ETX & DS TECHNICAL TIPS Last updated: 18 July 2005

Subject:	Virtually Eliminate Backlash on DS127 Mount
Sent:	Sunday, July 17, 2005 16:41:27
From:	Ron Masters (rmasters2@cinci.rr.com)
Not sure if you are posting for this mount any more, but I have modified
the internal components so that I see almost no perceptible backlash,
and am able to set my alt and az percentages to zero.  When training, I
do need to follow the advice on the "flight to right" posting, for both
az and alt training, in order to prevent the software from compensating
for backlash that no longer exists.  What a pleasure to press the arrow
and have the scope immediately respond, even with a heavy AR-5 refactor
and Canon camera on board!

What did I do?  Well, I found that a large amount of backlash exists in
the clutch mechanism on the mount that causes the motion from the motor
to begin turning the main gear.  I have attached JPEG pics showing how I
did the following 2 steps:

1. Solder (regular 60tin/40lead rosin core) the lock washer to the
washer that has the 3 internal prongs that move along the channels in
the main screw.  It is helpful to lightly sand the washers and clean
with alcohol to help the solder to flow better.  I pre-tinned each piece
with a light amount of solder using a 100W gun. Then I faced them
together and lightly clamped with 2 aligator clips.  Then I remelted the
solder to join the pieces using a butane torch.

2. I used a small drill bit to drill small craters on the facing surface
of the main gear to match up with the points on the lock washer.  This
was easily done by placing masking tape onto the gear, then pressing the
lock washer assembly made in step 1 against the gear with them lined up
on the main screw.  This provided the template for drilling - the
craters don't need to be very deep at all - just small indentations.

When assembled, the clutch mechanism works as normal - loosen the main
knob and the scope can be freely moved as needed.  To lock in place,
gently tighten the main knob, move the scope some until you can feel the
lock washer points catch on the indentations on the gear, then fully
tighten the main knob.

I hope this can other ds127 users as much as it has helped me.
 
Ron

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