HELP: Belt Modded EQ6, Dec not moving (not stalled motor)

[Peje]

Ah well, I partly figured I wasnt going to get off easy so earlier I removed the scope so removing the dec assembly wont be a huge pain. 

I dont fancy going through the pain of getting the motor back in, just to have to take it out again. 

[StarDodger]

3 minutes ago, Peje said:

Ah well, I partly figured I wasnt going to get off easy so earlier I removed the scope so removing the dec assembly wont be a huge pain. 

I dont fancy going through the pain of getting the motor back in, just to have to take it out again. 

No, for sure, give  it a good once over while you have it apart...hope you get it sorted...

Edited September 1, 2019 by StarDodger

[Peje]

3 minutes ago, StarDodger said:

No, for sure, give  it a good once over while you have it apart...hope you get it sorted...

Me too. If nothing else it gives me a better feel for the design for any challenges that arise later in the season when the stakes are higher. 

I had to redo the worm mesh adjustment from scratch last month so I'm comfortable enough with that, just the motor fitting that I need to get to grips with. Had I been doing the belt mod myself I would have cut out slots in the casing for an endoscope, in theory I could still do this for the dec. 

Pete

[StarDodger]

3 minutes ago, Peje said:

Me too. If nothing else it gives me a better feel for the design for any challenges that arise later in the season when the stakes are higher. 

I had to redo the worm mesh adjustment from scratch last month so I'm comfortable enough with that, just the motor fitting that I need to get to grips with. Had I been doing the belt mod myself I would have cut out slots in the casing for an endoscope, in theory I could still do this for the dec. 

Pete

Please keep us posted on how you get on...I have a project of my own, I have bought an EQ8 in mint condition just three years old for a steal of a price so could not resist, but it has the dreaded DEC backlash that has haunted these mounts, (only a bit mind) so I have to make  some minor adjustments and am just plucking up the courage to have a go... 😮

so just recently sold my belt modded EQ6 

[Peje]

7 hours ago, StarDodger said:

Please keep us posted on how you get on...I have a project of my own, I have bought an EQ8 in mint condition just three years old for a steal of a price so could not resist, but it has the dreaded DEC backlash that has haunted these mounts, (only a bit mind) so I have to make  some minor adjustments and am just plucking up the courage to have a go... 😮

so just recently sold my belt modded EQ6 

The EQ8 is where I wanted to go next too, the main thing holding me back is the talk of backlash issues. To be fair though, I haven't really seen a better alternative option at the same price

 

Pete

[Peje]

Stripped out the dec axis and no sign of the pullet being loose. It's so tight that I cant get it off. I've the dec refitted to the point where the idler goes in. 

Now I'm really stumped, where could the slip be coming from? The only bit I can see is the belt tension but it felt tight when I poked it with the back of a hacksaw blade. 

Any other thoughts? I cant see how the backlash adjustment could be to blame as that would likely be very noisy. 

Pete

[StarDodger]

1 hour ago, Peje said:

Stripped out the dec axis and no sign of the pullet being loose. It's so tight that I cant get it off. I've the dec refitted to the point where the idler goes in. 

Now I'm really stumped, where could the slip be coming from? The only bit I can see is the belt tension but it felt tight when I poked it with the back of a hacksaw blade. 

Any other thoughts? I cant see how the backlash adjustment could be to blame as that would likely be very noisy. 

Pete

Hmmmm, that is odd, I am stumped too... 🤔

[Peje]

Are we back to the motor pulley? 

[discardedastro]

Very odd. At risk of teaching you to suck eggs, could it be the clutch not providing enough grip? Nice and easy to test, at least...

If the worm's meshing properly and the cog on the worm is happy and being driven by a tight belt then there shouldn't be opportunity for problems mechanically. I'd be turning my attention to the stepper or drive circuits, though that starts to get hard to test...

[Peje]

Just now, discardedastro said:

Very odd. At risk of teaching you to suck eggs, could it be the clutch not providing enough grip? Nice and easy to test, at least...

If the worm's meshing properly and the cog on the worm is happy and being driven by a tight belt then there shouldn't be opportunity for problems mechanically. I'd be turning my attention to the stepper or drive circuits, though that starts to get hard to test...

I was wondering this myself, not so much the clutch but something else in the axis like where the worm wheel engages with the main dec axis up towards the saddle.

Typically I'm thinking about this after I've rebuilt that portion, at least that's easy to pull apart

[Peje]

After looking at the guide, it looks like the clutch is just a grub screw and it's what connects the worm wheel to the saddle part. 

So if it's not after the worm (clutch) then it must be before the worm which leaves me with my 3 original options; Belt Tension, motor pulley or worm shaft pulley. 

Will rebuild it all and retest. 

[StarDodger]

1 hour ago, Peje said:

Are we back to the motor pulley? 

Well, I would not like to hazard a guess now, as I was sure it was the worm pulley....but if that is solid, and the motor pulley is impossible to remove, so also solid, and the belt tight....and the worm is properly engaged, then yes, re build and see what happens, it’s all you can do...

[Peje]

Something I maybe didn't say previously, the motor pulley could slip easily when I loosened the second grub screw. 

For the worm shaft pulley, it was tight even after the grub screws were loosened. That said I couldn't get any real grip on the shaft to try and turn it

[tooth_dr]

When I removed the black cap covering the end of the worm shaft I could see the centre of the shaft spinning for a second before the scope would start moving. I deduced from this that the cog was loose.  

Did you remove the worm shaft?

[Peje]

Just now, tooth_dr said:

When I removed the black cap covering the end of the worm shaft I could see the centre of the shaft spinning for a second before the scope would start moving. I deduced from this that the cog was loose.  

Did you remove the worm shaft?

Didn't remove worm shaft as the pulley was really tight on it, I couldn't slide it off at all. I did a little tapping and got it to slide up a bit but it seemed like too much effort for no real gain and risk of breaking one of the bearings 

[Peje]

That's a good idea though, I can remove a cap and see what the worm shaft is doing when the scope is doing the 'hopping' thing, this would give me a direction for the issue. 

Edited September 2, 2019 by Peje

[tooth_dr]

Just now, Peje said:

Didn't remove worm shaft as the pulley was really tight on it, I couldn't slide it off at all. I did a little tapping and got it to slide up a bit but it seemed like too much effort for no real gain and risk of breaking one of the bearings 

I still think it could that shaft/cog. I think I would have removed it since you went that far anyway. Those bearings are around £3 for SKF ones from a motor factors, and pretty much they won’t break unless you hammer the bearing itself. 

[Peje]

Sorry, and another weird thing. 

For the shaft bearings, theres only a lock ring on one side. I found that when tapping I had pushed the pulley side bearing out a bit and the pulley fouled the casing. It wasnt difficult to fix though, I found it strange there wasnt a lock ring on both sides

[tooth_dr]

2 minutes ago, Peje said:

Sorry, and another weird thing. 

For the shaft bearings, theres only a lock ring on one side. I found that when tapping I had pushed the pulley side bearing out a bit and the pulley fouled the casing. It wasnt difficult to fix though, I found it strange there wasnt a lock ring on both sides

How is the other bearing held in place?

[tooth_dr]

Can you fire up pics Pete. It’s be easier to compare with what should be there. 

[spillage]

I would remove the cover to the worm shaft and remove the control panel. Using long nose pliers or normal pliers if they will fit manually turn the worn shaft and check that the motor turns without any play. Have you made any adjustments to the clutch lever and what happens if you run the mount without your scope attached, is the same thing happening?

I am sure there should only be one locking nut for the worm shaft.

Edited September 2, 2019 by spillage

[tooth_dr]

5 minutes ago, spillage said:

I am sure there should only be one locking nut for the worm shaft.

I think there is one on each side of the worm gear.

[spillage]

Too late to go out and check but I am sure when I was making adjustments to the worm shaft I kept unscrewing the wrong cap as there was not a slotted nut on one side. It has been a while since I had to touch anything on the mount though. What about the backlash grub screws. If they were too loose would it cause this issue. Did the op say it made a horrid sound? may be the teeth slipping.  Do you not just need to take out any float from the worm shaft? Cogs are tight and in place, belt is not really slack or stupidly tight.

Maybe try moving the dec housing 1/8th or 1/4 of a turn to push the worm gear closer.

[tooth_dr]

7 minutes ago, spillage said:

Too late to go out and check but I am sure when I was making adjustments to the worm shaft I kept unscrewing the wrong cap as there was not a slotted nut on one side. It has been a while since I had to touch anything on the mount though.

That sounds about right! Sorry for questioning you on that.   

[Peje]

8 hours ago, tooth_dr said:

I still think it could that shaft/cog. I think I would have removed it since you went that far anyway. Those bearings are around £3 for SKF ones from a motor factors, and pretty much they won’t break unless you hammer the bearing itself. 

I'm not sure, if it's solid on the shaft I'm not sure what's to be gained from wrestling it out and refitting. Maybe I'm not seeing something, what would you expect to see when it's removed?

8 hours ago, spillage said:

I would remove the cover to the worm shaft and remove the control panel. Using long nose pliers or normal pliers if they will fit manually turn the worn shaft and check that the motor turns without any play. Have you made any adjustments to the clutch lever and what happens if you run the mount without your scope attached, is the same thing happening?

I am sure there should only be one locking nut for the worm shaft.

This slipping only happened when the mount was under big load. It would work OK mostly but every few mins it would slip (motor sounded normal but no dec movement), it would also slip when I unbalanced the OTA to make it camera heavy. This is a good suggestion, similar to one tooth_dr said, with this cover off I can run the mount to see if the worm shaft is spinning when the dec fails to move. This will let me further refine the location of the problem.

7 hours ago, spillage said:

Too late to go out and check but I am sure when I was making adjustments to the worm shaft I kept unscrewing the wrong cap as there was not a slotted nut on one side. It has been a while since I had to touch anything on the mount though. What about the backlash grub screws. If they were too loose would it cause this issue. Did the op say it made a horrid sound? may be the teeth slipping.  Do you not just need to take out any float from the worm shaft? Cogs are tight and in place, belt is not really slack or stupidly tight.

Maybe try moving the dec housing 1/8th or 1/4 of a turn to push the worm gear closer.

No nasty noise, this directed me towards the belt drive end of the system. Something that is earlier in the thread is an image showing one of the grub screws that attach the belt pulley to the dec motor completely loose.