ATM Re: ALTITUDE DRIVE MOTOR

[astrojoe@erols.com]

Hi Jim,

Our arrangement is slightly different. The commercial unit we have built
for 3 large dobs ( 25", and a pair of 32" ) are using a clutched pulley
gear and the side of the altitude bearing. The belt runs around a 12"
upper clutched pulley to a lower driven pulley. The lower pulley is
about 20" awy from the main clutched 12" pulley. What we are seeing on
engaging the altitude drive is the pulley belt will slacken on the side
of the gear that it is being driven into. Simpler put, energize the
altitude motor and one side will go slack while the other stays tight.
Both sides are tight to begin with. I was thinking of using a heavy
spring to keep the altitude drive assembly in constant tension to avoid
the belt slacking problem. When I saw your PICS, I thought you had the
same problem, not realizing te real reason you used the spring ( clutch
action engagement ). I think I will post this one to the atm list and
see if anyone has an answer. Maybe Andy Saulitius........

Joe











Jim Fly wrote:
> 
> The spring you see on the altitude drive mechanism is actually used "in
> tension" when the clutch lever is engaged (pulled down) to keep the belt
> taut.  As you have already noted, the altitude motor is mounted on a
> sliding bracket and the motor and bracket are both leveraged down with
> engagement of the clutch lever.  The spring actually connects the clutch
> lever actuator to the motor bracket and it is subsequently stretched in
> tension as it meets the resistance of the belt being tightened as the drive
> pulley (on the motor) moves down during clutch engagement.  This puts
> "equal" tension on the belt on both sides of the pulleys (drive and
> driven).  This altitude clutch arrangement and mechanism came with the Dob
> Driver kit and it works very well.
> 
> Are you using a commercial or a home built drive system?
> 
> Regards,
> 
> Jim Fly
> ATM Craftsman & Engineer
> Huntsville, Al
> flyj@integrityonline12.com
> 
> CATSEYE(TM) Collimation System & CATSPERCH(TM) Observing Chairs
>         http://www.integrityonline12.com/jfly/cecphome.html
> My 8" f/5.9 Motorized DOB
>         http://www.integrityonline12.com/jfly
> Black Velvet or Felt Tube Installation Procedure
>         http://www.integrityonline12.com/jfly/velvproc.html
> Huntsville Von Braun Astronomical Society
>         http://members.aol.com/vbastrsoc/VBAS.html
> ----------
> > From: astrojoe@erols.com
> > To: flyj@integrityonline12.com
> > Subject: ALTITUDE DRIVE MOTOR
> > Date: Friday, September 11, 1998 12:42 PM
> >
> > Hi Jim,
> >
> > I am looking at your page on your Dob 2000 altitude installation. I
> > noticed that you used a compression spring on the altitude motor
> > assembly. Was this because you noticed that the drive belt went slack on
> > one side when driven. This is the problem we are experiencing with our
> > drive setup. We too are using a drive belt in the same manner. I assume
> > the altitude drive motor assembly moves freely up and down with the
> > spring load. If you could give me any experiences you have with this
> > setup it would be appreciated.
> >
> > Thanks and Clear Skys,
> >
> > Joe Castoro