. Electric railway journal . n an effective means of in-creasing the rating. In locomotive work it is customaryto use a separate motor-driven blower attached to thebody of the cab, which forces the air through a propersystem of piping into the motors. It is very difficult-to dothis on the ordinary electric car on account of the extremeswing of the trucks and the restricted space available. ( >neof the large manufacturers has attacked the problem bymounting the blower inside the motor case with the rotorattached to the armature shaft. This makes an almostideal simplification of apparatus but
. Electric railway journal . n an effective means of in-creasing the rating. In locomotive work it is customaryto use a separate motor-driven blower attached to thebody of the cab, which forces the air through a propersystem of piping into the motors. It is very difficult-to dothis on the ordinary electric car on account of the extremeswing of the trucks and the restricted space available. ( >neof the large manufacturers has attacked the problem bymounting the blower inside the motor case with the rotorattached to the armature shaft. This makes an almostideal simplification of apparatus but seems to be open tothe objection that the fan will suck in dirt and water as theyare thrown up by the wheels and the wind against theunder side of the car. If some effective means can befound of eliminating these objectionable materials fromthe air taken in by this method, it ought to prove veryuseful. INSULATION Raising the working temperature by the use of heat-resisting insulation has been tried in several instances with. Fig. 10—Equipment—Trailer Truck, Phillips Design, forCity Service very encouraging results. Under some operating condi-tions with the older type motors it was hardly worth whileto seek improvement in this direction, because the motorswere also working quite close to the limit of commutatingcapacity. With the introduction of interpole constructionthis limitation is removed, and the possibility of operatingat higher temperatures means greater horse-power from agiven motor or a smaller or lighter motor for a givenhorse-power. ELECTRIC RAILWAY JOURNAL. 858 ELECTRIC RAILWAY JOURNAL [Vol. XXXVIII, No. 16. Asbestos and mica have been used with some success asheat-resisting insulating materials; but the most encourag-ing results have been attained by the impregnation ofarmature and field coils with a recently discovered com-pound which upon being baked becomes hard and dense,like amber, and of great heat-resisting powers. Ordinarycotton insulation, so treated,
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