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R: R: counter wieght queistion



Hi Jens ZL2TJT, et al,

I agree and infact when the center of moment is coincident with the
pivot center of the antenna we loose completely the effect of
counterweight on high elevations around 90 degrees and the
back lash is the same as the system where exactly balanced in weigh
in that elevation angle.

As soon the center of moment M=Fxd flip over the pivot center
(boom) and the elevation decreases on the other side than again 
(d )start to be more and more not coincident with the pivot center
and (M) increases again to a maximum for zero deg elevation.

agree also to load counterweight at a point in wich the motor and
gear box has the capability to safely rise the array from zero degrees 
elevation wich represent the angle for  maximum moment and hence
of  torque applied to gears and pinion.

In this respect i would add that the procedure to calibrate the control
box  at 90 degrees elevation can produce a mistake between the real
antennas direction and position readout if high accuracy is required 
because the back lash in that position is not compensated  and it is not 
cancelled out by the counterweight effect.  

73" de i8CVS Domenico


----- Original Message -----
From: Jens Schmidt <j.schmidt@paradise.net.nz>
To: i8cvs <domenico.i8cvs@tin.it>
Cc: Bruce Nolte <brucenol@abs.net>; John W Lee <k6yk@juno.com>;
<molou@big-river.net>; AMSAT-BB <amsat-bb@AMSAT.Org>
Sent: Sunday, June 30, 2002 3:11 AM
Subject: Re: R: [amsat-bb] counter wieght queistion


> Hi Domenico, et al,
>
> I appreciate your practical engineering observation about the 'rocking'
> of the gears being what causes wear, more so than a _reasonable_
> constant load.
> In that respect, I would add that the placement of any counterweight
> should preferably be such that the center of moment of the antennas
> does not flip over the pivot center (boom), when higher elevations
> are used.
> Another way of agreeing that a constant load in the _same_ direction,
> all the way from horizontal to vertical is better, just so long as the
> load is not _heavy_ on the gears and motor.
>
> 73 Jens    ZL2TJT
> Amsat-ZL #218
> RE78nv
>
> i8cvs wrote:
>
> > Hi John K6YK,
> >
> > Normally i put a small counterweight in the front side of the array in
> > order to get the antennas a little bit  unbalanced with more weight  to
> > the director side.
> >
> > This unbalance force the gears teeth in contact and eliminate any
> > back lash in the gear box so that the elevation pointing and the
> > control box indication are more accurate.
> >
> > In addition if the antennas are exactly balanced in weight it happens
> > that any weeak flow of wind put the system going up and down
> > in to the space between the same last gears
> > teeth.............tic.tac.......tic...tac
> > and is this continuous movement in the same point that wears the
metal,not
> > the gears operation.
> >
> > 73" de i8CVS Domenico
>
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