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 «
*********************************************************************
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
=====================================================================
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


E X A M P L E S  ( from the Instruction Book, p.16 )
****************************************************

   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
=====================================================================
D I V I S I O N    355 / 113 = 3.141592920    in alternative ways ...
=====================================================================
      (  R E M A R K :    π = 3.141592654...    APPROXIMATION  )

               B                   355                B
               ---------------------+------------------
               A                   113                A
                    ...                        ...
               B            3.1416                    B
               ----------------+-----------------------
               A               1                      A

       or
               A'   113                               A'
               ------+---------------------------------
               B'   355                               B'
                                  ...
               A'                               1     A'
               ---------------------------------+------
               B'                            3.1416   B'
                                             ======

               Back to the THACHER's Main Page ...
impressum:
*********************************************************************
© C.HAMANN     http://public.beuth-hochschule.de/~hamann     01/22/14