. Electric railway journal . ough curves and switches, producesa heavy side thrust of the wheel flange against therail, thereby applying a powerful force couple to theaxle at the wheel hub. To this are added the verticaloscillation of the car on its springs, the effect of im- pact at rail joints, the torsion of the motor, the brakingaction, the gear vibration, etc. Furthermore, it is wellknown that the strain on a member is much more se-vere when for any cause the forces acting thereon arereversed rapidly in their direction, the magnitude alsodepending on the rapidity of the reversals, the eff
. Electric railway journal . ough curves and switches, producesa heavy side thrust of the wheel flange against therail, thereby applying a powerful force couple to theaxle at the wheel hub. To this are added the verticaloscillation of the car on its springs, the effect of im- pact at rail joints, the torsion of the motor, the brakingaction, the gear vibration, etc. Furthermore, it is wellknown that the strain on a member is much more se-vere when for any cause the forces acting thereon arereversed rapidly in their direction, the magnitude alsodepending on the rapidity of the reversals, the effect ofwhich on an axle running with 36-in. wheels at say is equivalent to 840 reversals per minute. While it is not practicable to calculate all of theforces, it is feasible to determine some of them and toanalyze their combined effect on the axle, with the re-sulting fiber stress. Then from experimental data andexperience the factor of safety necessary or desirableto use in the design can be judged. The fundamental. PIG. 1—DIAGRAM OF FORCES ACTING UPON AN ELECTRICCAR WHEN ROUNDING A CURVE facts are admirably covered in a report of acommittee headed by E. D. Nelson and con-tained in the proceedings of the Master CarBuilders Association for 1896. Time hasvery largely borne out most of the deductions reachedin that report and for the convenience of those to whomthis report is not readily available such passages as areof immediate interest are quoted here. The committee first turned its attention to the an-alysis of the forces acting on a car axle, these beingworked out by the late Prof. A. J. DuBois of the Shef-field Scientific School of Yale University. A calcula-tion was first made of the location of the center ofgravity of the car under consideration, which wasfound to be approximately 6 ft. above the head of therail. The committee then ascertained by a road testthat the vertical oscillation of the car on its springsadded about 26 per cent to the load on the journal
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