Order 1 of 10
The Barrel
Train readout
- Ratio
- —
- Hand
- —
- Escapement
- —
- Torque
- —
The mark wants 4.00 rpm, turning with the barrel.
Choose a wheel from the tray, then tap a seat on the plate.
A bench for promises about ratios
Pinion
A clock is a promise about ratios. You are the one who has to make it true: lay wheels on the plate until the escapement turns at the mark, the right way round, without snapping a tooth.
- Seats are cut for a sum. Two wheels mesh only when their teeth add up to sixteen times the width between them. The number scribed on the plate is that sum.
- A mesh reverses. A belt spans any distance and does not; a belt crossed over itself does.
- Torque grows where the train slows. A wheel carrying more than it can break glows, and then lets go of a tooth.
Ten orders on the bench. None wound yet.
The bench manual
How a movement works
The seat. A wheel of N teeth has a pitch radius of N sixteenths. Two wheels mesh when their radii add to exactly the width between their seats, so their teeth must sum to sixteen times that width. The number on the plate is the sum the seat will accept. Wheels on the same plane that overlap cannot both be fitted; wheels on different planes pass over each other.
The mesh. A mesh turns the far wheel backwards and swaps speed for torque. An open belt takes any two pulleys at any distance and keeps the direction. A belt crossed over itself reverses, like a mesh.
The double seat. Two wheels on one arbor do not cancel — they multiply, because the wheel that is driven is not the wheel that drives. That is where every useful reduction lives. A double seat always needs a belt, since two meshed neighbours would force both its wheels to the same diameter.
Torque. Torque times speed is what the spring supplies, so torque rises exactly where speed falls. Each wheel has a breaking torque; the load is shown against it. Past 100% the wheel glows, and after a moment of it the teeth snap.
The loop. If two roads deliver the same arbor at different speeds, the train locks solid. A closed loop with an odd number of reversals in it always does.
The spring. It runs down while you fit, and three times faster while the train is turning. When it is empty the movement is dead.
Held
The bench is still
The spring is not running.
Order 1 of 10
The hand keeps the mark
The bench