Marble Machine - a free 3D model from Shapekit

A marble machine that keeps running. An N20 gear motor in the base turns a screw lift, which picks up one marble per turn and carries it up a channel to the top. From there it rolls along the first track and drops onto a rocker. The rocker tips under each marble, so they go left and right in turn, down short tracks, along the lower track and back along the feed track to the lift, where a few wait their turn. Nine 16 mm glass marbles keep it busy. Every track is a V-groove, so the marbles run straight and steady. The parts hang on pegs on the board and the board stands in the base: no screws and no glue.

Parts (each STL is already placed the right way up for printing)
- marble-machine-base.stl: A hollow plinth, 30 mm tall. The motor drops into a pocket under the screw with its gearbox flush with the top, the board stands in a slot, and the battery box sits in a tray behind the board. Print: Upside down, its top on the bed. No supports: the slot, the motor pocket and the tray print as bridges.
- marble-machine-board.stl: The pegboard everything hangs on: Ø5 pegs for the column and the tracks, a long pivot peg and two stop pegs for the rocker. Print: Flat on its back, pegs up. It needs a 210 × 200 mm bed.
- marble-machine-lift-column.stl: The lift in one piece: the floor where marbles wait to be picked up, the channel they climb in, the bearing for the top of the screw and the first track, which ends in a drop above the rocker. Print: Lying on its back, the side that touches the board on the bed.
- marble-machine-screw.stl: Ø42 mm flight with a 24 mm pitch on a Ø18 mm shaft: one marble per turn. A D-socket at the bottom takes the motor shaft, a pin at the top turns in the column's bearing arm. Print: Standing on its bottom end, no supports: the underside of the flight is 45°. It is 183 mm tall.
- marble-machine-feed-track.stl: The bottom track, from the right-hand end back to the lift. The marbles wait in a row at its end. Print: Lying on its back.
- marble-machine-lower-track.stl: Catches the marbles from both sides and drops them onto the feed track at the far right. Print: Lying on its back.
- marble-machine-left-track.stl: A short track from the rocker's left arm to a drop onto the lower track. Print: Lying on its back.
- marble-machine-right-track.stl: The same on the right: from the rocker to a drop onto the lower track. Print: Lying on its back.
- marble-machine-rocker.stl: The flip-flop switch: a short V-groove with a fin on top. It rests 15° to one side; a marble lands beside the fin on the raised arm, tips it over and rolls off the other end. Print: Lying on its back, the pivot hole upright.
- marble-machine-rocker-cap.stl: Pushed onto the tip of the pivot peg, it keeps the rocker on. Print: Flat.

Also needed (not printed)
- 9 glass marbles, 16 mm: the standard size. 8 to 10 marbles work.
- An N20 gear motor, 6 V and 100 RPM, with a 3 mm D-shaft. On two AA batteries it turns the screw at about 50 RPM, nearly a marble a second.
- A battery box for 2 × AA with a switch, at most 70 × 37 mm (most are 58 to 66 × 32 to 35 mm), and two wires to the motor; solder them on or use a motor with wires already attached.

Print settings: 0.4 mm nozzle, 0.20 mm layer height, 3 walls, 15% gyroid infill, PLA or PETG material.

Assembly
1. Print the parts: Nothing needs supports. Print the base upside down, the board flat with its pegs up, the column, the tracks and the rocker on their backs, and the screw standing up. Clean the ends of the pegs so they slide into the holes.
2. Fit the motor: Lead the motor's wires through the slot at the bottom of the motor pocket and up through the hole in the battery tray. Push the motor into the pocket, shaft up, until its gearbox is flush with the top of the base. Connect the wires to the battery box and lay it in the tray.
3. Put the screw on: Push the screw's D-socket onto the motor shaft. It stands upright by itself for now.
4. Hang the parts on the board: Lay the board on its back. Press the lift column onto its five pegs and the feed, lower, left and right tracks onto theirs. Slide the rocker onto the long peg and press the cap onto its tip; the rocker should tip freely from one stop peg to the other.
5. Stand the board in the base: Hold the board upright and lower it into the slot in the base, guiding the pin at the top of the screw into the hole in the column's bearing arm.
6. Run it: Switch on: seen from above, the screw should turn clockwise. If it turns the other way, swap the two motor wires. Lay the marbles on the feed track; the lift takes one on each turn.

Safety: Marbles and small parts are a choking hazard: keep them away from young children. Take the batteries out when it is not running.

License: Creative Commons Attribution-NonCommercial 4.0 (CC BY-NC 4.0)
https://creativecommons.org/licenses/by-nc/4.0/
Print it, remix it and share it, as long as you credit Shapekit and don't sell the files or the prints.
