. Transactions of the Institution of Mining Engineers . ne-quarter Actual Size. and J. It has been designed by Dr. Henry Briggs, and isillustrated by the accompanying drawings and photographs (Figs. 1to 9). Experimental Investigations upon the Theory of the Pitot Tube and theWoltmann Mill, by A. Rateau, Trans. Inst. M. E., 1898-1899, vol. xvii., page124. tThe Velocities of Currents of Air in Mines, Trans. N. E. Inst., 1861-1862,vol. X., page 207. 92 TRANSACTIONS INSTITUTION OF MINING ENGINEERS. [Vol. LXII. The whirling rod on which the meter under test is mounted isrotated by means o
. Transactions of the Institution of Mining Engineers . ne-quarter Actual Size. and J. It has been designed by Dr. Henry Briggs, and isillustrated by the accompanying drawings and photographs (Figs. 1to 9). Experimental Investigations upon the Theory of the Pitot Tube and theWoltmann Mill, by A. Rateau, Trans. Inst. M. E., 1898-1899, vol. xvii., page124. tThe Velocities of Currents of Air in Mines, Trans. N. E. Inst., 1861-1862,vol. X., page 207. 92 TRANSACTIONS INSTITUTION OF MINING ENGINEERS. [Vol. LXII. The whirling rod on which the meter under test is mounted isrotated by means of a leather sewing-machine belt, I inch in diameter,from a special driving gear (Figs. 1 and 2). Owing to the very widerange required, it was decided to adopt a mechanical rather than anelectrical arrangement for obtaining different speeds. The variable-speed gear, which is worked from a shunt-wound motorthrough a worm and worm-Avheel, is of the epicyclic type. The verticalbevel-wheels D are carried round at constant speeds; they engage with ELEVATION. Fig. 2.—Elevation and Plan of Driving Gear for Anemometer , One-eighth Actual Size. the horizontal bevels G and E, of which the latter is in one piece withthe brake-wheel ¥. The brake is a motor-cycle belt, and is adjusted bythe screw and handle E. Tightening of the brake causes C, and therefore the drivmg-pulley,to rotate at a higher speed. By this means the rod can be whirled atany rate between 5 and 70 revolutions per minute, and this speed can bequickly and easily changed. Both the motor and gear are mounted ona wooden frame; they occupy little space, and are very portable. 1921-1922.] COOPER THE TESTING OF ANEMOMETERS. 93 The framework on which the whirling rod and small motor ismounted (Fig. 3) was also designed to be portable, so that the apparatuscan be moved aside after completing a test. The rod is of Chesterfieldsteel tubing, No. 21 gauge, 2 inches in diameter, 12 feet long, andweighs 8 pounds. It combine
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