EQ6-R Pro - worm tuning

[discardedastro]

Hi all,

I've been following the EQ6 guide for worm tuning here: http://www.astro-baby.com/EQ6 rebuild guide/EQ6 worm alignment.htm - this appears to be the same process as for the EQ6-R Pro, broadly, going off the PDF instructions from Sky-Watcher. I've adjusted my RA (Dec seems fine, but RA had some play in it) and run it 360 degrees a few times and it feels smooth (with some slight periodicity to the "hum", I'd say around 1.5-2Hz - but nothing significant enough to cause the ammeter to move). Full speed slewing pulls about 2A@13.4V (Nevada PSU). So I've now got RA with very nearly no play, all seems well.

However, when it comes to adjusting the end float adjuster, I've hit a difference between the mounts. The EQ6-R has an optical encoder on the worm - I'd assumed this was internal to the worm housing, but apparently not:

This looks to just be held onto the end of the worm shaft with a single posidrive screw (hopefully with some Loctite!) but the encoder head of course sits over the top of the plastic disc. I think this means the only way to get access to the adjuster must be with the worm carrier off the RA axis, with the encoder dropped in on top after adjustment is complete during manufacture.

Thought I'd document this here in case anyone else was thinking of doing the adjustments (which otherwise seem very simple and effective).

I did also pop the belt drive housing off while I made the adjustments, as I thought it could bind or otherwise hold the worm carrier to the main body of the mount.

That didn't yield much of interest - the belt was tensioned well, and there appears to be a tension adjuster (middle screw). The lower gear appeared to not be perfectly flat in running or in surface - the light reflecting off it came and went as it turned. Doubt that'd have any performance impact on the mount, but thought I'd mention it.

Slowly building up confidence to maybe take the RA axis apart and make sure absolutely everything is perfect, adjust/tweak shims if needed, etc, but maybe that's a "next year" project if I can get everything running well enough for now...

[StarDodger]

Be careful with the Astro Baby end float adjustment guide, as it’s a little bit outdated and not strictly correct...

It states if I am not mistaken , that you need to tighten the end float nut until a bit of binding occurs then loosen a tad...well if you tighten enough to get a little binding you may well have already damaged the small end float bearing and knocked it slightly out of shape, (I did) so my advice just tighten enough to take out and radial play, that’s all it needs...two fingers on the tightening tool or circlip pliers is all that’s required, just over finger tight..

[discardedastro]

7 hours ago, StarDodger said:

Be careful with the Astro Baby end float adjustment guide, as it’s a little bit outdated and not strictly correct...

It states if I am not mistaken , that you need to tighten the end float nut until a bit of binding occurs then loosen a tad...well if you tighten enough to get a little binding you may well have already damaged the small end float bearing and knocked it slightly out of shape, (I did) so my advice just tighten enough to take out and radial play, that’s all it needs...two fingers on the tightening tool or circlip pliers is all that’s required, just over finger tight..

Good to know, thanks. I'm inclined to leave well enough alone till I can test this with some starlight, and see how it's performing backlash-wise. If it's all happy, no problem - otherwise I'd want to do a full teardown and rebuild of RA (and I'd be inclined to replace the bearings as a matter of course with fresh SKF/FAG high-quality replacements all round).

Somewhat surprised that I can't find any EQ6-R Pro teardowns or rebuilds documented on the net. It's been out for over a year now! I'll definitely document my attempt thoroughly if I go ahead.

[dilipsharan]

Has anybody documented EQ6-R Pro teardowns or rebuilds ?

[discardedastro]

On 05/04/2020 at 00:11, dilipsharan said:

Has anybody documented EQ6-R Pro teardowns or rebuilds ?

Not that I know of. If I get brave I'll have a go this summer.

[Miguel1983]

Funny, i just did all the same on my own mount yesterday.

i haven’t touched the worm end cap tough.

testing is yet to be done, as with your mount i had the most play in RA and just a tad in Dec, but not evenly.

[FaDG]

Small RA backlash shouldn't be an issue because when imaging/guiding this axis does never revert its motion (unless guide speed >1x, which I have never seen). 

So, unless it leads to inaccurate gotos, you could well live with it. 

[Rob63]

I adjusted the backlash following the skywatcher guide (someone posted it on this site), it's pretty easy to adjust.

See post by ste7e on this thread page 3 for the pdf  

 

 

 

PHD 2 now reports "backlash is small, no compensation needed"

I also adjusted the stiction out of the Dec and RA axis which has made a difference (scatter graph on phd much tighter)

Guiding now averages 0.65" 

 

 

Edited April 8, 2020 by Rob63
added link

[dilipsharan]

On 07/04/2020 at 09:27, discardedastro said:

Not that I know of. If I get brave I'll have a go this summer.

Well if you do pluck up the courage I'd be keen to know the results!  PHD2 is moaning big time about the EQ6-R PRO DEC backlash. I might have a go at tightening the centre tensioning grub screen. Here's a link to a YouTube video about this 

  

[discardedastro]

2 hours ago, KevS said:

Before you go too mad I posted this the other day. Might be worth a look if you get problems.

K

 

That's a very good shout. PHD2 has been complaining about Dec rate variance lately and I will pop off the covers tomorrow and have a look at the belt tension - it's a super easy fix if required!

[dilipsharan]

16 hours ago, KevS said:

Before you go too mad I posted this the other day. Might be worth a look if you get problems.

K

 

Thanks will do

[mikey2000]

Just curious - when adjusting the belts pictured above, how tight should they end up?  If I twang mine like a guitar string, there is about 5mm of “lateral bounce”

[mikey2000]

I think maybe you mean movement of the belt teeth over the gear teeth ?   I’m talking about how much “twang” is right for  correct belt tension.  I’ve doodled on the photo from above to illustrate.   My red arrow measurement would be about 5mm.   In the video it looks like quite a lot of force being used to tighten the belt.  My query is how tight should it be?

[mikey2000]

Excellent explanation!  Thanks.   It sounds like my belts could do with a little extra tension maybe (my backlash graph is nowhere near as good as yours!)  they are getting old now and perhaps they have stretched a bit..

 

I think belt adjustment lies within my limited abilities but the rest of the worm/float adjustments sound like voodoo magic to me and until someone makes a step by step video in simple non-engineering terms, I think I’ll be satisfied

[mikey2000]

OK, I found the AstroBaby EQ6 worm adjustment instructions and in daylight managed to combine those with the official EQ6-R Skywatcher backlash instructions (mentioned above) to get a view on what goes on in the worms. It seemed to make sense.  I felt brave and gave it a go....

 

I had a slight RA play that seemed easy to tune out. Emboldened, I tried the Dec axis as PHD was now complaining about Dec backlash following my belt adjustment.  I wondered if I had over tightened the belt and the extra tension had pulled the worm away from the main gear.  Shocking Dec backlash! (see screen photo)  I could actually feel it if shift I move the axis, clunking from side to side.

So, I tried adjusting the DEC worm as per astrobaby.   I think I overtightened it  - it sounded OK slewing in the vicinity where I made the adjustment but on a longer slew, lots of unpleasantly new grinding noises in a certain part of the rotation.  The EQ6-R Skywatcher instructions say to adjust the backlash in the place where it is least.  I see know how important that is!   That must be the tightest part of the cycle and I suppose that is the limit on the adjustment. 

 

I'll fix it tomorrow and hope for enlightement on the function of the Worm End Caps... Still a bit of voodoo out there!

[Mike_tempus]

Hello

Has there been any post related to the worm bearings adjustment?  This thread ended in April.  I am very interested in this topic and your results.

Thank you

[Mike_tempus]

On 08/04/2020 at 12:11, Rob63 said:

I adjusted the backlash following the skywatcher guide (someone posted it on this site), it's pretty easy to adjust.

See post by ste7e on this thread page 3 for the pdf  

 

 

 

PHD 2 now reports "backlash is small, no compensation needed"

I also adjusted the stiction out of the Dec and RA axis which has made a difference (scatter graph on phd much tighter)

Guiding now averages 0.65" 

 

 

Hello

Would it be possible to know the procedure you followed to eliminate the stiction out of your mount?

Thank you

[billhinge]

I don't know if its of any interest, I bought mine second hand as new (original owner bought it new and sent it straight to be Darkframe stellardrive tuned https://www.darkframeoptics.com/product/darkframe-stellardrive6-spx-eq6-mount ). He then decided he wanted a bigger mount and I paid the original eq6-r price so I got a  freebie hypertune.

Anyway, Darkframe say they replace the original worm gear

[Rob63]

45 minutes ago, Mike_tempus said:

Hello

Would it be possible to know the procedure you followed to eliminate the stiction out of your mount?

Thank you

It's pretty simple especially for DEC.

DEC: Loosen the 3 grub screws around the weight bar collar (hemisphere where the weight bar comes out) then loosen the  dec axis by rotating the collar anti-clockwise. Loosen enough to get free movement but not so much there is any movement perpendicularly (i.e. in the direction along the weight bar). Then tighten the grub screws again.

I used the same principle for RA - it's a little more complicated and  I used Astrobaby's EQ6 stripdown guide to help.

Remove polarscope (screws out anti - clockwise), it's retaining ring and then loosen the RA axis nut - note there are four (not the three there were on the EQ6) grub screws. 

Then as before turn axis anti clockwise to loosen a bit (some peole have trouble with this as it can be very tight - mine waasn't) and then. re-tighten the grub screws and reassemble.

Dec stiction adjustment was far more important for me.

 

 

 

[mikey2000]

I haven’t tried with RA adjustment / it doesn’t seem to need it.

 

the DEC adjustment worked out in the end but took me a long time to “get” the procedure.  Once I understood what I was doing, it was Ok and the result was much improved.

 

i think to get really top notch results, a hyper tune might be in order

[KTAZ]

Hello all;

I understand how to do the backlash adjustments for the worms, but the question I have is whether the mount should be loaded or not when making these adjustments. I just did the RA and will test it later this week, but I question whether tightening those small grub screws with the OTA and counterweights attached is the proper approach. Seems logical to adjust loaded as in expected use, but I also worry about those little grubs lifting all that weight to bring the RA plate up against the worm.

Anybody have experience with this one way or the other?

[billhinge]

On 08/04/2020 at 14:29, KevS said:

I would also be interested if anyone out there has adjusted the backlash. I keeping getting nagged by PHD when calibrating that I have an enormous deficit in Dec, but once it starts guiding I can be within 0.5rms on both axes, after a fairly rough polar alignment and running on a tripod. I can however feel some slight "play" when I push the mount from side to side by hand. 

I didn't adjust it myself. I bought a new EQ6-R some one was selling after they had it commercially tuned straight from new. I only paid the new unused mount price so got the tuning free

The blurb here describes the tuning to 0.01mm to reduce backlash but not the detail of how  they did it https://www.darkframeoptics.com/product/darkframe-stellardrive6-spx-eq6-mount

Having self tuned my old CG5 (replacing every bearing with high end abec 7 - £80 single bearing), replaced motor, and belt modding it to my own design I decided to let someone else do the work for me