What can I build?

82 builds to choose from, each with animated step-by-step instructions and a printable booklet. Stars show how tricky a build is: one star is super easy, five stars is a big challenge.

Complete MightyCog booklet collection: 82 PDF booklets for $12.99. Instructions only; individual booklets remain free.

Explore the printable pack

🚀 Starter Builds

First rolling cars, gears and motors — start here!

🚗 Tiny Roller: Your very first rolling car — only 13 pieces! (level 1 of 5, about 5 minutes, 6 steps)
⚙️ Gear Friends: Three gears holding hands — spin one and they all dance. (level 1 of 5, about 8 minutes, 6 steps)
🌉 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)
🔬 Compound Counting Bench: Two five-to-one stages multiply: count 25 input turns for one output turn. (level 2 of 5, about 20 minutes, 7 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)
🌀 Coasting Wheel Bench: Spin a retained tabletop wheel gently, then measure how it slows down. (level 2 of 5, about 15 minutes, 8 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)
⭕ Rim Distance Bench: Two unequal wheels share one shaft: equal turns, unequal rim travel. (level 2 of 5, about 15 minutes, 9 steps)
📐 Crank Orbit Bench: Trace a crank pin’s circle and compare its one-axis travel at equal angle steps. (level 2 of 5, about 15 minutes, 10 steps)
🛒 Push Buggy: A sturdy buggy with a push bar held up by super-strong triangles. (level 2 of 5, about 15 minutes, 12 steps)
🏁 Pull-back Racer: Pull it back, let it go — ZOOM! A racer with a spring for an engine. (level 2 of 5, about 12 minutes, 10 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)
🏎️ Steering Go-Kart: Turn the steering wheel and the front wheels really turn — just like a real car. (level 3 of 5, about 30 minutes, 25 steps)
🏗️ Worm-Gear Crane: Crank the worm gear to lift the boom — then let go. It stays up by itself! (level 3 of 5, about 30 minutes, 15 steps)
🌬️ Bevel-Gear Windmill: Turn the handwheel at the bottom — the sails spin at the top! (level 3 of 5, about 25 minutes, 16 steps)
🔋 Motor Buggy: Your first car that drives by itself — with a forwards/backwards switch and headlights! (level 3 of 5, about 30 minutes, 20 steps)
📡 Spinning Radar: A motor-driven radar dish that sweeps round and round on a turntable — with a blinking light. (level 3 of 5, about 25 minutes, 15 steps)
🦾 XL Power Crane: The strongest motor plus a worm gear: 24 times slower and super strong. (level 4 of 5, about 35 minutes, 27 steps)
🛻 Bouncy Monster Truck: Four big wheels on four springy shock absorbers. Boing, boing! (level 4 of 5, about 45 minutes, 29 steps)
🪖 RC Tank: Two motors, two tracks, one remote. Spin on the spot and climb over anything! (level 4 of 5, about 60 minutes, 27 steps)
🚂 Floor Express: A remote-control locomotive with headlights, a chimney and a log wagon. (level 4 of 5, about 40 minutes, 17 steps)
🏆 RC Racer: A real remote-control car: motor drive, differential, servo steering and headlights. (level 5 of 5, about 75 minutes, 38 steps)

⚙️ Gearbox & Drivetrain Cars

Gearboxes, differentials, steering and 4WD — how real cars go.

🌀 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)
🔗 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)
🎡 Crank Cruiser: Turn the handle and the car rolls — every turn of your hand spins the wheels three times! (level 2 of 5, about 18 minutes, 9 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)
🔀 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)
🏎️ Ackermann Soapbox: Real car steering: the inside front wheel turns more than the outside one, so the tyres never scrub! (level 3 of 5, about 35 minutes, 20 steps)
🛺 Pull-back Trike: A three-wheeler with a spring engine — twist the front wheel and it drives in circles! (level 2 of 5, about 20 minutes, 9 steps)
🔥 Big-Wheel Dragster: Giant back wheels, tiny front wheels — the same spring pushes this car much further! (level 2 of 5, about 22 minutes, 10 steps)
💨 Gear-Up Speeder: The spring engine sits up high and turns a BIG gear, which spins the wheels faster! (level 2 of 5, about 25 minutes, 11 steps)
🐢 Pull-back Tortoise: Slow but super-strong: a spring car that can climb up a book! (level 2 of 5, about 30 minutes, 12 steps)
🎚️ Two-Speed Pull-back: Choose your gear before the race: CLIMB or SPRINT! Slide the back axle to swap gears. (level 3 of 5, about 35 minutes, 13 steps)
🚀 Launch-Lock Racer: Wind it up, and a little catch holds the spring tight until YOU press the launch button! (level 3 of 5, about 40 minutes, 21 steps)
🐾 Twin-Spring 4×4: Two spring engines — one for the front wheels, one for the back. All four wheels push! (level 3 of 5, about 35 minutes, 16 steps)
🌀 Pull-back Diff Racer: A spring racer with a real differential, so it zooms round curves without skidding. (level 3 of 5, about 40 minutes, 23 steps)
🪢 Belt-Drive Buggy: No gears touching: a loop carries the power from the motor down to the wheels. (level 3 of 5, about 35 minutes, 11 steps)
⚙️ Clutch-Gear 2-Speed Car: Push the gear lever and a driving ring grabs a different gear: 1st climbs, 2nd races! (level 3 of 5, about 45 minutes, 18 steps)
↩️ Reverse-Gear Truck: The motor only spins one way — the gear lever decides forwards or backwards! (level 4 of 5, about 55 minutes, 18 steps)
🎛️ One Motor, Knob Steering: The motor drives, YOU steer — turn the knob as you walk beside it. (level 3 of 5, about 40 minutes, 21 steps)
🔄 Reverse-to-Turn Car: Only one motor — but it can still turn! Drive backwards and the wheels swing round. (level 4 of 5, about 50 minutes, 24 steps)
🎮 First RC Car (Servo): Your first remote-control car: one dial drives, the other dial steers. (level 4 of 5, about 50 minutes, 27 steps)
🛵 Front-Drive Servo Trike: One front wheel does everything: its own motor drives it and the Servo swings it round. (level 4 of 5, about 50 minutes, 21 steps)
🏁 Three-Speed Car: Two little gearboxes in a row make a big one: crawl, cruise or fly! (level 4 of 5, about 60 minutes, 20 steps)
🚜 Skid-Steer Loader: No steering at all: left motor, right motor — spin it round on the spot! (level 4 of 5, about 65 minutes, 25 steps)
🧗 Worm-Drive Crawler: Super slow, super strong: worm gears drive both axles and it never rolls back. (level 4 of 5, about 50 minutes, 20 steps)
🔒 Diff-Lock Mud Truck: Stuck in the mud? Slide the diff lock and both wheels are forced to turn together! (level 4 of 5, about 60 minutes, 33 steps)
🏆 Independent Rally Car: Every wheel on its own springy arm, a differential, universal joints and Ackermann steering. (level 5 of 5, about 90 minutes, 47 steps)
🌐 AWD with Central Diff: All four wheels driven, with a differential in the MIDDLE of the car — like a rally car. (level 5 of 5, about 90 minutes, 28 steps)
🚧 Twin-Motor Dozer: Wide caterpillar tracks, one motor per track, and a blade that cranks up with a worm gear. (level 5 of 5, about 100 minutes, 33 steps)

🎡 Mechanical Wonders

Levers, cams, cranks, clocks and walkers that seem to move by magic.

⏱️ Pendulum Metronome: Give it a nudge: tick… tock… tick. Move the wheel to another hole and count again! (level 1 of 5, about 10 minutes, 9 steps)
⚖️ Balance See-Saw: A see-saw that is also a scale. Can one gear beat two? (level 1 of 5, about 12 minutes, 10 steps)
🌪️ Ripcord Top Launcher: Pull a toothed rack and watch two gear stages turn the top. (level 2 of 5, about 20 minutes, 18 steps)
🦀 Lazy-Tongs Grabber: Squeeze the handles and the criss-cross arms shoot out to grab things far away! (level 2 of 5, about 20 minutes, 11 steps)
🥚 Egg Beater: Turn the handle and two whisks whizz round in opposite directions. (level 2 of 5, about 20 minutes, 12 steps)
🌀 Flywheel Friction Car: Vroom it on the floor, let go — and it keeps on rolling! (level 2 of 5, about 25 minutes, 5 steps)
🎯 Spring Catapult: Cock the arm, click the trigger, FIRE! A spring flings the ammo across the room. (level 2 of 5, about 25 minutes, 14 steps)
🏰 Castle Drawbridge: Wind the handle and the heavy bridge slowly rises — and stays up when you let go. (level 2 of 5, about 30 minutes, 15 steps)
🐦 Woodpecker Automaton: Turn the handle and the woodpecker pecks: tok-tok-tok-tok! (level 2 of 5, about 20 minutes, 16 steps)
🎠 Chair-Swing Carousel: Crank faster and faster — the chairs fly out wider and wider! (level 2 of 5, about 35 minutes, 16 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)
🛠️ Ratchet Car Jack: Crank the handle — click, click, click — and lift a toy car. Let go and it stays up! (level 3 of 5, about 35 minutes, 15 steps)
🔥 Twin-Piston Engine: See inside a car engine: two pistons race up and down in turns! (level 3 of 5, about 40 minutes, 22 steps)
⏯️ Geneva Step Counter: Turn the handle smoothly — the pointer moves in jumps: click… wait… click! (level 3 of 5, about 30 minutes, 9 steps)
🌬️ Oscillating Fan: A desk fan that turns its head left and right all by itself! (level 3 of 5, about 40 minutes, 18 steps)
🛢️ Nodding-Donkey Pump Jack: A slow crank rocks a long beam up and down — nod, nod, nod, all day long. (level 3 of 5, about 45 minutes, 30 steps)
🛗 Scissor Lift: Turn the crank and the platform climbs straight up on criss-cross legs. (level 3 of 5, about 45 minutes, 29 steps)
🎡 Ferris Wheel: A big wheel turns slowly while its gondolas always hang the right way up. (level 3 of 5, about 45 minutes, 28 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)
📦 Conveyor Belt: A factory belt that carries your parts from one end to the other — and drops them in a box. (level 3 of 5, about 50 minutes, 22 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)
🚞 Cog Railway Climber: A mountain train that grips a toothed rail — it climbs super steep ramps and never slides back. (level 4 of 5, about 55 minutes, 20 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)
🕷️ Klann Walking Spider: A robot that WALKS instead of rolling — beams and pins turn a spinning crank into steps. (level 4 of 5, about 60 minutes, 17 steps)
🦾 Crank Excavator Arm: Crank the worm gears to swing the digger round and lift the boom — then dig! (level 4 of 5, about 50 minutes, 22 steps)
🤖 Robot Arm with Servo Claw: Swing, lift and grab! Three motors and a remote turn you into a factory robot operator. (level 4 of 5, about 60 minutes, 30 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)