CBS Fidget

thingiverse

A fun derivative of the curves of constant breadth rollers. This fidget is a roller bearing using the curves of constant breadth rollers as the bearings! The races are calculated based on the number and the roundedness (obliquity) of the rollers, leaving enough room for the rollers to pass by one another. Two key aspects of curves of constant breath come into play here 1) having a constant breadth the rollers are always in contact with both races, (just as you would expect with round rollers 2) the circumference of all curves of a given breath is 2PI*Breadth, so they roll around the races at the same average rate even as they jiggle a bit due to their odd shape. There is an odd tactile aspect to the motion as the uneven rollers apply varying pressure on the races and occasionally slide off one another. I don’t think I would use these as bearings, but they make a nice fidget, with some interesting math baked in. Rollers of roundedness less than ~.40 tend to get stuck as the “points” go around and rollers over ~.90 roundedness look round (not very interesting). All the prints I’ve done use a range of roundness, but the openSCAD code will support arrays of rollers that are the same, it’s up to you. Things to note while printing/making. Short rollers will spin sideways in the race, so it’s best if the height taller than the breadth, and rollers that are too tall tend to fall off the build plate when printing. The races fit together with a tongue and grove, normally the interference of the parts sliding together is enough to keep them tight but if they fall apart a drop of glue on the joint should be plenty.