This 3D-Printed Transmission Is an Impressive Piece of Miniature Engineering

The planetary-based gearbox functions similarly to an automatic transmission and uses a camshaft to select one of three gears.

By: Peter Holderith

Apr 28, 2024 at 9:00am ET

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Miniaturizing technology is not always about just making it smaller, it's about maintaining the core function of the object while modifying it to suit its new form factor. A tiny manual transmission may be cool, but it's even cooler if the design matches up the technology used to create it. This miniature three-speed manual transmission built by YouTuber PolyProject3D is a perfect example.

It's a manual transmission, sure, but in principle it works much more like an automatic, utilizing planetary gearsets and brake brands to change ratios. It's not a manual as we know it, but the design is very well suited to 3D printing, which isn't necessarily true of a conventional manual.

It's not just a device that exists in a vacuum, either. It mates up to one of PolyProject3D's other interesting creations, a tiny four-cylinder engine which runs on compressed air. As such, it has a bell housing and other design considerations like a recessed servo motor at the front to allow for clean mating between the two entities.

What do you think?

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The actual shifting is done by the servo, which operates a three-lobed camshaft. Rotating it to a certain position will tighten a specific shift band, which will brake one of the ring gears. Braking each ring gear provides a different ratio. Braking none of them means the transmission is in neutral.

The design, if anything, is a nice mix of both mechanical and aesthetic elements. It doesn't just achieve something, it takes advantage of the way it's made in doing so. It's a balance you don't often see, and certainly one worth highlighting.