31 replies to this topic

[KMHammer]

]I finally got around to doing some testing and found (and I should have realized this) that I had only balanced the scope in the declination axis. The RA axis was way off, largely due to the extra weight of the equipment driving the Dec on the right fork arm. Unfortunately, unlike with GEMs, fork type mounts do not allow for rebalancing the optical train by sliding it along a dovetail bar. And this was causing the gear slippage in the RA axis. To balance things out, I will need to offset that weight by adding some to the left fork arm. I will do this by adding symmetry, so that things look both visually and mechanically similar and appealing. So I will put a 5mm x 0.8 pitch threaded rod into the left Dec axis, just like on the right, followed by a matching 3D printed 240 tooth GT2 gear and knob. The rest of the weight will be metal (lead molded to the appropriate shape or steel rod cut to length?) inserted into the holes in GT2 gear.

 

 

I think it looks better this way, but the downside is the extra added weight. It would be better to adjust the optical tube fore-aft to balance, but that is not a realistic option.

 

It looks like I am going to need about 8 ounces to properly balance, so the optical tube plus fork mount overall weight will have increased by about 3 pounds total between the fork modification and the Dec balancing addition.

Edited by KMHammer, 01 February 2023 - 02:23 PM.

[KMHammer]

Just a brief update. The scope took 9 ounces of lead weight to properly balance the RA axis. I purchased 16 ounces of lead in the form of a 1/8" diameter rope (from Amazon). I added the rope to the left side of the fork and removed the lead, by cutting with a scissor, until balance was achieved. I then cut the lead into 4 equal lengths, coiled it and inserted a piece into each of the 4 holes in the GT2 gear. It now is very well balanced and I can slew the RA at the maximum speed with no gear skipping now. Eventually I will clean up the installation of the lead coils (possibly melt into properly sized discs to be glued in place) for a more professional look, but it works fine for now.

 

Still hoping to make a video and I also need to do a more complete tracking performance evaluation, although the preliminary test looked good.

[KMHammer]

Real Short update,

 

I fashioned a small cup out of aluminum the same ID as the four holes found in the large GT2 gear and cast the lead into ingots that I inserted into the holes using some Gorilla Tape to make a tight fit. Then I 3D designed and printed some red translucent covers to hide the lead. Additional covers were added to the other side for symmetry.  Once everything is fully checked out, I will do some cosmetic work on the parts, but the scope mount actually looks more refined in person as the 3D printing lines are exaggerated by the lighting in the photo. 

Attached Thumbnails

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Edited by KMHammer, 28 April 2023 - 03:34 PM.

[KMHammer]

Bump. Still haven't found the time to make an operational video.

[astroly]

I am inspired!

[Mason Dixon]

Fantastic tutorial, just what I was looking for, thanks!

[KMHammer]

Just checking in on my creation. Also, I would highly recommend using a FYSETC E4 (available from FYSETC) as the scope controller now as it is only $30, already assembled and has WiFi. It was designed for controlling 3D printers and already has high quality stepper drivers on-board. It is already assembled and less expensive than the Blue pill controller while having a processor that is ~4X faster. With four stepper controllers, it can also be used to control a focuser and a rotator. A true win-win situation. The guide for setting up and using this controller can be found on the OnStep Wiki. One of the beauties of this board is that the tracking info (gear ratios, etc.) is programmed by WiFi after installation, so it can be tweaked without having to do a complete reprogram.