FERRETGame engine over Babylon.js
Ferret

Mechanisms and drivetrains

Skill ferret-physics-mechanisms · download all skills · SKILL.md

When to use#

A gearbox, a winch that cannot run back, a wind or water turbine, a brake, a flywheel.

The model#

A Drivetrain holds shafts (inertia J, friction b) joined by couplings (gear, belt, clutch, differential, worm, cardan). Nothing is free: each mesh passes on part of the torque, the rest is heat, and the network keeps the account. Drivers push torque, loads take it. A gear with a limit or a shaft with diameter and shear breaks (machine:break { element, torque }).

Steps#

  1. d.shaft({ name, J, b }), couple them (d.worm(...), d.brake(...)), drive with d.drive(shaft, torqueFn).
  2. Turbines and propellers: windTurbine, waterTurbine, propeller with cpCurve.
  3. Step: d.step(dt, substeps); tie to a scene body with bind (kinematic) or couple (dynamic).
  4. A worm whose lead angle satisfies tan λ < μ is self-locking.
  5. Commands: machine.info|set|state|step.

Check afterwards#

Work by drivers equals what loads took plus losses plus stored spin; a locked worm holds the load; a heavier flywheel ripples less.

What usually goes wrong#

  • Output does not move: a brake is on (command 1) or the motor drives the wrong shaft.
  • A shaft spins up without bound: no load and no friction, give b.
  • Everything shakes: huge inertia ratio at a coarse step; raise substeps.
  • bind throws: the body is not kinematic.
  • machine:stall appears only on shafts that have a driver.

Files#

  • reference/mechanisms.md — Gearboxes, differentials, clutches, brakes, turbines and propellers: how rotation is carried from a motor to a load, and what makes a part break.
  • reference/api-physics-mechanisms.md — every export of @ferret/physics-mechanisms with signature and doc comment
  • reference/commands.md — 4 commands of these packages with their arguments
  • recipes/machines-and-circuits.md — Six recipes: a lamp that surges and burns, a rectifier that smooths, a transformer, a wind turbine lighting a lamp through a generator, a winch that cannot run back, a flywheel that evens out a pulsing drive.