Hi Kirk,
Really, all you need is a second rotor shelf with the correct size hole in
the center. Or, a rotor shelf with whatever size hole, bushed down with
something to the correct size. I got a good reply to essentially the same
question from Paul, K9PH, off list. I was planning to post to the list as
soon as I heard back from my query to the manufacturer concerning current
availability, pricing, etc. Unfortunately, they haven't replied to my
e-mail (yet).
Here are Paul's replies to me.
==== snip ====
I did not install a second bearing but rather a static mast clamp on the
middle shelf. The second bearing to my way of thinking just adds
complication to the alignment equation. The static clamp is in valuable if
you need to remove the rotor for some reason. The clamp adds lateral
stability and vertical positioning (holding) ability preventing the mast
from canting sideways when the rotor is removed. The mast can be held in
place indefinably with the rotor missing if necessary using the middle shelf
clamp. The clamp requires no maintenance and the holding bolts are left
fairly loose during normal use. I highly recommend the use of the clamp and
second shelf.
I would not recommend the use of a four wheeler to provide lifting
capability. There is a definite possibility of slippage and the lift control
is rather coarse. With a winch, hand or power, very fine smooth vertical
position control is possible. Using a snatch block to transition from
vertical to horizontal is not a bad idea as it allows the ground crew to
work safely outside the drop zone under the tower. It also allows for easier
anchoring of the static end of the winch. Look into the 120VAC winches
available from Harbor Freight. I think I paid about $80 for the one that I
used with my Trylon T500-72. An excellent investment.
And:
The device I used came from McFarlane Electronics
http://www.macfarlaneelectronics.on.ca/ it looks sort of like a thrust
bearing but with no moveable section. The base of the clamp used the
"standard" Ham IV mounting holes, it has six mast clamping bolts or three
pairs. The clamping ability is good and the device provides more then
adequate vertical and lateral support for my fully loaded mast. I purchased
the tower from McFarlane and he just threw in the mast clamp. So you may try
and contact the good people at McFarlane and ask about the availability of
such a clamp. When I use the device to support the mast I also apply a home
made muffler clamp above the thrust bearing and the mid section clamp as a
double (triple) safety. This mast clamp works great for me. If you have not
yet installed the tower there are some helpful installation tips on the
McFarlane web site. Also note that a constant taper tower like the Trylon
has some interesting visual effects once it is up. The most notable is that
the tower never appears to be vertical when viewed from the ground and
further as you walk around the tower the direction the tower is leaning
seems to change. The mast sticking out of the top of the tower never appears
to be vertical because there are no horizontal or vertical reference planes
for the eye to reference. Use a level when installing the mast! I actually
gave up trying to explain these effects to visitors and now simply state
that the tower was leaned in the direction of the prevailing wind. Much
easier then trying to convince people that the tower is actually plumb!
==== snip ====
Lots of good ideas out there.
73 - JC, k0hps@amsat.org
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of Kirk
Sent: Saturday, June 11, 2005 6:12 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] installing monster masts in
towers(and?twothrustbearings)
Dick,
This is a good point and one that I've also thought about. I've just
purchase the mast raising fixture (MRF) for my TX472. I have a top
thrust bearing but am wondering if I need another thrust bearing near
the rotator? As you point out Dick, this will keep the mast centered
while rising. I hate to purchase another thrust bearing and bearing
mount just to keep the mast stable while it's being raised into
position. Is there any less costly way to accomplish and maintain mast
stability? The mast I'm using is 20 feet in length and near the top of
the mast will be the STEPPIR four element. Lots of weight to control
while the mast is being raised and then lowered onto the Orion rotator!!
Kirk, K6KAR
Niceville, FL
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Dick Green WC1M
Sent: Saturday, June 11, 2005 2:08 AM
To: K7LXC@aol.com; towertalk@contesting.com; jerry@k0tv.com
Subject: Re: [TowerTalk] installing monster masts in towers(and
?twothrustbearings)
I'm a total novice at this, so pardon the dumb question. I can see where
the
middle thrust bearing adds no value and may be more trouble than it's
worth,
but isn't a middle bearing shelf useful for when you need to remove the
rotor for repair? I would think it better to have a collar around the
mast
in two places (top and middle plate) to keep it from wobbling around as
you
raise it. Also, with a middle plate you can distribute the weight of the
mast between two plates while the rotor is removed (using muffler
clamps, of
course.) Does this make any sense?
73, Dick WC1M
> -----Original Message-----
> From: K7LXC@aol.com [mailto:K7LXC@aol.com]
> Sent: Friday, June 10, 2005 1:31 AM
> To: towertalk@contesting.com; jerry@k0tv.com
> Subject: Re: [TowerTalk] installing monster masts in
> towers(and ? twothrustbearings)
>
>
> In a message dated 6/8/2005 7:29:19 PM Pacific Daylight Time,
> towertalk-request@contesting.com writes:
>
>
> > Thrust bearings normally only need to handle side to side
> forces. The
> rotors
> can bear the weight of the antenna(s) and mast with no
> problem. KC1XX tells me that the locking bolts should all be
> removed from thrust bearings. Let the rotor hold the vertical
> load and let the thrust bearings take the horizontal. My
> thrust bearings have no locking bolts whatsoever. No
> problems. When I need to take the rotor out, I put some U
> bolts on the mast.
>
> Amen to that, brother. My personal opinion is that mast
> vertical thrust
> bearings are highly over-rated and don't really contribute
> anything of value to
> the rotating system other than a being a nice mast bushing.
>
> IMO the amateur need for a special thrust bearing is sort
> of like the
> amateur perceived need for use of the 1-foot long "torque
> arms" that hams have
> put great value in for decades but in reality add little or
> nothing by its use.
> (The Great Ham Radio Urban Legends?!?)
>
> Rotators are designed to have some preload on them and
> their bearings.
> Why do you think all those bearings are there in the first
> place?!? The T2X has
> NINETY-SIX of them.
>
> For the reasons posted previously, a mid thrust bearing
> is just a total
> waste of money. (Unless you really did need that expensive
> bushing - hi.)
>
> People SCREW UP bearings in different ways. If they'd
> have just left them
> off, they'd have been in better shape! And that's not
> speaking to the bind
> that can be easily introduced to the rotating system. And I
> take my hard-hat off
> to anyone who can measure 0.01" with an instrument on top of
> a tower. Both of
> you.
>
> And don't get me started about the yucky eccentric collar
> TB that US
> Tower uses. They are really useless.
>
> Hey - that was fun!
>
> Cheers,
> Steve K7LXC
> TOWER TECH
> Steve K7LXC
>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
any questions and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
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