Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc. . 5X5280 ^^ , ^•^•=^3000X6^=- *The frictional resistance opposing the motion of the car is made up of several compo-nents: flange, a gearing and bearing friction, and air resistance. The last increases rapidly withthe speed while the others are nearly independent of it. Both of these differ
Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc. . 5X5280 ^^ , ^•^•=^3000X6^=- *The frictional resistance opposing the motion of the car is made up of several compo-nents: flange, a gearing and bearing friction, and air resistance. The last increases rapidly withthe speed while the others are nearly independent of it. Both of these differ from slidingfriction, such as that between brake shoes and wheels, which decreases as the speed increases. 230 ELECTRIC RAILWAYS 135 J L Curve Resistance. Curve resistance may sometimes be ofimport&.nce. The usual method of allowing for it is to consider thatthere is a certain amount ofresistance per ton per degreeof curvature, say number of degrees ofcurvature is the angle be-tween two radii of the curvedrawn at the ends of a chord100 feet in length. In termsof the radius r, the angleof curvature is twice theangle of which the sine is 50 —. This relation is shown diagrammaticallv in Fig. ILLUSTRATIVE PROBLEM (a) What is the curvature of a curve the radius of which is 50. Fig. 129. Graphical Determination of TrackCurvature 100 feet? As explained above, sine of ^ the angle=^^ = | From the table of sines w^e find that this is the sine of 30°. The angle ofcurvature is, therefore, 60°. (b) What additional resistance is caused by this curvature? 7^= pounds per ton Grade Resistance. Grade resistance, as was illustrated in con-nection with the series motor problems, is simply the tractive effortin the direction of car motion necessary to overcome the efYect ofgravity. It is numerically equal to the product of the weight ofcar, in pounds, and the grade, in per cent, divided by 100. ILLUSTRATIVE PROBLEM What tractive effort is necessar} to overcome
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