The locomotive style of boiler has a large steam dome in center and an ash pan under fire box. It is supported upon the long wooden skids by brackets bolted to the sides of boiler, the heater being also bolted to the skids.
The independent pump is connected to the heater, and bolted to skid.
The engine has a Plain Slide Valve, which receives its motion from the rocker arm, operated by the eccentric and rod. It has [Governor], [Steam Gauge], [Pop Valve] and all necessary fittings. These engines range in size from 20 to 30 horse-power, and are extensively used for driving portable saw mills.
RULES AND TABLES.
To find the steam pressure on slide valve, multiply the unbalanced area of valve in inches by pounds pressure of steam per square inch, add weight of valve in pounds, and multiply the sum by 0.15.
Safety boiler pressure according to the United States Government rule is as follows: Multiply ⅛ of the lowest tensile strength found on any plate in the cylindrical shell by the thickness expressed in inches or part of an inch of the thinnest plate in the same cylindrical shell, and divide by the radius or half the diameter, also expressed in inches, and the sum will be the pressure allowable per square inch of surface for single riveting, to which add 20 per centum for double riveting.
To find the water pressure on steam pipes leading from boiler to steam gauge, divide the difference in height between the highest point of pipe and the center of steam gauge by 2³/₁₀; the result will be the pressure exerted by the water in the pipe in pounds upon the gauge.
Area of a Circle.—To find the area of a circle when the diameter is given, multiply the diameter by itself, or in other words square the diameter and multiply the result by .7854.
Ex. Diameter 5 inches, 5 × 5 = 25 × .7854 = 29.635 area.