🌬️ Bevel-Gear Windmill: step-by-step build

Turn the handwheel at the bottom — the sails spin at the top!

How do you get spinning power from the bottom of a tall tower all the way to the top — and around two corners? With bevel gears! Their slanted teeth let two gears meet at a right angle. One pair at the bottom turns the spin upwards, a long axle carries it up the tower, and another pair at the top turns it sideways into the sails. Old windmills used exactly this idea to grind flour.

Level 3 of 5 (medium)
About 25 minutes
16 steps, 47 parts
Powered by: Hand-crank
Series: Starter Builds

What you will learn

Bevel Gears: Around the Corner: Slanted gears send spinning power around a corner.
Axles: An axle is a cross-shaped rod — anything on it turns together.
Frames: A frame is a ready-made strong rectangle.
Centre of Gravity: Keep the heavy stuff low and in the middle and your model won't tip.

Build these first

🧪 Gear Speed Lab: Two cranks, two gear pairs: one makes things FAST, one makes things STRONG. (level 2 of 5, about 20 minutes, 13 steps)

Parts you need

1 × Open frame 5×7
6 × Blue long pin
4 × Split pin block
4 × Red axle-pin
4 × Beam 11
2 × Axle 9
5 × Bush
2 × Beam 5
7 × Half bush
1 × Axle 5
4 × Corner gear (12 teeth)
1 × Axle 7
2 × Medium gear (24 teeth)
1 × Grey pin (smooth)
1 × Axle 12
2 × Black pin (grippy)

Steps

Lay the 5×7 frame flat.
Push two blue long pins up into the 2nd and 4th holes of the front short end. Press two split pin blocks onto them, one on top of the other.
Do the same on the back short end: two blue long pins and two split pin blocks.
Push a red axle-pin into the middle cross hole of both front blocks, pin end pointing inwards. Press an 11-hole beam onto the two pins, standing straight up.
The same at the back: two red axle-pins and the second 11-hole beam. This is the tower.
Stand two 9-axles in the middle holes of the frame's long sides. Slide a bush down each pole until it sits 4 holes up — the first shelf will rest on these.
Shelf 1: lay a 5-hole beam flat and slide it down both poles until it rests on the bushes. Then slide another bush down each pole on top of it.
Shelf 2: slide a second 5-hole beam down the poles onto those bushes, and lock it with a half bush on top of each pole.
Push the crank axle through the 3rd hole of the back beam. Add a half bush inside and a corner gear on the end.
Hold a corner gear under the shelves so it sits on the crank's corner gear, with a half bush on top of it. Push the tall axle down through both shelves, the half bush and the gear.
Put the handwheel on the outside, lock it with a half bush on the end of the axle, and push a grey pin into it as a handle.
Slide a bush onto the top of the tall axle, then a corner gear on top of it.
Push the long sail axle through the top holes. Add a half bush and the last corner gear at the back.
Slide the 24-tooth gear onto the front as the sail hub.
Pin the first sail across the hub with two black pins.
Push two blue long pins into the hub and hang the second sail straight up and down. Lock with a half bush.

Play time

Turn the handwheel and watch the sails. Can you make them spin the other way? What happens if you turn really fast?

Build next

🔗 Driveshaft 4×4 Pusher: Turn one wheel and ALL FOUR wheels turn — a spinning driveshaft joins the axles! (level 2 of 5, about 20 minutes, 15 steps)
🔀 Differential Demo Cart: Push it round a corner and watch: the outside wheel spins faster than the inside one! (level 2 of 5, about 22 minutes, 10 steps)
🥚 Egg Beater: Turn the handle and two whisks whizz round in opposite directions. (level 2 of 5, about 20 minutes, 12 steps)
🎠 Chair-Swing Carousel: Crank faster and faster — the chairs fly out wider and wider! (level 2 of 5, about 35 minutes, 16 steps)
🥁 Cam Drummer: Crank the handle and two drumsticks play a beat all by themselves. (level 3 of 5, about 30 minutes, 18 steps)
🌀 Spirograph Drawing Machine: A machine that draws flowers! The paper spins while an arm swings the pen. (level 3 of 5, about 45 minutes, 19 steps)
🏹 Counterweight Trebuchet: The heavy battery box drops, the long arm whips up — and your bush flies across the room! (level 3 of 5, about 40 minutes, 17 steps)
🌍 Sun-Earth-Moon Orrery: Push the arm round: the Earth circles the Sun, spinning as it goes, with the Moon in tow. (level 4 of 5, about 35 minutes, 12 steps)
🕰️ Spring Escapement Clock: A ticking pin-wheel clock powered by the pull-back motor's spring. Tick… tock… tick… (level 4 of 5, about 50 minutes, 22 steps)
🚂 Sun-and-Planet Beam Engine: James Watt's steam-engine trick: a gear that never spins makes the flywheel turn four times per pump! (level 4 of 5, about 50 minutes, 17 steps)
🧭 South-Pointing Chariot: Push it anywhere — the pointer keeps pointing the same way. No magnets, just gears! (level 5 of 5, about 75 minutes, 34 steps)