June 8, 2022
Description
By GuitsBoy at (Gmail, CloudyNights, OnStep)
CAUTION: This is still in heavy BETA mode. Continue at your own peril. Please tether your camera and/or anything you dont want to smash on the ground if something breaks, delaminates, slips, moves, twists, disintegrates, or exhibits any other unexpected behavior. The documentation and assembly instructions are very poor. If you've managed to figure out how to 3D print in general, then you should have no trouble assembling this thing after looking at a couple pictures.
lt-Azimuth Adjustable Base can be found here:
https://www.thingiverse.com/thing:5411792
Add-Ons / Modifications:
Some users have generously contributed modifications for this mount. Please scroll down to the bottom for MODS.
What is Still Under Development
Most materials / components can be found on amazon, though they will be more expensive than ebay or AliExpress.
Bill of Materials
Optional Materials
Misc Hardware:
Design Notes
I tried to keep the price point down to around $100 USD, not counting filament or a tripod. That probably requires printing your own 15/16T and 60T GT2 pulleys, and a vixen dovetail mount. But for higher precision, I suggest going with the metal upgrades.
I wanted to keep both the RA and Dec housed in the same body, so we wouldnt need a bunch of wires. And I went with a "sidewall and bearing block" layout to keep things modular. That way, if I or someone else decides to re-design a component, we only have to replace the single component, not reprint the entire body.
I originally intended to use 20mm axis shafts, however they are slightly larger than the ID of the bearing. Rather than turn them down, I incorporated shims into the shaft collars to allow the 18mm shaft to ride on the 20mm bearings.
One more important note. I did not add threads. Anywhere. All plastic holes are merely slightly undersized, and the screws cut their own thread. I havent found 3D printing such small threads to be reliable, and actually find having the screw cut it's own threads to work better. Ive used this method for a few years without any trouble. But just wanted to give you the heads up again it.
Choosing What to Print
Youll always need these:
Youll also need to choose which large pulleys to print. You can calculate your spacing here: https://www.technobotsonline.com/timing-pulley-distance-between-centres-calculator.html
91 to 92 mm spacing is nice, as long as your stepper motor wires/connector is not squished against the NEMA17 block. If you lave an obtrusive connector or wires, you might want to increase pulley spacing to 95 or 96mm. My first iteration used 15T and 168T pulleys for 96mm spacing, but I have since moved to 15T to 174T at 91mm spacing. I'd start with something in this area. Really, anything in the 15-16T x 164-176 range should work well with a 400mm belt. Let your stepper motor wire/connector determine how much space you need. Choose the right size for your application, and print two of them. They are the same piece for each axis.
Youll also need to print either the "Dovetail Clamp" part, which is a vixen style dovetail clamp, or youll need to print the "Saddle_Block" part which is simply a provision for you to mount your own alloy dovetail clamp.
I highly recommend buying metal 12T, 15T or 16T small GT2 pulleys. And to a slightly lesser extent, the 60T as well. I believe the larger axis pulleys can be printed without much added periodic error. But if youre really trying to cut costs, you can print the 15T and 60T pulleys included.
Youll need to add a spacer on top of the output shaft coming out of the NEMA17 bracket (gearbox). The spacer is needed to get the small pulley to teh same height as the big pulley. You may ned to tweak this a bit taller by stretching it in your slicer. Its a very quick print.
Lastly, youll need a way to connect your tripod and hold the RA shaft, which supports the entire tracker. I printed a simple 45º wedge that will hold the RA shaft. The shorter sides have a ~10mm hole, which I used to add a 1/4-20 metal insert. This allows for the relatively short threads of my tripod to grab into the metal insert rather than directly into soft plastic. Eventually I hope to design a proper adjustable Altitude-Azimuth base to replace this part.
Printing Notes:
Creality Ender 3 v2
Material: PETG
Nozzle Temp: 250º
Bed Temp: 75º
Bearing blocks were printed at 30% infill, 4 layer walls, top, and bottom.
Sidewalls and Pulleys were printed at 50% infill, 5 layer walls, top and bottom.
The one sidewall needs to be mirrored in your slicer to get the opposing side.
The 5x8 spacer can be stretched vertically in your slicer as needed
Assembly
It should be pretty easy to figure out how this thing goes together simply looking at the pictures. I'll try to sum up the steps anyway.
(2) Gear Box Assemblies
(2) Axis Block Assemblies
Counterweight shaft
Side plates
Tripod and Saddle
Electronics / Control
This part gets kicked over to the OnStep project. If youre unfamiliar, the main wiki should get you started. https://onstep.groups.io/g/main/wiki
This mount was designed to use the WeMos R32 / CNCv3 boards with OnStep. You can find more detailed information here: https://onstep.groups.io/g/main/wiki/19670
But to sum up, its mostly just snapping the two boards together, setting the microstep jumpers as needed, dropping the stepper drivers into the sockets, and connecting the stepper motor wires. Youll need to figure out how to get 12v to both boards. I typically solder some wire from the bottom of the wemos board, and insert into t he +/- terminals on the CNCv3 board. Or you can run 12v into them both individually. You can also power the WeMos via USB, however I try to use the USB socket as little as possible, since its delicate and prone to break off. For this reason, I prefer ASCOM over bluetooth.
Youll need to download the Onstep code, edit the config, and flash it to the WeMos. There's plenty of documentation available in the OnStep wiki, or on their users board. When flashing the config, dont forget to enable bluetooth if you plan to use a BT connection from your phone or laptop.
The included pulleys were created from Parametric pulley - lots of tooth profiles
by droftarts January 28, 2012. It can be found here: https://www.thingiverse.com/thing:16627
Some basic settings are as folows:
Teeth 172
Profile 12
shaft 18.3
m3 dia 3.6
hex 4
flats 6
depth 0
retainer 1
ht 1
idler 1
ht 1
pulley t ht 7
pulley b ht 10
pulley b dia 40
nuts 4
angle 90
distance 0
OK, That's about it. Feel free to ask any questions, or give me any feedback/suggestions you might have. Thanks and clear skies!
ADDITIONAL MODIFICATIONS / ADD-ONs:
Three Stage / 80T Pulley Mod - by physics23
Physics32 has generously contributed his modifications which add a third stage of reduction. He accomplished this by creating a piggy-back block to hold the additional belt reduction stage which attaches to the stock mount. The original motor blocks are simply run backwards. He modified the side plates with a window to aid in tensioning the 80T pulley, and modified the counterweight block for clearance. The 300mm axes tubes are long enough to accomodate the extra reduction stage as long as you havent cut them down, however a spacer is needed. Please reference the photos prefixed with "Mods - physics23" to see how this was assembled.
*5 Filess: *
Mods - 3 Stage GR 80T - add-on bracket.stl
Mods - 3 Stage GR 80T - nema17 add-on bracket.stl
Mods - 3 Stage GR 80T - Side Plate.stl
Mods - 3 Stage GR 80T - CW Block.stl
Mods - 3 Stage GR 80T - 18mm spacer.stl
3-Stage Mod instructions (refer to photos prefixed with "Mods - physics23"):
Recommended motor: 17ME15-1504S. This is a 400 steps motor, 38mm length. Any longer motor won't fit in the current Nema 17 add-on bracket.
Recommended materials:
6 x 12T pulleys
4 x 80T pulleys
4 x 180mm GT2 belt
2 x 400mm GT2 belt
10 x 605ZZ bearings
4 x 5mm shafts (90-100mm length, might need to be cut slightly depending on tripod mount)
2 x 176mm pulleys (3D-printed)
(2) Add-on bracket assembly
Tip: if there is friction in the rotation of the shaft, it means your printer is not perfectly calibrated and the three bearings are not perfectly aligned. This is most likely due to the "farther" bearing on the bottom of the add-on bracket. To remove the friction, one possibility is to remove the third bearing altogether. This shouldn't affect the functioning of the design too much. Alternatively, before inserting the shaft you can heat up the bottom bearing with a soldering iron until the plastic starts melting, then quickly insert the shaft through the 3 bearings+pulley before it cools down. This ensure that the third bearing aligns properly with the other two, removing the friction. Avoiding rotational friction of all shafts and axes is crucial for tracking precision.
(2) Attach the add-on bracket to the gear box
32º Tripod Block - by physics23
Physics23 has also created a lower angle tripod block which better suited his location.
*One file: *
Mods - 32 Degree Tripod_Block.stl
License:
Creative Commons - Attribution
GuitsBoy
