AIDS TO THE STUDY OF VALVE-MOTION.
An engineer or machinist who wishes to study out this peculiarity of connecting-rod angularity, will find that the use of a tram or long dividers will help him to comprehend it better than any letter-type description. All through the study of the valve-motion, there are numerous difficult problems encountered. The use of a good model will be found an invaluable aid to the study of the valve-motion, and every division of engineers or firemen should make a combined effort to furnish their meeting-room with a model of a locomotive valve-motion. In no way can the spare time of the men connected with locomotive running be better employed than in the wide range for study presented by a well-devised model. Great aid can be obtained in the study of the valve-motion from good books devoted to the subject, and they will impart more information than can be obtained by mere contact with the locomotive. The valve and its movements are surrounded with so many complicated influences, that an intelligent man may work for years about a locomotive doing valve setting occasionally, and other gang boss work, yet, unless he studies the valve-motion by the aid of the drawing-board, or by models, which admit of changing sizes and dimensions, he may know less about the cause of certain movements than the bright lad who has been a couple of years in the drawing-office. The man who thinks he can study the valve-motion, and understand its philosophy, by merely running the engine, deceives himself. The engineer who never looks at a book or a paper in search of information about his engine, knows very little about any thing not visible to the eye. Yet many men of this stamp, by looking wise, and by exercising a judicious use of silence, pass among their fellows as remarkably profound. But let a fireman, in quest of locomotive knowledge, put a question to such a man, and he is immediately silenced with a “You ought to know better” answer.
Where the use of a model can not be obtained, any one beginning the study of the valve-motion can assist himself by making a cross section of the valve and its seat, similar to those published, on a strip of thin wood or thick paper. By slipping the valve on the seat, its position at different parts of the stroke can be comprehended more clearly than by a mere description. With a pair of dividers to represent the motion of the eccentric, and strips of wood to act as eccentric, and valve rod and rocker, and some tacks to fasten them together, a helpful model can be improvised on a table or board. By the time a student gets a rig of this kind going, he will see his way to contrive other methods of self-help.