A. First, multiply the given steam pressure per square inch by the square of the distance between centers of stay bolts, and divide the product by 6,000, and call the answer “the quotient.” Second, divide “the quotient” by .7854, and extract the square root of the last quotient; the answer will give the required diameter of stay bolts at the bottom of thread.
Q. In what position would you place an engine, to take up any slack motion of the reciprocating parts?
A. Place engine in the position where the least wear takes place on the journals. That is, in taking up the wear of the crank-pin brasses, place the engine on either dead center, as, when running, there is but little wear upon the crank-pin at these points. If taking up the cross-head pin brasses—without disconnecting and swinging the rod—place the engine at half stroke, which is the extreme point of swing of the rod, there being the least wear on the brasses and cross-head pin in this position.
Q. What benefits are derived by using flywheels on steam engines?
A. The energy developed in the cylinder while the steam is doing its work is stored up in the flywheel, and given out by it while there is no work being done in the cylinder—that is, when the engine is passing the dead centers. This tends to keep the speed of the engine shaft steady.
Q. Name several kinds of reducing motions, as used in indicator practice?
A. The pantograph, the pendulum, the brumbo pulley, the reducing wheel.
Q. How can an engineer tell from an indicator diagram whether the piston or valves are leaking?
A. Leaky steam valves will cause the expansion curve to become convex; that is, it will not follow hyperbolic expansion, and will also show increased back pressure. But if the exhaust valves leak also, one may offset the other, and the indicator diagram would show no leak.
A leaky piston can be detected by a rapid falling in the pressure on the expansion curve immediately after the point of cut-off. It will also show increased back pressure.