk] US Tower motor belt

Sun Jun 7 11:30:48 PDT 2009

My feeling is that the belt is so cheap I might as well replace it. As long
as I'm going to the auto parts store to get the belt product, why not buy a
new belt?

Actually, I got a very informative reply from Skip, KJ6Y on how to replace
the belt. The belt part number is printed on the edge, which is visible when
you take off the guard (even after 12 years!) In my case, it was a Browning
4L390. It's a small V-belt designed for some alternator setups, HVAC systems
and lawn mowers. Grainger and my local NAPA parts store both have a
replacement. Grainger charges about $6, the NAPA charges about $12 (even
though it's several dollars less online.) 

Anyway, for removal, I loosened the four motor mounting bolts, which allowed
me to tilt the lower pulley enough to slip off the old belt. The new one
slipped on easily. The belt instructions, by the way, say not to force the
belt on and off the pulley. I found with the new belt that I had to increase
the belt tension from the previous setting to keep the belt from flying off.
There are four small nuts on the motor mounting bolts that are used to set
the distance of the motor from the mounting plate, and therefore the
tension. Easy to do. The new belt is working FB.

Unfortunately, as I was working on the belt, I discovered a new problem. A
couple of times the motor didn't start when I flipped the local Up/Down
switch. Just a "click" from the relay cabinet, then nothing. It did start
quite a few times during testing, so I didn't think much of it. That
evening, when I tried to lower the tower from the shack, nothing happened. I
went to the tower with a flashlight and found that the motor had the
non-starting problem, only this time it was consistent. I tried "helping" it
get started by turning the flywheel, but that didn't work. Was kind of
worried because I couldn't lower the tower. Figured I'd have to do it by
turning the flywheel by hand, which would have taken a really long time
(hundreds or thousands of turns?)

Anyway, the next day, prior to trying to lower the tower manually, I tried
the motor again. This time the motor started right up and I was able to
lower the tower. Phwew. The only difference is that the temperature was
lower and the humidity was higher when the motor wouldn't start. It was cold
and dewy the night it wouldn't start. It was sunny, warm and dry when it did
start.

I thought it might be the starting capacitor, so I checked it. The contacts
aren't corroded, but there's some white powder seeping past the metal ring
at the top. Could just be corrosion of the ring, or it might be
electrolytic. In any case, the cap is cheap ($6-$7) and I'll replace it.
However, Skip and others have told me the if the cap is bad, the motor
should hum and start with a little push. Since it doesn't do that, I'm
pretty sure there's another problem. It's quite possible one of the relays
in the control cabinet isn't working.  I haven't inspected inside the
cabinet yet. Could be moisture or insects in there. Also, Skip suggested
there could be insect debris fouling the starter throwout switch in the
motor. I have my work cut out for me, but will have to wait for a cold, damp
day to do it.

Final maintenance issue: the cable. My cable has held up very well for 12
years. Although we have our share of moisture here, we're far from the sea
and the atmosphere isn't all that caustic (much less acid rain since the EPA
stepped in with the midwest coal plants.) Lately, though, I noticed a light
coating of rust on the cable where it rests on the spool when the tower is
retracted, which is about 95% of the time (I only use the tower during
contests.)  Over our long winters, snow and ice sit on the spool and lower
pulley mechanism, and this eventually led to some rust. I've resisted
lubricating the cable for a number of reasons: 1) some have suggested lube
actually holds moisture against and inside the cable, 2) this is a tubular
tower and it's impossible to lube the entire cable without disassembling the
tower: some of it lives inside the tubes and some is exposed and out of
reach when the tower is fully extended (actually, there are small separate
cables for the upper sections that are completely out of reach.) Perhaps not
good reasons, but there they are. Anyway, given the rust, I decided it would
be best to try to lube as much of the cable as I could. I have a can of
Pre-Lube 6 from K7LXC's Champion Radio (plus two cans of the Whittmore stuff
he sold before that.) Lubing went well. I held a cloth soaked with Pre-Lube
6 against the cable let the cable run through the cloth as I raised and
lowered the tower. I kept spraying the cloth to keep it soaked. This put a
nice, thin even layer of lube on the cable, and also took off the light
layer of rust from that one lower section of the cable.

In the process of lubing, however, I found a spot in the cable where two of
the smallest threads were broken. There was no unraveling or other breakage.
Interestingly, this was not in a section of the cable that had the light
coat of rust. Other than those two small breaks, the rest of that area of
the cable looks fine. Nevertheless, this, and the rust lower down, are a
definite indication that the cable needs to be replaced, which I will do in
good time (I happen to have a complete set of replacement cables on hand.)
It's a huge project, but must be done. As owners of these towers know, US
Tower provides no instructions or diagrams for restringing the cables. I've
heard it's fairly straightforward, but we'll see.

73, Dick WC1M

From: K7LXC at aol.com [mailto:K7LXC at aol.com] 
Sent: Sunday, June 07, 2009 8:58 AM
To: towertalk at contesting.com; wc1m73 at gmail.com
Subject: Re: [TowerTalk] US Tower motor belt

In a message dated 6/1/2009 10:12:24 P.M. Central Daylight Time,
towertalk-request at contesting.com writes:

>  After about 12 years, the motor belt on my US Tower MA-770MDP seems to
have
loosened up. It's slipping intermittently. I can see a few cracks in the
material, so it's time to replace the belt. 

    I don't remember seeing any posts on this so I'll take a run at it. 

    What's "a few cracks"? Little cracks I wouldn't worry too much about.
You can spray some automotive belt product on it and it'll probably retard
the cracking and eliminate the slipping. It'll probably last for years like
this. 

>  Has anyone done this? I haven't
taken the guard cage off for a closer look yet, but I don't see a tension
adjustment. 

    The tension adjustment is made by adjusting the motor mounting bolts so
you move the motor a little ways away from the other pulley and it takes up
some slack. Like I said, using some belt prep will probably take care of it
anyway. 

>  I'm wondering how to get the old belt off and a new belt on with
the correct tension. Does anyone know? 

    Pull on the belt as you rotator the big pulley and the belt will shortly
come off of the pulley. To install, put the belt around the small pulley and
push it on while you're turning the big pulley. Or try putting it on the
little pulley. Either way will work. 

>  Also, is this a standard automotive
part (alternator belt, fan belt), or something I'd have to order from US
Tower?

    I don't imagine that UST goes out of their way to have a custom belt
made. Take your to your auto supply store and they'll be able to match it up
for you. 

Cheers,

Steve   K7LXC

TOWER TECH -

Professional tower services for hams 

Cell: 206-890-4188

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