Page:Stationary steam engines, simple and compound; especially as adapted to light and power plants (IA stationarysteame03thur).pdf/103

ELECTRIC LIGHTING PLANTS. 79 This governor is adjusted for an engine moving in the direction of the arrow. To adapt it to an opposite motion, the pins, b, b,are shifted to the other set of arms which are shown having bosses for their reception. Wooden buffers check the governor at the extremity of its range of motion. The range of expansion, as determined by the governor in this engine, is from the beginning up to two-thirds stroke. The engine has many interesting peculiarities of construction, in its details, which space will not permit us to consider.

A licensed engineering company formerly building this style of engine made a form of bed which is somewhat similar to that designed by the makers of the Porter-Allen engine, but which is particularly solid and graceful in appearance. It is seen on the opposite page.* This firm, as well as the original makers of engines built under Thompson's patents, thus tried to secure in their engines great weight in the parts in which is solidity is important, such large area of bearing surfaces as is essential in these engines, moderately high-speed of piston and of rotation, a steam pressure, usually of about 80 pounds per square inch, and adopt a ratio of expansion for their non-con- densing engines, of from four to five. Their table of powers of their standard sizes is based upon estimates for steam at 80 pounds and a cut-off at one-fourth. In construction, these engines are carefully made with all joints

of a "box-bed," and tlius to secure maximum vertical and horizontal stiffness in this manlier, so far as the knowledge of the writer extends, was Dr. E. D. Leavitt, Jr., who made such an arrangement in engines, in the design of which the writer assisted, as early as 1860.
 * The first designer to carry the line of the steam cylinder along the surface