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

[Peje]

As title,

I had my NEQ6 Pro belt modded by a friend and initially all seemed well, I had some minor niggles with worm gear mesh adjustment but got over that hurtle after some advice on SGL.

What I am now seeing is that the Dec axis sometimes isn't moving, the motor is running fine (no stalled noise) but no movement. I *think* I can provoke this behaviour by unbalancing the mount, even just a little. I first noticed it this evening when I put my dew shield on and the dec wouldn't move, remove the shield and it seemed happy. This is causing me other issues to do with plate solving but I think they will go away once this issue is cured.

Something else I do see from time to time is the scope 'hops' as the dec is slewing at full speed, rather than a smooth movement it is quite jerky, there are no unusual sounds when this happens.

My current best theory is that the tension on the dec belt is too loose, once the belt is loaded up then it is slipping. Before I start fiddling about I wanted to check if anyone here had any better ideas or had seen this before??

Any feedback would be greatly appreciated.

Pete

[StarDodger]

It does sound like either the belt is slipping, but I would expect more noise with that, or more likely, the pulley wheel that sits on the end of the worm shaft, is not tight And so slipping, this is a grub screw onto the shaft and is easy not to get tight enough and so slip under load, or maybe not tightened down into the flat of the shaft but the curved part instead and so will slip....this would account for your symptoms...

Edited August 31, 2019 by StarDodger

[Peje]

Hmmn... now that's something I hadn't thought of. Is it common for them to be not tightened enough? I guess tightening the belt would probably be the first thing to try as it involves less stripping.

I'm now wondering if the motor can be removed (to get at the grub screw) without stripping the rest of the dec assembly to bits? EDIT: Looking through the belt mod instructions, it seems like this should be OK (fiddly, but OK)

Edited August 31, 2019 by Peje

[StarDodger]

10 minutes ago, Peje said:

Hmmn... now that's something I hadn't thought of. Is it common for them to be not tightened enough? I guess tightening the belt would probably be the first thing to try as it involves less stripping.

I'm now wondering if the motor can be removed (to get at the grub screw) without stripping the rest of the dec assembly to bits? EDIT: Looking through the belt mod instructions, it seems like this should be OK (fiddly, but OK)

The belt would have to be very loose to slip or jump, I don’t tend to think this will be the case.

It does happen where this grub screw can either be a little loose, or more likely, not positioned correctly on the flat of the shaft, and so will slip under load, you can check this by removing the black cap off the end of the Dec worm shaft and testing, if it is slipping then you will see that the shaft is not turning while the motor is running...sure sign of slippage...but do it under load..

[Peje]

Thanks. The logic in my head right now is that the only places for the 'slip' to occur would be the belt side or the worm mesh side.

If the worm mesh adjustment was so far out that it was skipping I think it would be very noticeable, in terms of noise and play in the axis.

I think the pulley at the motor would be most likely, I'd just like to figure out the best way to attack it without risking making a mess of it. It looks like there are 3 bolts that need to be removed to take out the dec motor, doesn't seem like a complete nightmare other than how to know if the belt is engaged with the motor without being able to see it

[tooth_dr]

Hi Pete

Im pretty sure stardodger has hit the nail on the head. I loosely tightened the new worm gear cog when I did mine, and forgot to fully tighten it before reassembly. I had similar symptoms to you - no stalling noise and no movement.  You won’t get access via motor removal, this needs the mount pulled apart again.

It really sounds like the worm shaft cog is loose.  It’s not the belt.

I had my own issues this evening.  Mount stopped moving in RA during plate solving.  Somehow the belt had popped off the RA worm cog. I removed the motor but if you are familiar with the design of the housing it was impossible to slip the belt back on.

Yep I had to start stripping at 10pm.

Currently imaging the ghost Nebula with guiding between 0.6 and 0.9” so all went well 😂 I was very very close to throwing the head up when I couldn’t find an Allen key the right size, but I remembered advice from a Col Chris Hadfield show I was at - break the job down into single tasks, and get on with it. Cheesy but it helped.

 

Edited September 1, 2019 by tooth_dr

[StarDodger]

9 hours ago, Peje said:

Thanks. The logic in my head right now is that the only places for the 'slip' to occur would be the belt side or the worm mesh side.

If the worm mesh adjustment was so far out that it was skipping I think it would be very noticeable, in terms of noise and play in the axis.

I think the pulley at the motor would be most likely, I'd just like to figure out the best way to attack it without risking making a mess of it. It looks like there are 3 bolts that need to be removed to take out the dec motor, doesn't seem like a complete nightmare other than how to know if the belt is engaged with the motor without being able to see it

Yes @tooth_dr is correct you won’t sort it by getting to the motor, it’s the other end of the belt you need to get too..

Edited September 1, 2019 by StarDodger

[StarDodger]

8 hours ago, tooth_dr said:

Hi Pete

Im pretty sure stardodger has hit the nail on the head. I loosely tightened the new worm gear cog when I did mine, and forgot to fully tighten it before reassembly. I had similar symptoms to you - no stalling noise and no movement.  You won’t get access via motor removal, this needs the mount pulled apart again.

It really sounds like the worm shaft cog is loose.  It’s not the belt.

I had my own issues this evening.  Mount stopped moving in RA during plate solving.  Somehow the belt had popped off the RA worm cog. I removed the motor but if you are familiar with the design of the housing it was impossible to slip the belt back on.

Yep I had to start stripping at 10pm.

Currently imaging the ghost Nebula with guiding between 0.6 and 0.9” so all went well 😂 I was very very close to throwing the head up when I couldn’t find an Allen key the right size, but I remembered advice from a Col Chris Hadfield show I was at - break the job down into single tasks, and get on with it. Cheesy but it helped.

 

Kudos to you for sorting all that during an imaging session, fo most people that would have been a full days job.. 👍👍

[tooth_dr]

10 minutes ago, StarDodger said:

Kudos to you for sorting all that during an imaging session, fo most people that would have been a full days job.. 👍👍

Thanks, it was the first clear night in a month, and there was no moon so I was motivated!  I left it running at 1am, came out this morning to 70 x 300s good subs (35 per scope dual rig) so happy with that.  

[Peje]

Top marks for sorting it out mid-session!! TBH I wasn't sure what was wrong and with me being a bit bullish, I figured it was best to just leave it be.

Looking at the options I can see three potential causes:

(1) Dec Belt too loose
    > This should be easy to check without removing the mount from the pier, tighten it a little and see if the problem changes. If the problem gets worse then it points to item (2) or (3).
    > This could explain the 'hopping', mount moves but belt jumps a tooth, then it moves again, and so on.
    > This would be the happy path but it feels quite unlikely.

(2) 47 Tooth pulley (Worm shaft) grub screws loose
    > Not much else I can do other than strip the Dec to bits, ensure everything is solid and rebuild.

(3) 12 tooth pulley (Dec motor) grub screws loose.
    > I notice in the guide it say to file a flat on the motor, have asked the guy who modded mine if he did this.
    > This one could be easier checked that (2) but rebuild involves what I'm told is the hardest part, getting the motor back in with engagement on the belt. Any advice on how best to do this?

Thanks again for the great information.

Pete

[tooth_dr]

1 minute ago, Peje said:

Top marks for sorting it out mid-session!! TBH I wasn't sure what was wrong and with me being a bit bullish, I figured it was best to just leave it be.

Looking at the options I can see three potential causes:

(1) Dec Belt too loose
    > This should be easy to check without removing the mount from the pier, tighten it a little and see if the problem changes. If the problem gets worse then it points to item (2) or (3).
    > This could explain the 'hopping', mount moves but belt jumps a tooth, then it moves again, and so on.
    > This would be the happy path but it feels quite unlikely.

(2) 47 Tooth pulley (Worm shaft) grub screws loose
    > Not much else I can do other than strip the Dec to bits, ensure everything is solid and rebuild.

(3) 12 tooth pulley (Dec motor) grub screws loose.
    > I notice in the guide it say to file a flat on the motor, have asked the guy who modded mine if he did this.
    > This one could be easier checked that (2) but rebuild involves what I'm told is the hardest part, getting the motor back in with engagement on the belt. Any advice on how best to do this?

Thanks again for the great information.

Pete

Getting the motor on last night was footery but in reality just a matter of gently aligning and turning the end of the worm shaft back and forward 1mm at the same time (behind the black circular cover) and it will slide on. There is no solution that I’m aware of unless you want to cut a hole in the casing!

All of these things can be done while the mount is on the pier, makes it easier.

Remove the electronics cover and you can just see the belt. You might be able to work out what’s loose.

BUT either way you have to remove the motor to get the Dec axis off so I’d say just remove the motor and have a look  

 

 

[Peje]

Thanks. 

My slight struggle with doing it on the pier is that its outside so light isnt an readily available but I can figure that out. 

The guy got back to me, he didn't file a flat into either motor, maybe this is the problem.

Did you both file the flat?

Pete

[StarDodger]

1 hour ago, Peje said:

Thanks. 

My slight struggle with doing it on the pier is that its outside so light isnt an readily available but I can figure that out. 

The guy got back to me, he didn't file a flat into either motor, maybe this is the problem.

Did you both file the flat?

Pete

I did but only on the motor end, there was already one on the other end..

[tooth_dr]

The worm gear shaft is flat already, the other one I didn’t file as far as I can remember.  

[Peje]

Checked belt and it wasn't loose to I pulled out the motor and discovered one grub screw completely loose and the other seemed tight. (Image attached)

I removed both screws in an effort to remove the pulley to see underneath but it won't come off. It'll move about 1mm, I put it in the vice (wrapped in kitchen roll) and was able to move it around 10mm but decided not to push my luck so pressed (hard) to get it back on.

I'm guessing that this supports the slipping theory as it has probably gouged a lip into the shaft and this is stopping the pulley coming off.

Rain has stopped any further work at the mount tonight (I have a small roll off shed), I'm wondering if I should get some locktight onto the screws tomorrow??

[tooth_dr]

Can you spin/move the Dec cog inside the mount with your finger?

[Peje]

16 minutes ago, tooth_dr said:

Can you spin/move the Dec cog inside the mount with your finger?

Do you mean the idler?

EDIT: Oh, do you mean can I turn the dec pulley on the worm shaft? I doubt I'd be able to move it as the slip only happens under big load

Edited September 1, 2019 by Peje

[tooth_dr]

No the Dec cog that attaches to the worm gear shaft. To see if it moves independently of the shaft.  

[Peje]

Just now, tooth_dr said:

No the Dec cog that attaches to the worm gear shaft. To see if it moves independently of the shaft.  

You're too quick lol

No, haven't tried that. Will give it a whirl but I doubt I'll be able to move it as it only slips under heavy load

[StarDodger]

1 hour ago, Peje said:

You're too quick lol

No, haven't tried that. Will give it a whirl but I doubt I'll be able to move it as it only slips under heavy load

Well it that one on the worm shaft that we are indicating  is the culprit, not the one on the motor...as you show..

[StarDodger]

The Shaft on the motor does have a good flat already on it, so that should be good as long as at least one screw is against that...it the other end that will be the issue..you should be able to see the flat side if you look in the end then you will know if the tight screw is against it or not, I guess that’s why he left the other screw loose as it does nothing..

Edited September 1, 2019 by StarDodger

[Peje]

3 minutes ago, StarDodger said:

The Shaft on the motor does have a good flat already on it, so that should be good as long as at least one screw is against that...it the other end that will be the issue..

Damn, I was hoping it was too much of a coincidence that this was loose.

If it's not slipping, what would have caused the pulley to get jammed on the motor shaft?

[tooth_dr]

10 minutes ago, Peje said:

Damn, I was hoping it was too much of a coincidence that this was loose.

If it's not slipping, what would have caused the pulley to get jammed on the motor shaft?

I know exactly the reason. The motor shaft will have a little indent/scratch on it from the previous screw which held on the origin cog. I remember now having to smooth this off with sandpaper to get the new cog on. It was a tight squeeze to get it on. I couldn’t get it off again but it would move a little but not come off, like yours. I just left it on and tightened the screw.  I figured it didn’t need flattened at all.

 

I don’t think the motors will be strong enough to grind the steel, they will just stall. It’s going to be the other cog that’s loose  

 

 

[StarDodger]

17 minutes ago, Peje said:

Damn, I was hoping it was too much of a coincidence that this was loose.

If it's not slipping, what would have caused the pulley to get jammed on the motor shaft?

It may not have been a perfectly machined fit as some motor shafts can vary slightly, especially older mounts, so it was probably forced on a little in the first place...

edit, also what he said above...

Edited September 1, 2019 by StarDodger

[StarDodger]

Hmmm, my motors had a flat on there shaft...