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A friend and I set out to build an orrery - a mechanical model of the solar system - with accurate planetary orbits. Standard gear-based approaches required high-precision machining we couldn’t afford and produced bulky, noisy mechanisms. Furthermore, the mechanisms did not have a minimalistic look, which is what we were aiming for, and due to the large amount of space they take up would be impossible to conceal neatly.
Using first-principles thinking, I reimagined the drive system. My goal was to create an accurate mechanism, with minimal sound emissions and a compact, minimalistic exterior.
Something that was clear to me from the beginning was that I was going to use a planetary gear system. They allow for a large gearing ratio in a small space; in a certain configuration, the outer gear/ring would rotate, meaning that I could attach the planets to it and not worry about solving issues with component collisions; and, most importantly, the name of the gear system was too perfect not to use in an orrery.
After calculating the required gear ratios and modelling them using CAD, I had to figure out how to manufacture them without machining or other expensive, high-precision processes. My unique take on the planetary gear mechanism was to use friction rather than interlocking teeth to drive the gears. As a result, the mechanism would not emit distracting and unpleasant sounds while driving the planets. The friction in my prototypes were provided by o-rings, which come in many diameters and cross sections, allowing for large design flexibility.
Although still a conceptual project with some 3D-printed prototypes, the design solves multiple problems - cost, space and noise, while keeping a minimalist aesthetic. It’s an example of applying creativity and resourcefulness to re-engineer a traditional mechanism.
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