. The trackman's helper, a handbook for track foremen, supervisors and engineers . ) More creeping appears on imperfectly main-tained track. Mr. W. M. Camp (Notes on Track, p. 584) statesthat there are two longitudinal movements on rails;one, a molecular movement of expansion or contrac-tion in the metal, the other a progressive shifting ofthe rails bodily, commonly known as creeping or run-ning. He states also that the creeping is mostrapid during hot weather, and it is greater ondouble than on single track, and further that it isgenerally in the direction of the traffic. The mannerof the cre
. The trackman's helper, a handbook for track foremen, supervisors and engineers . ) More creeping appears on imperfectly main-tained track. Mr. W. M. Camp (Notes on Track, p. 584) statesthat there are two longitudinal movements on rails;one, a molecular movement of expansion or contrac-tion in the metal, the other a progressive shifting ofthe rails bodily, commonly known as creeping or run-ning. He states also that the creeping is mostrapid during hot weather, and it is greater ondouble than on single track, and further that it isgenerally in the direction of the traffic. The mannerof the creeping and the amount depend upon (1) the 172 THE TRACKMANS HELPER character of the ground or foundation for the track;(2) the direction in which the train loads are theheavier; (3) the proportion of the weight distributedon the two rails; (4) the speed of the trains; and (5)the manner in which the ties are spiked. The actual value of rolling resistance is difficult todetermine as any data are likely to include some of themany other factors which go to make up train Fia. 3] YTTTTTTr. b- Figure Direction of Rolling Resistance That it is a very insignificant part of train re-sistance is the contention of Mr. Webb (Economicsof Railway Location, p. 181). Mr. I. P. Church, inMechanics of Engineering, states that the wordfriction is hardly appropriate except when the road-way is perfectly elastic. Referring to Figure 31 hecontinues: The track being compressed, its resultantpressure is not at 0 vertically under the centre, butsome distance 0-D in front. The rolling-resistanceis therefore EFFECTS OF WAVE MOTION OF RAIL 173 R radius X weight. where ^b is the small distance 0-D. Mr. Pambour gives as the result of experiment onrailroad wheels of cast-iron inches in diameter. b = .0196 to inches. If the force of resistance or the resultant can beassumed as acting normal to the track at the centre ofthe area of contact, we have a triangle of forces oneangle of which
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