The Hemmi 154 'The Highest Class Electrical Engineer's 'Universal'Duplex Slide Rule with Patent Vector and Hyperbolic Scales,20 inches'

摘要

The Hemmi 154, a 50-centimeter "Vector" (hyperbolic scales) with two cursors, is one of the most sought after Hemmi slide rules. Why the quotes around "Vector" for a slide rule with hyperbolic scales? Hemmi used the term Vector for their Pythagorean scales (P', P, Q or P, Q, Q'). This short offering is for our guru of "Vector" slide rules with hyperbolic scales, Bill Robinson. However, you do not have to know anything about hyperbolic functions to appreciate the 154's design and scale implementation. You may find of interest this discussion of the Hemmi Vector, and the often-stated belief that Vector refers to hyperbolic scales.