. Electric trains . r per ton-mile. (6) Ditto, on the assumption of 100 per cent, efficiency of electricalequipment 72= ZTTT?: X 90*5 = 79*6 w hr per ton-mile. (c) Ditto, on the further assumption of zero train-friction— 0-0278 X 1-09 X 242 ^^ , . ^r;^^ = 58*1 w hr per ton-mile. The readily-obtained values set forth in Table XII. are also ofinterest— Table XII.—Allocation of Energy consumed by a Train during a Given Run. Ultimate allocation of the energy. W hr per tou-mile. Per cent, of totalinput. Energy transformed into heat at the brake-shoesf^90_\ Ditto into heat associated with useful pro
. Electric trains . r per ton-mile. (6) Ditto, on the assumption of 100 per cent, efficiency of electricalequipment 72= ZTTT?: X 90*5 = 79*6 w hr per ton-mile. (c) Ditto, on the further assumption of zero train-friction— 0-0278 X 1-09 X 242 ^^ , . ^r;^^ = 58*1 w hr per ton-mile. The readily-obtained values set forth in Table XII. are also ofinterest— Table XII.—Allocation of Energy consumed by a Train during a Given Run. Ultimate allocation of the energy. W hr per tou-mile. Per cent, of totalinput. Energy transformed into heat at the brake-shoesf^90_\ Ditto into heat associated with useful propulsion, into train-friction i —- = j Ditto into heat in the electrical equipment ( -^ = 1 38-6 26725-2 42-6 29-527-9 Total 90-5 100 38 ELECTRIC TRAINS The energy present as momentum at the instant of attaining crest speed is 581 w hr per ton-mile, which is (qtttk ^ 1^0 = j64*3 per cent, of the input to the train. This last value, and the three valuesin Table XII., are represented graphically in Fig. Fig. 20.—Diagram showing the Allocation of the Energy Input for a Servicewith an Average Distance of 0*30 Mile from Start to Stop, and a ScheduleSpeed of 12-7 ml ph (see Table XII., on p. 37). In considering the case of zero train-friction and 100 per cent,efficiency of the electrical equipment, the energy distribution is asfollows:— Input to train = Momentum energy = Brake waste. Allowing for losses in the electrical equipment, but retaining theassumption of zero train-friction, the distribution becomes— INFLUENCE OF MOMENTUM 39 -Heat loss in electrical equipment— Input to train- -Momentum energy (=Brake waste)— If 100 per cent, efficiency of the electrical equipment is againassumed, but allowance is made for train-friction, then the distributionis shown by— —^Brake waste-S —Momentum energy— f3 3 —pj ^ /Train-friction energy\ ,m j. 1 i. • ^ ~i after cut-off M Total tram-friction —- —Train-friction energy up to cut-off I propuls
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