Gearworks

About this bench

I built Gearworks because a gear train is easiest to understand when you can push the parts around. Drag a gear toward another and it snaps into mesh, turning so its teeth meet the gaps. Put a motor at one end and the rest of the train follows it, each gear turning the opposite way to the one before it, at exactly the speed the tooth counts give. Racks, pistons, a lift and a pump jack turn that rotation into straight or up-and-down motion.

The bench opens with a train already running that shows every part, so you can see what it does before you touch anything.

The parts

Every part shares one tooth size, module 1 as LEGO Technic gears have, so a gear's pitch diameter in millimetres is its tooth count. An 8-tooth gear beside a 24-tooth one sits two studs (16 mm) apart.

Built the way Technic is built

• Every gear stands on a cross axle, and an axle stands in a hole of a beam. Drop a gear and a beam, an axle and its bushes come with it. A gear whose axle or beam is taken away, or moved from under it, is flagged red as unsupported and does not turn. An axle no beam holds is flagged red too.
• A bush sits on an axle at a level, to hold a gear on or to space an empty level. A pin stands in a hole two beams share and holds them together; a pin in a hole of one beam joins nothing and is flagged.
• Axle holes sit on a half-stud grid (4 mm), so gears sit on it too. Two gears mesh only where the distance between their centres is exactly the sum of their pitch radii and lands on that grid: an 8 and a 24 mesh two studs apart, a 12 and a 20 mesh two studs apart, and a 12 and a 24 do not mesh at all.
• A rack meshes the spur gears only (8, 16, 24 and 40 teeth), not the double bevels (12, 20 and 36). So does a worm.

Parts list

Every element in the build on the bench, with its part number, so you could gather them and build it for real. The bench updates this list as you change it. It shows the example build until you do.

The axle lengths assume the bench's pressed 2 mm beam, which sits a little lower than a real one. For a real build, take each axle the next size up (a 3-stud axle where this list says 2 studs): a beam, a gear and a bush together need the extra stud.

Where the part shapes come from

The Technic part shapes are modelled from the LDraw.org Official Parts Library, which is licensed under CC BY 2.0 and CC BY 4.0. Each shape has been simplified: logos are removed and the detail is rounded off, so a part is a close likeness, not a copy. Two changes are for the bench rather than the shapes: the racks' teeth are stretched 2% so they mesh the gears exactly, and a beam is pressed to 2 mm thick instead of its real 8 mm so the gears and shadows above it keep their heights. The authors of the parts below are credited as the licence asks. Gearworks is not affiliated with, or endorsed by, the LEGO Group.

Help with fitting

While you drag a gear, a dashed ring round each nearby gear marks the meshing distance, and a stack shows a ring on every level where it and a neighbour both have gears. The part snaps onto a ring and turns to meet the gaps. Near two rings it snaps to the point where they cross, so it meshes with both. A rack snaps so its pitch line meets a gear's pitch circle.

A part that would overlap something shows a red outline and says why, for example "It would overlap the 30-tooth gear". Dropped there, it goes back where it was. Tapping a part from the cabinet fits it beside the selected gear for you, and an attachment picks a direction that fits, which you can turn by 90°.

What it does and when it stops

• Meshed gears turn in opposite directions, and their speeds follow the exact tooth ratio.
• Gears that no motor reaches stay still.
• A train jams when its gears form a loop that cannot turn, or when two motors in it disagree. It shows a jammed stamp and says why.
• The rack has limit switches at the ends of its travel. Hitting one reverses the train's motors, and the stop lights up.
• The lift has none. Its cam turns with its gear, so the platform rises and falls as the tip comes round while the motor keeps turning one way, and the lift cannot jam the train.
• Two meshes between the same pair of axles, one on each level, at different ratios jam the train: the ring of meshes would need a gear to turn at two speeds at once.
• Teeth stay interlocked however long it runs: every position is worked out from one master angle, so nothing drifts and no tooth passes through another.

Reading the colours

• Copper. The motor, a small boiler with a chimney. It drives the train.
• Brass. A gear a motor is turning.
• Steel. A gear that is not connected to a motor, so it stays still.
• Blued steel. The rack, the sliding bar.
• Axle black. A clutch gear a driving ring has locked to its axle. The clutch gears beside it that no ring locks turn free, in brass or steel.
• Dark brass. A piston, upright wheel, lift or pump jack.
• Red. A jammed gear, or where a part would overlap something.

Select a part and a specimen label opens with its teeth, pitch diameter, speed, mesh count and speed relative to the motor, plus its controls. The Speeds button prints each gear's rpm and direction, and the rack's and the lift's speed, up or down, in millimetres a second.

Controls

• Drag empty space to turn the view. Pan with two fingers, or Shift-drag, or right-drag. Pinch, scroll or use + and − to zoom. Arrow keys turn the view; 0 is Home, 1 Front, 2 Top, 3 Angled.
• Drag a part to move it, or tap it in the tray and then tap where it goes. R turns the selected part, Delete removes it, Ctrl or Cmd+Z undoes, Esc cancels.
• Drag a part off the bench to remove it. A driving ring slides instead: drag it along its axle to lock the gear above or below it, or to neutral. Its place is also a row of buttons in the panel, for the ring and for the stack it stands on.
• With a part selected, the arrow keys move it a grid step and, for a gear, plus and minus change its teeth. Space runs or pauses.
• Clear empties the bench and Undo brings back what was there. Example loads the starting train again.
• The bench is remembered on this device. If your device asks for less movement, the bench starts paused.