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Equipment Discussions >> ATM, Optics and DIY Forum

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anrran
member


Reged: 04/03/11

Question about slow motion alt/az locks
      #5686244 - 02/18/13 12:04 AM

I recently got to play with the orion versago III mount with the slow motion controls. In order to use the slow motion controls, you have to tighten a locking pin. Loosening the pin allows you to move the scope quickly. Does any one know what this pin locks down on? From what I've read, most mounts use a friction clutch, but that involves tightening a nut or some device that's on the rotational axis. These pins are tightened perpendicular to the axis. Does loosening them move the worm away from the gear so that the scope can be moved without damaging the gear? Or am I just way off base here?

Thanks,

Aaron


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Question about slow motion alt/az locks new [Re: anrran]
      #5686449 - 02/18/13 05:21 AM

Quote:

Does loosening them move the worm away from the gear so that the scope can be moved without damaging the gear?




Aaron:

The gears must always be engaged, these are worm gears and the adjustment of worm gears is critical. Basically the gear represents a shaft that is fixed to the mount that can be rotated by the slow motion controls. The scope is mounted on a shaft that is free to rotate, the friction adjustment/lock, adjusts the friction between the gear and the scope. The gears are strong...

The only mount I have ever seen that actually engages and disengages the gears is the 1960's vintage Asahi-Pentax mount for their 60mm F/13.3 refractors. Both axes use worm gears on levers that pivot. The lever serves to both engage the gear and as the slo-motion control. It's a sweet mount, best vintage 60mm I have ever seen.

Jon



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anrran
member


Reged: 04/03/11

Re: Question about slow motion alt/az locks new [Re: Jon Isaacs]
      #5688043 - 02/18/13 11:14 PM

Thanks for the info. I guess I'm just having a hard time trying to picture how a knob perpendicular to the shaft can adjust the friction between the gear and the scope. If the knob was on the shaft, I could see how tightening it would bring gear and scope together. Kind of like pressing the pedal on a hi-hat cymbal brings the two cymbals together.

This guy gives a good explanation of what I'm talking about. (It's in the friction clutch section)

http://www.astronomyasylum.com/largegem.html

Edited by anrran (02/18/13 11:14 PM)


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