. Steel rails; their history, properties, strength and manufacture, with notes on the principles of rolling stock and track design . ange in the vertical velocity ofthe load as the flat spot comes over the rail. Professor Hancock, of Purdue University, has made a very careful studyof the mathematical relations existing between the speed, impact, and lengthof spot.* Following Professor Hancocks analysis, letA, in Fig. 25, be the center of a car wheel Dinches in diameter, revolving as shown by thearrow, and CP be a flat spot L inches long justbeginning its contact with the rail. The wholewheel i
. Steel rails; their history, properties, strength and manufacture, with notes on the principles of rolling stock and track design . ange in the vertical velocity ofthe load as the flat spot comes over the rail. Professor Hancock, of Purdue University, has made a very careful studyof the mathematical relations existing between the speed, impact, and lengthof spot.* Following Professor Hancocks analysis, letA, in Fig. 25, be the center of a car wheel Dinches in diameter, revolving as shown by thearrow, and CP be a flat spot L inches long justbeginning its contact with the rail. The wholewheel is turning about the point C, and will soturn until P reaches R and the blow is struck onthe rail. At this latter instant A will have reachedA and will be moving downward with a velocityrepresented by the line he. If the velocity of A,which is practically the same as that of the train,is assumed as v feet per second, then A , CP L be = vsmd = V^:^ = V jz- If we regard the mass of the wheel and its load as concentrated at A and callthe total weight W pounds, the kinetic energy of the mass just before the railis struck will be: E. Fig. 25. — Flat Spot in Wheel(Hancock.) This formula will give for the energy of impact of a flat spot inches longin a wheel 33 inches in diameter, carrying a load of 20,000 pounds when the * Paper read before the Indiana Engineering Society, January, 1908. See also discussion byL. S. Spilsbury, presented by H. H. Vaughan in the American Engineer and Railroad Journal, December,1908. 56 STEEL RAILS train is traveling 60 miles per hour, 13,800 foot-pounds. At this speed it wouldseem, however, that the results obtained by the formula would be open toquestion. In the derivation of the formula it is assumed that the wheel turnsabout C until P reaches R. This assumption only holds true for speeds fromzero up to about five miles per hour; * at speeds greater than five miles per hourthe point C will tend to leave the rail, and the whole wheel will revolve
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