Boys' Book of Model Boats

and construction. In this way the model engineer will be able to design and construct model steam-engines according to his own ideas and in accordance with the raw materials and miscellaneous par

s engine, for which he will have no trouble in machining or producing the parts that enter into its constru

to the opposite end of the cylinder. If some means is then provided so that the steam can escape and the piston come back, another

the cylinder, and by the time the cylinder has arrived in the position shown by the dotted line C, the slide-valve moves over, closing the passage B. The steam under pressure forces the piston to the opposite end of the cylinder. When the piston reaches the opposite end of the cylinder, steam that has entered through the passage F again forces the piston back to its original position. This is ca

the steam acts on both sides of the piston. Single-acting cylinders are cylinders in which the st

iston. In model engines it ranges from 3/8 of an inch to 11/2 inches. The bore of a cylinder is its internal diameter. The bo

te and very difficult to regulate. The construction is also much more complicated, and this also holds true of the designing. On the other hand, single-acti

an be either brass or copper. Aluminum should not be used, owing to the fact that it is difficult to solder and difficult to work with. The piston is made so that it will fit nicely into the cylinder and move up and down without binding. It will be seen that a groove, M,

disk N, so that when this disk makes one revolution, the piston will move 7/8 inch in the cycle. Thus it will be seen that the distance of the crank-pin K from the center of the crank disk N will depend entirely upon the stroke of the engine. It may be well to mention here that the worker should always start desig

its downward stroke it uncovers these exhaust ports and permits the steam to escape. The momentum of the flywheel A pushes the piston upward, closing these holes. As these holes are closed the valve H uncovers the entrance I and permits steam to enter from

ric C must be mounted on the crank-shaft B so that the valve will close and open at proper intervals. When the engine is made, the eccentric can be shifted about by means of a set-screw, Q, until the engine operates satisfactorily. This set-screw is used to hold the eccentric to the crank-shaft. The word eccentric merely means "off center." Thus the eccentric in this case is formed by a little disk of brass with the hole drilled off center. The distances these holes are placed of

ings, D D. The flywheel is held to the

m 20 to 30 pounds of steam, and this pressure can easily be generated in