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[TowerTalk] Tips for Installing a US Tower MA-550MDP tower

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Subject: [TowerTalk] Tips for Installing a US Tower MA-550MDP tower
From: "K0FA" <>
Date: Tue, 15 Apr 2008 17:06:32 -0000
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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: 
>[] "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 

>[] "The cable lubricant that Champion Radio 
sells is called PreLube 6."

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