. Electric railway journal . nce steps, issue of Feb. 18, 1911. In anarticle on Resistance Standards, in the issue of May 11,1912, it was brought out that the number of resistance typeshad been decreased from nine to four, that there had beena decrease of per cent in the maximum starting torqueon the first notch, a decrease of per cent in the maximumstarting current, and a decrease of 9 per cent in the maxi-mum variation in torque during acceleration. The slotting of commutators by this company in connec-tion with the use of high-grade carbon brushes began in1908 with the slotting of t
. Electric railway journal . nce steps, issue of Feb. 18, 1911. In anarticle on Resistance Standards, in the issue of May 11,1912, it was brought out that the number of resistance typeshad been decreased from nine to four, that there had beena decrease of per cent in the maximum starting torqueon the first notch, a decrease of per cent in the maximumstarting current, and a decrease of 9 per cent in the maxi-mum variation in torque during acceleration. The slotting of commutators by this company in connec-tion with the use of high-grade carbon brushes began in1908 with the slotting of the commutators of the 150-hpelevated motors. The companys comprehensive tests withsuch brushes were described and tabulated in the issue ofJune 19, 1909, and the excellent results from the practiceof using these brushes with slotted commutators was de-scribed in the issue of April 22, 1910. IMPREGNATION OF FIELD COILS For two or three years previous to 1910 the companyhad in service several thousand field coils that were im-. B. R. T. Electrical Shops—Coils in Drying Oven pregnated by the manufacturers of the motors. The im-pregnated coils proved so satisfactory that the companydecided to install a plant of its own at the Fifty-secondStreet shops. This equipment, which is shown in an accom-panying illustration, consists of one vacuum and one pres-sure tank furnished by the Buffalo Foundry & MachineCompany. The tanks of this design are heated by a steam March 15, 1913.] ELECTRIC RAILWAY JOURNAL 483 jacket instead of steam coils, allowing them to be cleanedwith greater ease. No trouble has been experienced fromleakage of the steam jackets. This equipment has been inoperation from June 4, 1910, and from that date to , 1912, 12,817 field coils, or approximately per centof a total of 17,478 coils, had been impregnated. Experi-ence has convinced the company that impregnation haseasily paid for itself inlengthening the life of thecoils and thus minimizedtheir rewinding.
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