## Bill Robinson's Hyperbolic Slide Rule Archive |

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SYMBOLS AND GAUGE MARKS

The values of the symbols and gauge marks on the slide rule scales and on the cursors are as follows:

(Note: Do not be confused as some marks look similar, but can have different values).

Note: Not all gauge marks could be identified. Instead, where a mark is unknown, a numerical value is shown.

(Note: Do not be confused as some marks look similar, but can have different values).

Note: Not all gauge marks could be identified. Instead, where a mark is unknown, a numerical value is shown.

Symbol | Comment |
---|---|

π = 3.14159 | |

π / 4 = 0.7854 | This is to aid in finding the area of a circle by the formula; A = π D^{2} /4 |

v = π/6 = 0.5236 | This mark is on K scale and is used for calculating volume of sphere where V = (π/6) D^{3}; also v = 4π/3 = 4.189 is on K where V = (4π/3) r^{3}. |

R or ρ^{0} or ρ = 180/π = 57.2958° | The degrees in one radian |

M = 1 / π = 0. 3183, or 100 / π = 31.83 | |

C or C' = 4/π = 1.273 | f = 1 / 2π = 0.15915 |

c or C = (√ 4/π) = 1.128 | |

C1 = (√ 40/π) = 3.568 | |

1° = 1.745 * 10^{-2} = π / 180 | Marks for small angle calculations are usually on ST and read on C. The sine of one minute is = 2.909 * 10 ^{-4} ; the sine of one second is = 4.848 * 10^{-6} |

' or ρ' or 9' or δ' or ζ' or Q' = minutes in a radian = 3437.74 = (180 x 60)/π | If the mark ' is = 1.970, it is = 206,265 * (180/π) / 60 = 1.97 * 10^{5} ; where, 206,265 = (180 x 60 x 60) /π |

" or ρ" or 9" or δ" or ζ" or Q" = seconds in a radian = 206,265 = (180 x 60x 60)/π | If the mark " is = 1.182, it is = 206,265 * (180/π) = 1.182 * 10^{7} ; where, 206,265 = (180 x 60 x 60) / π |

ρ" or δ2 or ζ2 or Q2 = seconds in a radian (French decimal system 400) = 636,620 = (200 x 100 x 100)/π | |

KW or kW stands for Kilowatts. HP(*) stands for Horsepower in U.S. and Great Britain. HP(**) for Horsepower in Continental Europe. | |

HP(*) (value for this mark is = 1.341). Conversions are: Kilowatts (KW) times 1.341= HP(*); Ergs per Second times 1.341 times 10-10 = HP(*). | |

HP(**) (value for this mark is = 1.358) for HP metric. | |

PS1 = factor is 1.33413 | |

PS2 = factor is 1.3599 (this is for HP metric) |