FLYWHEEL, a wheel designed to pre serve or store momentum, as in a machine which is called upon to do considerable work set at intervals. It is always made with a heavy rim, and as it acquires speed its inertia assists its maintaining that speed, so that any sudden demand for extra power is available, and any tendency to run away or be cause of sudden release of load, is avoided. It affords a simple means of overcoming a dead centre, and of balancing a machine subject to irregular demands. The principles of the fly wheel are those of inertia and centrifugal force. It is well known that a rotating body tends to continue its motion and resist any change either of acceleration or retardation. The heavier it is and the larger its diameter and speed the more it resists a change, because of its inertia. It is thus apparent that a heavy fly-wheel may be speeded gradually, and then becomes a store of energy, so that if there is a sudden demand for an excess of power, with no noticeable change of speed, as when a heavy press comes together to stamp metal, the mechanism moves continuously, without the stopping or jerking which would occur if there were no attached fly-wheel. It may be called an equalizer of load. Fly-wheels for steam engines were formerly built very large and heavy, but rather numerous bursting accidents caused closer investigation of the strains to which they were subjected. In Benjamin's tests it appeared that cast iron fly-wheels might burst at from 190 to 425 feet per second speed of rim. It is now, therefore, deemed unsafe to design a cast iron fly-wheel to run faster than 100 feet rim-speed per second. Cast steel, however, is made that will safely sustain a speed of 230 feet per second. Well-made wooden fly-wheels are considered safe at 150 feet per second speed. It has been found con venient in transmitting power to utilize fly-wheels for carrying belts, and very large wheels with heavy belts are so employed in many factories. A steam-engine driving a lot
of heavy machinery would °race)" or run away when a number of the machines were discon nected suddenly, if it were not for the fly wheel, that equalizes conditions. The four cycles combustion engine cannot be operated at all without a fly-wheel, as it explodes only once in four revolutions. See STEAM AND STEAM ENGINES and INTERNAL COMBUSTION ENGINE.
FO, the name given by the Chinese to Buddha. See BUDDHISM.
FOA, foa, Eugenie, French author: b. Bordeaux 1795; d. 1853. Her maiden name was Fradis, and she was of Spanish-Jewish descent. Separated from her husband she sup ported herself by her pen, often writing under the name ((MARIA Her tales for young children arc delightfully clever. Notable among her works are 'Les Memoires d'un Polichinelle' (1839) ; 'Le Petit Robinson de Paris' (1840) ; and 'Le Vieux Paris' (1840).
Frederick John, English theologian: b. Ipswich, 10 Aug. 1855. He was educated at Eton and at Trinity Col lege, Cambridge. He was ordained in 1879 and from 1897 to 1912 was examining chaplain to the bishop of Peterborough. He became hon orary canon of Peterborough in 1901, and from 1882 to 1916 was lecturer at Jesus College, Cambridge, where he was dean after 1895. In 1916 he was Lowell lecturer at Boston and in the same year became Briggs professor of Christian institutions at the Union Theo logical Seminary, New York. He published 'History of Christian Church to A.D. 33P (1891; 6th ed. to A.D. 461, 1914) ; 'Christian Difficulties in the Second and Twentieth Centuries' ; 'A Biblical History of the He brews' (1903; 3d ed., 1910); 'Biblical His tory for Schools' (1912-13) ; 'St. Luke and a Modern Writer' (1916) and contributions to the Athenceum, Church Quarterly, Cambridge Review, Hastings' 'Dictionary of Religion and Ethics,' Harvard Theological Review, etc.