⚙️ Gear Friends: step-by-step build
Three gears holding hands — spin one and they all dance.
Meet the Gear Friends! They love holding hands, but they are a bit funny: whenever one spins to the right, its neighbour spins to the left. You will put them on a flat frame so you can watch every tooth push the next one. The biggest friend at the end carries a propeller, so you can see exactly which way it goes.
- Level 1 of 5 (super easy)
- About 8 minutes
- 6 steps, 17 parts
- Powered by: Hand-crank
- Series: Starter Builds
What you will learn
- Frames: A frame is a ready-made strong rectangle.
- Bushes & Spacers: Bushes stop things sliding off an axle.
- Gears: Gears are wheels with teeth that push each other round.
- Idler Gears & Direction: A gear in the middle flips the direction back.
Parts you need
- 1 × Open frame 5×11
- 3 × Axle 4
- 4 × Bush
- 2 × Medium gear (24 teeth)
- 4 × Half bush
- 1 × Giant gear (40 teeth)
- 1 × Beam 5
- 1 × Axle 3
Steps
- Lay the big 5×11 frame flat on the table.
- Push a 4-axle down through the 2nd hole along one long side. Slide a bush on underneath (a little foot!), drop a 24-tooth gear on top and cap it with a red bush as a turning knob.
- Do the same in the 5th hole: axle, a bush foot underneath, a 24-tooth gear on top that meshes with the first one, and a half bush to keep it on. Rotate the whole idler shaft so its teeth sit in the neighbouring gear gaps, not tooth against tooth.
- Push a 4-axle down through the 9th hole and slide a half bush on underneath so the axle can't lift out. On top, slide on the giant 40-tooth gear so it meshes with the middle gear.
- Slide the red 5-hole beam onto the same axle as a propeller, and lock it down with a half bush.
- Give the frame a third foot: push a 3-axle down through the far hole on the other long side, then slide a bush on the bottom and a half bush on top so it can't fall out.
Play time
Twist the red knob. Count how many times you turn it for the propeller to go round once.
Build next
- 🌉 Speed-Cancelling Gear Bridge: A 40–8–40 gear train: the middle turns five times, but the ends stay together. (level 2 of 5, about 15 minutes, 5 steps)
- 📏 Rack Travel Bench: Turn a small gear and measure the straight travel of a captured rack. (level 3 of 5, about 25 minutes, 13 steps)
- 🔀 Dual Output Gear Bench: One central input drives two unequal outputs: count each branch independently. (level 2 of 5, about 20 minutes, 14 steps)
🧪 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)- 🌀 Propeller Push Car: Push the car and the propellers on its back spin three times faster than the wheels! (level 1 of 5, about 12 minutes, 8 steps)
- 🔢 Odometer Cart: Five turns of the wheels make the flag go round just once — a cart that counts! (level 1 of 5, about 15 minutes, 9 steps)
- 🎠 Idler Parade Car: A parade of gears rides on top — each one spins the opposite way to its neighbour! (level 1 of 5, about 20 minutes, 13 steps)
🕹️ Sliding-Gear 2-Speed Cart: Your first real gearbox: slide the crank axle to switch between strong gear and fast gear! (level 2 of 5, about 22 minutes, 8 steps)- 🚧 Parking Barrier Gate: A long striped barrier that lifts with a tiny turn — thanks to a heavy counterweight. (level 2 of 5, about 20 minutes, 9 steps)
- 🥁 Cam Drummer: Crank the handle and two drumsticks play a beat all by themselves. (level 3 of 5, about 30 minutes, 18 steps)