----- Original Message -----
Sent: Tuesday, October 14, 2003 4:35 AM
Subject: Re: [M]: Retrograde Dec motion


> Doc,
>
> I'm also a member of the chorus of Mapugers that would like to get a
> handle on this retrograde problem of the dec drive. A have couple of
> additional questions prompted by your comments below.
>
> If the dec gear were made to be less flexible, would this improve the
> situation. Would a brass or a steel gear be better? Could a "stiff"
> plate be attached to the outside of the existing gear to reduce flexing.
> Is it too impractical to consider having a replacement gear made that
> is a true worm wheel?
>
> I read somewhere about a technique to slightly angle the worm shaft
> relative to the plane of the worm wheel to reduce play when the
> direction of a worm is reversed. Could the drive assembly be shimmed on
> one side to effectively rotate the worm axis to better "fit" the
> existing flat worm gear? A measurement I made on the worm indicated the
> drive assembly would have to be rotated between 5 and 6 degrees to get
> the worm to "seat" into the worm gear. The contact would probably still
> be a single point, but the angle of the contact would reduced.
>
> Regards,
>
> Rod Cook
Before looking at the gearing, it might be worth checking one other thing.
When I first got an LX200 'classic', it exhibited massive retrograde motion.
However I then noticed, that if I moved the scope, using the manual knob, on
a land target, the problem was vastly less. Looked carefully at what was
going on, and found that the aluminium knob, was far enough down it's shaft,
to _just_ touch the body casting at one point, when the gearbox 'flexed', as
the scope was driven. The amount of movement was tiny, but enough to make
the knob 'climb' the casting slightly, and cause awful retrograde motion!...
Moving the knob out on the shaft a fraction of an inch, reduced the problem
to a much more acceptable level. It may be that some of the posters with
really bad motion problems, have a similar fault.

Best Wishes

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