The frame of this engine is very heavy, with longitudinal and cross
ribs securely bracing it. It forms the lower guide for cross-head, and
contains the pillow block bearings at the front end. It also forms the
front cylinder head, to which the cylinder is bolted. The working parts
are placed as low in the frame as is possible, so that the strain is
brought in line with the line of greatest resistance.
The double disc center crank shaft allows of two small heavy band
wheels, one of which has the shaft governor attached to the inside,
that operates the valve automatically to give the point of cut-off in
accordance with the variation of load.
The valve is of a special design, and so constructed as to admit steam
to the cylinder port through four different openings. It also exhausts
steam through four different openings at once.
The engine frame rests its whole length and is securely bolted to the
sub-base, which is bolted to the floor, and the smaller sizes need no
elaborate foundations.
This style of engine ranges in size from 35 to 350 horse-power
approximately, the speed of the smaller ones ranging from 275 to 325
revolutions, and of the larger from 160 to 185 revolutions, and are
used extensively where high speed is required, and where the load is of
an intermittent character.
[Illustration: Watertown High Speed Engine.]