Caption from the video:
How and why I built a mechanical calculator. Basing it on the Arithmometer, I built this calculator by hand out of mostly plywood. I suspect it is the first of its kind built in over 100 years. Working on and off, it took me 8 years.
@otters_raft @girlonthenet ah… the adding columns are slightly rotated relative to each other so they can perform the additions in sequence lowest-to-highest.