. The Street railway journal . ently been slightlychanged by the installation of an improved pick-up compressoron the cab. The readers of the previous article will rememberthat the system employed is that of the Hopkinson switch, usinga high-voltage pick-up bobbin and a series hold-up picking up the switch there must, therefore, be a source ofhigh potential on the cab, and one independent of the powerhouse. In fact, one of the features of the B. & O. system is thefact that a source of high potential has been obtained in a re-liable manner without the addition of any large quantity o
. The Street railway journal . ently been slightlychanged by the installation of an improved pick-up compressoron the cab. The readers of the previous article will rememberthat the system employed is that of the Hopkinson switch, usinga high-voltage pick-up bobbin and a series hold-up picking up the switch there must, therefore, be a source ofhigh potential on the cab, and one independent of the powerhouse. In fact, one of the features of the B. & O. system is thefact that a source of high potential has been obtained in a re-liable manner without the addition of any large quantity ofauxiliary apparatus. This is accomplished by using an electricmotor air compressor, either in its normal function as an aircompressor for the brakes or as an air motor. In this serviceit takes air from the tanks and drives its motor as a dynamo,thereby supplying the necessary pick-up current, and also thelights for the cabs at such times when the rail section uponwhich the shoes are resting is dead. This compressor, which. FIG. L.—ELECTRIC MOTOR AIR COMPRESSOR has recently been redesigned, is of the Christensen type, andwas built by the National Electric Company. It is illustrated inFig. 1. It is a geared machine, carrying a motor on the top, the com-pressor proper being below. The latter has three cylinders, sothat there will be no dead center in starting, as an engine, andit is equipped with poppets in the ordinary way, the engine por-tion of the equipment-being provided for in the shape of a re-volving valve, which is driven by spur gearing from the maincompressor shaft in the same direction and at the same valve shaft can be moved to the right or left, and in oneposition admits and exhausts air in engine time, and in the otheris out of commission. The valve shaft is provided with a spline,which slides back and forth through an appropriate key in thedriving gear. The motion of the valve shaft is controlled byan air cylinder, shown at the right of the figure and
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
