My home made Schickard Calculator

As with most of my projects, it was a sudden and ill thought through decision to do it and rather than study or plan first what I intend to do I just jump in and make a start, so this is not historically correct etc. but is loosly based on information kindly provided by Jens Puhle HERE and adapted to be easy/cheap for me to build using materials easily available (mostly MDF) and using my home made CNC router.

I first learned of the existence of the Schickard Calculator on 10th November and on 29th I had finished building my own which has to be some kind of record? ;-)

Video by Jens Puhle about the Schickard Calculator
My collection of old mechanical calculators

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Discovering the correct shape for the indexing arms was crucial for the carry mechanism to function effectively. Although, when carrying across multiple wheels, some manual intervention may be required. I believe this is a common occurrence in these types of machines, as observed in other videos. This is not a problem though as it is easy to identify which wheels need a nudge to reach the next digit.
If you're interested, I can send you the drawings used to create this mechanism on my CNC machine via email. These are just simple Inkscape files, which were then converted to Gcode using JScut. I used brass coated welding rods for the axles, and I was very pleased with my idea to utilize electrical block connector inserts to attach the gear wheels to the axles.
I was very pleased with the way the adder unit worked out, there are several things I could improve to the rest of it, mainly due to my having no plan as I built it, just working it out as I went along. The windows to the Napiers Bones are too small for starters...

A video I made when first starting to test out the concept.


See a video of a gear being cut on my CNC router
A replica which was built in 1957
My collection of old mechanical calculators