Busch-Sulzer Diesel Engine.—This engine has the liner cast separately from the jacket, as appears in Fig. 66. The liner has a small flange at the top, which fits into a recess machined in the top jacket flange. The bottom is not anchored, being free to expand and contract. The head has four openings, for the exhaust, admission, fuel, and air valves. The Busch-Sulzer Co. has each cylinder head provided with a start ing valve opening. This is used with two cylinders while on the remaining cylinders of the engine the opening is plugged. Figure 67 outlines the head of this engine, with the various openings as indicated. The same general lines are followed on practically all other vertical engines.
Cylinders of A-frame Engines.—The Fulton Iron Works, and the McIntosh & Seymour Co. in their A-frame en gines, extend the frame to act as the cylinder jacket. The liner in many respects is the same as is found on a box-frame engine. This frame and cylinder construction is very popular with European manufacturers but is losing favor in the United States. It offers the serious objection of high replacement cost in event the cylinder-jacket wall fractures. This has happened on a few occasions in this country and led to its abandonment by at least one manufacturer. Figure 68 illustrates the McIntosh & Seymour A-frame cylinder. Their marine Diesel cylinder appears in Fig. 21.
Horizontal Diesel Cylinders.—Without exception all manu facturers of the horizontal four-stroke-cycle engine extend the frame casting to enclose the cylinder liner, thereby forming the water jacket without an additional casting.
Horizontal Diesel Cylinder Heads.—The manufacturers of the horizontal engine have two head designs from which to choose. If the head be of a symmetrical design, such as is found on the vertical Diesel engine, the valves must be placed horizontally. Figure 67 shows a very symmetrical casting that is closely followed on the Snow Oil Engine and on the De La Vergne F.D. Engine. This design entails increased wear on the valve stems, and the seating of the valve is difficult. To obviate this condi tion many manufacturers have had recourse to a head with the valves placed vertically. This head, in order to keep down the compression volume, must be built somewhat along the lines of Fig. 69. It is apparent that this form of head will experience certain casting strains which will develop into frac tures if they are not removed by the annealing of the entire head. If this procedure is followed, no great danger of fracture exists.
McEwen Diesel Cylinder 70 is a view of the cylinder head of the McEwen Diesel.
Diesel 71 gives a view of the cylinder of this engine.
Cylinder Diesel employs the head shown in Fig. 72. The valves are set vertically while the fuel nozzle rests horizontally in the center of the head cover.
National Transit Diesel Cylinder.—Figure 73 shows the cylin der and head of the first Diesels manufactured by this firm. Figure 96A is a view of the head adopted for the 1918 Diesels. The valves are in a horizontal position while the head casting is simple, thereby removing practically all danger of fracture.
Fractured Cylinders.—The difficulty of fractured cylinders has been largely eliminated as a better understanding of the necessity for proper cooling has come to the operating force. It can be safely stated that all cylinder fractures are traceable to improper cooling. Many plants follow a custom of cutting off the flow of cooling water as soon as the engine is shut down. Since there is about as much heat absorbed by the water as is given up in useful work, on shutting down a large quantity of heat remains in the iron parts—this must be taken up by the water contained in the cylinder jacket. This produces a rise in temperature sufficient to cause precipitation of the salts suspended in the water. These salts are deposited in the form of scale on the jacket walls. The action continues until the scale becomes so thick as to preclude the possibility of proper cooling. The cylinder walls attain a high temperature and develop fractures because of the inability of the red-hot walls to withstand the high cylinder pressure. Due attention to the cooling water will prevent any fracture in the cylinder liner.
Scored Cylinders.—In the chapter on pistons, several defects that would cause piston scoring were pointed out, and the discus sion applies to cylinders. Where the scoring is purely local in character, the surface can be placed in working condition by rubbing with an emery stone, finishing up with a patient applica tion of a scraper. Ordinarily, since the scoring is due to piston distortion, the defective surfaces are not in the plane of the crank and piston; consequently the reduction of the scored surface below the cylinder wall circle is not of any moment. Another type of scoring is at times encountered: this has the character of grooves and ridges. As long as the depth of the grooves is .005 inch or less no serious damage will occur. But when second ary ridges appear between the original ridges, the liner must be rebored.