Re: 1200 GTO RA gearbox backlash?


Dec 5, 2012

 


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

#38797 Dec 5, 2012

Hi all,

I have been trying to chase down some RA slack that appeared a couple of

times after we had an earthquake here a few months back. The movement is

not always there, but at one stage, I could grab hold of the counterweights

and move the shaft back and forth a small discernible amount.



I found the detailed instructions on the AP website for checking for

gearbox for worm gear backlash, but at that time, there was no slack in the

cwt shaft. I followed the procedure to check for loose mesh, and then also

checked to make sure that the grub screw was tight on the worm spur gear.

All was good on both series of checks.



The only thing that I did find was some unexplained backlash which appears

to be between the aluminium front gear and the similar sized metal spur

gear that is partly beneath it. Referring to Figure D in the AP procedure

"Adjustments to Remove Spur Gear Backlash on 1200 GTO Mounts Equipped with

Spring-Loaded Action Brackets" , the front gear is the one arrowed, and the

one beneath it is at the top of the picture. When I wiggle the front gear,

that amount of backlash movement is translating into approximately 3/4 of

one tooth pitch in the small pinion gear at the top RHS of the photo.



What I would like to know is whether this amount of backlash is normal, as

I was not expecting it. I suspect that it is this backlash that causes an

audible "click" when making RA movements from the hand-controller.



Any comments welcome. By the way, the mount is 2 years old.



Cheers, Chris

Australia





[Non-text portions of this message have been removed]



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

#38799 Dec 5, 2012

The internal gearbox mesh does not contribute to the worm backlash. In other words, if you see a small movement when you rock the counterweight shaft back and forth, there is no contribution to that movement from the internal gearbox. You could remove all the internal gears (and thsu have infinite backlash) and you would not change the movement on the counterweight shaft.



You may be seeing this slight motion on the counterweight shaft because it may be loosely screwed into the end of the RA axis. As such, the counterweight shaft is moving, but the gear may be fully meshed. I have seen this many times myself.



One more thing, no amount of backlash in RA will affect guiding or tracking. That includes any slight gearmesh in the internal gearbox spur gears and any looseness in the worm gear to worm wheel mesh. So it is pointless to try to eliminate all these small gear meshes in RA. In fact there has to be some clearance on the spur gears and some lightness in the worm mesh in order for the axis to run smoothly and track accurately. When gears are bound up too tight they will not run smooth. There is always some clearance built into our RA gearboxes for that reason, and since the gears are always tracking in one direction, there is never any delay in reversal of the guide star because the gears never unload and go in the opposite direction. It is only when you use the 12x and 64x centering motion that the gearbox actually reverses, and those speeds are never used in guiding. If there is delay when using these centering speeds, it is a simple matter to add a bit of RA backlash compensation in the keypad until the reversal actions are instant.



Rolando





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

From: Chris Morley morleycs@...>

To: ap-gto ap-gto@yahoogroups.com>

Sent: Wed, Dec 5, 2012 4:46 am

Subject: [ap-gto] 1200 GTO RA gearbox backlash?





Hi all,

I have been trying to chase down some RA slack that appeared a couple of

times after we had an earthquake here a few months back. The movement is

not always there, but at one stage, I could grab hold of the counterweights

and move the shaft back and forth a small discernible amount.



I found the detailed instructions on the AP website for checking for

gearbox for worm gear backlash, but at that time, there was no slack in the

cwt shaft. I followed the procedure to check for loose mesh, and then also

checked to make sure that the grub screw was tight on the worm spur gear.

All was good on both series of checks.



The only thing that I did find was some unexplained backlash which appears

to be between the aluminium front gear and the similar sized metal spur

gear that is partly beneath it. Referring to Figure D in the AP procedure

"Adjustments to Remove Spur Gear Backlash on 1200 GTO Mounts Equipped with

Spring-Loaded Action Brackets" , the front gear is the one arrowed, and the

one beneath it is at the top of the picture. When I wiggle the front gear,

that amount of backlash movement is translating into approximately 3/4 of

one tooth pitch in the small pinion gear at the top RHS of the photo.



What I would like to know is whether this amount of backlash is normal, as

I was not expecting it. I suspect that it is this backlash that causes an

audible "click" when making RA movements from the hand-controller.



Any comments welcome. By the way, the mount is 2 years old.



Cheers, Chris

Australia





[Non-text portions of this message have been removed]







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



To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gtoYahoo! Groups Links















[Non-text portions of this message have been removed]







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

#38802 Dec 5, 2012

Thanks Rolando, that all makes sense.

Chris On 06/12/2012 3:44 AM, chris1011@...> wrote:



> **

>

>

>

> The internal gearbox mesh does not contribute to the worm backlash. In

> other words, if you see a small movement when you rock the counterweight

> shaft back and forth, there is no contribution to that movement from the

> internal gearbox. You could remove all the internal gears (and thsu have

> infinite backlash) and you would not change the movement on the

> counterweight shaft.

>

> You may be seeing this slight motion on the counterweight shaft because it

> may be loosely screwed into the end of the RA axis. As such, the

> counterweight shaft is moving, but the gear may be fully meshed. I have

> seen this many times myself.

>

> One more thing, no amount of backlash in RA will affect guiding or

> tracking. That includes any slight gearmesh in the internal gearbox spur

> gears and any looseness in the worm gear to worm wheel mesh. So it is

> pointless to try to eliminate all these small gear meshes in RA. In fact

> there has to be some clearance on the spur gears and some lightness in the

> worm mesh in order for the axis to run smoothly and track accurately. When

> gears are bound up too tight they will not run smooth. There is always some

> clearance built into our RA gearboxes for that reason, and since the gears

> are always tracking in one direction, there is never any delay in reversal

> of the guide star because the gears never unload and go in the opposite

> direction. It is only when you use the 12x and 64x centering motion that

> the gearbox actually reverses, and those speeds are never used in guiding.

> If there is delay when using these centering speeds, it is a simple matter

> to add a bit of RA backlash compensation in the keypad until the reversal

> actions are instant.

>

> Rolando

>

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

> From: Chris Morley morleycs@...>

> To: ap-gto ap-gto@yahoogroups.com>

> Sent: Wed, Dec 5, 2012 4:46 am

> Subject: [ap-gto] 1200 GTO RA gearbox backlash?

>

> Hi all,

> I have been trying to chase down some RA slack that appeared a couple of

> times after we had an earthquake here a few months back. The movement is

> not always there, but at one stage, I could grab hold of the counterweights

> and move the shaft back and forth a small discernible amount.

>

> I found the detailed instructions on the AP website for checking for

> gearbox for worm gear backlash, but at that time, there was no slack in the

> cwt shaft. I followed the procedure to check for loose mesh, and then also

> checked to make sure that the grub screw was tight on the worm spur gear.

> All was good on both series of checks.

>

> The only thing that I did find was some unexplained backlash which appears

> to be between the aluminium front gear and the similar sized metal spur

> gear that is partly beneath it. Referring to Figure D in the AP procedure

> "Adjustments to Remove Spur Gear Backlash on 1200 GTO Mounts Equipped with

> Spring-Loaded Action Brackets" , the front gear is the one arrowed, and the

> one beneath it is at the top of the picture. When I wiggle the front gear,

> that amount of backlash movement is translating into approximately 3/4 of

> one tooth pitch in the small pinion gear at the top RHS of the photo.

>

> What I would like to know is whether this amount of backlash is normal, as

> I was not expecting it. I suspect that it is this backlash that causes an

> audible "click" when making RA movements from the hand-controller.

>

> Any comments welcome. By the way, the mount is 2 years old.

>

> Cheers, Chris

> Australia

>

> [Non-text portions of this message have been removed]

>

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

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gtoYahoo! Groups Links

>

> [Non-text portions of this message have been removed]

>

>

>





[Non-text portions of this message have been removed]



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

#38823 Dec 7, 2012

You don't know about what?



Backlash in Dec is not he same as backlash in RA, which the previous poster was concerned about.

Dec backlash causes delay in Dec reversal at guiding rates.

RA backlash does NOT cause delay in RA reversal at guiding rates.



Rolando





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

From: bakersfieldbiker fblue@...>

To: ap-gto ap-gto@yahoogroups.com>

Sent: Thu, Dec 6, 2012 11:32 pm

Subject: [ap-gto] Re: 1200 GTO RA gearbox backlash?





I don't know about that Roland, I have a little lash in the DEC. I opened the

gearbox and I can see that it is between the gears. Not a lot that is for sure

and it does not seem to cause any problem. But I was going to adjust it out and

saw that it was not in the worm and wheel, that is when I opened the gearbox.

Not sure it this was temperature related, I only noticed it on that day. I will

take a look again next time.

Floyd

--- In ap-gto@yahoogroups.com, chris1011@... wrote:

>

>

> The internal gearbox mesh does not contribute to the worm backlash. In other

words, if you see a small movement when you rock the counterweight shaft back

and forth, there is no contribution to that movement from the internal gearbox.

You could remove all the internal gears (and thsu have infinite backlash) and

you would not change the movement on the counterweight shaft.

>

> You may be seeing this slight motion on the counterweight shaft because it may

be loosely screwed into the end of the RA axis. As such, the counterweight shaft

is moving, but the gear may be fully meshed. I have seen this many times myself.



>

> One more thing, no amount of backlash in RA will affect guiding or tracking.

That includes any slight gearmesh in the internal gearbox spur gears and any

looseness in the worm gear to worm wheel mesh. So it is pointless to try to

eliminate all these small gear meshes in RA. In fact there has to be some

clearance on the spur gears and some lightness in the worm mesh in order for the

axis to run smoothly and track accurately. When gears are bound up too tight

they will not run smooth. There is always some clearance built into our RA

gearboxes for that reason, and since the gears are always tracking in one

direction, there is never any delay in reversal of the guide star because the

gears never unload and go in the opposite direction. It is only when you use the

12x and 64x centering motion that the gearbox actually reverses, and those

speeds are never used in guiding. If there is delay when using these centering

speeds, it is a simple matter to add a bit of RA backlash compen

sation in the keypad until the reversal actions are instant.

>

> Rolando

>

>

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

> From: Chris Morley morleycs@...>

> To: ap-gto ap-gto@yahoogroups.com>

> Sent: Wed, Dec 5, 2012 4:46 am

> Subject: [ap-gto] 1200 GTO RA gearbox backlash?

>

>

> Hi all,

> I have been trying to chase down some RA slack that appeared a couple of

> times after we had an earthquake here a few months back. The movement is

> not always there, but at one stage, I could grab hold of the counterweights

> and move the shaft back and forth a small discernible amount.

>

> I found the detailed instructions on the AP website for checking for

> gearbox for worm gear backlash, but at that time, there was no slack in the

> cwt shaft. I followed the procedure to check for loose mesh, and then also

> checked to make sure that the grub screw was tight on the worm spur gear.

> All was good on both series of checks.

>

> The only thing that I did find was some unexplained backlash which appears

> to be between the aluminium front gear and the similar sized metal spur

> gear that is partly beneath it. Referring to Figure D in the AP procedure

> "Adjustments to Remove Spur Gear Backlash on 1200 GTO Mounts Equipped with

> Spring-Loaded Action Brackets" , the front gear is the one arrowed, and the

> one beneath it is at the top of the picture. When I wiggle the front gear,

> that amount of backlash movement is translating into approximately 3/4 of

> one tooth pitch in the small pinion gear at the top RHS of the photo.

>

> What I would like to know is whether this amount of backlash is normal, as

> I was not expecting it. I suspect that it is this backlash that causes an

> audible "click" when making RA movements from the hand-controller.

>

> Any comments welcome. By the way, the mount is 2 years old.

>

> Cheers, Chris

> Australia

>

>

> [Non-text portions of this message have been removed]

>

>

>

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

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gtoYahoo! Groups Links

>

>

>

>

>

>

>

> [Non-text portions of this message have been removed]

>









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



To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gtoYahoo! Groups Links

















[Non-text portions of this message have been removed]







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

#38833 Dec 7, 2012

Hi,

Sorry, I thought you were saying that the gearbox gears could not contribute to the backlash. I guess I misunderstood your post.

Floyd

--- In ap-gto@yahoogroups.com, chris1011@... wrote:

>

>

> You don't know about what?

>

> Backlash in Dec is not he same as backlash in RA, which the previous poster was concerned about.

> Dec backlash causes delay in Dec reversal at guiding rates.

> RA backlash does NOT cause delay in RA reversal at guiding rates.

>

> Rolando

>

>

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

> From: bakersfieldbiker fblue@...>

> To: ap-gto ap-gto@yahoogroups.com>

> Sent: Thu, Dec 6, 2012 11:32 pm

> Subject: [ap-gto] Re: 1200 GTO RA gearbox backlash?

>

>

> I don't know about that Roland, I have a little lash in the DEC. I opened the

> gearbox and I can see that it is between the gears. Not a lot that is for sure

> and it does not seem to cause any problem. But I was going to adjust it out and

> saw that it was not in the worm and wheel, that is when I opened the gearbox.

> Not sure it this was temperature related, I only noticed it on that day. I will

> take a look again next time.

> Floyd

>

> --- In ap-gto@yahoogroups.com, chris1011@ wrote:

> >

> >

> > The internal gearbox mesh does not contribute to the worm backlash. In other

> words, if you see a small movement when you rock the counterweight shaft back

> and forth, there is no contribution to that movement from the internal gearbox.

> You could remove all the internal gears (and thsu have infinite backlash) and

> you would not change the movement on the counterweight shaft.

> >

> > You may be seeing this slight motion on the counterweight shaft because it may

> be loosely screwed into the end of the RA axis. As such, the counterweight shaft

> is moving, but the gear may be fully meshed. I have seen this many times myself.

>

> >

> > One more thing, no amount of backlash in RA will affect guiding or tracking.

> That includes any slight gearmesh in the internal gearbox spur gears and any

> looseness in the worm gear to worm wheel mesh. So it is pointless to try to

> eliminate all these small gear meshes in RA. In fact there has to be some

> clearance on the spur gears and some lightness in the worm mesh in order for the

> axis to run smoothly and track accurately. When gears are bound up too tight

> they will not run smooth. There is always some clearance built into our RA

> gearboxes for that reason, and since the gears are always tracking in one

> direction, there is never any delay in reversal of the guide star because the

> gears never unload and go in the opposite direction. It is only when you use the

> 12x and 64x centering motion that the gearbox actually reverses, and those

> speeds are never used in guiding. If there is delay when using these centering

> speeds, it is a simple matter to add a bit of RA backlash compen

> sation in the keypad until the reversal actions are instant.

> >

> > Rolando

> >

> >

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

> > From: Chris Morley morleycs@>

> > To: ap-gto ap-gto@yahoogroups.com>

> > Sent: Wed, Dec 5, 2012 4:46 am

> > Subject: [ap-gto] 1200 GTO RA gearbox backlash?

> >

> >

> > Hi all,

> > I have been trying to chase down some RA slack that appeared a couple of

> > times after we had an earthquake here a few months back. The movement is

> > not always there, but at one stage, I could grab hold of the counterweights

> > and move the shaft back and forth a small discernible amount.

> >

> > I found the detailed instructions on the AP website for checking for

> > gearbox for worm gear backlash, but at that time, there was no slack in the

> > cwt shaft. I followed the procedure to check for loose mesh, and then also

> > checked to make sure that the grub screw was tight on the worm spur gear.

> > All was good on both series of checks.

> >

> > The only thing that I did find was some unexplained backlash which appears

> > to be between the aluminium front gear and the similar sized metal spur

> > gear that is partly beneath it. Referring to Figure D in the AP procedure

> > "Adjustments to Remove Spur Gear Backlash on 1200 GTO Mounts Equipped with

> > Spring-Loaded Action Brackets" , the front gear is the one arrowed, and the

> > one beneath it is at the top of the picture. When I wiggle the front gear,

> > that amount of backlash movement is translating into approximately 3/4 of

> > one tooth pitch in the small pinion gear at the top RHS of the photo.

> >

> > What I would like to know is whether this amount of backlash is normal, as

> > I was not expecting it. I suspect that it is this backlash that causes an

> > audible "click" when making RA movements from the hand-controller.

> >

> > Any comments welcome. By the way, the mount is 2 years old.

> >

> > Cheers, Chris

> > Australia

> >

> >

> > [Non-text portions of this message have been removed]

> >

> >

> >

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

> >

> > To UNSUBSCRIBE, or for general information on the ap-gto list

> > see groups.yahoo.com/group/ap-gtoYahoo! Groups Links

> >

> >

> >

> >

> >

> >

> >

> > [Non-text portions of this message have been removed]

> >

>

>

>

>

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

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gtoYahoo! Groups Links

>

>

>

>

>

>

>

>

> [Non-text portions of this message have been removed]

>






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