Washington Sabatini’s impressive calculator

Washingtron Savbatini's H 39 reinforced concrete slide rule

Here is one impressive calculating device: Washington Sabatini’s reinforced concrete calculator. This complicated circular slide rule is one of the largest items in my collection. It comprises ten concentric aluminum rings covered with complicated scales and pointers. The rings are all movable except for the second largest; that one is fixed to the body of … Read more

Jacob Zedak’s wooden slide rule

What’s so special about a wooden slide rule, you ask? And indeed, for most of their 3½ centuries of existence — until the arrival of plastics — the material of choice for making slide rules has been wood… but that is the case with straight slide rules. Circular slide rules, by contrast, were almost exclusively … Read more