Time to belt up!

[Paul M]

An ongoing theme recently has been Guiding on my NEQ6 Pro struggling and eventually failing to calibrate. That's PHD2 on APT and Ekos and also Ekos internal guiding. All of which were fine at some point. RA calibration would fail after failing to return to the reference star and report backlash as a likely cause. 

If I'm going to start messing I might as well do the belt mod too, so I ordered the Rowan belt mod kit from FLO.

What could possibly go wrong

 

 

 

 

 

 

No point in a blow by blow tutorial. Anyone thinking of undertaking this mod would be well advised to watch a few tutorials. The kit included full written instructions also.

It all went smoothly and took about 6 hours including final fettling. Some experience of feeling for bearing play is helpful. These may well be chunky mounts but they aren't industrial machinery. A feather light touch is needed in final assembly and adjustment. The stilsons you see were only needed for one operation, removal of the polar scope collar. I just left them in the pictures for dramatic effect!

Final adjustment of the worm mesh turned out to be hugely more delicate than I'd imagined. The declination axis was straight forward. I just felt for play and very gently nipped it up. I did the same with the RA axis but on powering up and running both axes RA was a mess; stalling and what sounded like belt jump! I fiddled for some time with RA worm mesh. Eccentricity is the issue here. Tight in spots and slack in others. Without going further down the mod route and installing sprung worm tensioners the best I could do was compromise. I could still hear a change in tone of the motor on each rotation of the worm but backing off any further resulted in detectable backlash.

It all now seems very smooth. I ran both axes for a number of full rotations in each direction and I'm happyish with where I am. I'll load it up in daylight tomorrow and see how it copes with the torque required to get the big 10" Newt moving before trying real world guiding.

Non of the above means anything if it doesn't guide!

Edited October 31, 2020 by Paul M

[JamesF]

Sadly none of your photos appear to have worked, Paul.

3 hours ago, Paul M said:

Final adjustment of the worm mesh turned out to be hugely more delicate than I'd imagined. The declination axis was straight forward. I just felt for play and very gently nipped it up. I did the same with the RA axis but on powering up and running both axes RA was a mess; stalling and what sounded like belt jump! I fiddled for some time with RA worm mesh. Eccentricity is the issue here. Tight in spots and slack in others.

That's pretty much where I got to.  I need to return to it sharpish, really.  My tight spots all seemed to be in one quarter of the travel of the RA axis though, and I did wonder if I couldn't fiddle things around such that the offending section of the RA worm wheel never actually got used (so it would be in the "counterweights up" position if used, basically).  I got no further at the time, however.

James

[Paul M]

11 hours ago, JamesF said:

That's pretty much where I got to.

That's some kind of relief for me. I was wondering whether I'd landed my Raspberry Pi equivalent of the NEQ6 !

I think I'm there with it now but I suspect it's going to be very sensitive to scope imbalance. I could just back it all off and enjoy quiet drives with worse backlash than I started with but that's a bit silly. 

I'll put it down to "newness"; there'll be a sweet spot between now, when it's a tad tight and later when it's all worn in and sloppy

Of course someone will be along shortly to recommend some XYZ ceramic drive with absolute zero superconductor bearings and organic neural network controls. Need to up my imaging before buying one of those 🤣