400GTO


Roland Christen
 

I would not use this on astronomical equipment.

Rolando

-----Original Message-----
From: Chris White <chris.white@...>
To: main@ap-gto.groups.io
Sent: Mon, Jul 4, 2022 6:53 pm
Subject: Re: [ap-gto] 400GTO

This is the grease I have on hand: https://www.duniway.com/images/_pg/datasheet-DC-150.pdf

It is Dow Corning High Vacuum Grease. 

Silicone Base and rated for -40C to 204C degrees.

I remember reading something from Roland about avoiding sulfur, and I dont see that this contains any.

--
Roland Christen
Astro-Physics


Chris White
 

Got the AP grease kit and performed a full service.  Things are running much more smoothly now, although the DEC backlash issue remains. 

I wonder.  When meshing the gears I'm going as tight as I can so that when I slew there is no audible motor laboring.  (per instructions).  I've noticed that if I get a labor noise at 1200x slewing, but reduce it to 600x that I no longer hear that labor sound.  Would this mean that if I reduce the max slew speed of the mount that I can safely mesh a little tighter? 

This mount was upgraded to CP3, and I wonder if it wasnt intended to slew at 1200x in the first place? 

I dont want to cause any premature wear, but I also would like to know how far I can safely push the mesh.

Thank you,


Roland Christen
 


the DEC backlash issue remains. 
Are you feeling play at the end of the scope when you move it back and forth?

Roland


-----Original Message-----
From: Chris White <chris.white@...>
To: main@ap-gto.groups.io
Sent: Mon, Jul 11, 2022 7:01 am
Subject: Re: [ap-gto] 400GTO

Got the AP grease kit and performed a full service.  Things are running much more smoothly now, although the DEC backlash issue remains. 

I wonder.  When meshing the gears I'm going as tight as I can so that when I slew there is no audible motor laboring.  (per instructions).  I've noticed that if I get a labor noise at 1200x slewing, but reduce it to 600x that I no longer hear that labor sound.  Would this mean that if I reduce the max slew speed of the mount that I can safely mesh a little tighter? 

This mount was upgraded to CP3, and I wonder if it wasnt intended to slew at 1200x in the first place? 

I dont want to cause any premature wear, but I also would like to know how far I can safely push the mesh.

Thank you,

--
Roland Christen
Astro-Physics


Chris White
 

Yessir, I can feel a little bit of play in the axis.


Roland Christen
 

It's probably the end play nut that's loose. Don't try to push it further into mesh, it won't eliminate the end play.

Rolando

-----Original Message-----
From: Chris White <chris.white@...>
To: main@ap-gto.groups.io
Sent: Mon, Jul 11, 2022 11:29 am
Subject: Re: [ap-gto] 400GTO

Yessir, I can feel a little bit of play in the axis.

--
Roland Christen
Astro-Physics


Chris White
 

You're talking about the nut that is removed to slide the axis apart?  The instructions say to snug and back off 5 degrees?  

I can try to tighten that a little. Easy. 


Roland Christen
 

I assume you have this version of the 400 mount:
https://astro-physics.info/tech_support/previous/400_mounts/400qmd-dec-backlash.pdf

The end play nut is on the end of the worm. It keeps the worm from moving sideways:






-----Original Message-----
From: Chris White <chris.white@...>
To: main@ap-gto.groups.io
Sent: Mon, Jul 11, 2022 1:39 pm
Subject: Re: [ap-gto] 400GTO

You're talking about the nut that is removed to slide the axis apart?  The instructions say to snug and back off 5 degrees?  

I can try to tighten that a little. Easy. 

--
Roland Christen
Astro-Physics


Chris White
 
Edited

Ok. I was confused by what you were describing. 

My mount does not have that nut.  I also can confirm that there is no nut on the end of the worm gear inside the housing. 

Mine looks like the attached. Just a closed motor and gear housing. 

It's the GTO not the QMD.  These instructions apply to mine:  https://www.astro-physics.info/index.htm?products/mounts/400gto/400backlashhttps://www.astro-physics.info/index.htm?products/mounts/400gto/400backlash


Roland Christen
 

For that mount the worm adjustment is described here:

https://astro-physics.info/index.htm?products/mounts/400gto/400backlash

Roland

-----Original Message-----
From: Chris White <chris.white@...>
To: main@ap-gto.groups.io
Sent: Mon, Jul 11, 2022 4:25 pm
Subject: Re: [ap-gto] 400GTO

Ok. I was confused by what you were describing. 

My mount does not have that nut.  I also can confirm that there is no nut on the end of the worm gear inside the housing. 

Mine looks like the attached. Just a closed motor and gear housing. 


--
Roland Christen
Astro-Physics


Chris White
 
Edited

I understand that. I actually linked to that document below.

My previous post here https://ap-gto.groups.io/g/main/message/87165 describes the challenge I have with mesh, motor sounds and backlash. 

I'll try to keep tightening up the mesh and slow the slew speed. 


Roland Christen
 

If you have adjusted the mesh according to these instructions, then the only other item that can cause the axis to be loose is the end play nut. This is the thing that holds the worm in place. If it is loose, it allows the worm to rock back and forth as you apply pressure to the CWT shaft. In the case of this 400 mount the worm is inside the housing and the end play nut is not visible from the outside. There is a cover that can be removed and you can look inside to see the worm mechanism. Right now there is nobody available (after hours) in the shop. Tomorrow morning I will have someone disassemble the covers and take some pictures of the inside of the gearbox.

If it is not something that you are capable of adjusting, you can send the axis in to be examined and adjusted.

Roland

-----Original Message-----
From: Chris White <chris.white@...>
To: main@ap-gto.groups.io
Sent: Mon, Jul 11, 2022 5:19 pm
Subject: Re: [ap-gto] 400GTO

I understand that. I actually linked to that document below. 

--
Roland Christen
Astro-Physics


Chris White
 

Thanks Roland. I had it apart a couple days ago. There is no nut that I could see. It appears that the worm is fixed by a pressed in bearing right behind the spur gear. With the other end in a machined housing. 

I might have missed something but I didn't see anything to adjust. 


Chris White
 

On Mon, Jul 11, 2022 at 06:38 PM, Chris White wrote:
Thanks Roland. I had it apart a couple days ago. There is no nut that I could see. It appears that the worm is fixed by a pressed in bearing right behind the spur gear. With the other end in a machined housing. 

I might have missed something but I didn't see anything to adjust. 


This is what it looks like. Photo from the greasing manual. 


Roland Christen
 

All worm drives have end play washers. Sometimes they are accessible, sometimes not. In the case of this mount the end play washer is under the motor spur gear. Remove the spur gear and tighten the end play washer using a small spanner or needle nose pliers. Should be fairly tight, but you should also still be able to rotate the worm by your fingers on the shaft.



Make sure when you replace the spur gear that the setscrew is in contact with the flat on the worm shaft:



-----Original Message-----
From: Chris White <chris.white@...>
To: main@ap-gto.groups.io
Sent: Mon, Jul 11, 2022 5:38 pm
Subject: Re: [ap-gto] 400GTO

Thanks Roland. I had it apart a couple days ago. There is no nut that I could see. It appears that the worm is fixed by a pressed in bearing right behind the spur gear. With the other end in a machined housing. 

I might have missed something but I didn't see anything to adjust. 

--
Roland Christen
Astro-Physics


Chris White
 

Roland,


Awesome!  Thanks for this tutorial. I will definitely try this next. 

I REALLY appreciate your assistance with all of this. 

Thank you,


Chris White
 

Roland,

I had a go at that end play washer and it is completely siezed. I can't budge it at all. With the spur gear off the worm spins very very easy. I suspect it is the culprit and is too loose in that housing. 

The end play washer is a little buggered up too so I suspect that the previous owner was trying to service this and got it stuck. 

I'll email George and see about sending it it. I imagine that all you would need is the dec axis?  Or would it be helpful to send the entire mount in for a checkup now that I've discovered this?  Maybe RA has the same issue. 

Thanks!


Roland Christen
 

It's up to you what you want to send in. We can service either axis or both.

Roland

-----Original Message-----
From: Chris White <chris.white@...>
To: main@ap-gto.groups.io
Sent: Wed, Jul 27, 2022 1:54 pm
Subject: Re: [ap-gto] 400GTO

Roland,

I had a go at that end play washer and it is completely siezed. I can't budge it at all. With the spur gear off the worm spins very very easy. I suspect it is the culprit and is too loose in that housing. 

The end play washer is a little buggered up too so I suspect that the previous owner was trying to service this and got it stuck. 

I'll email George and see about sending it it. I imagine that all you would need is the dec axis?  Or would it be helpful to send the entire mount in for a checkup now that I've discovered this?  Maybe RA has the same issue. 

Thanks!

--
Roland Christen
Astro-Physics