Jud Oakes steamer Jud wife & Dog

Jud Oakes steamer Jud wife & Dog

Jud Oakes, his wife and dog and in a steam launch with its the skipper TYPICAL STEAM ENGINE USED IN A LAUNCH: Since the early times steamboats have used a very wide variety of engine and boiler types. There is no such thing as a "typical" small steam boat. Not only the hull design but also the power plant are dictated by several factors: the location of operation (river, lake, or sound); availability of machinery (many early engines and boilers were crudely built by local foundries); and, most important, the size of the owner's wallet. You boil water in a boiler, thereby producing steam which is under pressure. The steam is transferred via a pipe to the engine where a valve admits steam to the engine's cylinder at appropriate, set intervals, pushing a piston up and down. Through a connecting rod this motion is transmitted to a crankshaft which revolves and turns a propeller. No gear box or clutch is needed There are three primary elements: 1. the fire; 2. the boiler; and 3. the engine. The fire is contained in a firebox. If solid fuel is to be burned, there must be a grate to support the fuel so that air can reach it. The space under the grate is called the ash pit. Large quantities of air are needed to support combustion. This draft should enter through the ash pit door and flow UP THROUGH the fire. If liquid or gas fuel is used, there is no grate or ash pit and the air generally enters in a fashion similar to the oil or gas burner of a home furnace. Note: a 2HP steam engine suitable for an 18' steamboat will burn the equivalent of 1 gallon of furnace oil per hour - 135,000 BTUs. Three times the heat output of the average home furnace when running "flat out" The boiler holds a quantity of water in such a way that most of the heat from the fire can be transferred to the water. The water boils and gives off steam under pressure, so the boiler has the double purpose of transferring heat and containing pressure. The greater the surface area exposed to the fire, the more heat can be transferred to the water ( and the less wasted up the stack ), and the more steam produced. The best way to create this large surface area in a small space is to fill the space with pipes, or tubes. Therefore the heating surface of all steamboat boilers is made up primarily of tubes. Boilers are described as fire tube and water tube, depending on whether the hot gases from the fire pass through the tubes, or the water is contained in the tubes and the hot gases pass around them. A fire tube boiler is basically a cylindrical shell, or drum, with a top and a bottom plate and the tubes passing between; under full pressure and usually holding a large quantity of water. Thus it holds a great energy reserve in the heated water, permitting steady steaming even with fluctuations in the fire. A fire tube boiler is slow to raise steam, even in small sizes, and holds great potential, in the large mass of stored energy. It is easier and cheaper to build. Most small boilers as found in launches are of the fire tube type. Most launches use a single cylinder engine. When the steam reaches the engine, its admission to the cylinder to push the piston up or down must be controlled. A valve, usually moved by the engine crankshaft through an eccentric (much like the camshaft on an automobile), moves back and forth across a valve face to admit steam through ports to the cylinder and to exhaust the spent steam to the atmosphere or into a condenser. The valve is connected to the eccentric by an eccentric rod (similar to the "push rod" on an internal combustion engine). The valve may be a flat, rectangular affair - called a D or slide valve. Or it may look like a thread spool and move in a cylindrical chamber and be called a piston valve. Most marine steam engines are double acting. The steam alternately pushes against each side of the piston, so there are two power strokes per revolution of the crankshaft. This is one advantage of steam over internal combustion - a single cylinder steam engine supplies the same turning effort as a 4 cylinder gas engine of equal dimensions and cylinder pressure. This does, however, result in some additional complications. A piston rod slides through a packing gland which prevents pressure from leaking through. The piston rod is then connected to a crosshead, to which the upper end of the connecting rod is also joined. The crosshead is prevented from moving from side to side by the crosshead guides. The pieces of the engine are mounted on a bedplate which is in turn secured to the hull. Water is supplied to the boiler by a feed pump, usually driven by the engine so that the quantity of water provided is proportional to its use - as steam - by the engine. There should also be additional ways of getting water into the boiler, such as a hand operated feed pump or an injector, should the engine driven pump fail.