. The Street railway journal . rst car onaccount of the wind pressure. The third factor is to repre- sent side resistance, or the resistance offered by the atmos-phere to the side of the train. The fourth factor he terms os-cillating resistance, or increase in journal or rolling frictiondepending on the speed. When we combine, we have heretwo factors which are proportional to the weight of thetrain, and two which are independent of it. From the Engineering News, 1893, results are given,which if put into a formula would be as follows:R = 2 + .25 M D. L. Barnes has given as result of his observa
. The Street railway journal . rst car onaccount of the wind pressure. The third factor is to repre- sent side resistance, or the resistance offered by the atmos-phere to the side of the train. The fourth factor he terms os-cillating resistance, or increase in journal or rolling frictiondepending on the speed. When we combine, we have heretwo factors which are proportional to the weight of thetrain, and two which are independent of it. From the Engineering News, 1893, results are given,which if put into a formula would be as follows:R = 2 + .25 M D. L. Barnes has given as result of his observationsR = 4 4- .16 M These two formulas have been developed in connectionwith higher speeds up to 100 miles per hour. Dodd proposed, Street Railway Journal, September,1898: P = (18+ .2v) E4- (7+ .2v)TTh is is equal to the following if the train only is con-sidered: R = 7 4- .20 MLundie gives as a proposed formula: R = 4 + S (.2 + 35 4-T14 M ) Or, transposed, R = , 354-T Mr. Lundies formula was gotten from tests with the. 40 50 00 MILES PER HOUP FIG. 1 0 80 90 100 Street Railway Journal,!?. T, cars using electric motors. The friction of the electricmotor gears and eight extra bearings per car is a con-siderable factor in the total friction. His formula, there-fore, would give too high results. In ordinary train resistance there are three factors. Thejournals of the cars, the friction of the wheel on the rail,and the air resistance. In Mr. Lundies test he should alsoconsider a fourth, namely, the friction of the gears, and thebearings of the motors. All of the cars which he tested hadmounted on one of the trucks two 60 motors. Thefriction of gears and bearings of these motors whenrunning at 20 miles an hour is about 1400 watts,or 2800 watts per car. This is equivalent to , or, reduced to the term of train resistance,would be equivalent to lbs. per ton. FromMr. Lundies curve the train resistance at 20 miles is12 lbs. per ton, with a 20-ton unit; subtracting
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