. The Street railway journal . than on the two outside rails, a feature which quently found. In this case the question often arises whethersupplementary ground return feeders should be used orwhether the rails which have neared the end of their life shouldbe rebonded or welded. If the latter is proposed, care shouldbe taken to learn whether the roadbed is of sufficient stabilityto hold the rail so as to insure reliability in the bonding orwelding of the rail return circuit. The current flow on the pipes can be shown on a pipe map bya broad color band paralleling the pipe, the width of the line
. The Street railway journal . than on the two outside rails, a feature which quently found. In this case the question often arises whethersupplementary ground return feeders should be used orwhether the rails which have neared the end of their life shouldbe rebonded or welded. If the latter is proposed, care shouldbe taken to learn whether the roadbed is of sufficient stabilityto hold the rail so as to insure reliability in the bonding orwelding of the rail return circuit. The current flow on the pipes can be shown on a pipe map bya broad color band paralleling the pipe, the width of the linebeing proportional to the mean current flow on the pipe. Itmakes considerable difference whether tests for current floware made in summer or winter, as the current that leaves therail is less when the ground is frozen, but the conductivity ofthe rails is better at low temperature, and any metallic connec-tions between pipe systems and rail become accentuated, andare easily located by the direction of current flow on the Street Xy Journal FIG. 3.—LOCATION OF LOSSES IN A TWO-MOTOR GE 57 EQUIPMENT, WITH K2 CONTROLLER, 14 B3 TRUCK, CAR WEIGHT 36,000 LBS. greatly increases the ground return losses and does not fullyutilize the conductivity of the rail return. All these existingconditions have to be discovered, and their relative importancein the operating economy of the system determined in a com-plete physical report. By an autographic record the condition■of each bond is recorded, the locations of those which are de-fective are marked, and the current density which should becarried by the rails, as determined by the feeder outputs sup-plying equipments operating on that line, is obtained. Thereoccurs in every system critical points where the bonding playsa very important part, and the current may be diverted throughroundabout paths with large losses in the return circuit. Todesignate these bonds and to state definitely where the returncircuit is otherwise defective, for
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
