Old 18-01-2021, 10:18 PM
Rerouter (Ryan)
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Location: Sydney
Posts: 74
EQ3 Axis Improvement?

Newbie to astro, but familiar enough with mechanical to be dangerous,

I recently picked up a newtonion + eq3 motorised mount for $150, quickly found the binding and backlash issues, and started down a rabbit hole.

Pulled it down, re-greased it and tweaked the backlash, this improved the RA to the point I am happy with it, also found a solution to the RA setting circle grabbing (need a 0.5mm spacer, and then put some rubber bands around the groove to keep it held center and off the locking nut)

But the DEC is still left lacking, it has a ridiculous amount of friction on the fiber washers even without tension on the nut, and the ring gear teeth are not concentrically cut, with high and low spots, which all adds up to bad balancing, and bad tracking.

To the end of solving this I am hoping for some help from the DIY'ers who might be more familiar with what bearings / washer materials would be the best choice to make something of this cheap mount, also any tips about ways to clean up the ring gear teeth would be appreciated, I have marked the problem teeth, suspect I will need to selectively polish the high points until it levels out, unless someone might know the worm pitch.

Moving on the the main topic

The purple is the contact areas.

First thought is the top of the top of the dec ring gear could be widened to fit something like a 20x27x4mm deep grove ball bearing, inner race on the shaft, outer race on the ring gear, he would only come into play when balancing the axis, and that close to the firmest point of the shaft I don't see any problems with radial loading, other option would be a 20x35mm thrust bearing + washer, which consumes 2.5mm of thread from the nut, and adds the same gap between the head and the body, so not as keen with that.

The bottom of the ring gear is a challenge, as there are 3 moving faces in play, so I am imagining either the same as the top of the ring, with the inner race on the shaft / dec body, and the outer race set in the ring gear, the un-stocked unicorn KOYO TP2132D thrust bearing which chews up 2-3mm of thread, or bore out the bottom of the ring gear and fit a NX20Z

For the bottom nut, his friction seems very low, without any radial load issues, I don't think it needs any improving.

Alternatives I would like to try before all this would be some alternative to those red fibre washers, but I look forward to any input you can give on this matter,

I think I may have a small error and the RA shaft may actually be 1", If I was to ask for some suggestion there it would be some way to lock the ring without the set screws chewing up the thread, there is about 3mm of space between the top of the ring and the end of the thread of the polar scope
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Last edited by Rerouter; 19-01-2021 at 11:57 AM.
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Old 19-01-2021, 04:37 AM
bojan's Avatar

bojan is offline
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 6,363
Welcome to the club of never-ending tweakers and improvers
I had a similar problem, see here.

Good luck with your project
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Old 20-01-2021, 09:01 PM
Rerouter (Ryan)
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Join Date: Jan 2021
Location: Sydney
Posts: 74
Found someone to lathe in return of a favor, going to order up:
NX20Z for the bottom of the DEC Ring gear
61704 for the top of the DEC Ring gear
AS2035 / AXK2035 for the locking nut at the end of the shaft,

And from the lathe friend will need:
20x26x0.5mm shim for the top bearing to rest on.
20x26x1mm shim for the bottom to rest on,

The bearings are actually much cheaper than I first thought, about $65 posted for the 3, the AXK2035 is being ordered as an option, as the other 2 prefer some pre-load, and loading down that nut may introduce some binding on the larger washer, this will cost me 2-3 mm of thread on the nut,

The way I see it, preloading it up on these bearing surfaces, and the increased rigidity on the shaft should mean what I loose in surface area to support radial loads should be compensated for, while drastically reducing away any friction in this low load use case.


I started looking into the RA for no particular reason, more as a what if case, as that would be much harder, would need to machine the body instead of the ring gear to pull off, the way I see it,

the bottom of the body could have a 44643 tapered bearing fitted

The top of the body could have something like a 35x47x7mm bearing + spacer ring sunk into it to hold the ring gear centered and rigid to remove any axial / radial loading from the bottom

The top of the ring gear could maybe have a 30x37x4mm bearing + spacer ring, this holds the shaft centered and removes any axial / radial loading from the top

That should wrap up that plan if I was to act on it, but I think lathing the RA body is a bit beyond what that favor would pay for, pity the weird shaft sizes mean that it would need spacer rings

Last edited by Rerouter; 20-01-2021 at 10:43 PM.
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