Tom, I must congratulate you on a nicely written Arduino application. As you demonstrate, it's not critical what hardware gets used. The feedback/hysteresis loop in the program is nicely documented. It begs to be used.
Your design is much like mine. I was going to use tube stock rather than build it. The bearings are remarkably cheep, though. I found them for $$7bux.
From a simplicity point of view, building it from bicycle parts is as
common as you can get.
Have fun, Norm