Keufell & Esser Cooke-Radio 4139
This 12 inches long rule (10 inches long scales) was designed by the electronic engineer and instructor at the Navy Radio Materiel School, Lieutenant Nelson Magor Cooke (1903-1965), and was produced in the United States from 1942 through 1967. The 4139 was fabricated with Mahogany laminated with white celluloid plastic, hold with nickel metal braces, and wire framed crystal cursor screwed to plastic ends. Lt. Cooke, a leader in developing electronic schools of the United States Navy, created this rule to facilitate the rapid solutions of radio engineering problems, as well as for general use.
The Cooke Radio 4139 is similar to the K&E-4070 Polyphase Duplex Trig but without the cubic scale K, with the trigonometric scales S - ST - T in decimal format, and two additional scales: 2π, useful to solve problems involving inductance, capacity, or reactance, and LC, that provides a rapid method of determining the resonance frequency for any given combination of inductance and capacity, and for the solutions of problems involving resonance.
The 10 inches long scales on this rule are: L, DF [ CF, CIF, CI, C ] D, 2π, on the front side, and LC, A [ B, T Cot, ST, S Cos ] D, DI on the back face. According with the serial number on the model in this collection and the references found, I conclude that it was fabricated between 1937 and 1939,
With the possible exception of the problems requiring the direct use of the K-scale (but the L scale could be used ), an experienced user could solve with the standard scales of this rule the arithmetic problems in section I. The the special scales 2π and L along with standard scales, also allows to solve vector problems like those in section III:
SlideRulePractice-3.pdfThe 4139 also allows to solve, with one set of the rule, problems involving the Resonant Frequency formula: F=1/(2π√(L∙C)), and, with more than one setting, determine the components of the power triangle:
In the next document is explained how to solved some basic circuit problems using the 4139. More examples can be found in the K&E User Manual.
Solving Basic Circuits Using the Coke-Radio Slide Rule.pdfHere is a scan of the Cooke Radio's User and Supplementary Manuals. The first manual explains how to use the regular scales, while the second one, written by Lt. Nelson M Cooke, gives specific examples of how to solve specific electrical problems with this rule:
M107_KE_PolyphaseDuplexDecitrigSlideRules_1939-4071.pdfcook2.pdf
