GENERAL ENGINE INFORMATION The Murphy Diesel engine is of the solid injection, full Diesel type, in which the Diesel fuel is ignited by the heat of compression, without the aid of spark plugs or other external heat. The engine operates upon the common four stroke cycle principle, the events being as follows: 1. Inlet Stroke 2. Compression Stroke 3. Expansion or Power Stroke 4. Exhaust Stroke During the inlet stroke, the piston is traveling downward, and draws air only through the open inlet valves and into the engine cylinder. With the valves closed and the piston moving up, the air is compressed to approximately 575 pounds per square inch pressure. Because of the high compression pressure, the air is heated to a temperature of about 1000° Fahrenheit. Ignition takes place near the end of the compression stroke when a very fine spray of fuel is injected into the highly heated air. The heat of combustion creates a pressure, thereby forcing the piston downward on its power stroke. Near the end of the power stroke, the exhaust valves open, and when the piston moves upward on the exhaust stroke, the cylinder is cleared of burnt gas and is ready for the next cycle. General Description Murphy Diesel Engine The Diesel fuel is circulated through the injection system by a low pressure supply pump located at the side of the engine, and injected into the combustion chamber, under pressure by a single pump and injection valve above each cylinder. The pump and valve for each cylinder are combined into one campact unit called the injector that may be quickly removed and replaced. The injectors are located in the cylinder head in the exact center of each cylinder and spray the fuel through drilled holes in the nozzle injector tip into a plain, open combustion chamber, formed by the cup-shaped piston head and the flat cylinder head. The Murphy Diesel engine is a true Diesel, and because of the efficient injection system, it requires no precombustion chamber or pre-heating devices. The amount of fuel supplied to each cylinder is regulated with the hydraulic servo governor by rotating the injector plunger back and forth in its cylinder. This rotating action causes a helical groove at the lower end of the plunger to uncover a port in the injector barrel, thus allowing the excess fuel to by-pass back to the supply line. The two overhead camshafts operate the injectors as well as the intake and exhaust valves. The camshafts are driven from the flywheel end of the engine by a vertical shaft, through bevel gears on the lower end, and worm and gears on the upper end. This construction assures a positive, accurate drive to the injectors. The injector cams on the camshafts raise the injector rollers and tappets, and in so doing, compress the heavy springs in the upper part of each injector. The three springs force the plunger down in the barrel thereby injecting the fuel. This construction provides a safety feature that protects all injector parts in the event a nozzle tip becomes stopped up or a plunger sticks in its barrel. In such cases, the rollers will not follow the cams, and the noise resulting, caused by the cams striking the partially raised rollers, will indicate inoperation of an injector before any damage is done. GENERAL ENGINE INFORMATION—(Cont'd) The governor that controls the injectors is driven by the rear end of one camshaft. It is of the hydraulic Servo type, and utilizes the lubricating oil pressure as a source of energy. The governor flyball weights control the movement of a piston type oil valve that permits oil pressure to act upon the main governor piston. The oil pressure acting on the governor piston does the actual work of rotating the fuel control shaft to open the injectors, and a compression spring closes them. Utilizing the oil pressure results in a quick acting governor, and provides a particularly desirable safety feature in that a spring closes the injectors stopping the engine if the lubricating oil pressure falls below approximately 20 pounds. This protection provides against burnt out bearings and scored cylinders. The crankshaft has electrically hardened journals to which are fitted long life, copper-lead, steel-backed precision bearings. The main bearings. are 4" (3.979" actual) in diameter, and the connecting rod bearings are. 32" (3.498" actual) in diameter. The pistons are accurately machined from special cast iron for long trouble-free life. Pistons run extremely cool, because of oil cooling, thereby largely eliminating ring sticking, a common fault of some Diesel engines. The lubricating system is of the full force feed type, in which all of the moving parts of the engine including those in the camshaft housing and governor, are flooded in oil. This system employs an adequate oil cooler located at the front end of the engine, which transfers heat from the lubricating oil to the cooling water. This feature provides against excessive lubricating oil temperatures, and insures rapid warming of the oil when operating at low atmospheric temperatures. The ME series Murphy Diesel engines are started directly on the Diesel cycle by means of a 24-volt electric starting motor. The starting motor control is a lever located on the starter at the rear of the engine. The compression release and speed control are incorporated in a single lever at the rear of the engine. When the engine control lever is in the extreme upper position, the compression of the engine is released for easy cold weather rotation and emergency stops. When the lever is moved downward from the mid-position, it acts as a throttle to control the speed of the engine. |