GB240604A - Astronomical model - Google Patents

Abstract

240,604. Porter, C. Aug. 19, 1924. Orreries.-Relates to models of the kind described in Specification 242/15 for illustrating the revolution of the earth round the sun, the precession of the equinoxes, &c., and comprises a horizontal bar A, Figs. I-III, which is pivoted on a central fixed pivot C and carries spindles T, P at its ends, the earth globe E being mounted either upon the inclined upper portion of the rotatable spindle P, or on an axis M inserted in a socket r in an arm K secured on a sleeve l which is rotatable upon the spindle T. A pulley D fixed upon the central spindle C is connected by a crossed driving cord p to a pulley F secured upon the spindle P, the upper surface of F being bevelled to co-operate with a bevelled wheel G on a member H to which the globe E is connected by a pin t. When the bar A is rotated on its pivot rotation of the globe E is produced, the axis P of the globe being maintained parallel to itself in known manner by a sprocket wheel f at its lower end connected by a chain g to a fixed sprocket wheel e on the spindle C. The rotatable sleeve l on the spindle T is driven by a sprocket wheel k connected by a chain h to a sprocket wheel a on the spindle C, the gear ratio being such that k makes one revolution during approximately four revolutions of A. The sun globe S, Fig. II, is mounted at the end of a bar W, the other end of which is secured to a sleeve V on the spindle C, the eccentric mounting of the globe allowing it to be disposed near to the earth globe to illustrate the northern winter position of the latter. Provision is made for mounting the earth globe E in a socket r in the bar W, the globe S being removed. The pin N carrying the sun globe is inclined at an angle of 7‹. The upper portion of the inclined axis of the earth globe is provided with a small horizontal hole to receive a fine rod v, Fig. V, which projects therefrom and facilitates the counting of the sidereal rotations of the earth globe, and enables the angular difference between a sidereal and a synodic rotation to be observed. A loose disc L, Fig.. V, carrying two angle pieces is adapted to be attached to the earth globe E to indicate the angular heights of the sun as observed from London in midsummer and midwinter. A flat ring with outwardly projecting pins forming an extension of a diameter is adapted to be applied to the earth globe in the plane of the equator to illustrate the obliquity of the ecliptic. Another disc, adapted to be secured by a plug at its centre to various parts of the earth globe is used in conjunction with a ball which is carried on a string secured at one end to the centre of the disc and represents the sun, the disc representing the horizon. A ring and half ring each carrying a small ball slidable thereon are also used in conjunction with the disc and earth globe to illustrate the apparent motion of the sun.