150 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
On all multiple-unit trains, except such as are designed for very high 
speed, in which case there is a possibility of a gearless-motor develop- 
ment, the standard method of motor mounting I introduced on the 
Manhattan Elevated Railway in 1886, and which has been in vogue 
ever since, bids fair to continue. It provides for sleeving the motor 
and carrying a part of its weight upon the driven axle, to which it is 
connected by any required ratio of gearing, the free end being flexibly 
suspended from the truck above the side springs. 
Up to capacities of 250 horsepower, about the limit required and 
permissible for motor-car equipment, single driving on one end can 
be used; but when this type of motor is built for larger sizes, in con- 
nection with locomotives, it seems almost necessary to provide for 
gear driving at each end, which presents some difficulties in con- 
struction. 
The rigid wheel-base type of locomotive without leading trucks is 
illustrated by a direct-current machine built under the direction of 
some associates and myself a*number of years ago for experimental 
work’ on one of the lines running out of Chicago, and also by one 
class of double-unit locomotives which has been frequently proposed 
by various companies for single-phase alternating-current opera- 
LV@iae ae Ba 
An analysis of the action of a locomotive demonstrates beyond 
question that this general type of machine—that is, one having a rigid 
frame and no guiding trucks—is limited to moderate speeds, and 
would be unsafe if operated at high speed on a road with much 
curvature and special work. 
Particular interest naturally centers upon the distinctive types of 
locomotives installed on four important railway systems, the Valtel- 
lina and the Simplon Tunnel in Switzerland, the New York Central, 
and the New York and New Haven, which well illustrate three of 
the principal methods of construction developed to meet the demands 
of different electrical systems. I will briefly describe each, as well as 
make some comment upon a few of the many other types recently 
proposed. 
As illustrating a high order of electrical and mechanical engineer- 
ing, the work of the Ganz Company merits special mention, for it is 
undoubtedly true that the present status of the polyphase system, 
which stands on a favored plane with many Italian engineers, is 
owing almost entirely to the efforts of this company. 
The polyphase motor locomotives (pl. m) built for the Valtellina 
Railway and for the Simplon Tunnel are strikingly individual in 
their construction. The axle mounting of motors is abandoned, the 
motors being entirely separate units mounted on the locomotive 
frame, and coupled to each other and the 62-inch driving wheels 
through an ingenious combination of connecting and side rods. Of 
