Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Something for CGX Owners

  • Please log in to reply
40 replies to this topic

#1 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 09 December 2019 - 01:21 AM

Hi,

I'm not person who posts often (well very rarely at all), but I received a CGX mount that has a DEC guiding/backlash issue and was extremely tight in the DEC axis once the clutch had been released.  Making it almost impossible to balance. 

 

I have not yet had a chance to test yet....dam clouds....but what I determined is that the primary cause for the poor DEC backlash was to do with the fact that the free play was so stiff.  When the clutch is engaged, the worm gear rotates around the ring gear.  So my thinking is that there has to be increased strain on the motor drive system to move the axis, which makes me think that this mechanical strain would translate into the guiding too.  (note I have tried adjusting the worm drive block, without any improved success). 

 

I used to own a CGEM and performed my own hypertune and I remembered over tightening the tapered ring bearing in the base of the axis and this gave me the same feel in the effected axis.  So with tools in hand (yes this mount is out of warranty) I started to dismantle the bottom of the CGX.  I have to say the electronics are not that bad down there, a very simple IO board with opto switches on the PCB.  Removing all that reveals the bottom of the axis and the nut which locks against the tapered bearing.  Using the tips of my long nose pliers I was able to free the nut (there is some loctite on this nuts thread).  With it loosened I decided to take the tapered bearing out completely and clean it up and then apply my hypertune grease.  Make sure when you reassemble to add some loctite back on the thread.  I tweaked and tweaked it so that the tapered bearing is nice and snug, but not over tightened, I think you will agree from the before and after videos that I've definitely made an improvement. 

 

I've read lots of posts and seen videos of other peoples CGXs and the problems they have been having, so I hope maybe this will help someone.

 

Problem very stiff DEC axis

https://www.youtube....h?v=lOEJ4McLY9g

 

DEC and RA After Adjustment

https://www.youtube....h?v=Mk2N2vA58Es

https://www.youtube....h?v=qlEZSMcBPws

 

As mentioned I've not had a chance to test anything yet due to clouds....but I'm pretty sure this is going to be an improvement.

Attached Thumbnails

  • dec1.jpg
  • dec2.jpg
  • dec3.jpg
  • dec4.jpg
  • dec5.jpg
  • ra1.jpg
  • ra2.jpg
  • ra3.jpg

Edited by narcosisnz, 09 December 2019 - 01:43 AM.

  • Cyrano, dmdouglass, DuncanM and 2 others like this

#2 SkipW

SkipW

    Viking 1

  • -----
  • Posts: 548
  • Joined: 03 Feb 2011
  • Loc: Oklahoma, USA

Posted 11 December 2019 - 04:20 PM

It always helps to have the right tool on hand. Even better if it's nice and cold!

 

post-230766-0-29200300-1575871936.jpg


  • Cyrano likes this

#3 speedster

speedster

    Vostok 1

  • *****
  • Posts: 176
  • Joined: 13 Aug 2018
  • Loc: Abilene, Texas

Posted 11 December 2019 - 07:00 PM

I have the same problem and you have inspired me to fix it while the scopes are now off.  But, which part is the nut?



#4 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 11 December 2019 - 08:12 PM

I have the same problem and you have inspired me to fix it while the scopes are now off.  But, which part is the nut?

Hey Speedster, after you unclip the small round IO board, there is plastic guide with 2 screws that hold it to the bottom of the axis assembly, remove these screw, the plastic will come away and then you will see a nut...(probably more better described as a retaining ring), with 2 hole in it.  You put the tips of your needle nose pliers in them and turn anti-clockwise with a bit of force to break the thread locker, and then it should unscrew the rest of the way by hand. 

 

Hope this helps.

 

Regards
 


  • moonrider likes this

#5 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 11 December 2019 - 08:25 PM

It always helps to have the right tool on hand. Even better if it's nice and cold!

lol.gif lol.gif  I call it my Dutch courage motivator tool, without it I'd just sit and procrastinate about actually doing something about the mount......I even have a wee assistant around home, when things are getting tricky I just shout out "more dutch courage stat!" and my assistant delivers lol.gif


  • SkipW and moonrider like this

#6 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 29 December 2019 - 04:16 AM

Ok, an update on the above adjustment I made to the tapered bearing at the bottom of the axis.  It worked a treat, I had no calibration issues within PHD2, it calibrated perfectly and then guiding was awesome, I'm really happy I made these changes, it takes this mount from pretty much unusable to a now working mount that I can tweak further.  And that's exactly what I have done.  Check below if you've ever wanted to know what the internals of your CGX look like.  I can tell you that mechanically it's the same as the CGEM series (as mentioned above, I have done my own hypertune before), the pain in the butt additions is the new cable trunking for the electronics.  It's nothing scary, just fiddly as some of the cable trunks are too long and you have to tuck it away in the axis tubes.

 

What I did find is the usual over greasing of the ring gears, bearings, and housings.  I cleaned these hopefully improving the performance.  I've not replaced anything and I didn't disassemble the worm blocks, maybe another job, but I want to see how much improvement I get by giving the mechanicals a decent clean and then re grease with super-lube.

 

Anyway pictures below.



#7 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 29 December 2019 - 04:18 AM

..

Attached Thumbnails

  • 20191229_152517.jpg
  • 20191229_152658.jpg
  • 20191229_153333.jpg
  • 20191229_161531.jpg
  • 20191229_161602.jpg
  • 20191229_161718.jpg
  • 20191229_162718.jpg

  • moonrider likes this

#8 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 29 December 2019 - 04:19 AM

..

Attached Thumbnails

  • 20191229_163131.jpg
  • 20191229_163139.jpg
  • 20191229_164010.jpg
  • 20191229_165117.jpg
  • 20191229_165203.jpg
  • 20191229_165205.jpg
  • 20191229_165323.jpg

  • dmdouglass and moonrider like this

#9 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 29 December 2019 - 04:21 AM

..

Attached Thumbnails

  • 20191229_165337.jpg
  • 20191229_165342.jpg
  • 20191229_170114.jpg
  • 20191229_170151.jpg
  • 20191229_170232.jpg
  • 20191229_170235.jpg
  • 20191229_170300.jpg
  • 20191229_170643.jpg

  • dmdouglass and moonrider like this

#10 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 29 December 2019 - 04:22 AM

..

Attached Thumbnails

  • 20191229_170824.jpg
  • 20191229_171840.jpg
  • 20191229_171843.jpg
  • 20191229_173027.jpg
  • 20191229_173045.jpg
  • 20191229_173928.jpg

  • dmdouglass and moonrider like this

#11 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 29 December 2019 - 04:23 AM

..

Attached Thumbnails

  • 20191229_173922.jpg
  • 20191229_174211.jpg
  • 20191229_182331.jpg

  • dmdouglass and moonrider like this

#12 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 29 December 2019 - 04:25 AM

If anyone wants to know anything or ask a question, send me a private message, or ask me anything here.



#13 moonrider

moonrider

    Mariner 2

  • *****
  • Posts: 261
  • Joined: 16 Nov 2013
  • Loc: Murphy, NC

Posted 29 December 2019 - 02:10 PM

Great information! My CGX does not have any stiffness in either Axis. But I will disassemble to improve it by replacing the grease with Super Lube. The one thing I see for more improvement is the output shaft on the gearboxs. The bushing that is used has too much clearance causing the shaft to be pulled( by the belt tension) causing a cant which causes poor belt alignment. You need to replace the bushing with 2 bearings of high tolerances and this will cure this issue. Link for the bearings. You will need two per gearbox as they only come in 2mm wide. Bushing is 4mm.

https://www.cloudyni...-1577611395.jpg

 

https://rover.ebay.c...tm/292622766815



#14 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 29 December 2019 - 04:02 PM

Great information! My CGX does not have any stiffness in either Axis. But I will disassemble to improve it by replacing the grease with Super Lube. The one thing I see for more improvement is the output shaft on the gearboxs. The bushing that is used has too much clearance causing the shaft to be pulled( by the belt tension) causing a cant which causes poor belt alignment. You need to replace the bushing with 2 bearings of high tolerances and this will cure this issue. Link for the bearings. You will need two per gearbox as they only come in 2mm wide. Bushing is 4mm.

https://www.cloudyni...-1577611395.jpg

 

https://rover.ebay.c...tm/292622766815

Thanks for this tip, yes agreed that definitely will be added to my todo list. 



#15 SonnyE

SonnyE

    Apollo

  • -----
  • Posts: 1,240
  • Joined: 01 Nov 2015
  • Loc: Cali for ni a

Posted 29 December 2019 - 04:51 PM

I have the same problem and you have inspired me to fix it while the scopes are now off.  But, which part is the nut?

 

The one holding the tool...

Love posts like this, narcosisnz! To me, very interesting.

 

I have an answer to one of the questions, and mean no offence to you... (Above, in red.) wink.gif


  • narcosisnz likes this

#16 EFT

EFT

    Vendor - Deep Space Products

  • *****
  • Vendors
  • Posts: 5,450
  • Joined: 07 May 2007
  • Loc: Phoenix, AZ

Posted 29 December 2019 - 05:09 PM

Please be aware that narcosisnz's photos make this look like it is not a big deal to disassemble and reassemble the mount.  Believe me, it is anything but.  I've disassembled and reassembled a lot of mounts and the CGX/L are on the top of my list of mounts I hate at this time.  Eventually, I won't hate it as much but that is because I will have worked on a number of them.  As a one-off project, I cannot recommend completely disassembling the CGX/L and I'm not sure that I ever will.  There are a lot of things to screw up even when you document the process like I do.  


  • Joe Bergeron, moonrider, narcosisnz and 1 other like this

#17 narcosisnz

narcosisnz

    Sputnik

  • *****
  • topic starter
  • Posts: 39
  • Joined: 23 Jul 2014

Posted 13 January 2020 - 06:30 AM

Please be aware that narcosisnz's photos make this look like it is not a big deal to disassemble and reassemble the mount.  Believe me, it is anything but.  I've disassembled and reassembled a lot of mounts and the CGX/L are on the top of my list of mounts I hate at this time.  Eventually, I won't hate it as much but that is because I will have worked on a number of them.  As a one-off project, I cannot recommend completely disassembling the CGX/L and I'm not sure that I ever will.  There are a lot of things to screw up even when you document the process like I do.  

Thanks for your feedback, and I appreciate you voicing caution on this.  I am mechanically minded and find tasks like this easy. I must say though other than the new wiring and a little IO boards, the actual mechanics of this mounts axis are pretty much the same as the CGEM I owned and tuned.  I found it fun to work on.

While I agree with your caution I also have to say that for some locations in the world, like mine, quality expertise is not available and some of us just have to roll our sleeves up and get to it. I’ve taken an out of warranty mount, that could not be properly balanced or even calibrated in phd2 and completely changed it to something I can now get sub arc sec guiding.

 

If only there was a large AP community here in New Zealand I’d start a business fixing Celestron mounts.



#18 EFT

EFT

    Vendor - Deep Space Products

  • *****
  • Vendors
  • Posts: 5,450
  • Joined: 07 May 2007
  • Loc: Phoenix, AZ

Posted 13 January 2020 - 01:39 PM

If it wasn't for the internal cabling and the awful spring-loading system, it would be as easy to work on as a CGEM.  But getting the cabling and spring loading are critical.  

 

All I can do when people are not in the US is try to help when I can but I try not to lead people down the road of doing something they might not be able to finish and then have to ship it to me.  You simply can't ship mounts around the world.



#19 jdk

jdk

    Ranger 4

  • *****
  • Posts: 312
  • Joined: 06 Jul 2017

Posted 13 January 2020 - 01:42 PM

If only there was a large AP community here in New Zealand I’d start a business fixing Celestron mounts.

Let's all let that one sink in....

 

 

-former cgx owner


  • narcosisnz likes this

#20 dmdouglass

dmdouglass

    Surveyor 1

  • *****
  • Posts: 1,830
  • Joined: 23 Dec 2007
  • Loc: Tempe, AZ

Posted 15 January 2020 - 11:06 AM

jdk....

 

So.... it has been a couple of days, and it has been "sinking"....

 

BUT... just what is that was "sinking in"?

 

What was your point ?  ( Sorry... but sometimes i can be a little dense. )

 

- a current happy cgx (and cgx-l) owner.


  • Glass Eye likes this

#21 jdk

jdk

    Ranger 4

  • *****
  • Posts: 312
  • Joined: 06 Jul 2017

Posted 15 January 2020 - 11:17 AM

jdk....

 

So.... it has been a couple of days, and it has been "sinking"....

 

BUT... just what is that was "sinking in"?

 

What was your point ?  ( Sorry... but sometimes i can be a little dense. )

 

- a current happy cgx (and cgx-l) owner.

That there's apparently enough broken cgx's floating around that the OP thinks he could actually start an entire business based on fixing them.



#22 Glass Eye

Glass Eye

    Explorer 1

  • -----
  • Posts: 80
  • Joined: 30 Jun 2018
  • Loc: Ft. Bend County, Texas

Posted 15 January 2020 - 03:08 PM

That there's apparently enough broken cgx's floating around that the OP thinks he could actually start an entire business based on fixing them.

I believe he was referring to the number of AP people in NZ!

 

We have businesses here that do that!

 

Thanks for your feedback, and I appreciate you voicing caution on this.  I am mechanically minded and find tasks like this easy. I must say though other than the new wiring and a little IO boards, the actual mechanics of this mounts axis are pretty much the same as the CGEM I owned and tuned.  I found it fun to work on.

While I agree with your caution I also have to say that for some locations in the world, like mine, quality expertise is not available and some of us just have to roll our sleeves up and get to it. I’ve taken an out of warranty mount, that could not be properly balanced or even calibrated in phd2 and completely changed it to something I can now get sub arc sec guiding.

 

If only there was a large AP community here in New Zealand I’d start a business fixing Celestron mounts.

And thank you for the good information! 



#23 skaiser

skaiser

    Viking 1

  • -----
  • Posts: 620
  • Joined: 16 Oct 2010
  • Loc: dallas Texas

Posted 16 January 2020 - 12:18 PM

Yes , Very nice tear down of the CGX mount. 

As a retired Mechanical engineer who designed, built and supported robotic/machine vision systems , this is really neat .

For those who have the right skills and equipment, it's nice to know its not so hard for long term support.

Speaking of support.

Be aware for the drive motors. 

Yes you can replace the "one" main drive shaft bushing with the bearings identified, but you can still have an issue with the bushing on the other end of the shaft.

In my case the drive belt tension was so tight for both motors, it wore both the gear belt shaft bushings holes oblong.

This shows the "other" drive shaft bushing , that can't be replaced with a bearing.

rear motor shaft bushing

  • narcosisnz likes this

#24 EFT

EFT

    Vendor - Deep Space Products

  • *****
  • Vendors
  • Posts: 5,450
  • Joined: 07 May 2007
  • Loc: Phoenix, AZ

Posted 16 January 2020 - 01:55 PM

I've replaced a number of these motors now that had developed a huge amount of side to side play because of bushing damage caused by the belts being over-tightened (which I would say is the normal state of these belts when you get the mount).  I am trying out the bearing replacement and it appears to be a good idea in this case at least.  But skaiser is correct.  If the lower bushing is also damaged, then you have a problem that can be mitigated, but not completely solved.  The only real solution would be to get a new motor and replace the top bushing with one or two bearings (unfortunately, the bearings this size come in only 2mm and 2.5mm thicknesses while the bushing is a bit over 4mm thick so shims have to be used one way or the other).  Then, with the proper belt tightening, the motors would at least last longer.

 

The problem is really due to the belts when it comes down to it.  They are very short and thick which makes them difficult to adjust and leave a proper amount of slack.  It would probably be possible to find different belts, but then the torque issue may cause problems.

 

There is one piece of "good" news about the newer mounts.  On the original mounts, the motor shaft sprocket had no rim so that the belt consistently ran partially off the sprocket.  This was made worse by the damaged motor bushings.  The newer mounts now have rimmed sprockets on both the motor and the worm now to avoid that.  Of course, that present a problem that the belt still wants to run off the sprocket to the outside so that it now tends to rub on the rim which is not ideal.  It's difficult to say whether or not this has any effect on performance though.  The better solution would have been to use motor gearboxes with longer drive shafts so that the sprockets could be properly placed in regard to the worm sprocket.  Placing the motor sprocket as far out on the motor shaft as possible helps this, but they really can't be placed far enough out to have proper positioning. 


  • moonrider and narcosisnz like this

#25 skaiser

skaiser

    Viking 1

  • -----
  • Posts: 620
  • Joined: 16 Oct 2010
  • Loc: dallas Texas

Posted 16 January 2020 - 04:22 PM

I wonder what the "expected" life is for the drive motor with properly adjusted belts.

 

I was sloppy and did not take any measurements on the small diameter shaft end of the main shaft.

From my pictures , It looks like it was a flanged bushing.

Ed from your work on these, would you happen to know the ID/OD of the bushing on the small end of the shaft ?

It might be possible to get a bearing small enough for that end.

I know some instrument bearings go down to 1x3x1mm

might even be possible to use a Synthetic ruby jewel

Looking at long term (5-7 years) life for the motor.


  • moonrider and Glass Eye like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics