. Electric railways, theoretically and practically treated . f May 21, 1904, as follows : The instrument when operative consists of a strip ofpaper in roll form drawn by a spring motor at uniformspeed over a drum. The motor is fitted with a delicategovernor, by means of which the speed may be changedat will. The paper passes over the drum under three pen-cils, the pencils pressing the paper against the drum andproducing a record of time, current input, and wheel revo-lutions of the car. The pencils recording time and wheelrevolutions are actuated by electromagnets, the pencils pro-ducing serra
. Electric railways, theoretically and practically treated . f May 21, 1904, as follows : The instrument when operative consists of a strip ofpaper in roll form drawn by a spring motor at uniformspeed over a drum. The motor is fitted with a delicategovernor, by means of which the speed may be changedat will. The paper passes over the drum under three pen-cils, the pencils pressing the paper against the drum andproducing a record of time, current input, and wheel revo-lutions of the car. The pencils recording time and wheelrevolutions are actuated by electromagnets, the pencils pro-ducing serrated lines when the paper is in motion. A clock mechanism mechanically closes a local stor-age battery circuit through the time relay magnets at suc-cessive half-second periods. It is obvious that the lengthof line produced by the time pencil on the paper will bethe same between contacts, providing the paper move at auniform rate. Upon one extremity of one of the axles of the car isfitted a wooden drum containing a metal strip, A brush 48 ELECTRIC RAILWAYS-. HORIZONTAL PROJECTION. Fig. 20. — KEILEY SECTION VIEW. RECORDER. pressing upon the drum makes contact with the metal stripwith each revolution of the car wheel, thereby closing a RECORDING INSTRUMENTS. 49 local storage battery circuit through the second pair ofmagnets. The length of line produced by the revolutionpencil varies v^ith the car speed between successive con-tacts. At starting, the car wheel may make the first revo-lution in approximately one-half second. At a speed of 22miles per hour approximately four contacts will be made inone-half second. The duration of time per revolution pro-vides a means of plotting a speed-time curve when thecircumference of the wheel is accurately known. The third feature of the instrument, and by far themost important, is the device for recording current. Itconsists of an ammeter connected in series with the powerline of the train. The range of this instrument is of suf-ficient magn
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