Gear ratio& meshing.

A simple gear train for shop and engineering class. Name the driver and the driven, count teeth, and watch one tooth take the next space.

N drivenN driver Bigger driven gear, slower output, more torque. The idler changes direction and drops out of the ratio.

Setting the gear train on the bench…

Lesson Shop / engineering: gear ratio & meshing

Drag to look around the mesh. Brass marks track one tooth on each gear.

02 Bench Shop / engineering: gear ratio & meshing

Count the teeth.

Same module on every gear, so a larger count is a larger pitch circle. Only the end gears set the ratio.

Driver 16 T Idler 24 T Driven 40 T Driver rpm 7

03 · What to notice

Teeth in mesh

Each mesh is external: a tooth enters a space and the next gear turns the other way. Pitch circles stay tangent. The small gap is backlash so the teeth do not bind.

The idler reverses direction and cancels out of the ratio. Driver and driven turn the same way. Gear ratio still uses only N driven / N driver.

Try this

Pause on Reducer. Predict the driven turn count after the driver mark goes around once (0.40). Reset turns, play, and check the counter. Then change only the idler. The ratio should sit still. Turn the idler off and watch the driven mark reverse.

04 Shop floor Ten minutes at the bench

Ten minutesat the bench.

Use this page as the model next to a real pinion and gear. The classroom use is gear ratio and meshing, not a rendering study.

04.1

Learning objectives

Compute gear ratio as N driven ÷ N driver.
Predict output speed and whether torque rises or falls.
Explain that equal module is what lets unlike gears mesh.
State that an idler changes direction and not the ratio.

04.2

Classroom loop

Hand out the Reducer tooth counts. Students compute 40 ÷ 16 before looking at the readout.
Uncover 2.50 : 1. Ask how far the driven gear turns after one driver turn.
Run the train. Stop near one driver turn and compare the counter.
Move only the idler. Ratio stays. Then remove the idler and name the new direction.

04.3

Shop examples

Lathe change gears, a drill-press reduction, a clock train. This exhibit is spur gears in external mesh. It leaves out friction, shaft windup, and chain drives such as a bicycle.