Jürgen Weigert presents his mechanical calculators, built at the FabLab:

Schickard's Calculating Machine Turns 400
Over 400 years ago, Wilhelm Schickard designed a mechanical calculating machine that can rightly be considered the ancestor of all computers known today. The talk traces the history of the machine: its origins, its rediscovery, the first reconstruction in 1960, and the journey to a laser-cut, freely available kit. The machine can demonstrate addition and multiplication in a very tangible way, with up to six decimal digits. A further development of the design will also be presented, drawing on practical experience.

Mr. Leibniz Computes in Binary ...
Why do our computers don't actually calculate with decimal numbers at all, but internally do everything with only zeros and ones – in binary? The famous Gottfried Wilhelm Leibniz bears no small responsibility for this, having "invented" the binary system. His description of a calculating machine is incomplete, and there are several approaches to building one. A new interpretation will be presented: a mechanical ball adder that becomes a multiplier in exactly the way Leibniz described it.