VintageBigBlue.org

 

Re: [Losmandy_users] Play in the RA axis of G11


Sep 17, 2015

 


----------------------------

#56177 Sep 17, 2015

I have a Celestron G11, and I took the RA axis apart because themount had stopped tracking.�� When I put it back together there was someplay in the RA axis - in other words when I manually push the telescope,I can move it a little before the RA axis starts to move.�� I took theRA axis apart and put it back together, making sure to get all thefasteners snug.�� That helped, but there is still some play.�� Anysuggestions what it might be?

I do NOT have the Gemini module.



----------------------------

#56178 Sep 17, 2015

Mine is doing something similar. I can see the worm moving back and forth between the blocks maybe 1/32", which is huge. I assume the fix will be to just properly adjust the worm blocks; haven't tried that yet because I'm going to take the opportunity to clean and re-grease the gears.��

����-Les



----------------------------

#56179 Sep 17, 2015

There must be zero longitudinal play in the worm. It takes about a

minute to adjust by removing the worm cover, loosening the worm block

allen screw farthest from the motor, pressing the worm block toward the

motor and toward the gear at the same time while re-tightening the allen

screw. Do it a few times and you'll get the feel how hard to press and

it becomes very easy to make this adjustment which comes up also after

large seasonal temperature changes.



Tom

On 9/17/2015 4:30 PM, Les Niles les@... [Losmandy_users] wrote:

>

>

> Mine is doing something similar. I can see the worm moving back and

> forth between the blocks maybe 1/32", which is huge. I assume the fix

> will be to just properly adjust the worm blocks; haven't tried that yet

> because I'm going to take the opportunity to clean and re-grease the gears.

>

> -Les

>

>

> On Sep 17, 2015, at 12:48 PM, steve.fast@...

> mailto:steve.fast@...> [Losmandy_users]

> Losmandy_users@yahoogroups.com mailto:Losmandy_users@yahoogroups.com>>

> wrote:

>

>> I have a Celestron G11, and I took the RA axis apart because the mount

>> had stopped tracking. When I put it back together there was some play

>> in the RA axis - in other words when I manually push the telescope, I

>> can move it a little before the RA axis starts to move. I took the RA

>> axis apart and put it back together, making sure to get all the

>> fasteners snug. That helped, but there is still some play. Any

>> suggestions what it might be?

>>

>> I do NOT have the Gemini module.

>>

>>

>

>

>



--

Tom



----------------------------

#56186 Sep 18, 2015

Be warned that doing this also changes the mesh of the worm with the main gear, so be prepared to readjust that which isn't a 5 minute job at all :(



See many previous posts including mine and Michael Herman's on this subject.



Regards,

David Partridge

-----Original Message-----

From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com]

Sent: 17 September 2015 21:48

To: Losmandy_users@yahoogroups.com

Subject: Re: [Losmandy_users] Play in the RA axis of G11



There must be zero longitudinal play in the worm. It takes about a minute to adjust by removing the worm cover, loosening the worm block allen screw farthest from the motor, pressing the worm block toward the motor and toward the gear at the same time while re-tightening the allen screw. Do it a few times and you'll get the feel how hard to press and it becomes very easy to make this adjustment which comes up also after large seasonal temperature changes.



Tom



----------------------------

#56187 Sep 18, 2015

Got a somewhat similar issue. ��I don;t have worm play and my G11 normally tracks reasonably well but only when the OTA is on the west side of the mount (which is where I usually have to use it since my house inconveniently covers the entire NW quadrant and street light does a great job to the S and SW...But I thought I'd see what I could do with M57, usually a very easy target. ��It was near the zenith but west of the meridian so the OTA was on the east side with the DEC axis near horizontal - worst case I suppose. ��I turned off the autoguider and took some 30s images and got some very interesting, i.e., lengthy, ��E-W streaks. ��So I re-tightened the RA clutch (it was already pretty snug) - had no effect. ��I slid my lightest counterweight higher on the bar making the OTA side heavier - streaks went the other way. ��Tried to find a happy medium but I never found it. ��After a while I gave up and checked the balance and it was about what it should be, more or less.

I know the Losmandy mounts are designed for clutch slippage but not THIS much - I've already replaced the disks, roughed them up, etc. ��Any other ideas?



John



----------------------------

#56188 Sep 18, 2015

This discussion refers to the mounts with the dual worm-block

arrangement. This all has been discussed exhaustively over the years on

this group.



I presently own an old CG-11 mount. It's my second G11. I also owned a

GM8 with the same worm-gear arrangement on the two axes. The worm-gear

mesh must be dealt with whenever you adjust longitudinal play (and

vice-versa). The worm/gear mesh also must be dealt with sooner or later

on the two worm block arrangement with significant climatic temperature

changes.



In my opinion, if you own a dual worm-block Gm8 or G11 it's worth taking

a bit of time to experiment and get familiar with the assembly once and

for all. Initially it took me some time to get the "feel" of the

worm-gear arrangement but once I understood it I found it easy to make

adjustments. In a worst-case situation you may have to remove the motor

attached to that worm in order to adjust worm-gear tension, again, a

necessary part of dealing with the two worm-block worm-gear assembly.



My 2 cents...



Tom



On 9/18/2015 9:41 AM, 'David C. Partridge' david.partridge@...

[Losmandy_users] wrote: > Be warned that doing this also changes the mesh of the worm with the main gear, so be prepared to readjust that which isn't a 5 minute job at all :(

>

> See many previous posts including mine and Michael Herman's on this subject.

>

> Regards,

> David Partridge

> -----Original Message-----

> From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com]

> Sent: 17 September 2015 21:48

> To: Losmandy_users@yahoogroups.com

> Subject: Re: [Losmandy_users] Play in the RA axis of G11

>

> There must be zero longitudinal play in the worm. It takes about a minute to adjust by removing the worm cover, loosening the worm block allen screw farthest from the motor, pressing the worm block toward the motor and toward the gear at the same time while re-tightening the allen screw. Do it a few times and you'll get the feel how hard to press and it becomes very easy to make this adjustment which comes up also after large seasonal temperature changes.

>

> Tom

>

>

>

---------------

> Posted by: "David C. Partridge" david.partridge@...>

---------------

>

>

---------------

>

> Yahoo Groups Links

>

>

>

>



--

Tom







----------------------------

#56191 Sep 18, 2015

One method I have not tried but I think will work is after squeezing the two blocks together with

your fingers to preload the worm bearings, is to install the worm cover and snug down the retaining

setscrews. The cover has a short lip that goes over the bearing blocks and should hold them parallel

and make adjusting the worm mesh by now moving both bearing blocks in unison.



Don

----- Original Message -----

From: "tom loeblt@... [Losmandy_users]" Losmandy_users@yahoogroups.com>

To: Losmandy_users@yahoogroups.com>

Sent: Friday, September 18, 2015 10:14 AM

Subject: Re: [Losmandy_users] Play in the RA axis of G11





> This discussion refers to the mounts with the dual worm-block

> arrangement. This all has been discussed exhaustively over the years on

> this group.

>

> I presently own an old CG-11 mount. It's my second G11. I also owned a

> GM8 with the same worm-gear arrangement on the two axes. The worm-gear

> mesh must be dealt with whenever you adjust longitudinal play (and

> vice-versa). The worm/gear mesh also must be dealt with sooner or later

> on the two worm block arrangement with significant climatic temperature

> changes.

>

> In my opinion, if you own a dual worm-block Gm8 or G11 it's worth taking

> a bit of time to experiment and get familiar with the assembly once and

> for all. Initially it took me some time to get the "feel" of the

> worm-gear arrangement but once I understood it I found it easy to make

> adjustments. In a worst-case situation you may have to remove the motor

> attached to that worm in order to adjust worm-gear tension, again, a

> necessary part of dealing with the two worm-block worm-gear assembly.

>

> My 2 cents...

>

> Tom

>



----------------------------

#56192 Sep 18, 2015

Hi guys... .as we add new owners/users, it is easy to see similar topics coming up from time to time... .For those of us who have (permanently?) fixed these issues, it is easy to forget they ever happened.....So with that in mind... my 2 cents (sense) are:

John:. .I also replaced the clutch disks, but found that the design of the G11 is that the axes can slip so that one can move the scope by hand.So even with new clutch disks... my axes could slip. .This is NOT what I want to happen when doing astrophotography, of course!

.It is not enough to just put in new disks, or rough them up...you must also be sure to clean off any lubricant or oils that have crept into the disk area, top and bottom surfaces. . Automotive brake cleaning solvent (with heavy rubber gloves on your hands) can de-grease these surfaces well. .



. You also must be very careful to not have any camera cables getting snagged during your imaging... as these are at the end of the scope, they can have significant leverage to tug on the camera/scope and thus retard the imaging.. It doesn't take much...

. Even with all those issues taken care of, other users have found that the better way to lock those axes is by using the Losmandy 3-handle knobs on the RA and DEC axes.. They are advertised here on the Losmandy site at the top of this page:www.losmandy.com/access.html



The price is shown on this page:www.losmandy.com/pricelist.html



The pair of knobs is called: CKS CLUTCH KNOB SET (2) W/THREE (3) HANDLES, GM-8, G-9 & G-11 MOUNTS 125.00



. . .If you don't have them, then that is the common recommendation...then you get much more leverage to tighten down the slip disks. .

The 3 handle knobs are really beautiful. . But being short of cash, and long on craziness to make things, I bought two "spare" locking knobs off eBay, then bought some 2 inch long 18-8 threaded stainless steel rod handles from McMaster-Carr ($5.63 each).. I drilled, tapped and installed 2 long handles on each side of the two spare knobs.. These give me very strong leverage to tighten down the RA and DEC axes, and hand tightening these, I have no slippage at all.. That project is described on the bottom PDF on this webpage:www.michaelherman.net/#!losmandy-g11-mount

on the bottom PDF document. . I still have the two original knurled knobs which have not been drilled or tapped...but I will not go back to using them. .



Steve:. As David Partridge has said, I did a writeup about the problem, and what I think are simple cheap improvements to the worm block system (namely adding a Belleville spring washer to one end of the worm, to take up the side to side slack, even if temperature changes create a gap).. You will find that writeup here:www.michaelherman.net/#!losmandy-g11-mount

on the 2nd from top PDF document. .

Hope these comments help you resolve your issues.... you will be back to getting no sleep in no time.



----------------------------

#56202 Sep 20, 2015

Certainly on the stepper motor versions you have very little to lose by tightening up the worm. ��I actually used a c-clamp (felt on each end to prevent marring) to provide constant pressure (lengthwise, squeezing bearings together) while I tightened the bolts that hold the worm. ��

So you press the ends in towards each other with the c-clamp (not huge, don't crush anything) and also push the whole thing towards the worm gear (the teeth on the mount, or worm wheel). ��Tighten the two bottom screws that secure the worm blocks.

With a servo motor you don't want to do this because the servo may hit a tight spot and stall out or burn out. With the stepper motors the worst that will happen is that the stepper will say this is too hard and give up. ��(the don't burn out)

In practice, I've never had a tight spot cause the steppers any problem. ��They can power right through. ��I operate my stepper G11 with zero backlash. You want about an 1/8th inch or a "clunk" when manipulating by turning the dec shaft with servo motors (Gemini).

Greg N







----------------------------

#56203 Sep 20, 2015

A c-clamp is a good idea for both, ��the stepper and the servo versions. It'll keep the worm snug and square between the two worm blocks while you are adjusting the worm-to-gear distance.

Regards,

�� ��-Paul



----------------------------

#56204 Sep 21, 2015

Be careful using a C clamp on the bearing blocks. They only need finger pressure to squeeze them

together. The worm bearing are small bearings and can be easily damaged with excessive pressure.

These bearings are designed for radial loads only.



Don

----- Original Message -----

From: "yh@... [Losmandy_users]" Losmandy_users@yahoogroups.com>

To: Losmandy_users@yahoogroups.com>

Sent: Sunday, September 20, 2015 6:39 PM

Subject: [Losmandy_users] Re: Play in the RA axis of G11





>A c-clamp is a good idea for both, the stepper and the servo versions. It'll keep the worm snug

>and square between the two worm blocks while you are adjusting the worm-to-gear distance.

>

> Regards,

>

>

> -Paul

>



----------------------------

#56279 Oct 9, 2015

It took several attempts to get the worm gear and block to tighten up properly, but eventually I was able to get it.�� I realized that you need to loosen ONLY the screw that is farther from the motor and then push the block firmly up against the worm and against the motor at the same time while tightening the screw.

However, it has come loose again after several hours of observing.�� Is this normal, or is something worn out?�� I've thought of putting blue Loc-Tite on the threads of the screw so that it won't come loose.



----------------------------

#56280 Oct 9, 2015

Anonymous,

It is not normal to have to keep adjusting the worm, once set it should remain set permanently.

Also, you should not press the worm too tightly or the more will tend to stall at the tight spots.

What leads you to believe it has come loose?

Regards

Paul



On 9 Oct 2015, at 6:13 PM, steve.fast@... [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:

It took several attempts to get the worm gear and block to tighten up properly, but eventually I was able to get it.�� I realized that you need to loosen ONLY the screw that is farther from the motor and then push the block firmly up against the worm and against the motor at the same time while tightening the screw.

However, it has come loose again after several hours of observing.�� Is this normal, or is something worn out?�� I've thought of putting blue Loc-Tite on the threads of the screw so that it won't come loose.



Contact Us
This Site's Privacy Policy
Google's privacy policies

S
e
n
i
o
r
T
u
b
e
.
o
r
g