IN QUESTIONS AND ANSWERS For Machinists, Firemen, Electricians and Steam Engineers

Q. Now, if your rocker-arm stood at a quarter, and your eccentric out of plumb, how would you take the measure for the rods?
A. Simply bring them plumb and take the measure; that is the only right way.

Q. After you have measured the rods, what would you do?
A. They should be put on and the valve set.

Q. What do you move or do first, to set a valve after connections are made?
A. Move the eccentric in the direction the engine is to run, until the valve begins to take steam or lead, then tighten the eccentric temporarily with set screws, then move the crank-pin over to the other dead center, and see how much lead it has; if equal the valve is set.

Q. What is meant by the lead of valve?
A. The opening the valve has when the piston is at the beginning of its stroke.

Q. What lead should large engine have?
A. About ¹/₁₆ of an inch. High speed engines must have a quick opening or good lead.

Q. Now if you find the valve laps out ? of an inch on one end, and the proper lead on the other, what would you do?
A. Divide the difference, by moving the valve one-half it is out, by adjusting the valve-gear.

Q. How much?
A. The valve has ¹/₁₆ of an inch lead at one end and laps ? of an inch at the other end; the valve is out ⁷/₁₆ of an inch; then the valve must be adjusted by the nuts one-half it is out, making ⁷/₃₂ of an inch. then throw the crank on the other dead center, move the eccentric whichever way will bring you back to ¹/₁₆ of an inch lead, then tighten temporarily with set screws, throw crank over the other dead center, and the valve will be set. After valve is set, tighten the eccentric for good.

Q. But if it is not set, what would you do?
A. Go through the same performance until it is set. Some valve-rods have a yoke that slips over the valve, while the adjusting and jam-nuts are between the stuffing box and the rocker-arm pin. When a valve-rod has no nuts, the adjusting must be done at the eccentric rod. To lengthen or shorten the stroke of valve-rod, raise or lower the eccentric-rod pin in the slot, at the bottom of the rocker-arm, whichever way suits the circumstances.

Q. Now, after you have set your valve, keyed everything up properly, and there was a thud or dead sound in the engine or cylinder, what would you do, or where would you look for the trouble?
A. In the exhaust being choked. The steam chest cover must be taken off, then uncouple the valve, turn the valve up sideways and move it until the steam edge has the proper lead with the steam-port, then place a square on the valve-seat of the cylinder, and against the valve-face, to see how the exhaust lead on the opposite steam-port corresponds; if it is choked, then scribe it by allowing a little over double the steam lead.