Odhner

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Revision as of 23:11, 13 May 2013 by Wim (talk | contribs)

Specification

P1030648.resized.JPG
P1030649.resized.JPG
  • Original Odhner Arithmos pinwheel calculator
  • Serial 41603 (estimated from the late 1920's)
  • 9 decimals input
  • 13 decimals accumulator
  • 8 decimals counter

Origin

Donated in 2013.

Condition

Generally works, but:

  • a lot of the digits have lost their paint.
  • there seems to be a part missing to shift the carriage. there are some holes and pictures of similar models show buttons to advance the carriage by one position left or right.

Usage Hints

  • Input is given by setting the 9 levers.
  • The right hand counter is the accumulator. It stores the result of the addition or subtraction.
  • The left hand counter is the register. It counts the number of turns.
  • Input is transferred to the accumulator by turning the crank, clockwise turn for addition, counter-clockwise for subtraction.
  • The carriage can be shifted to align the input with a certain decimal of the accumulator and the register.
  • Both register and accumulator have a reset handle, give it a full turn to set all digits to zero.
  • The input can be easily reset by pulling the reset handle left while turning the crank until it pushes all levers to zero.
  • (other than the above) always turn the crank a full turn. You can always undo a turn by turning in the opposite direction.
  • A bell signals an overflow condition.

Addition

  • Reset accumulator
  • Input the first operand.
  • Turn clockwise.
  • Input the second operand.
  • Turn clockwise.
  • Read result from accumulator.

Subtraction

  • Reset accumulator
  • Input the first operand.
  • Turn clockwise.
  • Input the second operand.
  • Turn counter-clockwise.
  • Read result from accumulator.

Multiplication

  • Reset accumulator and register.
  • Shift carriage all the way to the left.
  • Input the first factor.
  • Turn clockwise as many times until the last decimal in the register equals the last digit of the second factor.
  • Shift the carriage 1 position to the right.
  • Turn clockwise as many times until the fore-last decimal in the register equals the fore-last digit of the second factor.
  • Repeat the last two steps for all digits of the second factor.
  • Read the product from the accumulator.

Division

  • Reset accumulator
  • Shift carriage to the right, allowing space for decimals.
  • Input the dividend.
  • Turn clockwise to transfer it to the accumulator.
  • Reset the register.
  • Input the divisor.
  • Shift carriage to align the leading digits of input and accumulator.
  • Keep turning counter-clockwise until the bell rings.
  • Turn clockwise to undo the last turn.
  • If accumulator contains all zeros, read exact quotient from register, else shift carriage one position left and repeat last two steps.
  • If not dividable, the process stops when the carriage is all the way to the left. Read approximate quotient from the register and remainder from the accumulator.

Square root

  • Reset accumulator
  • Shift carriage all the way to the right.
  • Input number
  • Turn clockwise to transfer it to the accumulator
  • Reset register
  • Shift carriage aligning left-most digit of input with left-most digit of the value in the accumulator
  • Set a 1 in the input that is aligned with the right-most digit of the value in the accumulator and turn counter-clockwise
  • Set the next odd number (3) and turn counter-clockwise
  • Repeat with next odd numbers (5, 7, 9, 11, 13, ...) until the bell rings.
  • Undo last turn by turning clockwise.
  • Subtract 1 from input
  • set a 1 in the next input digit (one decimal to the right)
  • shift carriage left.
  • repeat the process of subtracting odd numbers until the bell rings.
  • If accumulator contains all zeros, read exact result from register
  • If carriage reaches left-most position, read approximate result from register

See Also

http://home.comcast.net/~wtodhner/calcs.html