Build a water wheel

Let the stream turn a wheel that grinds grain or lifts water — the first worker that never tires.

a craft to master⏳ a seasontradition — not yet hand-tested

Everything before this, a person powered. Grinding a family's daily flour by hand takes one to two hours of hard rubbing, every single day. A water wheel does it while you do something else. This is the first machine in the tree that works when you sleep — the moment muscle stops being the limit of what you can do.

A stream is weight falling: water sliding downhill, pulled by gravity. A wheel with paddles stands in that falling water and gets pushed round and round, forever, for free. Catch that turning with an axle, and you can spin a grindstone, lift water into a field, or hammer anything that needs hammering.

You need

• A stream that never stops — even in late summer. You need water moving at a brisk walking pace or faster, or a spot where you can make it drop. A knee-deep stream two metres wide is plenty.
• A big paddle wheel — 1.5 to 3 metres across: two wooden hoops (the rims) joined by 8 to 12 flat paddles, each paddle about 30 by 50 centimetres, all fixed to a strong hub on a thick axle.
• A heavy axle — a straight hardwood beam, 15 to 20 centimetres thick, longer than the wheel is wide, with rounded ends to turn in bearings.
• Two bearing blocks — hardwood blocks with half-round notches, greased with fat, set on posts or stone piers either side of the wheel. These carry the whole spinning weight.
• A frame or two piers of heavy posts or stacked stone, sunk below where the water can dig.
• A channel (a "race") — a dug ditch or wooden trough that brings water to the wheel and takes it away. Controlling the water is half the build.
• A gate — a sliding board at the head of the race. This is the off-switch. Build it first, not last.
• Something for the wheel to drive — simplest: a round grindstone on the same axle, or pots lashed to the rim to lift water into a trough.
• Tools and helpers — axe, adze, drill, pegs, cordage, and at least one more pair of hands for the heavy lifts.

Steps

1. Study the stream for a full month across seasons if you can. Mark its highest flood line and lowest summer level. Your wheel must survive the first and still turn in the second.
2. Choose the wheel type by your water.
   • Fast, shallow water: an undershot wheel — the stream pushes the bottom paddles as it flows past. Simplest to build.
   • A drop of 2 metres or more (or one you can dig): an overshot wheel — water pours onto the top and its weight carries the wheel round. Two to three times stronger for the same stream, but needs the raised channel.
   • Start undershot. You can rebuild overshot once the site is proven.
3. Dig the race slightly to one side of the stream, with the gate at its head, so the wheel sits in a channel you control — never in the open stream, where floods own everything.
4. Build the wheel flat on the ground. Make two identical rims, peg the paddles between them evenly, fix the hub, and drive the axle through. Spin it on trestles: a good wheel turns true, with no wobble bigger than a finger.
5. Set the piers and bearings either side of the race, footed on rock or sunk half a metre below the channel bed. Set the bearing notches level with each other — check with a water-filled trough as your level.
6. Lift the wheel into its bearings (this is the day you need every helper). Cap the bearings with lashed straps so the axle can't jump out, grease well.
7. Open the gate a crack. The wheel should start on a trickle. Open further until it turns steadily — one turn every 4 to 8 seconds is a healthy working pace for a wheel this size.
8. Connect the work. Mount the grindstone on the axle's dry-land end over a fixed lower stone, with a hopper (a funnel of boards) feeding grain into the middle. Adjust the stone gap until flour comes out fine, not hot.
9. Tend it like a fire. Grease bearings every day of running. Clear leaves from the gate. Close the gate whenever no one is watching.

Watch out

• Floods. The river will one day rise higher than you believe. The gate and side-race exist so floodwater passes by the wheel, not through it. Never build in the main current.
• The machine doesn't stop for flesh. A turning wheel and grindstone will take fingers, hair, and clothing without slowing. Close the gate before touching any moving part, every time. Keep children back; fence the wheel pit.
• Undermining. Moving water digs under posts silently. Floor the channel under the wheel with flat stones and check footings after every high water.
• Dry bearings. A hot, squealing bearing chars, seizes, and can crack the axle. Grease daily; touch-check for heat.
• Ice. In freezing weather, a stopped wet wheel locks solid and splits. Either run it, or drain the race and let it stand dry.
• Impatience with the water. Most failed wheels fail in the channel, not the wheel. Spend your effort on the race and gate; a modest wheel with good water beats a grand wheel in a bad channel.

How it works

Falling water carries energy in proportion to how much falls and how far. The paddles catch that push and turn it into a steady twist on the axle — the same twist your arm gave a hand-mill, but delivered all day without tiring. An overshot wheel beats an undershot one because it uses the water's full falling weight through the whole drop, not just its shove as it passes.