ELECTRIC TRUNK-LINE OPERATION—-SPRAGUE. L57, 
Both machines are of the four-axle bogie-truck type, the trucks 
being linked together. The geared locomotive weighs 93 tons and the 
gearless 126 tons, but the weight per axle is well within the usual 
allowance. On each truck are four motors, connected two in series, 
to be operated at a maximum line potential of 1,500 volts. The 
geared motor construction is of the usual standard, but fitted with 
commutating poles, while the gearless machine has modified bipolar 
motors of the New York Central type. 
A comparison of the efficiency curves of the two machines is inter- 
esting, these showing for each from 87 to 88 per cent on a five-hour 
load, and falling only to 83 per cent with 50 per cent increase, while 
at half this load the efficiency of the gearless machine is much higher 
than that of the geared. Some adequate idea of the capacity of the 
gearless machine may be gathered from a statement that it will main- 
tain a drawbar pull of nearly 25,000 pounds at a good rate of 
speed for several hours continuously, and with natural ventilation. 
These extraordinary characteristics would, for the class of service for 
which these machines were considered, amply warrant the additional 
weight because of the simplicity of the gearless machine. 
A very promising type of machine (fig. 7), embodying many of 
the good features of those which had preceded it, is now under con- 
struction for use either on direct current or with a motor-generator 
set supplied from an alternating-current trolley. This machine is 
of the four-axle free bogie type, the drawbar pull being taken through 
the main frame. On each truck, and forming an integral part with 
it, are two bipolar gearless motors driving the middle pair of axles, 
and at either end of each truck is a pair of leading wheels of smaller 
diameter, which have a limited, spring-resisted side play. The nor- 
mal wheel base of each truck is 12 feet, the total wheel base 32 feet, 
and the length over all 36 feet. This machine should be capable of 
an almost unmatched speed and freedom in following irregular curva- 
tures, and with special ease of track approach. 
The various locomotives thus briefly described are but a fraction 
of those proposed by various makers to fit particular conditions and 
types of apparatus. Their construction does not, in many particulars, 
meet the preconceived ideas of some steam-locomotive builders, with 
whom a high center of gravity and all the weight possible carried on 
springs is a cardinal principle, and a very correct one when we con- 
sider the necessities of the steam locomotive. The electric locomotive 
has a lower center of gravity, that of the New York Central machine 
being about 44 inches, the New Haven 51, and the Ganz probably 
somewhat higher, while that of the steam locomotive is sometimes 
as high as 73 inches. The electric machine, therefore, will have less 
tendency to topple over, but a greater resultant side pressure in case 
of irregularity of track when entering a curve, or running on an 
