From: "Andrew Schott" 
To: 
Reply-To: "Andrew Schott" 


A friend of mine built something like you have in mind a while back.  His
had the chair with built in binoc mount that tilted back for altitude axis.
 He made the azimuth axis out of two disks cut from plywood, 3/4"
exterior grade if I remember right.  Some of the chair mount and it's
attendant braces were the same stuff.  It seems like he cut the whole works
out of one sheet.  The two disks were spaced and bearing'd by skateboard
wheels.  Seems like he used six arranged in pockets cut in the top disk. 
One of the wheels was powered by the guts of a variable-speed reversible
drill as was the altitude axis of the chair.  I'm not sure exactly how the
chair was configured as I only got to see the thing at night.  Like all
do-it-yourselfers he painted the dang thing black so you'd have to use a
floodlight to get enough light on it to make out the details.

The azimuth axis was slewed by a footswitch.  The drill had a piece of
1/4" steel rod in the chuck and that was pressed against one of the
wheels.  This gave enough reduction so the motion was predictable enough to
feel comfortable to operate while your eyes were on the stars.  I'm not
sure how the altitude axis worked but it was probably very similar.  I
think there was a momentary toggle switch on the armrest or on the binoc
mount.  The whole works was powered with a single motorcycle battery and
never seemed short on power.

The toggle switches could be replaced by some rheostat or a variable
powersupply that would give even more latitude of control.  It would be
nice to slowly creep up on a dark-fuzzy instead of jerking to the vicinity
then scanning manually.

Here in Florida, dew and sand is the bane of anything you use outside at
night but his rig wasn't bothered by either.  The soft rubber wheels would
easily roll over any grit and didn't seem to slip much when they got wet.

The skateboard wheels slipped enough that you could position the chair
before you got in and the standard slew rate was slow enough that you could
control your positioning well enough to align it.  During the short time I
used it, I didn't have much need for the altitude control.  I could tilt
the chair by slipping the wheels and I didn't have to reposition to change
the view in the binocs.  His chair was improvised from a seat out of a
Toyota or something.  It was almost too comfortable.

Shake was fairly noticable and it took a long time to get used to sitting
still enough as even your heartbeat was transmitted into the optics.  To
improve his design, I would lower the seat so your feet never leave the
platform (his seat was high enough that when you really leaned back, your
feet were dangling) go to the variable speed controls and see about
stiffening the base so it wouldn't respond to motion so much.






----- Original Message -----
From: "Jan and Rod Shea" 
To: 
Sent: Monday, May 19, 2003 4:53 AM
Subject: ATM ? Motorized Chair for binoculars?


>
> Hi All,
>
> Has anyone out there built something like a motorized table that you could
> put a reclining lawn chair on, so you could slew easily in azimuth, while
> lying down on said chair?  The idea would be to use it with hand held
> binoculars, with an option of putting some kind of bino mount on the table.
>
> I'm thinking of something like the azimuth part of a dob base, with cleats
> to hold the chair in place, that would be driven with a cannibalized
> rechargeable drill.  This would be attached to either a molded epoxy worm
> gear setup, or a friction roller drive.  The drill could be mounted on what
> would normally be the bottom of the rocker box, or could even be attached to
> the drive gears by a flexible shaft.  The drill I have in mind seems to have
> a separable speed control and forward/reverse switch, that you could put
> into a box, to hold in your hand.
>
> It doesn't need to track, but it would be fun/useful if it could slew
> reasonably quickly.  I do think variable speed would be useful, given the
> mass involved, to avoid acceleration and deceleration putting too much
> strain on the system, and maybe launching you out of the chair.
>
> Does anyone know of an inexpensive and/or easily built 12VDC control circuit
> for surplus steppers or servos that a non EE could make work for this?
>
> Thanks,
>
> Rod
>
>
>

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