Free · paper model & 3D print · Category V, Chapters 1–2

Build al-Jazarī's quarter-gear water machine

A desk model of the machine al-Jazarī described in 1206. Turn the crank: a gear with teeth on only a quarter of its rim lifts a ladle, then lets it fall. Put four on one axle, a quarter turn apart, and one ladle is always rising.

What you'll make

The model keeps al-Jazarī's own parts: a quarter-wheel with four teeth on one quarter of its rim, a runged (lantern) wheel below it, and a ladle fixed to the lower axle. In place of the animal on the upper deck, you turn a crank. The square upper axle is the trick for the four-ladle version: slide each quarter-wheel on turned 90° from the last, and their teeth come round one after another.

Downloads

Download	Size
Cut-out templates and instructions (PDF, 4 pages, Letter/A4) al-jazari-quarter-gear-build-kit.pdf	110 KB
All STL files for 3D printing (ZIP) al-jazari-quarter-gear-stl-files.zip	64 KB
Quarter-wheel · print 4 al-jazari-quarter-wheel-x4.stl	164 KB
Runged wheel with ladle · print 4 al-jazari-runged-wheel-with-ladle-x4.stl	146 KB
Side frame · print 2 al-jazari-side-frame-x2.stl	21 KB
Crank · print 1 al-jazari-crank-x1.stl	39 KB

Free under CC BY 4.0: print, share and remix, crediting “Ibn al-Jazari channel”.

You need

• Paper model: card or cereal-box cardboard, glue, a craft knife and ruler, 15 toothpicks per runged wheel.
• 3D print: PLA, 0.2 mm layers, 3 walls, 20% infill, no supports. The rung pins print in place. The frame is 242 mm tall: print it diagonally on a small bed.
• Axles: a ¼ in (6.4 mm) square dowel on top, a 6 mm round dowel below, plus a small board as the base and, if you like, a shallow dish of water under the scoops.

Steps

1. Print or 3D-print the parts. Print the PDF templates at 100% (check the 50 mm bar) and glue them to card, or 3D-print the STL files: 4 quarter-wheels, 4 runged wheels with ladles, 2 side frames and 1 crank.
2. Make the wheels. Cut each wheel from 2–3 glued layers of card. Keep the quarter-wheel teeth crisp and cut its square hole tight.
3. Fit the rungs. Push 15 toothpicks through both flanges of each runged wheel to make a lantern wheel. Printed wheels already have their pins.
4. Stand the frames. Glue the two side frames to a base board, about 50 mm apart for one ladle or 115 mm for four.
5. Fit the lower axle. Slide the 6 mm round dowel through the lower holes with the runged wheels on it; they must swing freely.
6. Fit the upper axle. Slide the ¼ in square dowel through the upper holes with the quarter-wheels on it, each turned a quarter turn from the last, right above the runged wheels.
7. Turn the crank. Fix the crank to the square axle and turn it. Each quarter-wheel lifts its ladle for a quarter turn and lets it fall; with four, one ladle is always rising.

Why it works

The quarter-wheel's four teeth are spaced exactly like the rungs below (16 tooth positions against 15 rungs), so while they pass through the rungs the lower axle turns and the ladle swings up. When the last tooth slips free nothing holds the ladle: in al-Jazarī's words, it “descends again to the pool with great force”. With one wheel the ladle is idle for three quarters of every turn. With four, each a quarter turn round from the last, as one ladle lets go the next tooth takes hold, and the crank, like al-Jazarī's animal, pulls a steady load.