Patent ID: 6308427
Filing Date: 2001-10-30
Classification: G04B

Abstract:
A method for adjusting a horizontal sundial by rotating an adjusting screw on said sundial in order to adjust the angle of a gnomon of said sundial to a correct angle for an intended latitude of use, said method comprising the steps of:providing a female thread in said sundial for receiving said adjusting screw so that said adjusting screw projects downwardly therefrom to engage an underlying support surface, said sundial comprising:a dial plate having north and south sides and a plurality of hour marks, including a noon hour mark formed on said north side of said plate; anda gnomon lying on a north-south line passing through said noon mark and mounted to said dial plate so as to extend perpendicular to said plate, said gnomon having an elevated end towards said noon mark and making an initial angle to the horizon when said dial plate is in a horizontal orientation;said female thread lying on said north-south line passing through said noon mark;calculating a number of turns of said adjusting screw that are required in order to move said gnomon by a predetermined number of degrees O, by(a) solving for X in the relationship ##EQU4##where O is the angle representing the difference between said initial angle which said gnomon makes with the horizon when said dial plate is in a horizontal orientation and said correct angle which said gnomon should make with the horizon when said sundial is employed at said new latitude of intended use;where Y is the distance along a line from a point at which the dial plate pivots as it is raised, to a point where the adjusting screw exits said dial plate through said female thread; andwhere X is the distance the gnomon will be raised by rotating the adjusting screw after the screw comes into contact with said underlying support surface; and(b) dividing X by a known distance between adjoining threads on said adjusting screw so as to calculate a number of turns of said screw that corresponds to said distance X; androtating said adjustment screw by said calculated number of turns after said adjustment screw comes into contact with said underlying support surface, so as to raise said gnomon to said correct angle to said horizon for said intended latitude of use.