There are many benefits to you, the rotor and the tower that are
realized by mounting the rotor at the bottom. I have used all of these
methods, from small to large antennas, many times.
All your mast choices are fine if sized adequately, but cost wise, I'd
use water pipe. Specifically 1.5" IPS S40 or 2" IPS S40.
Join the pipe using the muffler clamps and plate. If you were at
Visialia or Dayton you may have seen the AlfaSpid coupler which would be
an off the shelf solution for joining mast sections. I like to avoid
any drilling and pinning since it is likely to work it self loose over
the years. If you can weld, the flange couplers that industry uses to
join lengths of pipe are also a good way to go.
I would either make a very basic steady bearing from treated lumber or
by tying 3 ropes/nylon sling material, one from each leg to the next and
thus cradling the pipe in the center. You just need to keep the pipe
roughly in the center.
It shouldn't be hard to get 20 foot lengths of pipe into the Trylon, if
need be you can always temporarily unbolt and swing one of the cross
braces out of the way.
73 Don
VE6JY
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Bill Turner
Sent: Monday, June 12, 2006 3:55 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Mast for rotator at bottom of tower?
I'm thinking of moving my rotator to the bottom of my 80-foot Trylon
freestanding tower. I have read the archives about doing so, but am
still not clear on what is a suitable mast. I could use some advice.
I have a Cubex four element quad and a Yaesu G-1000DXA rotator. The
rotator is rated for a vertical load of 400 kg, and will be mounted
on the ground, not on the mast. At present I do not have any thrust
bearings installed and it would seem none would be needed unless I
use a really heavy mast material.
Questions:
1. What would be a good mast material? Aluminum tubing? Water pipe?
Chrome moly? Other?
2. Best way to join mast sections? Muffler clamps used with a single
steel plate? Boom-type two-part clamps? Other? Pin them?
3. Whatever mast material I use, there will probably be enough
side-to-side flexing that one or two supports will be needed part way
up the mast to keep it from whipping back and forth. Suggestions?
4. The Trylon tower is pretty wide at the base so I think I can
insert sections up from below thereby avoiding having to lower them
down from the top. I hope.
It would sure be nice to do rotator work at ground level. Any other
pitfalls I should be aware of?
73, Bill W6WRT
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