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

[StarDodger]

9 hours ago, Peje said:

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. 

I did mention this to you to try earlier in this thread... 🤔😀

[tooth_dr]

@Peje I would take it off, recheck and then you can be sure to rule out that as an issue.

[StarDodger]

Hold on a minute, you have it a bit wrong here you guys....

There is a black screw cap on both sides of the worm shaft, BUT only one lock screw on one side that is correct, the black cap on the other side should stay in place, as it acts as the correct spacer for the bearing, it keeps the bearing in the correct position so the pulley does not foul the case....that is how it works, if you remove that black cover the pulley and shaft will slide over and foul the side of the cast... 😮

Edited September 3, 2019 by StarDodger

[StarDodger]

@Peje you said it was an easy fix when the pulley was rubbing against the side of the case....

There is no way to fix that,  other than replacing that cover BEFORE you put the lock ring back on, or you will have major issues, it has to be done in the correct order...

Edited September 3, 2019 by StarDodger

[StarDodger]

9 hours ago, tooth_dr said:

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

NO, there is not, please read my last post... 😀

[tooth_dr]

7 minutes ago, StarDodger said:

NO, there is not, please read my last post... 😀

Read my last too. I acknowledged I was incorrect lol

[StarDodger]

Just now, tooth_dr said:

Read my last too. I acknowledged I was incorrect lol

Sorry, missed that, my bad.. 😀😀

[spillage]

So if it was my call and due to the fact there is not noise made I would be looking at the clutch. I would do up the clutch remove the lever and refit it a couple of cogs over and tighten it back up. A slipping belt or gears make a racket. You say I think you have checked the gears on the motors and worm shaft. But again just to be sure I would remove the panel and worm gear plug just to see what moves. The belt upgrade will mean that you now need good balance.

[Peje]

1 hour ago, spillage said:

So if it was my call and due to the fact there is not noise made I would be looking at the clutch. I would do up the clutch remove the lever and refit it a couple of cogs over and tighten it back up. A slipping belt or gears make a racket. You say I think you have checked the gears on the motors and worm shaft. But again just to be sure I would remove the panel and worm gear plug just to see what moves. The belt upgrade will mean that you now need good balance.

Slightly off topic but do I not need to have some imbalance to account for the backlash in the worm drive?

[spillage]

No because the belt system should take out nearly all the backlash, you may find you will have a few millimeters of backlash after fine adjustment of the worm gear spacing but this is normal for this type of mount. I always make sure the scope is neutrally balanced whether its the 130pds or the 8" quattro.

[Peje]

4 minutes ago, spillage said:

No because the belt system should take out nearly all the backlash, you may find you will have a few millimeters of backlash after fine adjustment of the worm gear spacing but this is normal for this type of mount. I always make sure the scope is neutrally balanced whether its the 130pds or the 8" quattro.

This seems strange, I can't understand how adding belts at the drive end would eliminate backlash at the payload end; but that's a topic for another day

If the mount was unbalanced slightly, what would you expect the behaviour to be? I presume it wouldn't be that the motor would turn but the OTA would not?

[spillage]

I would expect you tracking to be bad. But I guess how unbalanced it is. I would imaging that if its slipping on the clutch then it must be very heavily unbalanced.

[StarDodger]

2 hours ago, Peje said:

This seems strange, I can't understand how adding belts at the drive end would eliminate backlash at the payload end; but that's a topic for another day

If the mount was unbalanced slightly, what would you expect the behaviour to be? I presume it wouldn't be that the motor would turn but the OTA would not?

The EQ6 native mount has backlash in three places, two of them were between gears that you have now replaced with the belt drive, but one still remains that is between the worm and main crown gear, this will always have some play, as it the way they work and it’s impossible to remove it all, but it won’t be a few MM as mentioned, it should only be at most .5mm if adjusted well...

Edited September 3, 2019 by StarDodger

[Peje]

2 hours ago, spillage said:

I would expect you tracking to be bad. But I guess how unbalanced it is. I would imaging that if its slipping on the clutch then it must be very heavily unbalanced.

It's not heavily unbalanced, even the weight of a dew shield was enough to knock it off. Strangely it worked before so I get the feeling something came loose or it is temperature related (cooler temp, tolerances increase)

[StarDodger]

53 minutes ago, Peje said:

It's not heavily unbalanced, even the weight of a dew shield was enough to knock it off. Strangely it worked before so I get the feeling something came loose or it is temperature related (cooler temp, tolerances increase)

Having your dew shield unbalance it, is not that bad, in fact a little bias in both directions may help...

[Peje]

Motor back in, less than 5 mins. I think I've found the solution to getting the belt on the motor... for me it was to remember I bought a cheap (maybe 6quid) usb bore-scope off Ebay a while ago.

It took 3 or 4 mins to figure out the best angle for the camera and maybe 30secs to hook the belt over the motor!

Edited September 4, 2019 by Peje

[Peje]

Hi All,

Got the mount rebuilt this morning and backlash adjusted. Noticed when I run the dec at full speed I getting a periodic noise, it seems to coincide with the belt moving axially on the pulley (Video attached). It's not moving by very much so probably isn't a problem but I can't figure out what's causing it. I don't get the same movement or noise on the RA.

Any thoughts?

Going to test the slipping tonight and if all is well I'm going to pop the dec motor back out and thread-lock the grub screws. Potentially it could be this rubbing (and therefore vibration) that caused the screw to loosen.

[Peje]

Looks like everything is fixed

When I got home I refitted the scope and tested the dec to see if I could provoke the slip, even with the OTA being VERY unbalanced I couldn't make it slip. I loosened the belt tension a little and the strange sound went away also.

Once that was complete I removed the dec motor, put thread-lock on the grub screws and refitted it. The borescope makes fitting the motor an absolute gift.  The OTA is still on and I just need to re-attach the cabling over the weekend. which should only take a few mins because it's all tie wrapped together.

Thanks for all the help in diagnosing folks