EQM35: Low-Cost Belt Mod

[JeromeW]

Jim,

I tested it again, it worked correctly!! I believe the problem was that I did not hit 'sync to mount'.

Many thanks, it would not have been possible without all your help.

I plan on testing my rig outside on Monday night, hopefully we'll have clear sky's.

I will be making a major upgrade to the 'DEC Body ver 2.stl', there is way too much flex in the tab that holds the DEC motor.

You would be jealous to see the freedom of movement in my DEC Axis. I can now easily balance my telescope in the DEC Axis.

Quick question; if I wanted to use a 1.8° stepper motor, I would use a 50:1 gearbox. Is that correct?

Jerome

[jif001]

It would work the other way. By using a 1.8° motor you would be doubling the overall speed, so you would need to halve it again through the transmission. That would mean using a 200:1 gearbox.

Thanks for your input. You’ve moved the dec axis design on substantially from my original effort. I will eventually get a round to printing your designs, but right now we are in the middle of a house reconfiguration and my 3d printer is covered in dust 😬

I’ve recreated some of the components in Fusion 360 to make them editable and that’s kept me entertained for a while! I did wonder though - where does the nut barrel fit in?

Edited January 27 by jif001

[JeromeW]

I decided to use up some M4 square nuts that I had. They make it easier to locate and fasten the motor/gearbox/bracket assembly.

[JeromeW]

DEC Axis Assembly.pdf

[JeromeW]

I uploaded my improved 'DEC Body ver 2.stl' that adds gussets to stiffen the tab for the motor/gearbox/bracket assembly. We had a clear night so I took my rig outside and tested it. I was very pleased that my new DEC Axis worked perfectly and accurately. However, the guiding is not improved, and maybe worse. I strongly suspect the planetary gearbox has too much friction, because it turns noticeably slower.  I'm going to see if I can break it in, or in some way loosen it.

DEC Body ver 2.stl DEC Body ver 2.AD_PRT

[jif001]

The planetary gearbox will have introduced some backlash - perhaps that’s the issue. Do you use PHD2? If so then you can use PHD2 Log Viewer (a separate downloadable application) to analyse the guiding performance and pinpoint issues - see the example plots on the first page of this thread. 

[JeromeW]

I use the ASIAIR system with the EQMOD cable. I have absolutely no experience with planetary gearboxes at all. But I can feel no backlash whatsoever, the gearbox feels very tight. I have noticed the DEC axis now rotates noticeably slower. It feels tighter than it should be. It is Chinese made, and maybe some quality issues got through. The first thing I noticed was that the output shaft was out of spec, I had to grind the hole of the timing pulley to get it to fit. I had read a review where someone took one of these gearboxes apart and found that metal filings were jamming it. I plan on taking this gearbox apart, it will at least be a learning experience. 

I have noticed over the years that a lot of people build their own equatorial mounts. I'm now beginning to understand why, as I read deeper into the forums, the quality of equatorial mounts is an issue.

[JeromeW]

I am gradually making progress with my DEC Axis, and am now starting to get guiding on it. I put my planetary gearbox in an ultrasonic cleaner and flushed out all the old grease and replaced it with a light machine oil. I also removed the shaft seals, I can now back-drive the gearbox easily. 

I have had my rig outside several times now and have seen a few shortcomings with it:

• The primary one is that since it does not have a clutch, I need a stepper motor with a shaft at both ends so I can manually rotate the axis into position. 
• Also, I believe my timing belt should be wider. I feel the 6mm wide timing belt allows too much flex.

[JeromeW]

I also need to add some index marks on my 162 tooth timing pulley to line up my rig.

[jif001]

It sounds like you are making some good refinements. Unfortunately I’m still out of commission due to the ongoing house remodelling and will be for a while, in addition to which there has only been one clear night here in months! 

[Kilohertz]

Hey @jif001 I see some cool 3D printed parts on your mount, do you happen to have the STL files for the ALT/AZ knobs that you could share? 

Please and thanks.

CHeers

[jif001]

If you mean the yellow ones then those pics are not of my mount. @JeromeW is your man for those. 

[Kilohertz]

7 hours ago, jif001 said:

If you mean the yellow ones then those pics are not of my mount. @JeromeW is your man for those. 

Thanks Jim, I originally was asking about your white ones then I saw the yellow ones, Jerome has sent me the files.

Thanks to both of you for the content in this thread, very helpful.

Cheers

Paul

[jif001]

I’m happy to send the STLs for the white ones if you’re still interested, but Jerome’s are good. 

[Kilohertz]

I'm trial printing part of Jerome's now to see if they will fit, my mount is the NEQ-3PRO, castings look like they are slightly different.

Thanks Jim, I'll let you know.

I'm also trying to decide if I want to install my ONSTEP belt mod kit or keep tuning the stock Synscan setup with the gear train. I bought the Terrans kit a month ago to adapt for my Meade 856 but haven't done anything with it. It's the correct kit for my mount though, easy to put it on to try. Cloudy again for another 4-5 days so maybe I'll give it a whirl.

Cheers

[JeromeW]

Paul,

Did you use the needle thrust bearings as per the Super-Tune YouTube video on your Sky-Watcher mount? If so, how did they work out, any improvement?

Jerome

 

 

[Kilohertz]

1 hour ago, JeromeW said:

Paul,

Did you use the needle thrust bearings as per the Super-Tune YouTube video on your Sky-Watcher mount? If so, how did they work out, any improvement?

Jerome

That video as well as a few other posts on another forum are what inspired me but I took it further, used some teflon washers and didn't install several of the bearings Peter did as they aren't required for guiding and really throw off the alignment of the worm. I detailed my mod somewhere  back in December, can't recall which forum. I'll find it and link it.

And as I hadn't captured any images until last week, I can't comment on improvement, but it sure felt smoother when spinning by hand.

Cheers

[JeromeW]

Paul,

I certainly look forward to seeing your link!!

Were you able to get a good knob?

Jerome

[JeromeW]

To All,

I wanted to report my success tonight. I finally got my DEC to guide properly tonight. My primary problem was that I had my DEC Mode set to North instead of Auto.

Jerome

[JeromeW]

Also, I am very pleased with my 3D printed DEC Axis. I am now able to properly balance my telescope, and the plastic is proving to be strong enough.

[Kilohertz]

12 hours ago, JeromeW said:

Paul,

I certainly look forward to seeing your link!!

Were you able to get a good knob?

Jerome

In case you missed my update, it's in a separate thread...here is the link.

NEQ-3PRO my modifications and upgrades

[JeromeW]

AWSOME!! The PTFE sounds like a great idea. I have already tried the bearing upgrade and didn't find it beneficial. 

[JeromeW]

Here is the list of hardware for my 3D Printed DEC Axis

 

Nema 17 Stepper Motor 0.9deg Dual Shaft Bipolar 63oz.in 1.68A 42x48mm	StepperOnline	17HM19-1684D	https://www.ebay.com/itm/235351748408
GT2 Timing Belt Pulley, 45Tooth-Width 6mm-Bore 8mm			https://www.ebay.com/itm/224906185463
Nema17 Planetary Speed Reducer Gearbox 100:1 L51mm Input 5mm for Stepper Motor	SUMTOR		https://www.ebay.com/itm/266597215798
Shoulder Screws Allen Bolt ￠12 x M10 x 150mm long			https://www.ebay.com/itm/155522517177?var=455761398479
NSK 6201 ZZ Deep Groove Radial Ball Bearing 12x32x10mm	NSK	6201 ZZ	https://www.ebay.com/itm/285429579423
GT2 2GT 2M 2mm Pitch Closed Loop Synchronous Timing Belt 6mm Width Pulley, 79 teeth 158mm GT2-6mm			https://www.ebay.com/itm/144886431913?var=444107948548
HELIMAX-XP Camera Telescope Optical Instrument Focusing Helicoid Grease PTFE	MicroLubrol	MLHXP-1	https://www.ebay.com/itm/123651606955

[JeromeW]

I added Index Markers for my RA and DEC. I also added a weight to counterbalance the focuser motor. Finally, I added a knob to my motor shaft to adjust my DEC Axis.

[Kilohertz]

Nice work! That whole mount looks awesome! 

We finally had some clear skies this past week so I have been beating my head against the wall for another reason, although last night was a near perfect session, from 7:30 until 1:30am... no screw ups, great captures...now we have 5 days of crap weather so I will have a chance to learn processing software technics....I see more pain and anguish on the horizon. 

The darkroom days were so much easier. 🤕