Introduction

The Pinwheel Machine

Martin (US), page 12

Martin (Dtsch), page 15

"In Germany this is frequently called the Odhner machine because Odhner was the first in Europe to employ the pinwheel mechanism in calculating machines. By pinwhee I mean a gear with a variable number of teeth. Odhner may, in fact. have reinvented this mechanism, but this has not been definitely established yet. It should be noted that prior to Odhner, the variable toothed gear had been patented by Frank Stephen Baldwin in America and had been used in devices for a number of years. It seems also to have been known to Leibniz,  Poleni. and Dr. Roth."