Parametric Bearing

This a parametric bearing. I wrote it as a little challenge to myself, to see if it could be done in a tweet :) The OpenSCAD source file here is the full expanded source, because the tweet version is a little harder to read ;) They both do exactly the same thing, however.

Find it (ahem or not any more) on Twitter here: https://twitter.com/kevfquinn/status/998301858010685441

Update - following the Muskification of Twitter (now "X" for ridiculous reasons), if you visit the above without logging in to Twitter, it won't show you my other tweet with the Openscad code wholly within a tweet - which was a big part of the reason I created this in the first place! That tweet is here: https://twitter.com/kevfquinn/status/998301357676335105 but in case Twitter closes its public doors even further (or ahem if I lock the account because a certain person turned what was Twitter into a cesspool), here's the parameterised OpenScad in less than 280 characters:

r=15;t=2;h=9;c=0.4;l=0.2;a=2*asin(h/2/r);n=180/asin(2*l/h); rotate_extrude($fn=360)translate([r,0,0])offset(r=1,$fn=30)offset(delta=-1)difference(){square([h+2*t,h],center=true);circle(d=h,$fn=n);} for(i=[0:a:360-a])rotate([0,0,i])translate([r,0,0])sphere(d=h-c,$fn=n);

There are a couple of example STLs - the numbers in their filenames are the values of the various parameters used to create them. Note the last number is the resolution of the STL - this can be read as a layer height; printing at a lower layer height will not yield a more accurate model.

Parameters are:

1. Bearing radius to ball center
2. Bearing wall minimum thickness
3. Bevel radius
4. Bearing height (channel radius)
5. Clearance between bearing and balls
6. Resolution of inner channel and bearing balls (~layer height)

Key parameters are the bearing radius and the height. The radius is from the centre of the bearing to the centre of the balls. The height determines also the size of the balls; the ball diameter is the height less the clearance amount.

Clearance may well need adjusting in line with the accuracy of your printer. For me, 0.2mm either side of the ball (so 0.4 setting for the clearance parameter) is enough that the balls are almost free - having them not quite fully free after printing helps with removal of the support material under the balls, then they're easily freed with a little encouragement.

Note: at the time of writing (May 2018), for some reason this isn't working properly with the Thingiverse customizer which just complains there are no parameters. It works fine in OpenSCAD itself, which has a built-in customizer GUI in the 2018 nightly version.
Also the OpenSCAD preview thumbnail image that Thingiverse created is clearly broken; presumably caused by the same problem.