Let's Twist Again!
A Reciprocating Rotating Mechanism
Following on from my last project, the Reciprocating Rack mechanism, where turning the crank drove a slider back and forth, I wanted to explore a related idea. This time, the output is a rotating shaft that twists back and forth. The result is the Reciprocating Rotating mechanism… or perhaps a better name is simply the Twister!
Turning the crank sets in motion a pair of pinions, each reduced to just five surviving teeth. These pinions are mounted opposite one another, 180 degrees apart on the axle.
Above them sits a twelve‑tooth gear, firmly fixed to the vertical shaft. As the crank rotates, the first pinion engages with the gear, driving the shaft in one direction. Continuing the turn, the second pinion comes into play, reversing the motion.
The effect is a gentle oscillation: the vertical shaft twists back and forth, completing roughly one‑third of a full revolution each way with each cycle of the crank.
All of the gears and pinions are enclosed neatly within a box. From this housing, the vertical shaft emerges through a hole, ready to twist back and forth, while the crank axle extends from the side for easy turning.
This compact arrangement forms an Essential Mechanism: a self‑contained unit that demonstrates the pure delight of motion. It can be enjoyed as an exercise in mechanism alone, or serve as the foundation for your own character‑based paper automata project.
Download and Make Your Own:
The Twister Mechanism is available as a downloadable project from my website. It comes in two PDF files:
Parts + Instructions – includes all the pieces along with clear, step‑by‑step guidance.
Parts Only – a simplified sheet of components, perfect if you’d like to add your own colours or adjust the shapes and sizes before building.
This flexibility makes it easy to adapt the mechanism into your own creative project.
If you are a premium subscriber to this newsletter, you can download the files for free at the foot of this page. Thank you so much for your support, it makes projects like this possible!
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Ideas to Try
Once built, the Twister Mechanism is a springboard for imagination. Here are a few playful directions you might explore:
🐶 A dog twisting its head from side to side
🎿 A rabbit skiing gracefully down a slope
🐟 A shoal of fish linked together, moving in unison
💃 A dancer performing the twist
Of course, these are just starting points, the only limit is your imagination. See what characters or scenes you can bring to life!
Making is at its heart an act of curiosity and joy, each mechanism a doorway to new ideas, each project an invitation to play. I hope the Twister Mechanism sparks your imagination and leads you to create something uniquely yours.
If you’re already a premium subscriber, thank you for helping keep this workshop turning and these projects flowing, I literally couldn’t do it without your support. And if you’d like to join, becoming a premium member gives you access to this project and dozens more, while helping sustain the community of makers who delight in bringing paper and motion to life.
So crank the handle, let the gears dance, and see where your creativity takes you.