⏯️ Geneva Step Counter: step-by-step build

Turn the handle smoothly — the pointer moves in jumps: click… wait… click!

Old film projectors had a problem: each picture had to stand perfectly still on the screen, then jump to the next one, 24 times a second. The answer was the Geneva drive, invented by watchmakers in Switzerland. A spinning pin catches a star wheel, pushes it one step, then lets it go and waits. Your counter uses a knob wheel as the star and the handle of a crank as the pin. Every turn of the handle gives one click — 20 clicks move the pointer once round the dial.

  • Level 3 of 5 (medium)
  • About 30 minutes
  • 9 steps, 23 parts
  • Powered by: Hand-crank
  • Series: Mechanical Wonders

What you will learn

  • Geneva Drive: Turns smooth spinning into step-pause-step.
  • Gears: Gears are wheels with teeth that push each other round.
  • Gear Ratio: Fast or Slow: A big gear turning a small gear makes it spin faster.
  • Frames: A frame is a ready-made strong rectangle.

Build these first

  • 🐦 Woodpecker Automaton: Turn the handle and the woodpecker pecks: tok-tok-tok-tok! (level 2 of 5, about 20 minutes, 16 steps)
  • 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)

Parts you need

  • 2 × Open frame 5×7
  • 1 × Giant gear (40 teeth)
  • 5 × Black pin (grippy)
  • 1 × Thin beam 4
  • 3 × Axle 7
  • 2 × Hand crank
  • 4 × Bush
  • 1 × Knob wheel
  • 1 × Half bush
  • 2 × Beam 7
  • 1 × Tiny gear (8 teeth)

Steps

  1. Stand a 5×7 frame up on its long side. This is the back wall.
  2. Build the counter dial now and set it aside: push a black pin into the 40-tooth gear and pin the 4-hole pointer on its middle.
  3. Input shaft: push a 7-long axle through the middle hole of the left side. Add the driver crank, handle facing forward.
  4. Star shaft: push a 7-long axle through the top row, up and to the right of the input. Slide on a bush, the knob wheel and another bush.
  5. Counter shaft: push a 7-long axle through the top row near the right end, and put a half bush on its back end so it can't slide out.
  6. Slide the front wall on over all three axles.
  7. Push two black pins into the bottom row of each wall, on the outside.
  8. Add the two feet.
  9. Slide the dial onto the front of the counter shaft. Put the outside crank on the back of the input shaft. Slide a tiny 8-tooth gear onto the front of the star shaft so it meshes with the big gear, and lock it with a bush.

Play time

Turn the handle slowly and watch the knob wheel: move, stop, move, stop. Count 20 handle turns — has the pointer gone all the way round? Use it to keep score in a game!

Real-world inspiration

Geneva drive — https://en.wikipedia.org/wiki/Geneva_drive ; TechnicBRICKs TechTip 006 — http://www.technicbricks.com/2009/01/tbs-techtips-006-geneva-mechanism.html