A Gentleman's Orrery

The title "A Gentleman’s Orrery" is meant to evoke the idea that during the Enlightenment, intellectual pursuits and scientific tools like the orrery were often associated with the educated, elite class—particularly gentleman who had the resources and leisure to engage in intellectual activities. The term "gentleman" in that period was not just about social status, but about being cultivated, well-versed in philosophy, science, and the arts.

This project is about a planet spinner that has the looks of an orrery of the period, but mechanically works very different. It is mainly made of brass and is perhaps a bit complicated to duplicate as is, but hopefully this will inspire you to make a similar one using different materials (wood, 3d print, acrylic etc). Therefore this instructable mainly gives you the dimensions of the parts so you can easily enlarge them as needed. I challenged myself by making it pretty small.

1. battery, with high output current (so the voltage doesn't drop when the motor runs)
2. Seeed studio Xiao esp32c6 (its a tiny cpu, and has a battery charging circuit on the pcb)
3. low voltage stepper motor controller, STSPIN220 that runs on 3.7 V
4. surprisingly cheap touch controller ( 10 of them for $1.40)
5. 4mm magnetic power connector
6. A tiny stepper motor that runs on the 3.7 V from the battery. (i have the 42 reduction but I probably replace it with the 118 reduction, as the motor sometimes stalls due to friction).
7. reed switch
8. 10k Ohm resistor. (to pull down the STBY pin of the motor controller)
9. miniature gears (2 x 12 teeth, 2x 8 teeth, both 0.3M)
10. gear, 10 teeth, 2mm hole
11. brass tube 1mm, 0.1mm wall thickness (for moon/earth, from local hobby store)
12. brass rod 0.8mm diameter (axle for moon/earth, from local hobby store)
13. brass tube 2mm, 0.5mm wall thickness (the vertical parts holding the planets)
14. brass rod 1mm (arms to planets), brass rod 4mm (central column, from local hobby store)
15. brass rod 10 mm (for the bridge central screw)
16. earrings in various sizes for the sun, moon, and planets
17. brass sheet 3mm, 2mm, 1.5mm, 1.0mm, 0.5mm (ali, amazon)
18. tiny magnet (1mm thickness max, 4mm diameter max, I had one laying around)
19. tiny screws
20. some rubber parts (I cut them, and used three of them as feet)

for equipment I mainly used a 3-in-1 3d printer that has, besides 3d print head, a cnc and a laser. As an extra I used the rotary add-on for making gears, and lasering the side.

this is a 2mm thick brass disk displaying the signs of the zodiac and the calendar months. I used my 3-in-1 3d printer to make this. The printing head can be exchanged for a cnc head or a laser head. To make the engraving of this disk, the cnc head was used with a small 0.2mm v-bit. The small point made it possible to make the fine engravings. I used a crude line drawing I found on the internet of each of the zodiac symbols and asked an AI to create a smooth looking grey scale image. That went pretty well, however the AI wasn't capable to generate a height map (used for the engraving depth) directly. So I used the image to 3d converter at makerworld.com to generate an acceptable 3d model from those images. Then loaded those images in 3dsmax to scale them down to size and flatten them to approximately 1mm height. The result can be found in the attached fusion 360 file zodiac.f3d. I went pretty slow with the engraving in brass, because the printer isn't really sturdy enough to handle a cnc job in metal. So the speed was set to 40mm/min. The stepdown of 0.01mm was used to capture as much of the details as possible in the contour. The other file is used to engrave some text onto the brass.

Next I used the cnc to create a blank for a gear with 48 teeth (for some reason I named it dial, can't remember why). Screwed it onto a thick brass rod and put it in the rotary attachment. I used chatgpt (because I don't speak python) to help me create a program that would run a 40 degree, v-shaped endmill across the blank so it made the perfect (almost perfect) involute tooth profile (I don't have the skills to make this into a generic program for any gear). Unfortunately the system doesn't allow me to add a python file to this instructable.

Tap some M2 holes in the zodiac disk and screw this gear to the zodiac disk, making sure it is perfectly centered and the top of the screws is flat with the gear surface.

The outside is made out of 0.5mm brass. The bottom is cut using the cnc and has an opening for the power connector.

I had a cheap mini vice lying around, which due to its low quality was never used, but using some ball bearings I turned it into a metal roller, that makes a nice circular ring by simply moving it back and forth between the rollers and slowly tightening the vice. then I soldered the ring to the bottom plate, but the almost at half the ring height. And closed the ring using some solder as well. If you do it carefully and do some sanding afterwards, the seem in the ring becomes almost invisible. Next I used the Infrared Laser, to engrave the moon phases on the brass, together with a scale per day (it takes 29.53 days to complete a moon cycle). You can use the supplied image to do the same (btw I created this image using 3dsmax for accurate phases, but it turns out that close to new moon or full moon, the correct phase are almost indistinguishable for the new or full moon, so I cheated a bit to make it look visually appealing). The little knob an top of the zodiac disc will match up with these moon phases.

Cut the extra part from the ring using a Dremel and use a file to make it look nice.

The inside holds all the electronics, the battery and the motor. The structure itself is 3d printed. The main item is the motor. Drill a 2.9 mm hole in the 10 teeth gear (which has a 2mm hole). Cut the axle of the motor to 4mm. Heat the gear in a flame (this will make the hole larger) and push it onto the drive shaft of the motor. When it cools down it sits as tight as possible. The motor itself was temporarily disconnected from the reduction gears, and rotated 180 degrees to put it back in place. This is to make room for the connecting wires.

The motor doesn't take the full height of the structure, which leaves room for the touch controller that is placed underneath the motor.

The battery and the esp32 are stacked on top of each other. The structure has the side open next to the esp32, so it is possible to slide it out, even with all the wires connected. That way you can use the usb port for the programming. The stepper motor controller fits on its side on the other big opening. Remove the pull up resistor from the board. We use a 10k pull down resistor on the STBY pin. There is a little ridge on top of the structure, this is the place for the reed switch. Note there is a big grove going around the structure. This is for the wiring (one pair of wires for the reed switch, and one pair for the power), at the bottom there is room for the wiring from the touch controller.

I used some of these brass inserts for M2 screws and melted them in the structure. With the tiny screw, the brass bridge is hold in place. If you look at the image you can see some central part sticking out. This flange nut I made from the 10 mm rod, and made the top part smaller so it fits through the hole in the bridge. It sticks out of the bridge by 4mm. In it's center there is a m4 threaded hole. The central axle will be attached here and the zodiac disk with its gear rotates around this.

The central column consists of the 4m rod, with a m4 thread added at the bottom, and a smaller 2 mm part with m2 thread at the top. A 1 mm groove is added to the side using a cnc endmill. There are little rings that rotate freely around this column, to which the 1 mm arms to the planets are attached. The rings are made using the cnc, and the tiny 1mm hole for the arm were made using a 1 mm drill. The 1mm arm is bend upwards at the end for about 4 mm. A piece of the 2mm rod slides over this bend arm, but only after I made a small slot at the end using a dremel. This way a tiny piece of the 2mm rod sticks out. A small piece of 1mm rod is superglued inside this end (have a look at the video in the beginning again). This is the piece that grabs the other planet's arm when rotating.

in between the rings are separator disks with a small tab that fits into the groove. This prevents the planets from rotating, when a planet below it starts rotating. The little ears around the tab have no function accept that the give the 1mm endmill the room to make the tab. I named the parts venus, but you have to make them for all the planets accept for mars and earth.

Mars is special is it needs to make room for the tiny bevel gear inside. Use some loctite to secure the bevel gear inside the gear-part1.

Make the earth 4.14 part using the cnc and continue to the next step.

The tiny gears with 8 teeth have a hole that is 1mm in diameter, but our axle is a 0.8mm rod. In order to make them fit, cut about 10mm from the 1.0 mm tube, and glue that into the gear using loctite. The 10mm isn't needed but it helps to hold the gear while gluing it. Use a file to remove the rest of the tube when you're done gluing. The central part of of the gear inside the central part (on the right in the picture above) is a bit to high. Use a file until it fits comfortably inside the disk for the earth arm. Now it is time to mount the arm. First push the tube a fraction of a mm into the disk (to prevent glue from going inside), then apply some loctite and push it in further. Next put the tiny gear in position and guide the 0.8mm rod thru the tube and the center of the gear, push it 2 mm further than needed, and carefully apply a tiny bit of loctite. Then pull the rod back so it matches the end of the gear.

Take a piece of 2mm tube, and near the bottom drill a 1mm hole. This tube holds the earth and you glue it to the 1mm tube. The 0.8 mm rod sticks out at the other end, and this is where the other 8 teeth gear goes. For the moon I used a piece of 1mm thick brass in some nice shape. Drill a 3mm hole in the center and glue the 12 teeth bevel gear in it, with the teeth on the down side. At the other end drill a 0.8mm hole and glue the moon in place.

Carefully mount everything together, add some acid free oil, to make it rotate as smooth as possible. Screw the moon ring to the bottom of the central column. Then, screw the central column in place. Slide a normal ring than the disk for Neptune followed by a separator disk. Keep adding planets disks and separator disks until you reach Mars, and add the Mars disk with the gear part. Next comes the earth moon system. Add Mercury disk to the sun column, a separator disk, Venus disk and another separator disk. Then screw the sun column to the central column. It should be a tight fit, but still allow the planet disks to rotate freely.

For now I adapted some of my software from my other planet spinners, but added support for a deep sleep mode (for both the esp32 and for the motor controller). However honesty is a good thing, and the software isn't finished yet. It rotates the planets fine, but doesn't calculate the correct planet orientation yet, nor does it calculate the moon's orientation. (previous implementation fetched the data directly form NASA, but I want this version to run on battery and to save battery I don't want to use WiFi). For now it used some fixed values. Calculating the orientation based on a given date is pretty easy, and should be done within a week. The touch sensor will be used to enter the date, after which the esp32 will remember it as long as there is some power in the battery. Of course the software will be made available here. So have a look at the current, included version, which already runs fine, and was used for making the video.

As an alternative, I took a piece of soapstone (a very soft material, easily scratched with your nails), and used a pair of big hole drills that only cut around the edge of the hole. Using the cnc I engraved 16 indentations for the phases of the moon. The Moons were first colored dark brown using the Infrared laser, then cut with the cnc. I drilled a hole for behind the full moon, for a wire that goes to the touch sensor. The above brass version, simply fits inside this stone version. This also explains the bit long wires on the power connector. You can loosen the power connector from the brass version and thread it down the extra hole in the 3d printed structure. Now the power connector can be used with the stone version.

I'm still not sure which version I prefer. The stone one or the brass one. Let me know which one you prefer.

Now you might get the impression that I'm a fine machinist, but really I'm not. I'm just a hobbyist who learns from failures. Let the above image illustrate that, as ideally I needed only 8 disks for the planets, but clearly I wasted many of them. I don't make very detailed plans, and the plans I do make change while making them. I just love making thinks.