EQ6 Pro Dec axis issue

[SteveA]

This has turned into one of those jobs I wish I hadn't started....

My EQ6 is around 10 years old now and has always had an issue with a stiff dec axis. I've managed to live with it over the years and despite two previous strip downs and re-greasing I've never been able to cure it. It certainly has made balancing that axis problematical though in operation the mount has worked reasonably well.

I decided the other week to try and super tune the mount...I emphasise TRY!

I decided on replacing all of the bearings and these are now installed. However, I had an absolute nightmare of a job getting the dec spindle and collar re-installed. It was extremely tight and now the stiffness in this axis is actually worse. Clearly the issue is with the barrel of the dec worm gear binding within the collar. I'm not sure why this should suddenly be worse but it is. I've double checked that all of the bearings are seated correctly and they look okay. 

I feel like the barrel needs some lubrication, but all the tips I've seen on re-assembly suggest not applying any grease to the outside of the barrel? I can understand keeping the section of the barrel that the clutch button engages with grease free, but is it really necessary to avoid lubrication on the rest of this?  Having said this I'm not altogether sure that lubrication would cure the issue anyway and I'm considering taking to the barrel of the worm gear, or the inside of the collar with a fine abrasive to see if I can reduce the binding. I'm feeling like this could do it but I'm some what nervous of totally wrecking the thing. 

Has anyone else had a similar problem?

Steve

[spillage]

so is this with the clutch mechanism removed, worm adjust well away from the worm gear and the weight bar collar slack?

[souls33k3r]

Apologies in advance but i don't know a solution to this but what i can suggest is to send it off to Dark Frame and let them take a look and fix and then hypertune it?

I sincerely do hope it works out for you mate.

[SteveA]

Yes....I have the clutch removed and the weight collar is just as loose as it can be, however the gear is engaged with the worm to keep it static.  The dec setting circle isn't binding and can be rotated freely. With the weight collar as loose as it is I can pull the dec collar over the barrel of the dec gear by about 7 mm and its still binding.

 

 

[SteveA]

2 minutes ago, souls33k3r said:

Apologies in advance but i don't know a solution to this but what i can suggest is to send it off to Dark Frame and let them take a look and fix and then hypertune it?

I sincerely do hope it works out for you mate.

I did think about that...I simply can't afford it unfortunately. Though having spent over £100 on bearings..I'm wondering now if I made the right call!

 

[souls33k3r]

Just now, SteveA said:

I did think about that...I simply can't afford it unfortunately. Though having spent over £100 on bearings..I'm wondering now if I made the right call!

 

I totally get that mate. I'm not a DIY guy so not very confident in making this work for my NEQ6. I know it will be a hard pill to swallow but in the end i will send my mount to Dave and ask him to fix it rather than me trying to over engineer it. But that's just me.

[tooth_dr]

I have twice stripped my mount too and the Dec axis is exactly like yours was. It’s stiff and despite numerous adjustments remains stiff. I’ve replaced bearings too.  Balancing takes practice aldo. It’s as if the brass barrel is too wide and when the clutch is off it still binds. My mount is 10 years old too, I’m just going to stick with it until I can upgrade to a larger mount.  Mind you my backlash is ok since my last adjustment. 

[spillage]

If memory serves me right the rear bearing is tapered. (just checked on astrobaby and it is). Slacken off the collar and allow the bearing to slide out just a bit.

Slowly start to tighten the collar back up then rotate the dec a few times and do it up a little more and repeat. This will allow the bearing to bed in correctly. You mentioned that you did the hypertune, this may be the cause and you might need to increase the shim on the bottom of the gear. I found with mine I had to add hoc a bit on the numbers produced.

It might be worth adding exta shims to the dec and see if this removes the binding.

[SteveA]

6 minutes ago, tooth_dr said:

I have twice stripped my mount too and the Dec axis is exactly like yours was. It’s stiff and despite numerous adjustments remains stiff. I’ve replaced bearings too.  Balancing takes practice aldo. It’s as if the brass barrel is too wide and when the clutch is off it still binds. My mount is 10 years old too, I’m just going to stick with it until I can upgrade to a larger mount.  Mind you my backlash is ok since my last adjustment. 

I’m glad it isn’t just me?. It seemed strange to me when I bought it, that it didn’t spin freely, but at the time I was a bit of a newbie, so I just accepted it. I would probably have sent it back if I had been more knowledgable.

Interesting that you have the same problem on a mount of the same age, maybe there was an issue with the casting at that time. I agree with you, that the barrel and the collar aren’t sized correctly. As I say though, new bearings have actually made things worse, so maybe even the spindle isn’t “true”. 

I’m also thinking about upgrading the mount....not that I can afford it though?

Steve

 

 

[tooth_dr]

1 minute ago, SteveA said:

I’m glad it isn’t just me?. It seemed strange to me when I bought it, that it didn’t spin freely, but at the time I was a bit of a newbie, so I just accepted it. I would probably have sent it back if I had been more knowledgable.

Interesting that you have the same problem on a mount of the same age, maybe there was an issue with the casting at that time. I agree with you, that the barrel and the collar aren’t sized correctly. As I say though, new bearings have actually made things worse, so maybe even the spindle isn’t “true”. 

I’m also thinking about upgrading the mount....not that I can afford it though?

Steve

 

 

It’s like a parallel universe lol

[SteveA]

7 minutes ago, spillage said:

If memory serves me right the rear bearing is tapered. (just checked on astrobaby and it is). Slacken off the collar and allow the bearing to slide out just a bit.

Slowly start to tighten the collar back up then rotate the dec a few times and do it up a little more and repeat. This will allow the bearing to bed in correctly. You mentioned that you did the hypertune, this may be the cause and you might need to increase the shim on the bottom of the gear. I found with mine I had to add hoc a bit on the numbers produced.

It might be worth adding exta shims to the dec and see if this removes the binding.

I will check the taper bearing later, I hadn’t thought about that, but I have a feeling that isn’t the issue. 

I have a set of shims as well...just in case?

[tooth_dr]

In my case I spent a lot of time on the tapered bearing, made no difference. 

[SteveA]

I just found this document on the EQ6 Yahoo group..

https://groups.yahoo.com/neo/groups/EQ6/files/Rebuild_and_Adjustment_Tips/?guccounter=1

Its regarding the same issue as far as I can see on the RA axis, so will see if helps in my case...

 

EQ6 RA Clutch Fine Tune.pdf

[SteveA]

I spent a fun filled evening with a couple of sheets of 2000 & 3000 grit wet and dry lapping the inside of the Dec axis collar!

I tried marking the inside of the collar with a magic marker as suggested but I found it difficult to identify specific areas that needed rubbing down, I decided therefor to lap the entire inner surface of the collar. I did however find couple of small rough edged pits at the top of the collar, which I rubbed smooth with the abrasive paper as these were clearly contributing to the binding and roughness when rotating the axis.

I cut several strips of abrasive paper about 70mm long and as wide as the depth of the collar, I found that I could hold the paper against the inside of the collar and applying even pressure rotate the collar and spindle on my work bench. this I felt removed material evenly from the entire inner circumference of the collar. I worked gradually using plenty of 3:1 oil to lubricate the paper and cleaning before reassembly and testing. This did make the whole process rather time consuming, in total I guess I spent a good three hours working on this. I dare say a rougher paper would have got through it quicker, but I was paranoid about removing too much material and rendering the mount...knackered.

 I also added an additional Delrin shim to the top of the Dec gear, raising the collar slightly to try and stop any pottential binding in that area as I could see that the brass barrel was marking the underside of the collar. I have ended up with a slightly larger gap  between the collar and the worm housing than I would have liked, but this seems a small price to pay for the added smoothness.

The inside of the collar is now silky smooth, there is no binding when reinserting the spindle and...most importantly the axis is now very smooth to rotate with no binding.

I still have to reinsert the tapper bearings and tighten everything up but so far as I can't see this has made a massive improvement.

Steve

[tooth_dr]

7 hours ago, SteveA said:

I spent a fun filled evening with a couple of sheets of 2000 & 3000 grit wet and dry lapping the inside of the Dec axis collar!

I tried marking the inside of the collar with a magic marker as suggested but I found it difficult to identify specific areas that needed rubbing down, I decided therefor to lap the entire inner surface of the collar. I did however find couple of small rough edged pits at the top of the collar, which I rubbed smooth with the abrasive paper as these were clearly contributing to the binding and roughness when rotating the axis.

I cut several strips of abrasive paper about 70mm long and as wide as the depth of the collar, I found that I could hold the paper against the inside of the collar and applying even pressure rotate the collar and spindle on my work bench. this I felt removed material evenly from the entire inner circumference of the collar. I worked gradually using plenty of 3:1 oil to lubricate the paper and cleaning before reassembly and testing. This did make the whole process rather time consuming, in total I guess I spent a good three hours working on this. I dare say a rougher paper would have got through it quicker, but I was paranoid about removing too much material and rendering the mount...knackered.

 I also added an additional Delrin shim to the top of the Dec gear, raising the collar slightly to try and stop any pottential binding in that area as I could see that the brass barrel was marking the underside of the collar. I have ended up with a slightly larger gap  between the collar and the worm housing than I would have liked, but this seems a small price to pay for the added smoothness.

The inside of the collar is now silky smooth, there is no binding when reinserting the spindle and...most importantly the axis is now very smooth to rotate with no binding.

I still have to reinsert the tapper bearings and tighten everything up but so far as I can't see this has made a massive improvement.

Steve

 

That's great news Steve.  I'm just afraid to do this and knacker my mount!  If you don't mind keeping us updated on how it performs post-sanding.

[SteveA]

Just now, tooth_dr said:

That's great news Steve.  I'm just afraid to do this and knacker my mount!  If you don't mind keeping us updated on how it performs post-sanding.

I know the feeling....I wouldn't have done this if I felt I had any option, but after stripping down and installing the new bearings the axis was so tight I was doubtful I could have got close to balancing it. I know it is risky, but using fine abrasives and not going OTT, has  I think resolved things. The fact that this has cleared the binding and the stiffness clearly points at this as having been the problem and the axis is far easier to turn than it has ever been.

Clearly the proof will be when the mount is loaded up, so I'll definitely update you.

Steve 

[SteveA]

On 10/10/2018 at 11:03, tooth_dr said:

That's great news Steve.  I'm just afraid to do this and knacker my mount!  If you don't mind keeping us updated on how it performs post-sanding.

So...the first chance since re-assembling the mount to get it re-installed in the observatory and mount the telescope.

First thing I realised is that I have NEVER had the telescope properly balanced! I mounted the Quattro in the normal way and with the now tuned mount it was way off balance in both DEC and RA, I was properly stunned believe me. Both axis are now beautifully free to move with no binding or tight spots. Even the RA axis on which I did the minimum amount of work has significantly improved due to the new bearings and a polished brass gear. It's the DEC axis though that has shown the most improvement though and I now realise how poor it was before. I'm pleased that I took the chance and lapped the dec axis collar, it has totally transformed that axis and together with the new bearings it feels like a completely different mount. I'm hoping that my ability to properly balance the whole setup will lead to better tracking/guiding which was of course the whole point of doing this.

I was thinking of trying the old "propeller" test...but I bottled it. I know it would do it, but I just can't quite bring myself to start spinning it like a kiddies toy...just in case it comes off the mount.

Just tuning out a bit of free play in the worm and will then get it all polar aligned once the weather improves...fingers crossed!

And a bit of a p.s.

When I was stripping the mount down, I removed both of the motors, which I had previously modified with the Rowan belt mod kit. I made an interesting and slightly disturbing discovery. On both the RA and DEC motor mounting plates the nylon rollers which are part of the belt modification were extremely loose. What had happened was that the small roller axle which screws into the aluminium mount plate had worked themselves loose. The movement of the belt between these rollers had on both motors caused one of the axles on each assembly to essentially un-screw its self. This was particularly pronounced on the DEC motor and the axle was close to falling out...see the included picture. It was a simply job to tighten these up, but maybe a worth while check for anyone who has modified their mount with this kit. I did my modification about three years ago.

Steve