ELECTRIC TRUNK-LINE OPERATION—SPRAGUE. Silt 
the three pairs of main drivers, the middle only is journaled in the 
main frame, each end pair being journaled at one end of a pivoted 
guiding truck, at the outer end of which are guiding wheels about 
one-half the diameter of the driving wheels. ‘The end drivers have 
a limited end play, and one king bolt has a similar freedom of move- 
ment, while the other is fixed, resulting altogether in great freedom 
of adjustment to track curvature. The two motors, spring-supported 
through the locomotive frame, are each quarter-cranked and con- 
nected to side rods having downwardly projecting jaws which loosely 
engage the driving pins of the middle drivers, the centers of which 
are somewhat below the centers of the motors. On each side of the 
jaws of the side rod are coupled the connecting rods of the outer 
drivers, provision being made in all bearings for the necessary free- 
dom of movement and adjustment. 
In an earlier type the locomotives were equipped with two sets of 
twin motors for high and low tension, the low tension to be operated 
in cascade relation to get slow speed in starting and for running on 
grades, then to be cut out,and the regular running to be with the high- 
tension motors alone. In the latest machines the twin-motor con- 
struction has been abandoned, and the locomotives are equipped with 
two 15-cycle high-tension polyphase motors, one having 8 and the 
other 12 poles, and an arrangement of field circuits in the latter ma- 
chine such that it can be temporarily made a low-tension motor oper- 
ating in cascade relation with the other. This combination permits 
of three regular operating speeds of about 16, 26, and 40 miles per 
hour. At the lowest speed the motors are in cascade relation, with 
high draw-bar pull; at middle speed the 12-pole motor is in operation 
alone on high tension; and at the highest speed the 8-pole motor is 
used alone, likewise on high tension. Of course the physical connec- 
tion of the two motors together and to all drivers makes this method 
of operation possible. The rated capacity of the motors, as given by 
Valatin, is extraordinarily high, that with the 12 poles being stated as 
1,200 horsepower, and that with 8 poles 1,500 horsepower, based upon 
the one-hour rise of temperature to 75°. The motors average about 
13 tons each. 
The use of connecting rods in this locomotive is not as objection- 
able as the use of the driving and connecting rods in a steam loco- 
_ motive, because the strains are very different, and the rotative weights 
can be far more perfectly balanced. It can be fairly said to have the 
advantage that with the minimum possible weight of locomotive 
there is no such thing as slipping an individual wheel, a trouble 
which will occur at times with all locomotives having independently 
driven axles if equipped with powerful enough motors, because of 
variation in motor characteristics, track and wheel conditions, and 
unequal wheel pressure caused by the drawbar pull. 
41780—08——14 
