Sectional View of Simple Engine,
Showing Cylinder, Steam Chest, Plain Slide Valve, Steam and Exhaust Ports, Piston and Rod, Engine Frame, Cross-head, Connecting Rod, Crank Disc, and Rocker Arm and Rod for Operating Valve.
STEAM CYLINDER.
The Steam Cylinder is that part of an engine in which the piston travels; it also contains the steam and exhaust ports and is one of the most expensive, as well as essential, parts of an engine. The cylinder should be made of the best quality of cast iron, and the greatest care taken in boring it perfectly true and round. It should be counter-bored at each end to allow the piston in its travel to overlap at the end of each stroke. Without the counter-bore, a shoulder would be formed at both ends of the cylinder as it became worn by the piston rings, which in time would cause a knock or pound at the end of every stroke; the only remedy being to have the cylinder re-bored.
Special attention should be paid to keeping the cylinder well oiled with the best quality of cylinder oil to prevent it from being cut by the piston rings. If allowed to run dry and cut, it will cause no end of trouble.
The size of cylinder is not always the measure of the power of the engine. The power depends upon the heating surface of the boiler and steam pressure; as the piston speed can always be increased, by running the engine faster, until the maximum evaporating capacity of the boiler is reached.
PISTON AND ROD.
The Piston is another very important part in the construction of an engine, and it conveys the power of the steam to the crank. It is composed of a piston head, on which are placed the piston rings held in position by the follower plate, and is securely attached to the piston rod. Great care should be taken in the construction of the piston rings to have them fit the cylinder perfectly tight, at the same time to have the least possible friction. Piston rings should always be made of a softer metal than the cylinder so that the greater part of the wear will be upon the rings instead of the cylinder, as the rings can easily be replaced.
There are a great many kinds of packing for piston rings, but the most commonly used at the present time are the steam packing rings. The character, accuracy in construction and condition of the piston make a great difference in the quantity of fuel consumed and the amount of power developed by the engine.