Hi everybody!
If you have ever thought of tuning your EQ6-R – or any other similar Sky-Watcher mount – this might be interesting for you.
Last weekend I did a bearing replacement on my EQ6-R, according to the excellent Youtube video by “Astrobloke” Glenn Clouder:
https://www.youtube.com/watch?v=qujs7Kt_6_c
Thanks very much to @Glenn for his great video tutorial!
If you have hesitated to disassemble your mount – be assured, for anybody with basic “home improvement” skills, this is no complicated or difficult task. I did hesitate, because my guiding was actually quite good with the mount out of the box (approx. 0.2-0.4 arcseconds RMS depending on seeing). So “never touch a running system” was a concern – and I have been using my EQ6-R for 3 years now.
But after disassembling the mount, I was glad that I did just that, so I could get rid of a number of flaws and mechanical issues that were not apparent from the outside.
So first, getting all the replacement bearings is no problem – wherever you live, you will find a local supplier of quality bearings. I went for the SKF bearings (a Swedish company), but the RA tapered roller bearing was unavailable from SKF, so I got that one from Austrian company NKE (quality felt even better than the SKF bearings, by the way).
If you don’t rush with the procedure and clean everything thoroughly, you will need an afternoon’s time for every axis (DEC, RA).
DEC-Axis:
Disassembly was easy and everything went according to Glenn’s video. There was no excessive grease or abrasion on the worm gears. Drive belts were OK, no sign of troublesome wear after 3 years of use.
However, I noted that the large aluminium gear (the one that is driven by the belt) was glued onto the worm shaft, also the small-grub screws locking the gear onto the shaft were glued into place. So it was a bit tricky to get these grub screws loose, risking to brake the allen socket of these screws.
The cog teeth of the aluminium belt gear had some metal burrs on one side causing slight abrasion on the belt, so I removed all of those with a triangular file and sandpaper.
When putting everything back together, I also glued the belt gear onto the shaft again, using a 2-component epoxy glue. However, I did not glue the grub screws in place.
RA-Axis:
Same thing here, the belt gear was glued onto the worm gear shaft, causing slight problems loosening these grub screws. No burrs on the belt gear of the RA.
But instead, the RA worm gear showed excessive grease all over the place and some abrasion residues on the gear. These showed as metal filings on the bottom of my bowl after brushing off all gears with parts cleaner fluid and an old toothbrush. I believe these filings were leftovers from the production process, not from excessive friction between the worm and the cog.
Both, RA and DEC showed signs of serious mechanical flaws:
The large end-nut that holds everything in place on the central shaft was screwed-on way too tight, exerting great longitudinal pressure (along the shaft) on the ball bearings – a load no ball bearing is designed to withstand. So out of curiosity I disassembled two of the ball bearings (they did not feel bad actually!) and found a ball with a serious circular abrasion on it.
So when screwing everything back together (including the “washer screw” holding the worm gear shaft in place) I recommend only to moderately tighten everything (“hand-tight”). As soon as there is no more longitudinal movement on the shafts, the end nut is properly tightened – no need to tighten any further!
Generally, I found that everything was tightened up way too much: For example, the large holding handle on the main housing had its screws tightened to the brink of breaking. This also caused a slight deformation of the main housing, so that the RA tapered roller bearing would not fit into its seating. Only after unlocking the holding handle screws could the roller bearing be inserted!
The RA shaft also had a slight burr on the bearing seating surface, apparently resulting from trying to force a bearing onto the shaft non-square. I removed this burr and smoothed everything with sandpaper – this was only a minor issue not interfering with the seat of the bearing.
I have yet to wait for a clear night to test the mount’s guiding. However, as Glenn pointed out in his video, the mechanics of the mount are overall much smoother now.
I hope this was interesting, clear skies!
Chris
If you have ever thought of tuning your EQ6-R – or any other similar Sky-Watcher mount – this might be interesting for you.
Last weekend I did a bearing replacement on my EQ6-R, according to the excellent Youtube video by “Astrobloke” Glenn Clouder:
https://www.youtube.com/watch?v=qujs7Kt_6_c
Thanks very much to @Glenn for his great video tutorial!
If you have hesitated to disassemble your mount – be assured, for anybody with basic “home improvement” skills, this is no complicated or difficult task. I did hesitate, because my guiding was actually quite good with the mount out of the box (approx. 0.2-0.4 arcseconds RMS depending on seeing). So “never touch a running system” was a concern – and I have been using my EQ6-R for 3 years now.
But after disassembling the mount, I was glad that I did just that, so I could get rid of a number of flaws and mechanical issues that were not apparent from the outside.
So first, getting all the replacement bearings is no problem – wherever you live, you will find a local supplier of quality bearings. I went for the SKF bearings (a Swedish company), but the RA tapered roller bearing was unavailable from SKF, so I got that one from Austrian company NKE (quality felt even better than the SKF bearings, by the way).
If you don’t rush with the procedure and clean everything thoroughly, you will need an afternoon’s time for every axis (DEC, RA).
DEC-Axis:
Disassembly was easy and everything went according to Glenn’s video. There was no excessive grease or abrasion on the worm gears. Drive belts were OK, no sign of troublesome wear after 3 years of use.
However, I noted that the large aluminium gear (the one that is driven by the belt) was glued onto the worm shaft, also the small-grub screws locking the gear onto the shaft were glued into place. So it was a bit tricky to get these grub screws loose, risking to brake the allen socket of these screws.
The cog teeth of the aluminium belt gear had some metal burrs on one side causing slight abrasion on the belt, so I removed all of those with a triangular file and sandpaper.
When putting everything back together, I also glued the belt gear onto the shaft again, using a 2-component epoxy glue. However, I did not glue the grub screws in place.
RA-Axis:
Same thing here, the belt gear was glued onto the worm gear shaft, causing slight problems loosening these grub screws. No burrs on the belt gear of the RA.
But instead, the RA worm gear showed excessive grease all over the place and some abrasion residues on the gear. These showed as metal filings on the bottom of my bowl after brushing off all gears with parts cleaner fluid and an old toothbrush. I believe these filings were leftovers from the production process, not from excessive friction between the worm and the cog.
Both, RA and DEC showed signs of serious mechanical flaws:
The large end-nut that holds everything in place on the central shaft was screwed-on way too tight, exerting great longitudinal pressure (along the shaft) on the ball bearings – a load no ball bearing is designed to withstand. So out of curiosity I disassembled two of the ball bearings (they did not feel bad actually!) and found a ball with a serious circular abrasion on it.
So when screwing everything back together (including the “washer screw” holding the worm gear shaft in place) I recommend only to moderately tighten everything (“hand-tight”). As soon as there is no more longitudinal movement on the shafts, the end nut is properly tightened – no need to tighten any further!
Generally, I found that everything was tightened up way too much: For example, the large holding handle on the main housing had its screws tightened to the brink of breaking. This also caused a slight deformation of the main housing, so that the RA tapered roller bearing would not fit into its seating. Only after unlocking the holding handle screws could the roller bearing be inserted!
The RA shaft also had a slight burr on the bearing seating surface, apparently resulting from trying to force a bearing onto the shaft non-square. I removed this burr and smoothed everything with sandpaper – this was only a minor issue not interfering with the seat of the bearing.
I have yet to wait for a clear night to test the mount’s guiding. However, as Glenn pointed out in his video, the mechanics of the mount are overall much smoother now.
I hope this was interesting, clear skies!
Chris
