[TowerTalk] RE : Mast for rotator at bottom of tower?

Mon Jun 12 18:17:57 EDT 2006

Bill Marc,

I dont agree completely Marc, as far as I can admit that the Yeasu 2800 has
been constructed the same way as the G-2000RC who is an older version with
AC motor.
My rotor is bolted on a removeable and calibrated platform at a hight of 5
meter. ( Tell you why later ).
I agree that a steel mast is quite heavy to be supported continously by the
sole motor ( Max dead weight 250 Kg or 550 lbs max momentary vertical weight
800 Kg or 1760 lbs).
 But one can, as I, use a thrust bearing near the top. ( Yeasu GS-065 ) max
diameter 65 mm and clamped with 8 bolts. I inserted even steel straps as not
to tighten de bolts on the mast itself.
Further I dont use a steel mast, but aluminium, 50 mm diam. The first and
the last section are 5 mm thick, the others only 3 mm thick. 
Its done this way as not to crush the parts where  antenna and the motot are
fixed. The rest of the sections only have to support the torque. One should
know that the torque on a full rod doesn't change that much compared with a
pipe. The assembling of the different sections has been done as follows.
Inside the pipe I chased a calibrated hard plastic rod, outside there is a
callibrated alu. sleeve  Eight bolts eight mm ( inox ) diagonally keeps the
whole thing fixed.
One could argue OK but the torque in high winds!!..... OK I stated a torque
of some 6 to 8 degrees, but it isn't very important as the solenoid wedge
has only 90 stop positions ( every 4° )so what!. When firing with a long
boom rifle on VHF/UHF things might be much more important I agree, but not
on HF.
Why my motor has been mounted at 5 m height? Well, the is system is mounted
as a lift. Five meters of the mast come out of the top of the tower. Some
lightweight antenna on top of the mast, while the 5 elements beam is
tightened only a few cm ( inches ) from the top of the tower. And here it
comes.... Loose the thrust bearing on top, loose the motor platform wich is
now held in place by three counter poise with nearly the same weight as the
total weight ( motor platform mast and all the antennae ). Now one can loose
the beam which will sit on the top of the tower while pushing the whole
system downwards with one hand untill the motor on its platform reaches
ground level, and the top of the mast reaches the top of the tower.
When the job is done , proceed the inversed way........Just bear in mind one
should compensate the total weight if it has changed to much.
The nice thing here is that every thing sits back exactly on the same place
after maintenance or changes have been executed etc etc.

This systems works for me since 2001. My son tolds me it works quite well
and should be very easy in use after doing it a couple of times. I do no
more climbing work my self at the age of 72,the more I lost my right ear and
lots of my equilibrium.......
Guess I wont be a good sailor as I used to be at 18 yy..........!!! 

My 2 cents of experience.
Have fun guys.

Jos ON4KJ  OS5N, OR6G when working contest for my club ONZ. 

Nb: By the way OS5N just reminds me the Ostend coastal stations call OSN,
when I used to be a spark in the Belgian Navy half a century ago....

-----Message d'origine-----
De : towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] De la part de marc wullaert
Envoyé : lundi 12 juin 2006 20:21
À : towertalk at contesting.com; Bill Turner
Objet : Re: [TowerTalk] Mast for rotator at bottom of tower?

your rotator is not designed to be on the ground turning 90+ feet of steel.
it could be on the ground for maintaince thats all .

If you wanna do this ,look for a worm type rotor lyke the prosistel or
proppitch. You need thick and strong steel tubes with flanges to rotate. and
you need a trust bearing for the heavy load.

I'm now busy to build up a tower for DOoc ON4IZ  with big OPtibeam antennes
,driven by a worm rotator from ground.If ready I will post some pictures
from the total system on my webpage.

Marc on4ma

----- Original Message -----
From: "Bill Turner" <dezrat at copper.net>
To: <towertalk at contesting.com>
Sent: Monday, June 12, 2006 3:54 PM
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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