. The Street railway journal . position ready to grind, and theother side dropped below on a double hinge. When the machine islowered in the pit, a car can be run over the machine without anyinterference. When raised to position the grinding head is brought The moment of resistance to oscillation can be increased infour ways. First, by increasing the stiffness of the outer springs;second, by increasing the distance of the springs from the center ofgravity of the car body and load; third, by increasing the wheel base(distance from center to center of wheels); and fourth, by counter-balancing th
. The Street railway journal . position ready to grind, and theother side dropped below on a double hinge. When the machine islowered in the pit, a car can be run over the machine without anyinterference. When raised to position the grinding head is brought The moment of resistance to oscillation can be increased infour ways. First, by increasing the stiffness of the outer springs;second, by increasing the distance of the springs from the center ofgravity of the car body and load; third, by increasing the wheel base(distance from center to center of wheels); and fourth, by counter-balancing the ends by the weights of the motors, wheels and axles,so that a tendency of either end of the truck to rise will be checkedby the weight of these parts, which will keep it down. If we assume the spring system to be sufficiently strong to sup-port the car body and load at rest, it is undesirable to increase thestiffness of the springs in such a system, as increasing their stiffness 58 STREET RAILWAY JOURNAL. [ XIV. No. :FIG. 2.—STRAIN DIAGRAM will tend to make the car ride hard; consequently, in order to obtain,with the same spring system, sufficient resistance to oscillation andsufficient flexibility to insure ease of riding, it is necessary to makethe spring base, as well as the wheel base, as long as possible, thusobtaining from a set of springs with a given weight sustaining power,the greatest possible amount of resistance opposed to the oscillationsof the car body. The exact relation between the length of spring base to thetendency to oscillation is shown mathe-matically in Fig. 2, in which B, is thecenter of gravity of the car body andload, A D the axis of the end sup-porting springs, F A E the arc ofoscillation around this center of gravity,and A C a. tangent drawn to this arc atthe point, A. The moment of resist-ance of any given spring to oscillationtherefore equals JV X A CX cos C AD, in which W equals the resistanceper inch of spring compression, and AC\s m
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
