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Vixen Porta Mount II motion controls sticking

equipment mount
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#1 JoeVanGeaux

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Posted 19 January 2021 - 06:00 PM

I recently (a few hours ago) acquired a hardly used Vixen Porta Mount II (Standard).  The alt-az adjustments are sticking about as tough as one of my 50+ year old Royal Astro GEMs - before I restored it.  Its like its "lubricated" with epoxy that's designed to only partially set, you know, like pine tar!!.

I have scoured CN and only found one reference to the same problem.  One of the responders said they had to contact Vixen for help (I think they said that - I can't find the post again!).  Anyway, does anyone know of how to disassemble those components and what I should be watching out for?  I recall that one post mentioned said it wasn't as straightforward as it looked and some parts got strewn about  during disassembly (thus, the call to Vixen).  For all I know, its those two small set(?) screws or friction adjustment(??) screws that are just too tight.  Before I just loosen them, I'd like to know is stuff will just come shooting out once they are loosened... (That's how I lost that little ball bearing and spring in my pressure washer - haven't been able to suck up soap since!  lol.)

I found a copy of the manual online but it isn't a "service manual".  I have taken apart some really complex things before but learned to heed warning from those that have been there before.  (I admit it did take me a while to learn that.)

 

Any hints are welcomed!!

 

All the best!

Joe


Edited by JoeVanGeaux, 19 January 2021 - 06:18 PM.


#2 DLuders

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Posted 19 January 2021 - 06:36 PM

See Posts #2 and #7 on this previous Cloudy Nights Forum topic.  smile.gif


Edited by DLuders, 19 January 2021 - 06:37 PM.


#3 JoeVanGeaux

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Posted 19 January 2021 - 08:57 PM

See Posts #2 and #7 on this previous Cloudy Nights Forum topic.  smile.gif

Ahhh!  The magic word was "stiff"!! 

I would have thought my fat-fingering on the keyboard would have at least stumbled onto that search term.

Thanks!

 

Joe



#4 JoeVanGeaux

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Posted 22 January 2021 - 01:56 PM

A follow-up question that may be beyond expectations - to be up front about it.

Does anyone know what a reasonable torque range is for moving either the ALT or AZ worm gears on these mounts?  I have several older Royal Astro (TASCO) scopes on GEM mounts and I can turn the worm gears on all of them with my fingers.  On the Porta Mount I can only do that with a borrowed flex cable (from my TASCOs).  To me, this is too tight and I would feel uncomfortable with just any 'ol choice of steppers as a drive motor, since motorizing the mount is my goal with this mount.  Of course, gearing would overcome nearly any such issue, but this would probably be at the cost of loosing some desired slewing speed options.

There is a method I've used on other non-astro projects to get a good idea of the torque (that is, mounting a disc to an axle, horizontally, and determining how much water in a container hung by fishing line on the perimeter of the disc to the point where the added water overcomes resistance - then crunch the numbers).  However, short of that, I wondered if a "finger tight" qualitative test gets me even close to what others consider easy and smooth (of course, too easy and smooth has its own issues with backlash, etc., so a good compromise could work).

Thanks for any input.

 

Joe




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