Pickett-Eckell Model 3
The Model 3 slide rule was produced in the United States from 1947 until 1959, when was replaced by the Model N-3. Fabricated with magnesium coated with very thin celluloid, transparent plastic cursor screwed to aluminum ends, and hold with steel end posts. Scales were photographically printed on the celluloid.
This powerful rule has all the characteristic to be used by Scientists and Engineers. The 27 scales on the Model 3 are : 3√ #1, 3√ #2, 3√ #3, DF [ CF, T Cot, ST, S Cos, CI, C ] D, DI,√ #1, √ #2 on the front face, and 1/N1, 1/N2, 1/N3, 1/N4, DF/M [ CF/M, Digits, CI, C] Co/D, N1, N2, N3, N4 on the back face, was very well suited for demanding numerical operations.
One remarkable characteristic is the long scale to calculate accurate cubic roots (30 inches long split in three portions), and the square roots scale (20 inches long split in two portions). It also has eight Log-Log scales (An 80 inches long scale split in 8 parts), labeled N and 1/N, able to operate values with a precision up to four decimals. It has also on the slider back face, a set of instructions of how to read significant digits in the trigonometric, log-log, and root scales.
According with the kind of logo on the specimen in this collection, I estimated it was fabricated by 1950:
Using the Model 3, it is possible to solve the next problems with a precision of two or three decimals:
SlideRulePractice-3.pdfNext is the scan performed by the ISRM of the Model 3 User Manual
M103_Pickett_HowToUseDualBase_1953.pdf
