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NEQ6 post-belt mod problems

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#1 petercoxphoto

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Posted 07 August 2020 - 06:49 PM

Hi guys -

I modded my NEQ6 with a Rowan Belt Mod and have not been able to get it working well since. The mod went well, the mount was in good condition inside with no real wear and the tolerances were good. I cleaned and regreased everything with the Geoptik grease and I replaced the worm bearings with better ones. 

 

Now there are problems with both RA and Dec, but Dec is particularly bad. I'm attaching my guide log from tonight where I tried to sort this out. The guiding assistant measured the backlash as fairly large in Dec, but I can't feel any wiggle when I physically try to move the Dec axis. Certainly in the log, in the 6 minute guide session you can see what looks like Dec oscillating back and forth and falling into backlash every time.

 

dec oscillation.jpg

 

I wonder what I can do to correct this? I've adjusted the worm set screws by finding the physical backlash wiggle, then tightening the worm a quarter turn at a time until the wiggle goes away, then I tighten everything down. After seeing the apparent backlash in PHD, I tried tightening it further but that just led to the mount binding.

 

RA isn't great either, as you can see, but that seems to be a different problem. Any suggestions? I'm at my wits' end with this.

 

Cheers,
Peter

 

 

Attached Files



#2 EFT

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Posted 08 August 2020 - 06:53 PM

Unfortunately, from my experience, if the mount was previously working better, all I can suggest is to remove the modification and go back to the spur gears.  I have installed a number of these for customers and I have also had to remove a number where the mount simply would not work in one or both axes regardless of what we tried.  I can't say exactly what the problem is (backlash in the belt system is one), but I think that you are better off tuning the mount up rather than modifying it.  I do not recommend this modification.

 

The one thing I can recommend other than removing it is to conduct your worm spacing adjustment differently.  You will get the best adjustment by using the sound of the mount to determine where you are.  Just do the following:

 

1. Loosen the four allen head cap screws just enough that the worm housing will slide on but will not lift off the motor housing.

2. Release the axis clutch.

3. Slew the axis at top speed.

4. Adjust the set screws to where the worms starts to bind (or actually binds).

5. Back off on the upper set screw slightly until the motor sounds normal.

6. Tighten the four allen head cap screws down while continuing to slew the axis.

 

That way you will have as little backlash as possible while not binding the worm.


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#3 sky-man

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Posted 10 August 2020 - 12:46 AM

Perhaps the driver and motor are not of high quality. a lot of videos on the internet how these motors skip step 5 or 6. Perhaps the setting of the step motors is not correct, there is also a video about this. there you need to consider the voltage and adjust the subscript resistor on the drivers so that there is no drawdown between steps and there are no gaps, or incomplete steps.

just check. stick a stick 10-15 cm long with plasticine to the motor gear and shoot a video of how it moves in tracking mode, if there are jerks this is the reason. it would be interesting to watch the video in general.

Edited by sky-man, 10 August 2020 - 12:50 AM.


#4 Dek Rowan

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Posted 11 August 2020 - 02:35 AM

Hi guys -

I modded my NEQ6 with a Rowan Belt Mod and have not been able to get it working well since. The mod went well, the mount was in good condition inside with no real wear and the tolerances were good. I cleaned and regreased everything with the Geoptik grease and I replaced the worm bearings with better ones. 

 

RA isn't great either, as you can see, but that seems to be a different problem. Any suggestions? I'm at my wits' end with this.

 

Cheers,
Peter

Hello Peter,

 

If you would contact us by email we'll run through some other things to check.

You appear to have a significant amount of backlash in DEC and if you have minimised the backlash in the worm gear mesh it is possible the belt tension is not correct.

Once set up, you won't need to reinstall the gears.

 

Anyway, drop us an email and we'll go through our usual checks. (I've PM'd our email so the bots don't spam me).

 

BR

Derek.



#5 petercoxphoto

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Posted 11 August 2020 - 03:04 AM

Thanks for the replies guys. Derek, I've responded to your PM, thanks for reaching out!

 

I'd had success setting up the Dec backlash compensation in PHD and it's now guiding acceptably, but clearly there's room for improvement, I'm keen to iron out the wrinkles in the system.

 

Cheers,
Peter




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