Quick builds you can finish in 20 minutes

Short on time? Each of these builds takes about 20 minutes or less, so it fits before dinner or at the end of a lesson.

Start with Tiny Roller for free

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

Explore the printable pack

Before you start: Quick builds are great for warming up before a longer project, or for a classroom starter activity.

24 builds, easiest first

  1. Tiny Roller🚗 Tiny Roller: Your very first rolling car — only 13 pieces! (level 1 of 5, about 5 minutes, 6 steps)
  2. ⚙️ Gear Friends: Three gears holding hands — spin one and they all dance. (level 1 of 5, about 8 minutes, 6 steps)
  3. 🌀 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)
  4. 🔢 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)
  5. 🎠 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)
  6. ⏱️ 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)
  7. ⚖️ 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)
  8. 🌉 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)
  9. 🌀 Coasting Wheel Bench: Spin a retained tabletop wheel gently, then measure how it slows down. (level 2 of 5, about 15 minutes, 8 steps)
  10. 🔀 Dual Output Gear Bench: One central input drives two unequal outputs: count each branch independently. (level 2 of 5, about 20 minutes, 14 steps)
  11. ⭕ Rim Distance Bench: Two unequal wheels share one shaft: equal turns, unequal rim travel. (level 2 of 5, about 15 minutes, 9 steps)
  12. 📐 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)
  13. 🛒 Push Buggy: A sturdy buggy with a push bar held up by super-strong triangles. (level 2 of 5, about 15 minutes, 12 steps)
  14. Pull-back Racer🏁 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)
  15. Gear Speed Lab🧪 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)
  16. 🔬 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)
  17. 🎡 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)
  18. 🛺 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)
  19. 🌪️ Ripcord Top Launcher: Pull a toothed rack and watch two gear stages turn the top. (level 2 of 5, about 20 minutes, 18 steps)
  20. 🦀 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)
  21. 🐦 Woodpecker Automaton: Turn the handle and the woodpecker pecks: tok-tok-tok-tok! (level 2 of 5, about 20 minutes, 16 steps)
  22. 🚧 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)
  23. 🔗 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)
  24. 🥚 Egg Beater: Turn the handle and two whisks whizz round in opposite directions. (level 2 of 5, about 20 minutes, 12 steps)

More ways to choose