Ambitious and improbable gears: video

Back in September, I blogged Quilty1987's mesmerizing YouTube tutorial on making weird, erratically shaped gears that really mesh and spin. At the time, I pondered what these would look like if they were part of a larger, more ambitious project. Now I know: here's another Quilty1987 (AKA Clayton Boyer) video of several geared creations that do improbable and wonderful tricks with teeth and spins.

These Gears Really Work? (via JWZ)


  1. This is the same dude whose ornate wooden clocks were posted on here a few months back. Guess we’re getting a look at the insides of them now.

    FWIW, “Quilty” is his wife who is crazy good at making quilts. I wonder if it’s a creative/competitive synergy or if the personality types just naturally attract.

  2. That’s great. I loved the spirals and especially the fish/squid combo around 1:35 — I never even thought about gears sliding along each other like that!

  3. I’m not 100% on this, but I think the only real necessity for two gears to function properly is that the centers of rotation for each gear must always remain equidistant (for the two gears to remain stable, at least). A circle is the obvious choice because there’s no angle matching issues, but it’s a really cool feat to create these intricate shapes that interact in such a way that the rotation points remain the same distant apart. I like it!

    1. I think that’s right. The circle is also a more practical one because you can have much more flexible gear ratios – no problem to do 17:13 or whatever. The pentagon-square-triangle is 5:4:3 (each side has the same number of teeth). Still totally and completely awesome, but industry went to the circle for a reason.

  4. Has anyone called Terry Gilliam yet? I can’t imagine how these don’t make it into a Gilliam film.

  5. ISTR seeing a design for a bike with an eliptical gear even up the torque deliverd to the wheels. (since you deliver much more torque when the crank is horizontal than when it is vertical)

  6. Ah, brings back memories of studying and designing gears in college. We had to design teeth that would mesh cleanly (I vaguely remember cycloidal something something) calculate force, velocity, acceleration, and jerk. It’s really cool to now see them in action and be able to see the odd motion.

    Weird gear shapes are, or were, frequently used in printing. One of the weirder shapes looks like paisley.

    Here’s a quick link for those that are curious to learn more:

  7. Neat. I’m impressed by the triangle-square-pentagon set. Of cours ethe main reason that people usually use round gears is that they usualy want to convert one (nearly) constant angular velocity to a different (nearly) constant angular velocity. With these gears, a constant input would lead to a varible output. To a much lesser extant, this usually happens even with round gears because the point of contact on the gear teeth changes distance from the gear as the gears mesh.

  8. The weird thing about this video is that he saved the least impressive thing until last. The last thing he shows is just a set of plain old circular planetary gears. All those non-circular gears were really cool though.

    1. “Of course they work. The shapes are reciprocal, and the directions alternate.”

      Not if you turn them upside down.

  9. Cornell University has a great collection of eccentric gear pairings. I could never figure out why anyone would want to use these in practice though.

  10. I just saw some eccentric gear displays at the Boston Museum of Science. The last set looks like something out of a transmission.

  11. The first set of four square gears would make and awesome grinding apparatus, with the shape-shifting negative space in the middle of the gears.

  12. For workable gears you need a bit more than that the combined distances are constant; you need that the gears don’t slide or jam against each other internally, and that there is a constant pressure angle. This leads to distinctive profiles of the teeth, for example the involute of a circle.
    Incidentally, there was a 19th century engineer, Franz Reuleaux, whose mechanical models (many involving irregular gears, including versions of the ones here) are the pride of many engineering departments.

  13. what is cool about the last set, but not explored in the video is that the centre cogs don’t need an axle. so long as they are prevented from moving forward or back, they will stay in place and rotate.

    this video sort of shows this as well as some other cool non circular gearing.

  14. About the elliptical gearing for the bike..
    I had a bike with Shimano Biopace chainring, which is elliptical.
    Pretty good stuff too.

  15. This fella (and folks like him, of which I’m sure there are plenty) could to wicked stuff with 3D printers.

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