Computermuseum der Fakultät Informatik

Curta 1 - Stepped Drum

Central Stepped Drum

The stepped drum consists of two nested parts. The switching between 
addition and subtraction is done by pulling the crank and thus pulling 
the stepped drum in axial direction by one cog-size.
In contrast to the pinwheel machines, where addition and 
subtraction are switched by a rotation to the left or to the right, 
you only rotate in the same direction when using stepped drum machines.
There has to be an explicit switching between the two ways of
calculation.