I've had a US Tower MA770MDP 72' motorized rotating tubular tower up for about
22 years (purchased new.) I agree with Rick on the pulleys, though I've not had
one fail. That may be because I don't raise or lower the tower very often.
Typically, I leave it fully nested (22 feet) except for maybe half a dozen
contest weekends per year, and I never leave it fully extended when winds are
over 25-30 MPH. With the max wind load at the top, the fully-extended tower can
sway like a wet noodle in strong gusts, so I retract it or I pull it down to
50', where it's way more stable and should withstand any winds that would be
likely in my area. Nevertheless, I keep it fully retracted when not in use so
as to put minimum stress on the sections, cables and pulleys.
Eventually I removed one of the pulleys because the cable would pop off it when
the tower flexed in the wind, causing the cable to rub against the pulley
housing. It wasn't clear to me that the pulley served any real purpose anyway.
UST verbally suggest it was OK to remove the pulley (with lots of caveats to
limit their liability, of course.)
Not clear from your post if the pulleys are hard to assess because they're
still in the air or if you don't know what to look for. If they're in the air,
don't agree to purchase the tower until it's on the ground and you can inspect
the pulleys. If you don't know what to look for, get a qualified person to
help. The pulley in the tilt-over fixture and its cable attaches to on the mast
should be inspected, too.
All cables should be inspected as well. There should be little or no rust.
There's a limit to the number of broken strands permitted on a given size/type
of wire rope. You should look that up. If the tower is more than 10 years old,
and especially if it's been in a harsh environment (e.g., near salt water), I'd
seriously consider replacing the cables. It's not the easiest thing to do
because you have to disassemble the tower, which takes some careful planning. I
believe you'd have to attach the mast to the base in the tilted-over position
(which you have to do anyway), and support the mast on sawhorses so you can
pull out each section. I'm sure there are posts on TowerTalk describing the
process and likely some current members who have done it. I don't believe the
cables are very expensive, but UST may have changed that since I last looked.
If the tower is still up, you'll want to make sure it raises and lowers OK, and
that none of the sections is bent or damaged. Two ways I can think of for the
sections to get damaged: 1) wind load spec greatly exceeded, 2) cable failure
causing rapid collapse of the sections, 3) on the motorized version, coax snag
causing tower to pull hard over (happened to me, but luckily the antenna balun
exploded, freeing the coax before the tower or cable were damaged.)
If it's the standard winch-only (no motor) version, you'll want to inspect the
winch. If you have the motorized version, you'll want to inspect the motor, the
belt (easy and cheap to replace -- just an auto fan belt), and the electronics
in the motor control cabinet (no semiconductors, just relays and timing relays.)
Make sure the tower has the number of standoffs it's supposed to come with. I
purchased an additional standoff to go below the motor (if you have one), which
I think is essential to prevent snagging and should be provided by UST.
If the tower has the rotating base, make sure the bearing at the bottom of the
mast turns freely and looks like it's been maintained (should be some evidence
of grease having been applied through the grease nipple. If the tower is up,
make sure it rotates without binding.
The nuts that secure the base to the J-bolts in the concrete could be rusted
beyond hope, requiring the bolts to be cut off with a Sawzall, but are easy to
replace. The nuts and bolt threads below the base are supposed to be grouted to
protect them, but I wouldn't be surprised if they aren't. Of course, you'll
need a new set of J-bolts, ideally from UST, so perhaps if you can break
through their unresponsiveness you can get some replacement pulleys, too.
On that subject, back when I was installing and troubleshooting my UST tower
(especially after the near-disastrous cable snag, I managed to get through to
the President of the company. He wasn't always forthcoming with information
(likely due to fear of liability), but did provide quite a bit of help,
There's a lot to installing and owning one of these towers. You have to give a
lot of thought to how to install it and how to attach/maintain the antenna. The
tiltover fixture is great, but bear in mind that the antenna boom and elements
prevent lowering the antenna far enough to reach all the parts unless you use a
large step ladder or have a "swinging" mast plate. Also, depending on the tower
configuration, tilting over the tower can be quite involved. In my case, with
the rotating motorized version, I have to carry the 80 lb winch to the tower,
lift it up and attach it to the base, connect the cable to the mast, unscrew
the bolts in the lower tilt bearing and unscrew the bolts in the upper
"bearing" (just a metal hoop). All that needs to be reversed when done.
Eventually, I gave up on tilting the tower and service the antenna by strapping
a 22' extension ladder vertically to the tower so I can climb up. However, I
also climb my 110' Rohn 55 tower and have the safety gear to do so.
YMMV.
If you have any questions, feel free to ask.
73, Dick WC1M
-----Original Message-----
From: Richard (Rick) Karlquist <richard@karlquist.com>
Sent: Friday, August 30, 2019 11:04 PM
To: FRED MATOS <blainefred@verizon.net>; towertalk@contesting.com
Subject: Re: [TowerTalk] US Tower Tubular Tower
On 8/30/2019 7:26 PM, FRED MATOS via TowerTalk wrote:
> I am considering buying a used US Tower tubular tower with tilt over feature.
>
> I would appreciate tips on what to look for in my evaluation.
The state of the pulleys is hard to assess and UST isn't very helpful about
replacing them. Having said that, I had one of these for over 30 years and it
was still working when I sold it. AFAIK, the pulleys were still OK. But they
can fail.
The other issue is that the antenna will swing back and forth in the wind and
make banging sounds on the tubes. This may or may not be OK with neighbors.
Getting the rotor set up seems to be obvious, but it's not. Nothing is
documented about this.
Rick N6RK
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|