Make a wheel and axle

Build a solid wooden wheel that turns true — the shape that carries civilisation.

hard⏳ a weektradition — not yet hand-tested

A wheel looks obvious and is anything but. The first real wheels were not slices of tree trunk — a trunk slice cracks apart along its growth rings within weeks. They were discs built from three planks joined edge to edge, and that is exactly what you will build. Paired with an axle — the round bar the wheel spins on — it turns dragging into rolling, and one person's push into a cart-load moved.

Take the full week. A wheel that "turns true" — spins without wobble or bump — is the difference between a tool and firewood, and truth comes from patient fitting, not force.

You need

• Seasoned planks — wood dried for months, a year is better. Green (fresh-cut) wood shrinks and warps, and a wheel has no room for either. Three planks, each 5 cm or more thick, together wide enough for your wheel — 50–80 cm across is a good first wheel.
• A straight-grained hardwood pole for the axle — ash or oak or your toughest local wood, arm-thick.
• Saw, axe, and adze or rasp — for cutting the disc round and smoothing it.
• An auger (a spiral hand drill) or chisel and patience, for the centre hole.
• Wooden pegs and a mallet — to join the planks.
• String and charcoal — a string compass for marking a true circle.
• Grease — animal fat or tallow. A dry wooden bearing destroys itself in a day.

Steps

1. Join three planks edge to edge into a rough square a little bigger than your wheel. Fasten them with two battens — cross-pieces pegged across the back face — or with pegs driven into holes in the plank edges. Tight joints; no gaps.
2. Find the centre of the square (cross the corner-to-corner lines), press a peg there, and scribe your circle with a string and charcoal.
3. Cut the circle: saw off the corners just outside the line, then work down to the line with axe and adze. Slow near the line; you can't put wood back.
4. Bore the centre hole, sized a little bigger than the axle arm will be (start around 5–6 cm). It must go through square to the face — bore halfway from each side, checking constantly, so the two holes meet straight.
5. Make the axle: a straight hardwood bar. Carve each end — called the arm — round, smooth, and slightly narrower than the middle. These arms are the bearings, the surfaces the wheel actually turns on.
6. Bore a small hole near each axle tip for a linchpin — a stout peg pushed through that stops the wheel sliding off the end.
7. Fit and grease. Slather the hole and the arm with tallow, slide the wheel on, add a wooden or leather washer (a flat ring), and push in the linchpin.
8. True the wheel: prop the axle level, spin the wheel, and hold a fixed marker near the rim. Wherever the rim swings out or scrapes, mark it, take it down with the adze, and spin again. Repeat until it runs even all the way round.
9. Finish the bearing fit: the wheel should spin freely with just a whisper of side-to-side play — "finger-loose." Shave the arm or the hole a sliver at a time until it does.
10. Use it: one wheel in a frame makes a wheelbarrow; two wheels on one axle under a platform make a cart. Grease again before every heavy day.

Watch out

• Tree-slice wheels split. Wood shrinks unevenly around its rings, so a trunk slice always cracks. Build from planks, grain running side by side.
• Green wood betrays you slowly: the hole goes oval, the joints loosen, the disc cups. Seasoned wood only — or accept re-fitting everything in a few months.
• An off-centre hole makes a thumping, load-shaking wheel. Find the true centre twice before you bore.
• A hole bored at a slant makes the wheel lean and wobble. Bore from both faces toward the middle, checking square each time.
• Too tight binds and burns — a seized bearing can smoke. Too loose wobbles and wears. Finger-loose, greased, checked often.
• A dry bearing eats itself in a day of hauling. Carry grease with the cart the way you carry water with yourself.

How it works

Dragging slides wood against the ground along the whole load; a rolling wheel touches the ground without sliding at all. The only sliding left is at the greased axle arm — a small, slick surface. Better still, that friction acts close to the centre while the ground pushes at the big rim, so the wheel out-levers its own bearing. Big wheel, small arm, good grease: that ratio is why carts roll and civilisations move.