Common types of Mechanical Calculator Mechanisms:
There are also other, less common, types of mechanical calculator.
Olivetti Summa Prima (with Sterling currency keyboard)
Close up from the right end showing the pin wheels with the number of pins raised on each wheel depending on the number set by each lever (from top to bottom 0087654321).
These pins act as gear teeth when the crank handle is turned.
Madas (driven by electric motor)
Addiator (sterling currency version)
Bowler Countess (Sterling currency version)
© Text & photographs copyright Nigel Tout 2000-2018 except where noted otherwise.