Plate 01 · A working model

Overshot
Gristmill

Water falls into the buckets and its weight turns the wheel. The gears turn the stones eighteen times faster, and the stones grind.

T + 0.0 s

Runner speed

Band: 110–130 rpm, where millers kept the stones

Drag the dial to turn the model

0°

Drag to orbit · Scroll to zoom · Click any part

Cutting stone

00Try a scenario

One click

Each one sets the sluice, the stones and the feed, then lets the physics play out.

Sluice gate

Gate opening a80 mm 075150

How far the sluice is drawn. More opening means more water in each bucket.

Head over the gate H0.60 m 0.20.61.0

Depth of water behind the gate. It sets how fast the jet leaves, and so where it lands.

4.8 m · 36 buckets

water, bucket model load now

1 : 18

Shaft	Teeth	rpm	Torque
Wheel shaftpit wheel	84	–	–
speed ×3, torque ÷3, less 7 % in the face gearing
Uprightwallower, great spur	28 · 108	–	–
speed ×6, torque ÷6, less 5 % in the spur gearing
Stone spindlestone nut, per pair	18	–	–

The gears trade torque for speed. The wheel turns slowly with great force, and the stones need speed. About – kW goes to friction on the way.

1.22 m French burr

Each pair in gear adds its load to the wheel. Lift a stone nut out of gear to stop that pair.

Grain feed ṁ, per pair180 kg/h 0150300

More grain means more meal, and more load on the wheel.

Stone gap Δ0.80 mm 0.10.81.5

Closer stones grind finer, but each kilo takes more energy and the meal runs hotter.

kW, to scale

Fig. 2: Power from the falling water to the grinding, with what is lost at the wheel and in the gears.