I got my author's copies earlier this week, but haven't read that article in depth. A quick scan of some of the drawings and text describes the three gears running concentric but with different tooth counts, some meshing the teeth inside or outside the typical pitch diameter.
Looks like a nice project I'd like to do.
Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
~Practitioner of the Electromechanical Arts~
Theory & Practice-
Theory is when you know something but it doesn't work.
Practice is when something works but you don't know why.
It it dangerous to combine Theory & Practice;
nothing works and you don't know why.