Slide rule gear selector

Claim 1

A SELECTOR FOR GEARS HAVING A PREDETERMINED INVOLUTE TOOTH FORM COMPRISING, IN COMBINATION: A PAIR OF MEMBERS MOVABLE WITH RESPECT TO ONE ANOTHER; ONE OF SAID MEMBERS HAVING FIRST, SECOND AND THIRD WINDOWS AND A NARROW SLOT WITH A LOGARITHIMIC GEAR R.P.M. SCALE ADJACENT THE FIRST WINDOW AND A LOGARITHMIC GEAR RATIO SCALE ADJACENT THE NARROW SLOT; A LOGARITHMIC HORSEPOWER SCALE AND A LOGARITHMIC PITCH DIAMETER SCALE AND A LOGARITHMIC FACE WIDTH SCALE ON THE OTHER OF SAID MEMBERS, A PORTION OF SAID HORSEPOWER SCALE UNDERLYING SAID FIRST WINDOW AND VIEWABLE THERETHROUGH, A PORTION OF SAID PITCH DIAMETER SCALE UNDERLYING SAID SECOND WINDOW AND VIEWABLE THERETHROUGH AND A PORTION OF SAID FACE WIDTH SCALE UNDERLYING SAID THIRD WINDOW AND VIEWABLE THERETHROUGH; AND A POINTER MEMBER ARRANGED FOR PIVOTAL AND SLIDING MOVEMENT RELATIVE TO SAID PAIR OF MEMBERS, SAID POINTER MEMBER HAVING A VISIBLE CENTER LINE ADAPTED TO OVERLIE SELECTED PORTIONS OF SAID PITCH DIAMETER AND FACE WIDTH SCALES AND A PIVOT PIN ARRANGED WITHIN SAID NARROW SLOT; SAID SCALES BEING LATERALLY AND LONGITUDINALLY ALIGNED AND THE LENGTHS OF SUCCESSIVE LOGARITHMIC CYCLES ON EACH OF SAID SCALES BEING CALIBRATED TO PERMIT SELECTION OF GEARS IN ACCORDANCE WITH PRESELECTED SURFACE DURABILITY RATING FORMULAE.