[TowerTalk] installing monster masts in towers

[Roger K8RI on Tower]

>>      Also (and I just thought of this with this posting), I would not
>> feel
>> all that comfortable with this heavy mast hanging by a couple of muffler

I have no problem at all  using muffler clamps to raise and lower the mast
and antennas into the rotator.
As Ed says, I never, ever put my hands directly under the mast no matter
what is holding it.

However as to the muffler clamps. If properly secured they are about as
solid a clamp as you are going to find.  I also use them as safety devices
in case everything else slips.  I also use blocks under the mast as I raise
it.

As to alignment, I use a top and middle thrust bearing with the rotor being
the third point.  The procedure is more complicated to describe than it is
to acomplish.
Once the mast is positioned in height which is usually with about a 1/4 inch
clearance under the bottom of the mast in the rotator, I center the mast in
the top thrust bearing using  a small measuring stick such as a machinists
square, or ruller.   That will be close enough.  The next part is the rotor
clamp.  Here it depends on the type of clamp.  Some are very easy and some
take a bit of work.

Measuing from each leg make sure the rotator is centered in the tower.  You
may need to shim the rotor plate to leg clamp if the mount does not allow
for adjustment.  I've seen some plates that were nearly a 1/4" off.  Be
careful when installing the rotor and bearing plates not to spring the tower
legs.

If the mast clamp is the adjustable type, or self centering, loosen the
bolts that hold it to the rotor.  Tighten the mast in the clamps.  Lightly
tighten the clamps to the rotator body.  Again, using a measuring stick
(clamped to a tower leg this time) measure the distance to the mast.  Have
some one run the rotor through 360 degrees (You can do it with 180 but 360
is easier to describe).   You should find a high spot and a low spot.  They
*should* be inline with the adjustment slots where the mast clamp mounts to
the rotator body.  Calculate the span (difference between the high spot and
low spot).  Loosen the mast to rotator bolts just enough so you can move the
mast by tapping on it with a mallet or dead blow hammer.  Move the mast
toward the low spot (away from the high spot) by half the span.

Again, check the high and low spots by having someone run the rotator
through 360 degrees while you measure.  If it comes out within 1/16 of an
inch, be happy.  If not, repeat the adjustment procedure.

The key here is to not get the thrust bearings too close to each other or
the rotator.  I would not want the bottom bearing with in two feet of the
rotator. Three feet would be better, but not necessary and it might be more
than a little inconvenient.  The two thrust bearings should be at least
three feet, if not six feet apart. (Mine are 12' apart) Using those
dimensions, a 1/16" here or there should not cause any undue stress or
binding.  Usually you can get them closer than that.

Once the tope bearing and rotator have been centered, use the same method to
center the bottom thrust bearing, only you may have to move the bearing on
the mounting plate to center the mast.  *After* centering the mast in the
bearing, turn the bolts in until they just touch the mast. Then taking a 1/4
turn at a time, just go around the mast tightening them until they are
tight.

I prefer a muffler clamp setting on top of the bearing as a safety device.
If you use them on both bearings put them *only* on top of the bearings.
That way, thermal expansion and contraction will not cause additional stress
on the installation.

I use the muffler clamps as safety stops and only raise the mast about 6
inches at a time when the antennas are in place.  I have had them drop and
that 6 inches creats quite an impact.  I also use heavy wood blocks/stops
under the mast if the clamps slip.

I hope I got all of that straight.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
>> clamps above my hands while I'm installing the rotator plate just below
>> it.
>> 73 de
>> Gene Smar  AD3F