METHOD OF SETTING SLIPPED ECCENTRICS.
The slipping of one eccentric is a trifling matter, which can be quickly remedied if the set screws are in a position where they can be reached conveniently. If it is a go-ahead eccentric, set the engine on the center of the disabled side,—no matter which center,—put the reverse-lever in the back notch of the quadrant, and scratch a line with a knife on the valve-stem close to the gland. Then put the lever in the forward notch, and move the slipped eccentric till the line appears in the point where it was made. Fasten the set screws, and the engine will be found true enough to proceed with the train. Care must be taken in moving the eccentric to see that the full part is not placed in the same position as the other one, or they will both be set for back motion. A back-up eccentric slipped, while the go-ahead one remains intact, can be adjusted in a similar way; the scratch on the valve-stem being made with the engine in full forward motion, and the adjustment of the eccentric done in full back motion. The philosophy of this method is, that the valve is in nearly the same position at the beginning of the stroke for the forward or back motion; and the position of the eccentric, which has not moved, is used to find the proper place for the one which slipped. Should the unusual circumstance of both eccentrics on one side slipping overtake an engineer, he will have to pursue a different method of adjustment. The most systematic plan is to place the engine on the forward center, and set the go-ahead eccentric above the axle, and the back-up eccentric below the axle. With the reverse-lever in the forward notch, advance the top eccentric till the front cylinder-cock shows steam, which can be ascertained by blocking the wheels, and slightly opening the throttle. That will put the go-ahead eccentric near enough to the proper position for running. For the back-up eccentric, pull the reverse-lever into back motion, and turn the eccentric towards the crank-pin till steam appears at the front cylinder-cock; and that part of the motion will be right. Or the back-up eccentric can be set by the forward eccentric in the manner described where one eccentric has slipped.