. The Street railway journal . of all the shoes with increase of load tendto flatten and converge. This peculiarity has been observed in the Berlin-Zossentests made in Germany in 1902 in connection with cast-ironshoes on steel tires, where it was found that the coefficientof friction was very nearly constant at speeds between 45and 60 miles an hour, but as the speed decreased below 45miles an hour the brake-shoe friction rapidly increased, asshown by the following table : 68 miles an hour, average coefficient of friction 62 miles an hour, average coefficient of friction 47 miles an
. The Street railway journal . of all the shoes with increase of load tendto flatten and converge. This peculiarity has been observed in the Berlin-Zossentests made in Germany in 1902 in connection with cast-ironshoes on steel tires, where it was found that the coefficientof friction was very nearly constant at speeds between 45and 60 miles an hour, but as the speed decreased below 45miles an hour the brake-shoe friction rapidly increased, asshown by the following table : 68 miles an hour, average coefficient of friction 62 miles an hour, average coefficient of friction 47 miles an hour; average coefficient of friction 31 miles an hour, average coefficient of friction 15 miles an hour, average coefficient of friction 5 miles an hour, average coefficient of friction The convergence of the curves of the different shoestoward a common meeting at some higher speed or loadindicates the effect of heat upon the structure of the shoeface. Under conditions of low rate of heating each par-. CHART NO. 1.—SHOWING LOCATION OF VARIOUS SHOES ONCHILLED AND STEEL-TIRED WHEELS—SIMILARCONDITIONS OF LOAD AND SPEED LaboratoryNumber Description of ShoeA-96 Soft cast Hard cast Soft cast steel. H-96 Soft cast iron, wrought-iron Medium hard cast iron. 49- 1901 Cast-iron body, white-iron inserts. 50- 1901 Hard cast-iron body, chilled ends, sofe cast-iron Hard cast iron, expanded steel inserts. ticular material holds up in proportion to the strength ofthe particles forming the wearing face. The hard chilledor tough ductile surfaces polish over and slide, where theopen or granular structure or the composite material in thefilled shoes make more intimate contact with the wheel faceand hold better. As the intensity of heat generation increases by the con-tinued application of the shoe or by the extra pressure orwork done in a given time, the whole structure of the faceof the shoe undergoes a change. Unchi
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
