laserpuzzle Open the app

Gear train generator Pro

Ask for a ratio and get the gears, in a frame with a crank and a dial.

Open Gear train in the app Pro generator: explore its settings in the app; cut files come with the Pro plan (coming soon).
Two large laser-cut gears and a small pinion in a frame with a crank

In short: Involute spur gears that turn the ratio you ask for: the solver picks the tooth counts for up to three stages. Laminated gears on rod axles in a frame, a crank on the input and a pointer over a dial on the output. Checked for clean meshing and for collisions while it turns.

Enter the ratio you want and the generator works out a gear train that turns it: a solver picks the tooth counts for up to three stages, so a 1:20 reduction becomes something you can actually cut, rather than one tiny pinion and one enormous gear.

The gears have true involute teeth. Each is laminated from several sheets and pressed onto a rod axle that turns in a frame. A crank drives the input, and a pointer on the output moves over an engraved dial, so you can see the ratio at work.

Gears are unforgiving of small mistakes, so the design is checked for clean meshing (no interference, enough teeth in contact) and for overlaps while the crank turns a full circle. It makes a good desk demonstration of gearing and a base for your own mechanisms; the automaton is built on it.

You need: plywood, steel rod for the axles, and glue. Cut the fit test to get the rod holes right.

Settings

All of these can be changed in the app, and the 3D preview updates as you type. The name under each setting is its key in a share link, e.g. https://laserpuzzle.app/app/#/gears?ratio=…; a link only needs the settings that differ from the defaults.

Gears

SettingDefaultWhat it does
Ratio
ratio		12Crank turns per turn of the output. Above 1 slows down (more force), below 1 speeds up. From 0.03 to 200.
Ratio tolerance
tolerance		0.5%How far the real ratio may be from the one asked for. Fewer stages and smaller gears are chosen within it. From 0 to 20 %.
Stages at most
max_stages		3Pairs of meshing gears. Each stage turns up to 6:1. From 1 to 3.
Output turns
direction		eitherDirection of the output relative to the crank. Every stage reverses it. Options: either, same, opposite.
Tooth counts (optional)
train		—Set the train by hand instead, as driver:driven per stage from the crank, e.g. '12:36 15:45'.
Fewest teeth
min_teeth		12Smallest gear the solver may use. Pairs that wouldn't mesh cleanly are skipped anyway. From 6 to 100.
Most teeth
max_teeth		60From 8 to 200.
Module
module		2.5 mmTooth size: pitch diameter = module x teeth. 2.5-4 mm suits 3 mm plywood. From 1 to 10 mm.
Pressure angle
pressure_angle		20 °25 deg gives stronger teeth and allows smaller pinions; 20 deg runs a little smoother. Options: 20, 25.
Backlash
backlash		0.15 mmEach tooth is this much thinner at the pitch circle, so the gears don't bind. From 0 to 1 mm.
Gear thickness
layers		2 sheetsSheets glued together per gear. Thicker gears mesh more reliably. From 1 to 4 sheets.

Frame

SettingDefaultWhat it does
Layout
layout		straightStraight keeps the axles level, for a low frame; zigzag folds them up and down, for a shorter one. Options: straight, zigzag.
Crank on the input
crank		onOff: the input axle sticks out at the front instead, to drive it from something else.
Pointer and dial on the output
pointer		onOff: the output axle sticks out at the back instead.

Pins

SettingDefaultWhat it does
Pin diameter
pin_diameter		4 mmMeasured diameter of the dowel or rod used for the axles and the crank handle. From 2 to 8 mm.
Press-fit hole offset
press_fit		-0.1 mmHole = pin + this, where a pin is fixed (and in the wheels). Find it with the fit-test hole strip. From -1 to 1 mm.
Axle hole offset
axle_fit		0.2 mmHole = pin + this, where an axle or shaft turns, or a pin has to come out by hand. From -0.2 to 1 mm.

Plus the material and machine settings every generator has: material thickness, kerf, slot clearance, sheet width, sheet height, part spacing, engrave part labels, cut line colour, engrave line colour.

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