Large gears on a bridge in Geneva, Switzerland

Gear Up: A 15-Minute Intro On Involute Gears

If you’re into CNC machining, mechanical tinkering, or just love a good engineering rabbit hole, you’re in for a treat. Substack’s [lcamtuf] has written a quick yet insightful 15-minute introduction to involute gears that’s as informative as it is accessible. You can find the full article here. Compared to Hackaday’s more in-depth exploration in their Mechanisms series over the years, this piece is a beginner-friendly gateway into the fascinating world of gear design.

Involute gears aren’t just pretty spirals. Their unique geometry minimizes friction and vibration, keeps rotational speeds steady, and ensures smooth torque transfer—no snags, no skips. As [lcamtuf] points out, the secret sauce lies in their design, which can’t be eyeballed. By simulating the meshing process between a gear and a rack (think infinite gear), you can create the smooth, rolling movement we take for granted in everything from cars to coffee grinders.

From pressure angles to undercutting woes, [lcamtuf] explores why small design tweaks matter. The pièce de résistance? Profile-shifted gears—a genius hack for stronger teeth in low-tooth-count designs.

Whether you’re into the theory behind gear ratios, or in need of a nifty tool to cut them at home, Hackaday has got you covered. Inspired?

Old Christmas Tree Gets A New Spin

A couple of Christmases ago, [Nick] got tired of trying to evenly decorate his giant fake tree and built an MDF lazy Susan to make it easy as eggnog. But what’s the point of balanced decorations if one side of the tree will always face the wall? This year, [Nick] is giving himself the gift of a new project and motorizing the lazy Susan so the tree slowly rotates.

The saintly [Nick] decided to do this completely out of the junk box, except for all the WS2811 RGB LEDs on order that he hopes to synchronize with the tree’s movement. He started by designing a gear in OpenSCAD to fit the OD of the bearing, a task made much simpler thanks to the open-source gear libraries spinning around out there.

It was hard to get slow, smooth movement from the NEMA-23 he had on hand, but instead of giving up and buying a different motor, he designed a gear system to make it work. Our favorite part has to be the DIY slip ring [Nick] made from a phono connector to get around the problem of powering a rotating thing. This is a work in progress, so there are no videos just yet. You can watch [Nick]’s Twitter for updates.

[Nick] didn’t specify why he chose to use WS2811s, but they have gotten pretty cheap. Did you know you can drive them with VGA?

Via Adafruit’s CircuitPython newsletter