. Train resistance : a consideration of its elements and a discussion of experiments made with the university dynamometer car . with which a load is being hauled. If one train gives aresistance of,say,eight pounds per ton and another a resistance often pounds per ton,both being under the same conditions,we know thatthe second train is not as economic as the first. Results of anytest should contain a statement of the distribution of the load onthe wheels. ELEMENTS OF TRAIN RESISTANCE. The several component parts 3 of train resistance may be grouped under the following heads: 1. Grade resistance
. Train resistance : a consideration of its elements and a discussion of experiments made with the university dynamometer car . with which a load is being hauled. If one train gives aresistance of,say,eight pounds per ton and another a resistance often pounds per ton,both being under the same conditions,we know thatthe second train is not as economic as the first. Results of anytest should contain a statement of the distribution of the load onthe wheels. ELEMENTS OF TRAIN RESISTANCE. The several component parts 3 of train resistance may be grouped under the following heads: 1. Grade resistance 2. Curve resistance 3. Rolling resistance 4. Journal friction 5. Effects of velocitya. Air resistance b. Resistance caused by oscillationsThese elements will now he taken up and discussed in the ordernamed. RESISTANCEWork must he done upon a train to raise it up a grade. Thisconstitutes a tax upon the locomotive. The number of pounds pullrequired to raise one ton up a grade can be accurately computed,andhence there oan be no question about this part of train amount of the force is found as follows:. V/e hav^ P*=W sin«* = YY tan ot (approximately). Since <x isalways very small the relation is almost exactly true. If YY be taken as one ton, Resistance per ton = 2000 tan pounds = 20 x per cent of grade. 2. CURVE RESISTANCEA truck in passing around a curve is rotated about a vert-ical axis. If the gage of the track is just equal to the gage ofthe wheels, this axis passes through the center of the truck. Ifhowever the gage of the track is enough wider than the gage of thewheels to allow the rear axle to take a radial position,the axispasses through the point of contact of the rear inner wheel. Thiswas determined hy Wellington by experiments on model trucks. Thisrotation must produce a sliding of the wheels on the track,becausethe3 rotate only in vertical planes parallel to the longitudinalaxis of the truck. Since the longitudinal motion of two wheels onth
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