Mechanical & Aerospace
Gear Train Lab
Set the tooth counts and the gears mesh and turn in real time at their correct relative speeds and directions. A bigger driven gear trades speed for torque (gear reduction); a smaller one overdrives. Drop in an idler and watch it flip the output direction back without changing the ratio at all — the classic gotcha. The readouts give the ratio, output speed, torque multiplication and direction.
2.00 : 1
Gear ratio
30 rpm
Output speed
2.00
Torque ×
Reversed
Direction
The method, with your numbers
Gear ratio = tooth ratio
- 1
Gear ratio from the tooth counts
i = N_driven / N_driver
i = 36 / 18 = 2 : 1
Ratio above 1 is a speed reduction: the driven gear is bigger, so it turns slower but pushes harder.
- 2
Output speed
ω_out = ω_in / i
ω_out = 60 / 2 = 30 rpm
- 3
Torque multiplication (ideal mesh)
τ_out = i · τ_in
τ_out = 2 · τ_in → ×2
Power P = τ·ω is conserved through an ideal mesh, so whatever factor you lose in speed you gain in torque — that trade is the whole point of a gearbox.
- 4
Spin direction (each mesh flips it)
direction = (−1)^meshes
(−1)^1 → reversed
One mesh: two directly meshing gears always counter-rotate. Toggle the idler on to restore the input direction.
Drag any control above — every number here recalculates. Want this method for any problem? Step Sheets →
A bigger driven gear trades speed for torque (and vice-versa). An idler flips the direction back — but, surprisingly, doesn't change the ratio at all.
How to use this simulation
Set the tooth counts and the gears mesh and turn in real time at their correct relative speeds and directions. A bigger driven gear trades speed for torque (gear reduction); a smaller one overdrives. Drop in an idler and watch it flip the output direction back without changing the ratio at all — the classic gotcha. The readouts give the ratio, output speed, torque multiplication and direction.
Everything runs in your browser — no sign-up, no download. Change a value and the result updates instantly, so you can build a feel for how each input shapes the outcome. It pairs with Crameleon's practice exams and step sheets when you want to go from intuition to working the problems.