Plan a mill’s week from the grain the village eats and the kilograms an hour its power can grind: 100 people eating 1.5 lb of grain a day need 68 kg a day and 476 kg a week. A 3 m, 0.2 m3/s overshot wheel mills that in about 2.3-9.2 hours a week, a single horse would need 12-72 hours, and the mill should run only 2-3 days a week so flour is never older than 1-2 weeks.
Part of Community Grain Mill
Turning a mill’s capacity into a working week: how many hours the village’s grain takes, how a milling day is run, and what to record.
Hours Of Running Come From Two Numbers: Need And Rate
The carrier gives the need: 1.5 lb of grain per person a day, so a village of 100 needs 150 lb, which is 150 x 0.4536 = 68 kg a day and 68 x 7 = 476 kg a week. The rate is the kilograms an hour the power gives at the stone (Bushels per Hour by Power Source). Hours a week are need divided by rate.
| Power source | Rate (kg/h) | Hours per week for 476 kg |
|---|---|---|
| Overshot wheel, 0.2 m3/s, 3 m head | 51.6-206.6 | 476 / 206.6 = 2.3 up to 476 / 51.6 = 9.2 |
| 20 ft sails in a 6 m/s wind | 41.8-167.0 | 2.9 up to 11.4 |
| One horse | 6.6-39.7 | 12 up to 72 |
| Hand quern | 2.7-5.4 | 88 up to 176 |
A week has 168 hours; one horse working 5 hours a day gives 35, so one horse cannot do 72, and even the best case of 12 hours takes more than two days of a horse’s shifts. A village on animal power needs several animals or a better source. A village on hand power is the 88-176 person-hours a week of the table, which is why the quern is a backup.
A Milling Day Has A Fixed Order
Step 1: Check the grain. Dry and clean, from the moisture and cleaning checks (Grain Moisture and Milling Readiness).
Step 2: Brush the stones and check the gap and feed. Brush the vat, hopper and shoe so old meal does not carry over.
Step 3: Start the drive, then the feed. Never feed a stone that is not yet turning at speed.
Step 4: Run grain at a steady rate and check the meal at the spout for texture and temperature (not above 40 degrees C by hand).
Step 5: Sift or store. Sift only what is wanted white (Bolting Cloth and Sifting Systems).
Step 6: Weigh, log and stop. Record the grain in, the flour out, and the hours run; stop the feed first, let the stones clear of meal, then stop the drive.
Run Two Or Three Days A Week, Not Every Day
The carrier recommends 2-3 days of milling a week with households bringing grain on assigned days, and milling only 1-2 weeks of flour at a time because whole-grain flour spoils. In the example, a wheel that needs 2.3-9.2 hours a week fits easily into 2-3 days. Dividing 476 kg over 3 days gives 159 kg a day, which needs 159 / 206.6 = 0.8 h up to 159 / 51.6 = 3.1 h of running each day.
What To Record
- Hours run, since stone dressing and bearing grease are scheduled in operating hours (Stone Dressing Schedule).
- Grain in and flour out, to check for losses and settle the toll (Toll Milling and Community Scheduling).
- Power state, such as the wheel’s flow or the wind, to build up your own rate figure.
Common Mistakes
- Planning from the best case. The low end of the rate table is the dry season, and it is when the village most needs the mill.
- Milling the whole year’s flour in a wet week. It spoils; mill little and often.
- Skipping the log. Without hours run you cannot schedule dressing.
Starting and stopping a loaded mill
Start the drive before the feed and stop the feed before the drive, so the stones are never driven loaded from rest or left to run bare. A bare running stone heats and strikes sparks, and flour dust explodes in a cloud: keep open flame out, sweep the dust and never test for dust with a flame. Keep hands out of the hopper, shoe and stones, and name the stop: the stone nut or sluice gate, reachable from the mill floor.
What’s Next
- Learn next: Grain Moisture and Milling Readiness - the check before any run
- Combine with: Toll Milling and Community Scheduling - who brings what, and when