I am going to be installing a new US Tower MA-550MDP tower in the next few
weeks and given the lack of included documentation with the tower have
researched the archives of Tower Talk for all relevant advice on how to do this
without missing some key steps. To that end, I have compiled a list of all the
relevant posts that I found below under the appropriate installation step and
with credit to the original poster (by call if available, otherwise by name or
e-mail address). My tower base was poured last fall, so I have only included
tips on installing the tower on the base and not on construction of the base
itself. I would be grateful to any readers with prior experience on the US
Tower MA series of tubular towers who would review the list and see if there
are any assembly tips that I have missed. My thanks to the many who originally
provided these extremely valuable tips and in advance to those who can validate
these recommendations and/or add to them.
Key MA-550MDP Installation Tips
Leveling the tower:
>[K7LXC] "What sticks out of the concrete base are the threaded base
bolts. The tower sits on a nut and big washer and there is a nut
on the top of the tower base flange. You level it by adjusting
the bottom nuts. You don't have to worry about it being level at
all since you level it when the concrete has set (usually 2 weeks
or more). The base bolts can be askew but you can still get the
tower level with the base nuts."
>[WC1M] "This is easier than you might think. U.S. Tower supplies
four 24" long by 1" diameter anchor bolts for you to embed in the
concrete pad. There are nuts welded on one end of each bolt to
prevent it from pulling out of the concrete (they used to supply
J-bolts, but don't anymore.) The tower base consists of a square
vertical member welded to a square base plate that has four 1"
diameter holes drilled in the corners. You screw a nut onto each
bolt, drop a washer on top of it, then lower the tower base onto
the bolts so that the base plate it sits on the washers and nuts.
Then you drop another washer on each bolt and loosely thread
another nut on the top side of the base plate. To level the base,
you simply run the bottom nuts up and down until the base is
level, then secure with the top nuts.
However, it's important to note that plumbing the base vertical
member will not necessarily plumb the tower mast. After
installing the tower mast, the base should be re-leveled so that
the mast is plumb -- it doesn't matter if the vertical member is
plumb or not.
As for installing the bolts in the concrete, U.S. Tower provides
a plywood template with a hole pattern for the anchor bolts. You
screw a nut on to each anchor bolt, drop a washer on the nut,
insert the anchor bolt in the template, and drop on another
washer, and secure it with the remaining nut. I can't remember
whether U.S. Tower supplied washers or if I went out and bought
some. Once the bolts and template are assembled, you nail the
template to a 2x4. You lay the 2x4 on top of the wooden frame
used to form the top of the concrete pad, suspending the bolts
and template over the hole. Then fill the hole with concrete. You
have to be careful not to let the template/bolt assembly move too
much when the concrete is poured. Alternatively, I think you can
just shove the bolts down into the concrete after it has been
poured (I didn't do it that way.)
Either way, you also have to be careful that the plywood template
doesn't crack or warp under pressure from the concrete. I think I
had the nuts screwed down a little too tightly, which caused one
corner of the template to flex a little. That threw off one bolt
by about 1/8 inch. I was able to slip a PVC pipe over the threads
and tap it into alignment with a hammer. The tower base slipped
on relatively easily and was a snap to level.
You can specify that the base template be shipped ASAP when you
place your order. That way, you can have the pad and bolts
installed and ready when the tower arrives. Then, the machine you
use to unload it from the truck can be to carry it to the tower
site and place it on the tower base. Allow 28 days for the
concrete to fully cure (although many would say it's safe after a
couple of weeks."
Installing the Rotor Mounting Plate:
>[WC1M] "At this point, we need to talk about the rotor mounting
plate. If you're like me, you were a bit perplexed about how to
mount the plate to the base. It can be mounted with the vertical
plate pointing up or down -- the plate as viewed from the side being
either L-shaped or inverted-L-shaped. It turns out the vertical and
horizontal portions of the plate are not exactly perpendicular, so
it makes a difference which way the plate is oriented. U.S. Tower
uses a jig to weld the two plates, so this is deliberate. I believe
that the reason for this is that the base vertical member isn't
exactly parallel to the tube, as mentioned above. It leans slightly
away from the tower. Anyway, the plate is supposed to be mounted so
that it's L-shaped when viewed from the side -- vertical plate
pointing up. I originally mounted mine the other way because there
wasn't enough clearance between the plate and base bolts to mount my
rotor. As mentioned above, that was due to a manufacturing defect.
The point is that if you mount the plate upside down, it won't be
perpendicular to the tube mounting and the tower may bind.
Assuming you have it mounted correctly, raise the rotor mounting
plate flush against the rotor base. Make sure the plate is level and
flat against the base of the rotor before you tighten the bolts that
hold it to the base. Insert the rotor mounting bolts and gradually
tighten in a cross pattern, like you would with a cylinder head. You
may have to play around with this to get the alignment right. It
might be better to tighten the rotor mounting bolts before the plate
mounting bolts. However, the coupling pipe ensures that the
alignment doesn't have to be perfect."
Greasing the rotor base:
>[KH7M] "Don't forget to use a grease gun on the bearing on the
rotating base assembly if you are using the MARB base."
Preventing Binding in the Upper Collar:
>[K7LXC] "I just installed a MA-850 .... with the rotating base. We
spent several hours chasing a bind in the rotating system which
turned out to be mostly in the upper collar - there were some high
spots that needed to be filed away. We also spent a bunch of time
centering the bottom bearing which seemed to help the bind problem."
Adjusting the Base Bearing Collar:
>[Barry Merrill] "I have recently received my MA-550 with MARB
rotator base from UST. All arrived in fine condition. Included
with the base bearing is a collar with setscrew. Collar is
machined with an eccentric 'rabbet' (for lack of a better word)
in one of the two flat sides. The bearing has a mating eccentric
machined on it. The shaft of the mast is not large enough to
enable the collar's setscrew to fix it in position. The OD of the
shaft is 1 1/2", the ID of the bearing is 1 3/4". Not exactly a
sliding fit. Can anyone tell me what's going on here."
>[N5YA] "This collar is a locking eccentric and it has a hole in the
side for a pin wrench (or whatever) to tighten it. This centers
it automatically in the bearing. Don't throw it away - just make
it work. It's a common way that it is done. It's probably Peer
Lubricating Upper Collar bearing of the MARB Base
>[KH7M] "Good idea, I think, to put a little "bar and chain"
lubricant on the upper "collar bearing" of the MARB base also. That
is a specially formulated oil for the bar of a chain-saw over which
the chain rides at a pretty high speed. This oil seems to adhere
very well and, to me, seems ideal for that upper collar support
Lubricating Base Top Ring:
>[WC1M] "U.S. Tower informed me that the top ring must be lubricated
for the tower to rotate smoothly and avoid abrasion between the ring
and tube. Crank the tower down, connect the cable from the tilt
fixture, open the top ring, remove the small bolts from the thrust
bearing and tilt the tower over until it is clear of the ring. Smear
a good layer of grease on the inner circumference of the ring. You
can use automotive grease, lithium grease, or any grease that won't
wash away easily in the rain. Also smear some grease around the tube
where it will contact the ring. Crank the tube back to the vertical,
close and bolt the ring and put the small bolts back in the thrust
bearing assembly. Disconnect the cable from the tilt fixture. Do not
raise the tower at this time. Note: you should periodically squirt
some grease in the gaps between the ring and tube if it looks like
the grease is wearing off."
Lubricating the Thrust Bearing
>[WC1M] "While you have the grease out, lubricate the thrust bearing.
It has a grease nipple in the front (the direction the tower tilts)
for this purpose. You need a grease gun with a female fitting to do
this. They're available at any automotive supply. Pump grease into
the bearing until you just see it begin to squirt up between the
mounting and bearing race. Get a male grease fitting, too. You can
use it to squirt grease in the ring gaps, per the above."
Positioning the Tilt Over Cable Clamp on the Tower:
>[dino@K6RIX.com] "Straight out from the pulley at the top of the
tilt-over bar. In other words, the cable should go UP and then out
at a 90 degree angle. Remember, the cable goes out to the tower and
BACK to the tilt over bar!"
Checking for Proper Tower Rotation:
>[WC1M] "Remove the rotor and lower the rotor mounting plate. At this
point, the tower should rotate easily and smoothly all the way
around when you turn it by hand. When properly leveled and greased,
even my 1200-lb MA-770MDP with a big antenna mounted can be turned
easily by grasping the bottom tube and turning it. Without an
antenna mounted, I can even grasp the small drive shaft at the
bottom and turn the tower all the way around. If your tower still
binds with the rotor removed, there's a mechanical defect. It could
be a bad thrust bearing, in which case the bearing probably will
have to be replaced. Another possibility might be a bent drive
shaft, perhaps the result of shipping damage. If that's the case,
you'll have to contact U.S. Tower for advice. Another, less likely,
possibility would be a manufacturing defect in the top ring or
bottom mount. My tower base was not built exactly according to
specifications - clearance between the bottom mount and base was a
couple of inches less than spec, forcing me to cut off the tops of
the base mounting bolts to get enough clearance for my rotor!"
Coupling Rotor and Tower Drive Shaft:
>[WC1M] "I had binding problems with my MA-770MDP with the rotating
base. The primary culprit was the coupling between the rotor and the
tower drive shaft. Having no instructions, I tightened the nut on
the bolt that connects the short coupling pipe to the drive shaft.
Unbeknownst to me, the coupler acts as a poor-man's u-joint. The
coupling has to be able to flex in order to compensate for the fact
that the tower can never be made perfectly plumb. The bottom tube
itself isn't perfect, and you will find that it sways ever so
slightly as it rotates. That's because there's no upper thrust
bearing, just a retaining ring."
Aligning Rotor, Coupler and Drive Shaft:
>[WC1M] "If the tower rotates freely with the rotor removed, then
you're in good shape. You just have to make sure the coupler is set
correctly and the rotor is properly aligned with the drive shaft.
Loosen the nut on the bolt connecting the coupling pipe to the drive
shaft enough so that the pipe can swing back and forth freely. It's
an aircraft nut, so it won't come off. It's been many years since I
set mine, so I don't recall if I left any clearance between the nut
and pipe. I think I left very little, but you can play around with
that. I believe the main object of the game is for the pipe to swing
around the bolt, not slide back and forth on it. Clamp the coupling
pipe in the rotor jaws. This will leave the rotor dangling from the
pipe, and it should align itself with the drive shaft."
Plumb the tower:
>[WC1M] "Adjust the base mounting bolts so that the *bottom tube* is
plumb all the way around its circumference. Use a 4-foot carpenter's
level if you can. *Do not* attempt to plumb the base vertical
member! It may not be perfectly parallel to the bottom tube. It's
the tube that must be plumb, not the base member."
Checking Tower Rotation after Raising:
>[WC1M] "At this point, the rotor should turn the tower through the
entire rotation without binding. If it does, raise the tower and
make sure that's still the case (I assume you have an antenna
If the tower binds only when extended, then the load at the top may
not e properly balanced and is throwing the bottom tube too far out
of plumb to rotate freely. You can either try to adjust the antenna
boom mounting point a little at a time, or remove the antenna and
find the balance point."
Lubricating the Cables
>[KH7M] "Hi, I have had an MA-550 up for about 10 years out here.
Had the cable rust through and break about 3 years ago! Happened
for two reasons: (1) I was careless about keeping some sort of
rust prevention spray on the exposed portion of the cable on the
winch; it was a section of the cable which spent the great
majority of the time wrapped on the winch which is where most of
the cable is when the tower is up. I had lowered the tower for a
period of heavy winds, so most of the cable was off the winch.
When I started to raise the tower again, it got up several feet,
but as the rusty part of the cable began to coil again around the
winch-- wham! Cable snapped, down crashed the telescoping
sections which drove the top section right down through the
"stop" plate at the top of the bottom section, and the boom of my
Force 12 C4 antenna snapped off at the boom mounting plate!!
So, at least keep an antirust "lubricant" on the cable on the
winch! I am now using a product called "Whitmore's Wire Rope
Lubricant", it comes in a spray-on can. There are others out
Odd, but none of the cable which was "out", that is the run you
can see up the side of the tubular sections was rusted at all;
just the coils on the winch seem to rust over. Suppose the water
tends to stay there, while the sun dries the exposed wire rope
>[firstname.lastname@example.org] "The cable lubricant that Champion Radio
sells is called PreLube 6."
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