. The railroad and engineering journal . and the rail have each a smooth surface where theycome in contact, and the tractive power is due simply to may be exerted, the drivers cannot turn without either abackward or forward motion of the engine. In otherwords, the drivers cannot slip. There are various systems of rack-railroads, but theyall depend upon this one principle, that the power acts insuch a way upon the rail by means of cogs or teeth, as toremove all possibility of slipping. The most general form is to have the rack-rail a thirdrail between the two smooth rails upon which the carsrun
. The railroad and engineering journal . and the rail have each a smooth surface where theycome in contact, and the tractive power is due simply to may be exerted, the drivers cannot turn without either abackward or forward motion of the engine. In otherwords, the drivers cannot slip. There are various systems of rack-railroads, but theyall depend upon this one principle, that the power acts insuch a way upon the rail by means of cogs or teeth, as toremove all possibility of slipping. The most general form is to have the rack-rail a thirdrail between the two smooth rails upon which the carsrun. In this case the toothed drivers on the locomotiveare placed in the center one behind the other. Where thegrade is very steep, in order to guard against all chancesof an accident from a runaway train, there is often a me-chanical device so arranged that if the brakes do not act,or if the rack-rail or driver breaks, the whole train can belifted bodily from the track, resting simply upon shoes,which make it impossible for it to the adhesion between these two smooth surfaces. As hasbeen stated, this adhesion varies with the state of the railand the wheel, whether moist or dry, etc., and also di-rectly as the weight on the drivers ; but it may be takengenerally as one-quarter the weight on the drivers. Fromthe resistance due to grade and that opposed to the move-ment of a train upon a straight and level track, we can atonce see that a rate of grade which gives a very slightvertical angle will soon consume all the tractive power ofthe locomotive. That is, the resistance opposed to themotion of a train upon a grade soon becomes equal lo orgreater than the adhesion between the rail and the driver. Where circumstances are such that a grade is requiredso steep that this adhesion between the smooth railand the driver is insufficient, then there is introduced arack-rail, as shown in Plate LllI, fig. i, and Plate LIV,figs. 3 and 4, or a toothed rail, on which runs a pinion ordr
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Keywords: ., bookcentury1800, bookdecade1880, bookidrailroadengi, bookyear1887
