156 
ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
motors a motor-generator set, comprising an induction motor taking 
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gearless motors. 
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Fie. 7.—High-speed bogie truck direct-current locomotive, 
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Weight, 80 to 110 tons, 
current directly from 
the line, and driving a 
continuous-current gen- 
erator to supply the 
motors, this converting 
set being carried in the 
main cab, with provi- 
sion made for the ex- 
tra weight by bogie 
trucks at each end, or 
in an independent ten- 
der taking the place of 
the steam tender in ex- 
isting steam practice 
(fio755).) “OL course 
this is the introduction 
of a moving substation 
individual to the loco- 
motive which is oper- 
ated by it, and makes 
the latter subject to all 
the idiosyncrasies of 
the intermediate appa- 
ratus, besides laying up 
an enormously expen- 
sive machine in case of 
any special trouble. 
Where the motor-gen- 
erator set is carried in 
a separate tender, this 
disablement only cuts 
out a part of the equip- 
ment, which can be re- 
placed by another like 
part, but in any case it is 
debatable whether such 
a moving substation 
offers any advantage 
over the stationary one. 
Some time since I 
made a very careful in- 
vestigation of the pos- 
sibilities of direct-cur- 
rent gearless and geared motors (fig. 6), the former of the bipolar 
type, for identically the same service, a very severe one. 
