F.415 Data Sheet MJS-p-0429

The Spirule Co., Spirule, 1959

Serial Number or Date Stamp:

Country: USA Primary construction material: pl Case included?: envelope

General Description: Specialty circular slide rule

Length of 1 decade = 3.5 in, and overall scale length = 3.5 in. The largest physical dimension is 12 in.

Front Scales: D [ Deg Slope _ Damp _ Log ]

Back Scales:

Notes: Device designed to help solve control system stability problems graphically, through the use of logarithmic scaling of vector lengths and angles; well used first variant; instruction sheets copyright 1959 included

References: https://www.sliderulemuseum.com/MiscUSA/Spirule_Walter_R_Evans%20Memoriam_OrbitMagazine2000.pdf

Date Acquired: 05/23/2026