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THACHER's  SLIDE RULE
by Keuffel & Esser, NewYork

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 ``` T H A C H E R ' s SLIDE RULE Model » 4012 « ********************************************************************* Keuffel & Esser, NewYork / USA (1917) SN = 4689 Edwin Thacher ( 1839-1920 ), an USA engineer ( well known for its work on reinforced concrete constructions ), was the inventor of this ingenious cylindrical logarithmic slide rule with a "real" length of 30 feet ( ~ 9 Meter ) - giving a precision of 5 digits. It was patented in 1881 and build & marketed by K & E, NewYork. S C A L E C O N F I G U R A T I O N OF THE THACHER's SLIDE RULE ===================================================================== The 30' scales are segmented in 18" scales having 2 portions each: An EXTERNAL Segmented Cylinder that rotates with Scales ... UP LOOKING ------------------------------------------- LOOKING UP | LEFT-C = sqrt(X) if X has ODD No. of Digits | | RIGHT-C = sqrt(X) if X has EVEN No. of Digits | | B = X 20 Segments | =============================================================== | A = X 20 Segments | +-------------------------------------------------------------+ O== A movable INTERNAL Cylinder that also rotates w. Scales ... ==O +-------------------------------------------------------------+ | A' = X' ( 9" left-shifted X ) 20 Segments | =============================================================== | B' = X' ( 9" left-shifted X ) 20 Segments | | RIGHT-C' = sqrt(X') if X' has EVEN No. of Digits | | LEFT-C' = sqrt(X') if X' has ODD No. of Digits | DOWN LOOKING --------------------------------------- LOOKING DOWN The THACHER's came in a MAHOGANY BOX with a 72 p.INSTRUCTION BOOK. A C O P Y of this INSTRUCTION BOOK can be found in ... http://sliderulemuseum.com/SR_Library_British.htm Remark(1) THACHER's Model 4013 has a MAGNIFYER-"Cursor" (s.BookCover) REMARK(2) Compare & ADMIRE the Simplizity of the ATLAS CIRCULAR ... Historical Remarks ... impressum: ********************************************************************* © C.HAMANN http://public.beuth-hochschule.de/~hamann 06/13/11 ```