MOTIVE PO^^'ER AND ROLLING STOCK 345 
placed under the forward end of the locomotive and the other 
under the tender. 
Power is furnished by two single-cylinder engines attached to 
the frame one on each side of tlu; boiler. Each (nigine is inclined 
at an angle of 45 degrees from the vertical and the reciprocating 
parts are connected directly to a central single-throw, articu- 
lated driving shaft. 
Spur wheels are fitted to the center of the forward and the 
rear axles and pinions attached to each end of the driving shaft 
mesh into them. The spur wheels and pinions are enclosed in 
Fig. 116. — A Shay Geared Locomotive. 
a tight case which is designed to prevent the entrance of grit and 
other foreign substances. 
(2) Side Shaft. — There are two makes of side shaft locomo- 
tives, namely, the Shay and the Willamette, both of which are 
similar in design. The former, built in weights ranging from 13 
to 150 tons, has been on the market for many years, whUe the 
latter has only recently been offered for sale. 
The frame of the Shay is made of hea\^ steel "I" beams 
braced with trusses, and is supported on from two to four pairs 
of four-wheeled swivel trucks. Locomotives weighing 55 tons 
and less have two trucks; those from 65 to 105 tons, inclusive, 
three trucks; and the 150-ton locomotives, four trucks. The 
third and fourth trucks on locomotives weighing from 65 to 
150 tons are used to carry the tender. 
The boiler is of the horizontal locomotive type with extra 
large fire box and steam space. The engines are of the vertical 
type and are attached to the boiler plate on the right-hand side 
just in front of the cab. Locomotives of from 13 to 20 tons 
weight are equipped with two cylinders, and those of greater 
