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Old 07-01-2019, 10:29 AM
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The_bluester (Paul)
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Info for AZEQ6/Orion Atlas pro users

Just thought I would share this one. I decided to lash out after Christmas and buy a new cooled OSC camera, giving one last night with my old Canon 350D.

On that night and the first couple with the new camera I was running into tracking problems, the RA clutch would occasionally slip even when tightened down more than I was happy with mechanically.

Eventually I tracked it down to the design of the clutches in the AZEQ6 which are a completely different arrangement to the EQ6. In the EQ6 the axis are supported on tapered roller bearings like a car wheel bearing, with end play/float set by shimming the bearings for correct tension and spacing of the various parts when the retaining nut is tightened. The clutch appears to be a matter of the worm driving the ring gear which is a large drum, this turns freely inside the mount until you lock the clutch when the clutch drum is locked in place inside the fixed part of the axis so the worm then turns the axis around the now fixed ring gear.

In the AZEQ mount the axis is supported by two needle roller bearings instead of tapered bearings. The driven/ring gear is on a bearing of some description (I did not pull mine down far enough to see what it was, I just pulled the RA and Dec shafts from the housings)

The ring gear turns freely inside the mount and the clutch is now a felt disc between the ring gear and the fixed part of the relevant axis. The retaining nuts on both axis instead of setting up tension in the bearing, are more or less there to keep the shaft from falling out! With the clutches released each axis will have heaps of end play that you won't see on an EQ6. When you tighten the clutch, the end play is removed by pulling the shaft through the fixed housing and bearings, compressing the clutch disc between the fixed part of the housing body and the ring gear.

All good in theory and I can see some advantages, however what I identified as happening to my mount is that as the felt clutch discs have compressed over time, the moving part of each axis (RA most noticeably) has started to foul on fixed parts, making the clutch slip and encouraging you to tighten it further, which compresses the disc even more and increases the friction on the parts fouling, a viscous circle. In the end mine would sometimes just stop tracking but when I pulled the side cover off, the RA worm was still turning happily away.

I am now waiting on some spare parts to replace the clutch discs with new ones having tested the theory by adding heavy paper card shims to pack the thickness of the clutch out and found it to track nicely again. I am going to look at shimming it by adding the new discs when they arrive but leaving the old compressed ones in it, if the secondary encoders still work with the extra spacing, all good.

When I tear it down I might as well go the whole hog and strip it completely and clean the gears etc and set it up with some care/tune it properly. I will take pics as I go as there do not seem to be too many teardown guides for this mount.

If you think it might be happening there is a quick test. If with the locking screws loosened on the setting circles you can turn them freely with the axis clutch released but not with it tightened, welcome to my world! The only sort of teardown guide I have found on these mounts showed clear witness marks on the encoder cover that this was happening to that user too.

TL;DR version.

There is an inherent issue in the clutch design of the AZEQ6 type mount which many users will probably confront sooner or later with clutches slipping. Don't do the clutches up tighter than you need to for good drive and you will get longer before it happens. Your mileage may vary, I consider myself to have lots of mechanical sympathy and purposely avoided going to town on the clutches and it has happened to me after maybe two dozen observing sessions. I have heard of people breaking the RA clutch lever on these!

Last edited by The_bluester; 07-01-2019 at 11:18 AM.
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Old 07-01-2019, 11:24 AM
casstony
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I found a couple of tear down guides. This one looks good: https://drive.google.com/file/d/1QEU...WYKeGLWl5/view

Could you simply remove the setting circles to alleviate the issue?
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Old 07-01-2019, 11:31 AM
Wavytone
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Very interesting to know - thanks. Sounds like a better solution is needed for the clutch disks than felt, something which has a little give but won't compress permanently.

There was a disassembly guide linked a while back which I have saved on my Mac for when the time comes.
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Old 07-01-2019, 11:35 AM
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I wondered about removing them, all I use them for is putting the mount in the initial parked position on set up. If I don't have any joy getting new clutch discs I will look closer at taking them out. It would depend on if the setting circle rings are deeper than the machined part of the housing they turn on.

I had seen bits of that guide but not the whole thing. You can see on his pics that it was fouling on the RA encoder cover, so this one either had the issue or it was/is going to have it.

Edit: and yes, if I don't have any joy getting spare clutch felts I will look at making my own and make them out of something more resilient, they don't really do much work, even nylon discs would probably do the job of transmitting the torque required.
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Old 07-01-2019, 11:41 AM
casstony
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I find that I need to tighten the RA axis lock a little more after the mount cools or it risks slipping. I suppose the aluminium body might contract more than the steel shaft as well as the felt disc compressing.

Having purchased new with a 5 year warranty I won't be stripping my mount down within that time, but it's handy to be aware of the potential issue.
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Old 07-01-2019, 11:45 AM
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Quote:
Originally Posted by casstony View Post
I find that I need to tighten the RA axis lock a little more after the mount cools or it risks slipping. I suppose the aluminium body might contract more than the steel shaft as well as the felt disc compressing.
I never found that to be much of a problem after the first few nights use when I worked out what tension was required to keep it working nicely all night. I have seen it mentioned elsewhere that if it is set right the axis will probably move if you bump it. I tended to go a little tighter than that but not a lot.

edit: The only warranty information I can find regards the Orion version is one year, I have had it almost four years.
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Old 07-01-2019, 04:38 PM
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I am actually considering not worrying about new clutch felts and just make some shims out of 0.5mm aluminium. That way the felts are about as compressed as they will get.
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Old 07-01-2019, 04:49 PM
casstony
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Quote:
Originally Posted by The_bluester View Post
I never found that to be much of a problem after the first few nights use when I worked out what tension was required to keep it working nicely all night. I have seen it mentioned elsewhere that if it is set right the axis will probably move if you bump it. I tended to go a little tighter than that but not a lot.

edit: The only warranty information I can find regards the Orion version is one year, I have had it almost four years.
The difference in warranty is a good reason to pick the white one.

I checked how much gap there is with my axes locked - I can still put a fingernail between the setting circle and body, though the mount is only a few months old.
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Old 07-01-2019, 05:39 PM
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When I bought mine the Orion version was hundreds of dollars cheaper than the Skywatcher, I can't recall what the warranty difference was then, if any.


The cynic in me hears them after inspection saying "You have been doing the clutches up too tight"
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Old 07-01-2019, 06:11 PM
casstony
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I'd opt to save a few hundred and forego the extra warranty too. It doesn't look hard to dismantle the mount and while you're at it remove the swarf.

I've found Skywatcher Australia reasonably good to deal with regarding warranty.
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Old 14-01-2019, 07:15 AM
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Just for info, I made up packers from .5mm alloy sheet yesterday and fitted them up, taking the chance to inspect the worm and ring gears on the dec axis while I was at it. They seem to be somewhat better assembles than the EQ6 at least in my case so I did not strip down the gear itself on the RA axis.

The packers increase the spacing of the mount a little but the aux encoders still work properly so I am going to leave it that way. I decided to make the packers up and fit them along with the now compressed clutch discs as I reckon if I fitted new ones it would happen again sooner or later.

Both axis now lock up nicely and driver properly, I took the opportunity to set the depth of the worm a bit better and reduce the backlash that was present in the RA axis prior. Hopefully a star test this weekend, with the moon more or less full there wont be any pressure to be imaging so I can just work away at testing things.
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Old 14-01-2019, 07:38 AM
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Incidentally, I can understand the design intent behind the change in how these are laid out compared to an EQ6 and I reckon it is all about assembly time in the factory.

Where the Astrobaby EQ6 guide really is in depth (and needs to be) regards setting up the bearings with shims so that the axis move feely but don't have undue end float (The factory would have to do the same within a reasonable tolerance) in the AZEQ design with parallel needle roller bearings on the shaft and thrust bearings at both ends, bearing setup is much simpler.

All they really need to do is to select an end shim that aligns the worm and ring gear properly and the rest more or less looks after itself unless it is so far out that the encoders don't work or the clearances close up and cause fouling between parts when the clutches are engaged. When the clutches are released there is actually significant end float in both axis and this is actually a function of how the clutches work.

Tuning wise I think the main thing to be done on these mounts would be cleaning any swarf and re-lubricating. And I found that the grease used was in much better condition than I expected. My only gripe is one of the socket screws for the Dec worm assembly (That you loosen to set the worm mesh) had it's thread destroyed from new, it had been stripped on assembly and put back in snug instead of tight with threadlocker on it. A job for another day to work out a thread repair.
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Old 14-01-2019, 08:54 AM
casstony
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I recently had to shift my RA clutch lever to the next hole along - I wonder if there will be a bunch of 4yo mounts going in for warranty service
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Old 14-01-2019, 09:27 AM
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I reckon they might, but in all likelyhood most mounts will sit unused for a lot of the time and the compression of the clutch felts may not get to the point that the RA will start misbehaving. The design of the dec clutch lever would mean that they will tend to have a lot less tension applied. Assuming the thread pitch is the same, the lever you are using on the RA clutch is about twice as long as the dec so it is easy to apply a lot more force to it.

It may also be hit and miss as to how the tolerances stack up. Other mounts might compress down as far as they are going to without a problem.
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