THACHER's SLIDE RULE
by Keuffel & Esser, NewYork
DETAIL & EXAMPLES
Back to the THACHER's Main Page ...
T H A C H E R ' s SLIDE RULE Model » 4012 «
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Keuffel & Esser, NewYork / USA (1917) SN = 4689
S C A L E C O N F I G U R A T I O N OF THE THACHER's SLIDE RULE
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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 |
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| A = X 20 Segments |
+-------------------------------------------------------------+
O== A movable INTERNAL Cylinder that also rotates w. Scales ... ==O
+-------------------------------------------------------------+
| A' = X' ( 9" left-shifted X ) 20 Segments |
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| 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
E X A M P L E S ( from the Instruction Book, p.16 )
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PROPORTIONS: A / B = A' / B' <==> A / A' = B / B'
MULTIPLICATION: [ B = 1 ] ===> A' = A * B'
DIVISION: [ A' = 1 ] ===> A = B / B'
MULTIPLICATION (Fig.4) 5 x 106 = 530
|
DIVISION (Fig.5) 282 / 3 = 94
E X A M P L E TO DEMONSTRATE THE PRECISION OF THE » THACHER « SR
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D I V I S I O N 355 / 113 = 3.141592920 in alternative ways ...
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( R E M A R K : π = 3.141592654... APPROXIMATION )
B 355 B
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A 113 A
... ...
B 3.1416 B
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A 1 A
or
A' 113 A'
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B' 355 B'
...
A' 1 A'
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B' 3.1416 B'
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