. Electric railway journal . burningof the balls and race. Moisture and dirt collect on thesurface of the insulation, and the current then has aneasy path to the ball race. Again, contact shunts aresometimes torn off entirely and current then passesover the surface of the insulation from the socket cast-ing to the race. When new ball races are installed care should betaken to see that the lower edge of the ball race doesnot project beyond or come flush with the contact sur-face of the socket casting. This precaution will pre-vent the contact shunts from bearing on the race, forthen they cannot
. Electric railway journal . burningof the balls and race. Moisture and dirt collect on thesurface of the insulation, and the current then has aneasy path to the ball race. Again, contact shunts aresometimes torn off entirely and current then passesover the surface of the insulation from the socket cast-ing to the race. When new ball races are installed care should betaken to see that the lower edge of the ball race doesnot project beyond or come flush with the contact sur-face of the socket casting. This precaution will pre-vent the contact shunts from bearing on the race, forthen they cannot touch the edge of the race while stillremaining in contact with the face of the socket casting. BURNED OR BROKEN SHUNTS AND BURNED-OPF LEADS ORTERMINALS Of necessity, trolley bases must be made very a result, the distance from the socket casting to thebase plate is usually not more than 1 in. to l1^ , then, is all the space that is available for contactshunts. It is very difficult to get in this space a spring. Trolley Bases—Bushings Pressed in Yoke which is efficient enough to give the necessary currenttransmitting pressure of the contact shunt against thesocket casting. The springs soon take a permanent setand arcing then takes place between the contact surfaceof the socket casting and the shunt. As a result, theshunt is burned away or else the contact surface of thesocket casting becomes so rough from the arcing thatthe shunts are torn off. The surface of the socketcasting is thus destroyed, and in most cases it is nec-essary to install a new casting. A second drawing shows a brass contact ring which was made to screwto the face of the socket casting. As this ring is ofbrass, it forms a better conducting surface than thesteel casting, and if it becomes burned it can easily bereplaced at small expense. This ring also permits there-use of socket castings that have become slightlyburned since the lower face of the casting can beturned off for the reception of t
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