From the Loftsmith Workshop
Galton board for 3-6 mm balls, flip to reset
A desk toy that shows how chance builds a bell curve. Tip it over and the balls funnel through a triangle of pegs, then pile up in a hump at the bottom. Flip it again to reset. Change the ball size and peg rows to suit the balls you have.
3 parts · 95 g · 132 × 65 × 183 mm
Ask for the sizes you want to tweak, e.g. “make the width adjustable”.
How to print it
Parts
- board · PLA · Flat on its back, pegs and walls pointing up (printRotate -90,0,0). No supports.
112 x 179 x 13.3 mm at the defaults; about 64 g, 88 min. PLA because it is an indoor desk toy and stiff PLA gives crisp small pegs (2.7 mm at the defaults, 2.25 mm with 3 mm balls). Needs a 0.4 mm nozzle.
- cap · PLA · Front face down (printRotate 90,0,0).
About 5 g, 11 min. Closes the top end over the cover sheet; print it in the accent colour. Its rolled front edge and countersinks touch the bed and overhang slightly; the engine estimates no support is needed.
- stand · PLA · Flat as shown, slot up.
About 27 g, 40 min. Low tapered plinth, 132 x 65 x 12.5 mm at the defaults, with a slot 0.4 mm wider than the board on each side; the board sits in it either end down.
Print settings
- Layer height
- 0.2 mm (0.16 mm gives rounder pegs with 3 mm balls)
- Walls
- 2
- Infill
- 15%
- Supports
- None
- Notes
- All three parts at 2 walls / 15% infill: about 98 g and 2 h 23 min in PLA (board ~64 g, stand ~27 g, cap ~5 g). With 3 walls / 15% it is about 133 g and 3 h 13 min. At the default sliders each part fits a 180 mm bed. Each slider at its own maximum fits a 256 mm bed; combining large balls with many r
Hardware
- 2 × M3 x 10 countersunk screw · Self-tapping into 2.6 mm pilot holes in the board's top end; 3.9 mm bite at the defaults. Use M3 x 12 with a 2.5-3 mm cover sheet (the Cap screws bite check names the length for your settings).
- 2 mm clear acrylic sheet, 99 x 165 mm · Size for the default sliders; the Cover sheet captured check shows the cut size whenever you change ball size, rows, ball count or gap. A printed PETG plate of the same size also fits, but it is trans
- 70 × 4 mm steel bearing balls or glass beads · Match the Ball diameter and Number of balls sliders (3-6 mm, 40-140 balls).
Assembly
- Print the board on its back, the cap front-face down and the stand flat. Peel the protective film off the acrylic sheet.
- Lay the board flat and drop the balls into the bins or the reservoir.
- Slide the sheet in from the open top end along the two side grooves until it seats in the groove at the bottom end.
- Fit the cap over the top end so the sheet's edge goes into the slot under it, then drive the two M3 countersunk screws into the pilot holes. Stop when the heads are flush; PLA strips if you overtighten.
- Stand the board in the stand. The balls run from the reservoir through the pegs into the bins.
- To reset, lift the board out, turn it upside down in its own plane and set it back in the stand. The balls roll down the funnel underside, through the neck and into the reservoir. Turn it back over to run again.
Good to know
- The engine checked the geometry, not the distribution: how close the bins get to a bell curve depends on friction, ball finish and how level the board stands, so the result has not been tested.
- Small balls are a choking hazard; this is not a toy for young children.
- If balls bridge across the funnel neck (9.6 mm at the defaults), a light tap on the board frees them.
- The acrylic cut size changes with the ball, rows, balls and gap sliders; read it from the Cover sheet captured check before ordering.
- Ball sizes are limited to 3-6 mm because larger balls would need a board taller than 256 mm. At 6 mm balls (other sliders at default) the build logs a 251.3 mm tall board, so it needs a 256 mm bed; adding rows or balls on top of 6 mm balls can exceed the bed, which the Fits a 256 mm bed check report
- Ball and cap screw fits assume typical PLA shrinkage; the stand slot leaves 0.4 mm per side.
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