The Quest For The Reuleaux Triangle Bearing

[Angus Deveson] published a video on “solids of constant width” nearly a year ago. Following the release of the video, he had a deluge of requests asking if he could make a bearing from them. Since then, he’s tried a number of different approaches – none of which have worked. Until now…

What is a solid of constant width? A shape whose diameter is the same in all orientations, despite the fact that they aren’t circular. In particular, the Reuleaux Triangle is of interest; if you’ve heard of square drill bits, a Reuleaux Triangle is probably at play. Constructed from three circles, they make a neat geometrical study. When placed between two surfaces and rolled, the surfaces will stay parallel, despite the fact that the center of the triangle does not stay level.

In theory, this means they could be easily substituted for spheres in a classic roller bearing, but this turned out to be problematic – the first attempt determined how hard it was to get the shapes to roll instead of slide.

[Angus] finally arrived at a working bearing after a ton of suggestions from the community, and trying a number of attempts until he was able to achieve what he set out to do. The trick was to create a flexible insert (3D printed as well) for the center of the triangle edge, which grips the surfaces the triangle comes into contact with. A frame is also made to hold the bearings in place and allows their centers to move up and down as necessary.

If the thrill seeker within you still isn’t satisfied, maybe you should try the Reuleaux Coaster

20 thoughts on “The Quest For The Reuleaux Triangle Bearing

      1. I think of anything that compresses a fluid by reducing its volume as a piston. Technically piston does fits the dictionary definition “a disc or short cylinder fitting closely within a tube in which it moves up and down against a liquid or gas, used in an internal combustion engine to derive motion, or in a pump to impart motion”

    1. I was thinking along these lines too. Attach a rod in the direction of motion to the centers and you get a reciprocating motion. If those centers can be timed in the right way, you might be able to drive a crank in the center if the device.
      Could it transmit a usable force?
      What is the relationship of input force to output force?
      What sort of backlash is there?

      I’m willing to bet someone has studied all this and it’s in an old, obscure book of mechanisms somewhere.

  1. this is very cool indeed. I’m not a mechanical engineer so i just wonder if this was done just for fun or if there is actually a practical application for such a bearing?

  2. If he wanted to give it more functionality he could make make it into a clock.

    Attach a glass plate to the bearing cage and mount the hand mechanism in the middle and it could become something like a Jefferson Mystery Clock.

  3. I once heard from a professor about a time he’d been asked to help out a major bowling ball factory where their QC testing left something to be desired. They had been accidentally making Reuleaux triangle bowling balls and weren’t catching them in QC.

  4. I wonder if the inserts ‘migrate’ in the opposite direction of rotation with respect to the bearings like the flexspline does on strain wave gearing assemblies.

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