EQ6 Belt Drive Modification
I'm not going to write down the whole process of stripping down the EQ6 mount as there is already many very good and detailed tutorials on how to do it.
Here I want to point out some tips that I acquired being a part of great EQ6 Yahoo group and some modification to the mount I had to do, to complete this belt drive modification.
What was important to me, is that I would be able to use Synscan controller after the mod and at that time the complete kit of pulleys and belts I found at Tavsco Centrum in Budapest. They are 2 x 47 tooth and 2 x 12 tooth pulleys with 2 timing belts.
First thing to note after disassembling the mount is that the worm housings on both axes have white paint leftovers that should be removed.
Here you can see that the worm housing were sanded and polished to provide good flat contact with the mount casting. And new pulley with the belt already installed.
While at it, the worm bearings were also replaced with much better quality ones.
Because the new pulley were thiker than the stock one, I had to modify the slot in the mount casting.
Filing down those couple of milimeters didn't take too long,10 minutes and it was done.
I had to do it on both axes and of course remove and polish the white paint leftovers from the casting too.
Very important is to keep the work clean and after you done, spend a great time on cleaning everything, so that no single particle won't find his way to the worm or the ring gear.
My mount had a history of what I call "Prefered Axis", there was a point when rotating RA axis it where binding too much and nothing helped until I went and replaced all of the 3 large bearings and one cone bearing for the whole RA axis. The bearings I got are branded SKF, Germany. Only then the problem has gone and I had very smooth rotation for full 360° turn.
After you Install the motors and apply tension to the belt, you will be doing it blindly, because there is no way you can see how the belt sits on both of the pulleys and if it slide sideways.
The solution is simple, you drilling large holes in the places shown on images, from which you'll be able to see both of the pulleys and the belt.
Here is the second hole for inspecting DEC belt and pulleys.
While not servicing the mount, you can simply cover the holes with adhesive tape, but I made my own caps to keep the dust away.
I used M12 x 1.75 tap drill to tap the holes.
Then I modified the bolts by shorting them and grinding a bit their heads to make them thinner. You can see one of those bolt-caps already screwed in it's place.
Before re-assembling, everything were greased with high quality synthetic grease.
Here is the another great tip to use gas rubber hose on the worm shaft when meshing the gears. That way you can easily turn the worm full rotation and check for binding problems while adjusting the mesh.
And now is the fun part. This is the USB endoscope camera which you can get really cheap on ebay and that what I gonna use to inspect the belt modificaton when mount completely assembled back. It have four white leds around the camera which brightness you can also adjust.
I did small modification to the camera by removing the clear plastic in front of the camera, that gave much clearer picture. Also I removed the protective plastic shell to make camera thinner, so it will fit to the holes I made.
Here is the actual video showing inspection of belt mod on both axes from inside the mount using that endoscope camera. (No Sound)
That video with sound I recorded in a silent room, so you can hear how the sound of the mount changed after belt mod. No more rattling sound.
EQ6 mounts, as arrived from the manufacturer, on average produce Periodic Error between 20-30 arcseconds and that can be certainly improved by Hypertuning the mount or better yet, perform the belt modification. I did both on my mount and the results speaking for them self. You can see that the Peak to Peak error is about 11 arcseconds and RMS PE is 3.2 arcseconds. Definitely worth the money and time spent.