Geared Flapping-Wing Bird: Redesigning a Wooden Automaton in Inventor

🌏 繁體中文版：[學習3D 機械設計軟體] - 齒輪飛行翼：運用 Inventor 重新設計會拍翅的木製鳥

This hand-cranked wooden bird that flaps its wings started as a 3D mechanical design course assignment. The mechanism is based on a metal flapping-bird model I found online; I rebuilt it from scratch as a wooden version in Autodesk Inventor, ran a motion simulation on the computer first, and only then laser-cut, scroll-sawed, and assembled the real thing.

The finished piece: the gear train sits in the central wooden box, with wing linkages on both sides

How the mechanism works

The whole machine has exactly one input: the hand crank. Power flows like this:

1. The crank turns a small gear.
2. The small gear drives a large gear. Small-driving-large is a speed reduction, so cranking takes less effort and the wings move slowly and smoothly.
3. The two large gears mesh with each other and turn in opposite directions.
4. An off-center pin on each large gear drives a connecting rod, converting rotation into the up-and-down swing of a wing.

Because the two large gears counter-rotate, the left and right wings move as mirror images. That is what makes it look like flapping, instead of one wing going up while the other goes down.

Laying out the gear train and linkages in Inventor

Motion simulation: catch jams before cutting wood

Linkages have two classic failure modes: locking up at a certain angle, or parts colliding with each other. So before machining anything, I ran a motion study in Inventor, turned the crank through a full revolution, and checked that the whole stroke was smooth.

Motion simulation in Inventor

Next, I found the four extreme positions of the large-gear rod: lowest, widest, highest, and closest. These four positions define the wing's range of motion, and they are exactly where the parts are most likely to hit the box or bind.

The four extreme positions of the large-gear rod: lowest, widest, highest, closest

Flipping to the front view during simulation to check gear mesh

Fabrication: laser cutter + scroll saw

Flat parts such as the gears, box panels, and links were laser-cut. The wing feathers have slots, which I cut on a scroll saw.

Cutting the slots in the wing feathers on a scroll saw

All parts laid out before assembly, with a file for cleaning up the holes

The real thing in motion

Cranking the finished bird

Front view: gear train and left/right linkages

Wings spread

Takeaways

This project covers the basic mechanism-design loop: reduce speed with gears, convert rotation to oscillation with a linkage, use motion simulation to find the extreme positions, and finally break the 3D model down into flat parts that can actually be cut. The mechanism itself is borrowed from an existing design; the point was to model it from zero in Inventor, simulate it, and end up with a piece that really works.

If you like this kind of crank-driven automaton, see also the crocodile-and-fish cam box, which uses one shaft to drive two different motions.

Related tools: Gear Ratio Calculator

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This post is adapted from the Traditional Chinese original on Vic's Iteration Notes.