As the calculation of elution volumes and retention in CCC and CPC are using multiplications and divisions it is possible to do these on a circular slide ruler (or a normal one) by using logarithmic scales (because additions in that space correspond to multiplications in linear scale).
So with some transparent acrylic, metallic with black background acrylic and some plywood (and those M3 or M4 screws, see explanation in Here):
The red bar was made by etching with the laser on the transparent acrylic and using a permanent red marker. That way it is still translucent, looks nice and doesn’t go away when people play with the device.
The static part:
The moving part, glued. Careful with superglue it tend to make the transparent acrylic whitish. I had to glue the back of the printed acrylic on a sheet of transparent acrylic and glue another layer of transparent on top, with extra care to not touch where the writings are.
To be honest, the first version was linear, but it was ugly and not that user-friendly.
An SVG animated version. (PS: animating SVGs isn’t the funniest thing to do… For such simple designs it is somewhat working, for things moving on multiple axes, it is just horrible…)