ENGINES AND ENGINE COMPONENTS

Before World War II, these engines were used almost exclusively on submarines. With the expansion of the Navy, however, these engines have also been used on destroyer escorts, amphibious craft, escort type patrol vessels, and various auxiliary craft.

The following sections are devoted to the discussion of basic diesel engine construction and the application of these basic principles to the General Motors and Fairbanks-Morse engines.

3A2. General Motors engines.Two models of GM main engines are found in fleet type submarines today, Model 16-248 and Model 16-278A. The former was installed exclusively in General Motors engine equipped vessels until early in 1943 when Model 16-278A was introduced. All General Motors installations since that time have been Model 16-278A engines (Figures 1-10 and 1-11). Basically the two models are similar. The principal differences are in the size and design of the parts, methods of construction, and type of metals used. In the following chapters all references are based on the current Model 16-278A. Important differences between the two models, however, will be noted.

The GM engine is a 16-cylinder V-type engine with 2 banks of 8 cylinders each The engine operates on the 2-stroke cycle principle, is air started, and is rated at 1600 bhp at 750 rpm. The size of the bore and stroke of the 16-248 engine is 8 1/2 inches and 10 1/2 inches respectively as compared to 8 3/4 inches and 10 1/2 inches for Model 16-278A.

The General Motors Corporation also

The tables at the end of this chapter, pages 78 and 79, contain engine data, ratings, and clearances for General Motors main engines and auxiliaries.

3A3. Fairbanks-Morse engines.There are two types of F-M main engines in use in modern submarines (Figures 1-12 and 1-13). The model number for each is 38D 8 1/8. The basic difference between them is the number of cylinders, one being a 9-cylinder and the other a 10-cylinder engine. Both engines have the same bore and stroke and in most respects are similar in principle, design, and operation.

The F-M 38D 8 1/8 model is an opposed piston, in-line, 2-cycle, 9- or 10-cylinder engine employing air starting and rated at 1600 bhp at 720 rpm. Bore and stroke are 8 1/8 and 10 inches respectively.

An auxiliary engine, Model 38E 5 1/4, is also supplied by Fairbanks, Morse and Company. This is a 7-cylinder, opposed piston, 2 cycle, air starting engine rated at 300 kw generator output at 1200 rpm. The bore is 5 1/4 inches and the stroke 7 1/4 inches.

The tables at the end of this chapter, page 80, contain engine data, ratings and clearances for Fairbanks-Morse main engines and auxiliaries.

3A4. Classification of engine components. To simplify the study of the design, construction, and operation of the component parts of the diesel engines in the following sections of this chapter, the parts have been classified under three subjects as follows: 1) main stationary parts, 2) main moving parts, and 3) valves and valve actuating gear.

Section 3B deals with engine components as listed above, in general. Sections 3C and 3D deal with the same components as applied to the GM and F-M engines respectively. In all

The framework used in most modern engines is usually a combination of these types and is commonly designated as a welded steel frame. A frame of this type possesses the advantages of combining greatest possible strength, lightest possible weight, and greatest stress resisting qualities.

The welded steel type of construction is made possible by the use of recent developments in superior quality steel. For diesel engine frame construction, steel is generally used in thick rolled plates which have good welding quality. In this type of construction, deckplates are generally fashioned to house and hold the cylinders, and the uprights and other members are welded, with the deckplates, into one rigid unit.

b. Oil drain pan. The oil drain pan is attached to the bottom of the cylinder block and serves to collect and drain oil from the lubricated moving parts of the engine. The bottom of the oil pan is provided with a drain hole at each end through which oil runs to the sump tank. In some installations the bottom of the pan slopes toward one end or the other of the engine.

Oil drain pans require little maintenance. They should be cleaned and flushed of any residual dirt during major overhaul periods. New gaskets should be installed at these times to assure an oiltight seal.

c. Access doors and inspection covers. The cylinder block walls are equipped with access doors or handhole covers. With the doors or covers removed, the openings furnish access to cylinder liners, main and connecting rod bearings, injector control shafts, and various

d. Cylinder and cylinder liners. The cylinder is the enclosed space in which the mixture of air and fuel is burned. A cylinder may be constructed of a varying number of parts among which the essentials are the cylinder jacket, the cylinder liner, and in most cases the cylinder head. In most designs the space between the cylinder jacket and the liner is cored to carry circulating water for cooling purposes.

There are two general types of cylinder liners. One, the wet type, is a replaceable liner that makes direct contact with the cooling water; the other, the dry type, is a replaceable liner that fits into a water-cooled jacket without making direct contact with cooling water. All submarine diesel engines under consideration here use the wet type cylinder liners.

e. Cylinder head. The cylinder head seals the end of the cylinder and usually carries the valves. Heads must be strong enough to withstand the maximum pressures developed in the cylinders. Also, the joint between the cylinder and the head must be gastight. Due to the high temperatures encountered, cylinder heads must be water cooled. To accomplish this, water passages are cored in the head during the casting process. Valves usually found in the head are the exhaust valves, injection valves, and air starting valves.

3B2. Main moving parts.a. General. The main moving parts of a diesel engine are those

1. Those parts having rotary motion, such as crankshafts and camshafts.

2. Those parts having reciprocating motion, as, for example, the pistons and piston rings.

3. Those parts having both reciprocating and rotary motion, such as the connecting rods.

b. Crankshaft. The crankshaft transforms the reciprocating motion of the pistons into rotary motion of the output shaft. It is one of the largest and most important moving parts of a diesel engine.

The materials used in the construction of crankshafts vary greatly, depending on the size of the shaft, speed of the engine, horsepower of engine, and number of main bearings. Regardless of materials used, crankshafts are always heat treated. This is necessary in order to give uniform grain structure, which increases ductility and capacity for resisting shock. The tensile strength of crankshaft materials varies from 60,000 psi to as much as 100,000 psi. Crankshafts may be either forged or cast. They may be either made up in one section, or in two or more with the sections interchangeable for economy in construction and replacement. Crankshafts are machined to very close limits with a high finish and are balanced both statically and dynamically.

The crankshaft consists essentially of a number of cranks placed at equal angular intervals around the axis of the shaft. Between the cranks are the crankshaft supports commonly referred to as the journals. Each crank on a crankshaft is made up of the crankpin, which is the journal for the connecting rod bearing, and two crank webs (Figure 3-1).

Journals, crankpins, and webs are drilled for the passage of lubricating oil (Figure 3-2). All such holes are usually straight to facilitate construction and cleaning of the passages. In larger engines, crankshafts are practically always constructed with hollow main bearing journals and crankpins. This construction is

Figure 3-2. Sections of crankshaft showing oil passages and hollow construction.

c. Main bearings. The function of the main bearings is to provide supports in which the crankshaft main bearing journals may revolve. In the diesel engines under discussion, modern bimetal or trimetal, split sleeve, precision type main bearings are used exclusively. Bimetal bearings consist of a thin inner layer of soft low-friction metal encased in a shell of harder metal fitted to the bearing support or bearing cap. Trimetal bearings have an intermediate layer of bronze between the shell and soft metal layers. Both types are split sleeve, divided horizontally through the center, for installation. Precision type manufacture requires that the bearing housing be precision bored to a close tolerance and that the bearing halves, when tightly drawn together, align perfectly and fit the bearing journals with a predetermined clearance. The purpose of this clearance is to provide for a thin film of lubricating oil which is forced under pressure between the journals and bearing surfaces. Under proper operating conditions this oil film entirely surrounds the journals at all engine load pressures.

All main bearings contain oil inlet holes and oil grooves which permit the oil to enter and be evenly distributed throughout the inside of the bearing. These oil inlets and grooves are invariably in the low oil pressure area of the bearing.

Proper bearing lubrication depends upon accurate bearing clearances as well as the type of lubrication. Too little clearance will cause the bearing to run hot and wipe out under continued operation. At high operating speeds with too little clearance, the load pressure on the bearing does not leave sufficient room for the

Proper seating of the bearing shells and proper clearances of precision type bearing shells require that the bearing caps be drawn to the proper tightness. This is done with a torque wrench by means of which the proper torque limits in foot-pounds are obtained. As this torque varies with engine models, the current instructions should be consulted.

d. Pistons. The function of a piston is to form a freely movable, gastight closure in

Figure 3-3. Main bearing shells.

The piston crowns on both the GM and F-M engines are concave. The purpose of this shape is to assist in air turbulence which mixes fuel with air during the last phase of the compression stroke.

Pistons are usually constructed of either a cast iron or aluminum alloy. They must be designed to withstand the gas pressure developed in the combustion chamber during the compression and expansion strokes. They must also be light enough to keep the inertia loads on the piston pins and main cranks to a minimum.

e. Piston rings. Piston rings have the following three primary functions:

1. To seal compression in the combustion chamber.

2. To transfer heat from the piston to the cylinder wall.

3. To distribute and control lubricating oil on the cylinder wall.

In general, piston rings are of two types. One, the compression type ring, serves primarily to seal the cylinder against compression loss; the other, the oil type ring, distributes oil on the cylinder walls and controls cylinder wall lubrication by collecting and draining excess oil.

Piston rings are generally constructed of cast iron. On the average diesel piston there are four to five compression rings and two or three oil control rings.

f. Piston pins. Each piston is connected to the connecting rod by a piston pin or wrist pin. This connection is through bored holes in the piston pin hubs at the center of the piston

g. Connecting rods. Just as its name implies, the connecting rod connects the piston with the crankshaft. It performs the work of converting the reciprocating, or back-and-forth, motion of the piston into the rotary, or circular, motion of the crankshaft. The usual type of connecting rod is an I-beam alloy steel forging, one end of which has a closed hub and the other end an integral bolted cap. The cap is accurately located by means of dowel pins. Through the closed hub, the connection is made between the piston and the connecting rod by means of the piston pin. At the other end, the connecting rod bearing connection is made between the connecting rod and the crankshaft. The shaft of the connecting rod is drilled from the connecting rod bearing seat to the piston pin bushing seat. Through this passage, lubricating oil is forced from the connecting rod bearing to the piston pin bearing for lubrication and piston cooling.

h. Connecting rod bearings. The purpose of these bearings is to form a low-friction, well-lubricated surface between the connecting rod and the crankshaft in which the crankpin journals can revolve freely. The bearings used are generally of the same material and type as the main bearings. Connecting rod bearings consist of two halves or bearing shells. The backs of these shells are bronze or steel, accurately machined to fit into a precision machined bearing seat in the connecting rod. The shells are lined with a layer of soft metal of uniform thickness. When the bearing caps are drawn tight on the connecting rod, the contact faces of the bearing shells form an oiltight joint. Also, because of the precision manufacture of all parts,

Figure 3-4. Connecting rod bearing shells.

3B3. Valves and valve actuating gear.a. General. Control of the flow of fuel, inlet air, starting air, and exhaust gases in a diesel cylinder is accomplished by means of various types of valves. The timing and operation of these valves, for the various processes in relation to piston travel and correct firing sequence, are the main functions of the valve actuating gear.

Since certain phases of timing, such as the geometrical angle of the crankshaft cranks and the geometrical angle of the camshaft cams, are fixed, timing adjustments are made through the valve actuating gear. Hence, timing adjustments must be made with extreme accuracy and the valve actuating gear must function perfectly for efficient engine operation.

b. Camshafts. The purpose of the camshafts in submarine diesel engines is to actuate exhaust valves, fuel injectors, fuel injection pumps, and air starting valves according to the proper timing sequence of that particular engine.

In order to perform these functions at the various cylinders in relation to their proper firing order, the camshafts are timed or synchronized

Camshafts are usually constructed in one or two parts. The number of cams on a camshaft is determined by the type and cycle of engine. The cams and camshafts are usually forged integral and ground to a master camshaft.

c. Valves. The important valves found on typical diesel cylinders and their functions are:

1. Exhaust valves. Exhaust valves are used to allow the exhaust gases of combustion to escape from the cylinders. They are subject to extremely high temperatures and are therefore made of special heat-resistant alloys. In some large engines, the exhaust valves are water cooled.

2. Inlet valves. Inlet valves are used to govern the entrance of air in the cylinder of a 4-stroke cycle engine. Inlet valves are not used

Figure 3-5. Valve actuating gear assembly.

3. Fuel injection valves. Fuel injection valves are used to inject the fuel spray into the cylinder at the proper time with the correct degree of atomization. In addition, some injection valves also measure the amount of fuel injected.

4. Air starting valves. Air starting valves are used to control the flow of starting air during air starting of an engine. These valves are normally of two types, air starting check valves and air starting distributor valves.

5. Cylinder test valves. Each cylinder is provided with a test valve which is used to vent the cylinder before starting. This valve is also used to relieve the cylinder of compression when turning over the engine by hand. The same valve is used far taking compression and firing

6. Cylinder relief valves. A cylinder relief, or safety, valve is located on each cylinder of all submarine type engines. The function of this valve is to open and relieve the cylinder when pressure inside the cylinder becomes excessive. These valves are adjustable to be set at varying pressures according to the particular installation. When pressure drops below the setting at which the valve opens, the valve closes automatically.

d. Valve actuating gear. Motion of the cams on the camshaft is transmitted to valves, injectors, and injector pumps by means of rocker arms or tappet assemblies. The rocker arms and tappets normally are spring loaded and make contact with the cams by means of cam rollers. Adjustments of the various springs and rods are very important, as they are normally the means by which the engine is correctly timed.

3C2. Main stationary parts.a. Cylinder block. The cylinder block of the GM engine (Figure 3-8) is fabricated from forgings and steel plates welded together to form a single unit. The assembly is designed with two cylinder banks, the axes of which are 40 degrees apart, forming the V-type design of the engine. The unit is fabricated from main structural pieces called transverse frame members, upper and lower deckplates for each bank, and cross braces all welded into one rigid compact unit. The upper and lower deckplates are bored to accommodate the cylinder liners. The space between these deckplates, as well as the space between the two banks of cylinders, serves as a scavenging air chamber.

The forged transverse members in the bottom of the cylinder block form the mounting pads for the lower main bearing seats. The camshaft bearing lower seats are an integral part of the cylinder block. These bearing seats and their caps are match-marked and must be kept together.

Removable handhole covers close the

b. Engine oil pan. The engine oil pan is bolted to the bottom of the cylinder block. The bottom of the oil pan is provided with a drain hole at each end. One end of the oil pan is fastened to the camshaft gear train housing and the other end is fastened to the blower bottom housing. The lubricating oil from these units drains into the oil pan. The pan is constructed of welded steel in the 16-278A and of an aluminum alloy casting in the 16-248.

c. Cylinder liner. The cylinder liner (Figure 3-11) is made of cast iron with a cored or hollow space in the wall through which cooling water is circulated. Water enters through a synthetic rubber gasket sealed connection near the bottom of the cylinder and circulates out through similarly sealed steel ferrules into the cylinder head. The cylinder liner is held in the engine block by the lower deckplate and a

Figure 3-9. Crankcase handhole covers, GM.

The distance from the upper ends of the scavenging air ports to the finished top of the cylinder liner must be closely held to the required dimension, so that the opening and closing of these ports by the travel of the piston are accurately timed in relation to the respective opening and closing of the exhaust valves.

In recent years it has been found that the wearing qualities of the liner can be greatly increased by chrome plating the inside of the liner. These chrome-plated liners are used in all late installations.

d. Cylinder head. The cylinder head attaches to the cylinder liner to form the top closure of the combustion chamber. It forms the support and houses the four exhaust valves, the unit injector, and the rocker lever assemblies. It also contains the overspeed injector lock, air starter check valve, cylinder relief valve, and cylinder test valve (Figure 3-12).

The cylinder head is an individual unit for each cylinder. It consists of an alloy iron casting, cored with water cooling passages. Cooling water flows from the cylinder liner through synthetic rubber sealed steel ferrules, and circulates through the cylinder head. It then passes through a watertight connection into the water jacket of the exhaust elbow. All cylinder heads are equipped with a pressed steel or aluminum alloy cover secured by a handwheel nut. This cover has breather openings which serve as ventilating ports for the crankcase breather system. Each cylinder head is fastened to the cylinder block by four hold-down studs and nuts. The joint between the cylinder liner and

cylinder head is sealed against compression loss by a solid copper gasket which is slightly recessed in a groove of the cylinder liner. All other joints or openings of the cylinder head are made watertight or oiltight by gaskets.

3C3. Main moving parts.a. Crankshaft. The GM crankshaft (Figure 3-15) is an integral type, alloy steel forging, heat treated for stress and wear resistance, and dynamically and statically balanced. Shaft and crankpins are hollow bored to reduce weight and bearing load. The entire crankshaft is machine finished, and the main bearing and crankpin journals are precision ground. Crankshafts for right-hand and left-hand engines are interchangeable. There are eight cranks spaced 45 degrees apart and nine main bearing journals on each crankshaft. In both right-hand and left-hand engines, the cylinders are numbered from 1 to 8 inclusive in the right bank, and from 9 to 16 inclusive in the left bank. Cylinders 1 and 9 are at the blower end of each engine. Two pistons that are

The firing interval is alternately 5 degrees and 40 degrees and these intervals are determined by the angle between the cylinder banks, which is 40 degrees, and by the relation of the crankpin positions of successively fired cylinders, which is 45 degrees. Two successively fired cylinders are connected either to two separate crankpins that are 45 degrees apart, or to one crankpin. When two successively fired cylinders have crankpins that are 45 degrees apart, which is 5 degrees greater than the bank angle of 40 degrees, the firing interval is 5 degrees. When two successively fired cylinders are connected to one crankpin, the firing interval is the same as the bank angle, which is 40 degrees.

Oil passages are drilled through each crankpin, crank webs, and main bearing journals, for lubricating oil to flow under pressure from the main bearings to the connecting rod bearings. The connection between the crankshaft and the main generator is by means of an elastic coupling.

b. Main bearings. The crankcase contains nine bearings (Figures 3-16 and 3-17) for the support of the crankshaft. Each main bearing consists of an upper and lower double flanged precision bearing shell. Two types of main bearing shells are used. One type is bronze backed with a centrifugally cast lining of high lead bearing metal known as Satco metal. The other type is steel backed with an intermediate lining of bronze and lined with Satco metal.

The bearings are carried in a steel bearing support and held by a steel bearing cap. Both bearing supports and bearing caps are made of drop-forged, heat-treated steel. Each of the bearing supports is secured to the main frame of the crankcase. Two large dowel pins locate the supports for perfect alignment.

The upper bearing shell is mounted in the bearing cap, the lower shell in the main bearing seat. The joint faces of the upper and lower bearing shells project slightly from the seat and cap. This is to insure that the backs of the shells will be forced into full contact when the cap is fully tightened. A drilled hole in the upper shell

Figure 3-13. Cylinder head cross section through exhaust valves, GM.

Figure 3-14. Cylinder head cross section through injector, GM.

Bearing caps are held down on the bearings by jack screws locked with cotter pins. The jack screw fits into a recess in the arch of the crankcase frame and takes the upward thrust on the bearing cap. Close fit between shoulders on the crankcase frame prevents side play in the bearing cap. End play is controlled by two dowel pins. When the bearing supports and caps are assembled on the crankcase frames, the seats for the bearing shells are accurately bored in dine, and the ends of its faces are finished for a close fit between the bearing shell flanges.

Each bearing shell is marked on the edge of one flange. For example, the designation 2-L-B.E. indicates that the shell is for the No. 2 main bearing, that it is the lower shell, and that the flange of the shell thus marked should be placed toward the blower end of the engine. The main bearing nearest the blower end of the engine is the No. 1 main bearing. The rear main bearing

Each lower bearing shell has an oil groove starting at the joint face and extending only partially toward the center of the bearing surface. The upper bearing shells are similarly grooved except that the groove is complete from joint face to joint face.

The main bearings are lubricated by oil under pressure received from the oil manifold under the bearing supports. The oil is forced up through a passage in the bearing support and through holes drilled in the lower bearing shell. From these holes, oil flows the entire length of the oil groove formed by the combined upper and lower shells. The oil lubricates the entire bearing surface and is carried off through the

c. Pistons and piston rings. The pistons for GM engines are made of cast iron alloy which is tin plated. Each piston is fitted with five compression rings at the upper, or crown, end and two oil control rings at the bottom, or skirt, end. In latest installations, the oil control rings are of the split type backed by expanders. All piston rings are made of cast iron.

The bored holes in the piston pin hubs are fitted with hard bronze bushings which are cold shrunk in the piston bores. The outer ends of the bore for the piston pin are sealed with cast iron caps to prevent injury to the walls of the cylinder from floating piston pins.

The bores in the piston pin bushing are accurately ground in line for the close, but floating, piston pin fit. Each bushing has a number

A cooling oil chamber is formed by an integral baffle under the piston crown. Lubricating oil under pressure flows from the top of the connecting rod, through a sealing member, and into the cooling chamber. The oil seal is a spring loaded shoe which rides on the cylindrical top of the connecting rod. The heated oil overflows through two drain passages.

d. Piston pins. The piston pin used on the GM engine is full floating, hollow bored, and case hardened on the bearing surface. The connection between connecting rod and the piston is by means of the connecting rod piston pin bushing. This bushing rotates freely inside the integral end of the connecting rod, and the connection is completed by pushing the piston

In some older installations a needle type bearing containing three rows of 53 small roller bearings each was used instead of the connecting rod piston pin bushing. These have now been replaced by the bushing type of bearing.

The connecting rod piston pin bushing is constructed of steel-backed bronze. The entire length of the inner surface of the bushing is grooved to provide for lubrication of the piston pin assembly.

e. Connecting rods and connecting rod bearings. GM connecting rods are made of alloy steel forgings. The rod is forged in an I-section with a closed hub at the piston pin end and with an integral cap at the lower end. The cap is saw-cut from the rod in the machining operation. The cap is accurately located on the

The connecting rod bearing is made up of upper and lower bearing shells. There are two types of connecting rod bearing shells used in the Series 16-278A engines. One type is bronze backed with a centrifugally cast lining of Satco metal of the same composition as that used in the main bearings. The other type is steel backed with an intermediate lining of bronze and an inner lining of the same bearing material. Connecting rod bearing shells are marked similarly

to main bearing shells to indicate their position in the engine.

In both types of bearings the lower bearing shell is located in the connecting rod bearing cap by means of a dowel pin. This pin prevents the lower shell from rotating. The joint faces between the upper and lower shells are compressed when the cap is fully tightened to make the joints oiltight and to force the backs of the shells into full bearing in their seats.

Each connecting rod bearing is lubricated with oil received from the adjacent main bearings through oil passages drilled in the crankshaft. The oil passage in the crankpin has two outlet holes in the connecting rod bearing that are 90 degrees apart, and from one or the other of these outlets, oil flows continuously into two grooves in the connecting rod bearing surface. These oil grooves are on opposite sides of the connecting rod bearing surface to insure a constant flow of oil regardless of the position and rotation of the crankshaft.

Two oil holes, drilled through the bearing shell, connect the upper end of each groove in the bearing surface with an oil groove in the upper part of the bearing shell seat in the connecting rod. An oil hole, which is rifle drilled through the center of the connecting rod, conveys the oil from the groove in the bearing shell seat to the piston pin end of the rod.

The upper and lower connecting rod shells now being manufactured are interchangeable. Any shell of present design may be installed either as an upper or lower. However, shells previously furnished were not interchangeable, and if not machined for interchangeability, must be installed in the correct position. Upper and lower shells of the old design must not be interchanged unless the shells have previously been machined to make them interchangeable.

3C4. Valves and valve actuating gear.a. Camshafts. There are two camshafts on the GM engine, one for each bank of cylinders. Each camshaft is made up of two sections which are

Each camshaft is supported in 16 bearings in the cam pocket on the cylinder block. The bearing bases are integral with the cam pocket and have forged steel caps. The bearings consist of upper and lower shells with flanged steel backs and babbitt linings. The upper shell of each bearing is held from turning by a dowel pin in the bearing cap.

Each of the two camshafts is bolted and doweled to a camshaft driving sleeve at the drive end of the engine. The sleeve in turn is driven by the camshaft gear of the camshaft drive gear train. The camshaft thrust is taken at the camshaft gear.

The camshaft bearings in each bank are lubricated by oil piped from the main lubricating oil manifold to the camshaft gears. The oil flows under pressure through a passage in each driving sleeve to the hollow bore in the camshaft and then through radial drilled holes to each bearing on the camshaft. Tubes from the camshaft bearing caps carry the oil to the cam pockets. The cam pockets provide a reservoir into which the cams dip, insuring lubrication as soon as the engine is started.

b. Rocker lever assembly. Each cylinder head is equipped with three rocker levers; two of them operate the two pairs of exhaust valves, the third operates the unit injector. All three are made of alloy steel forgings. The rocker levers rock up and down in a fixed shaft which is clamped in a bearing support. They are fitted with cam follower rollers which operate in contact with the exhaust and injector cams.

Bushings are pressed into the lever hubs and are reamed for the bearing fit on the rocker lever shaft.

The roller follows or rolls with the cam on the camshaft. The high point on the cam forces the roller end of the rocker lever up and the opposite end down. It is this motion that actuates the valves and injector. Each of the exhaust valve rocker levers is fitted at the outer end with a nut-locked, adjusting screw that has a ball point. The ball point fits into a ball socket on the exhaust valve bridge. Thus, the downward pressure on the rocker lever end is transmitted to the valve bridge which actuates a pair of exhaust valves.

The injector rocker lever is fitted at the outer end with a nut-locked adjusting screw having a ball socket at the end. A hardened steel shoe fits around the ball socket to give flexibility of movement. Downward pressure of the rocker lever end causes the shoe to bear down on the plunger follower in the injector. The rocker lever assemblies are lubricated

c. Exhaust valves and valve bridges. Each cylinder contains four exhaust valves. The valves are operated in pairs by the rocker levers through the valve bridges.

The exhaust valves are made of special analysis, heat-resisting, alloy steel. They are held in operating position by cast iron valve stem guides. Valve springs secured to the ends of the valve stems by locks draw the valve

The valve bridges are made of forged steel and have a hardened ball socket into which fits the ball end of the adjusting screw on the rocker lever. The valve bridge has two arms, each of which extends over an exhaust valve stem.

Each arm is fitted with an adjusting screw at the valve stem to equalize valve clearance. The lower part of the valve bridge is ground for a sliding fit in the valve bridge guide. This guide has a ball and socket bearing in the top of the cylinder head. The valve bridge spring keeps valve bridge tension off the valve stems until the bridge is actuated by the rocker lever. When the valve end of the rocker lever is pressed down by the cam action, the valve

The ball and socket bearings in the valve bridges and the valve stems are lubricated by the oil spray that is thrown off by the rocker lever.

Clearances between the valve bridge adjusting screws and the valve stem caps are adjusted by loosening the lock bolts and turning the adjusting screws. A lock wire in the counterbore of the spring seat at the upper end of the valve stem prevents accidental separation of the spring seat from the cap and the split spring lock from the valve stem. If a valve spring breaks, these assembled parts are held together so that the valve does not drop into the cylinder. The lock-wire also guards against accidental removal of the cap when the rocker lever is not in place.

d. Cylinder test valve. The cylinder test valve is located in the cylinder head and is made up of a valve body which is screwed into the cylinder head, and a valve stem which has a threaded fit in the body and a handwheel at the outer end. The valve itself has two faces, an inner face and an outer, or secondary, face. From the valve seat two passages are bored in the cylinder head casting, one leading to the inside of the cylinder and the other leading to the outside. This outside connection is fitted with an indicator adapter which is used when a pressure indicator reading is taken of hot or cold compression pressure. When the handwheel is in the closed position, the inner valve face seats against the main valve seat, closing the passage to the combustion chamber, and preventing the pressure in the cylinder from escaping to the outside. If the handwheel and valve stem are open, the passage to the outside is connected to the passage to the inside of the cylinder. When the valve stem is at its full open position, the outer or secondary valve face bears against the valve body, thus preventing the passage of exhaust gases through the valve body.

e. Cylinder relief, or safety valve. Each cylinder head is equipped with a safety valve (Figure 3-29) which opens if the cylinder pressures exceed a safe operating limit. This valve

Figure 3-28. Cylinder test valve, GM.

f. Camshaft drive. The camshafts are driven from the control end of the crankshaft through a train of helical spur gears, with a crankshaft idler gear and a camshaft idler gear between the two camshaft gears and the crankshaft gear. The camshafts run at the same speed as the crankshaft but in the opposite direction of rotation. The drive gear for the lubricating oil pump is driven from the left bank camshaft gear in a left-hand rotation engine and from the right bank camshaft gear in a right-hand rotation engine. All of the other gears are in the same location regardless of rotation. These gears are made of steel forgings.

Each of the two idler gears and the lubricating oil pump drive gear are mounted on a heat-treated steel shaft, which is pressed into the gear hub. The two idler gear shafts are supported in inner and outer bearing supports fitted with single-flanged steel bushings, which are lined with babbitt. The bearing supports are accurately aligned with dowel pins and fastened together with studs. The pump drive gear is supported in the bearing supports of the mating camshaft gear.

The hub projections on the outside of the camshaft gears are finished to form journals, and are supported in babbitt-lined steel bushings which are pressed in the inner and outer bearing supports. The inner and outer bearing supports are accurately aligned with dowel pins and are fastened together with studs. The gear

The outer flange of each camshaft driving sleeve is fastened to the outer face of the camshaft gear hub by capscrews. The inner end of the driving sleeve is flanged and doweled to the flanged end of the camshaft. The camshaft is driven through the dowel pins in the connection, and a bolt, smaller than the dowel pins, prevents incorrect assembling of this drive connection. The holes in the outer flange of the driving sleeve are slotted, so that the camshaft may be accurately adjusted to the correct timing position. When this adjustment has been made, the timing position is permanently fixed by dowel pins, through which the driving sleeve and the camshaft are driven.

Oil for lubricating the gear teeth and the gear bearings is received from two oil-distributing blocks in the camshaft drive housing. The two distributing blocks are supplied with oil from the main manifold in the oil pan. The engaging gear teeth are lubricated with jets of oil delivered through tubes and nozzles. The outer bearings of all the gears, except the

Figure 3-32. Camshaft drive lubrication, GM.

The gear train is enclosed in an oiltight housing. The housing is accurately located on the end of the crankcase with dowel pins and is held in place with studs, some of which secure both the housing and the gear assemblies. A pressure relief opening in the top of the housing is fitted with a spring-loaded plate.

g. Accessory drive. The accessory drive is located on the blower end of the engine and consists of a train of helical gears transmitting the rotation of the crankshaft to the blower and water pumps. The gears are enclosed in a case bolted to the blower housing.

The blower and accessory drive gear, which drives the water pump idler gears and the blower drive gear, is driven from the crankshaft through a splined shaft, one end of which fits into a hub that is bolted to the crankshaft, while the other end fits into the blower drive gear hub. The water pump drive gears are driven by

3D2. Main stationary parts. a. Cylinder block. The cylinder block is the main structural part of the engine and is designed to give the engine the necessary strength and rigidity. It is constructed by welding various structural members and bracings into one unit. The transverse vertical members together with four horizontal decks farm the enclosures and housings for the various operating or functional parts. The four

The cylinder block consists of the following compartments:

1. Control end compartment, forming an enclosure for the timing chain, controls, and flexible gear drive for the attached pumps and governor.

2. Vertical drive compartment, forming the enclosure for the bearing assembly housings of the vertical drive shaft connecting the upper and lower crankshafts.

3. Upper crankshaft compartment,

Figure 3-36. Vertical drive compartment spring-loaded access plate, F-M.

Figure 3-37. Inspection covers, F-M.

4. Scavenging air compartments and air receivers running lengthwise on each side of the cylinder block, forming a passage for scavenging air to the inlet ports of the cylinders.

5. Valve compartments, forming enclosures for the injection nozzles, injection pumps, air start check valves, cylinder relief valves, and governor control shafts.

6. Exhaust manifold and belt compartment, extending lengthwise on each side of the cylinder block. With the installation of the exhaust belt and two exhaust manifolds in this compartment, a passage is formed for the exhaust gases from the cylinders to the external exhaust system.

7. Lower crankcase compartment, forming the bearing saddles for the lower crankshaft bearings.

The block is sand blasted after welding. It is then stress relieved by seasoning in an

The air receiver, vertical drive, and control end compartments are provided with covers. The upper crankcase compartment is closed with a sheet metal top cover having several small inspection covers over the cylinders. These inspection covers are spring loaded so that in an emergency undue pressure in the crankcase compartment will be relieved. One of the vertical drive compartment access plates is spring loaded for the same purpose.

b. Cylinder liner. The cylinders are bolted into the cylinder block in a row along the centerline of the engine. They are spaced so that the lower end will enter the bored hole in the exhaust belts. The spacing must be horizontally correct so that the pistons and connecting rods coincide with the throws of the crankshafts. No. 1 cylinder is always at the control end of the engine.

The tangentially shaped scavenging air inlet ports are located near the top of the liner and are opened and closed by the upper piston. The exhaust ports are located near the bottom of the liner and are opened and closed by the lower piston. Each cylinder liner has four valve ports bored near its center for two injection nozzles, an air start check valve, and a cylinder relief valve with indicator cock which are adapted together.

Circular ribs or radiating fins are provided near the top of the liner to allow the scavenging air to carry away some of the heat of combustion. Vertical ribs in the liner between the inlet and exhaust ports direct the water travel upward, absorbing heat from this part of the cylinder. The liner is bolted to the top deck of the cylinder block by means of lugs. The liner is held rigid at this point and any expansion of the liner due to the heat of combustion is downward through the counterbores of the engine framing and exhaust belts. Tapped holes for lifting eyebolts are also provided in the lugs that bolt the liner to the cylinder block.

3D3. Main moving parts, Fairbanks-Morse. a. Crankshafts. Each Fairbanks-Morse engine has an upper and a lower crankshaft. The upper pistons are connected to the upper crankshaft and the lower pistons are connected to the lower crankshaft. Both crankshafts are of the integral type, constructed of machined, fine grain cast

Both crankshafts on the 10-cylinder engine have ten cranks. The 9-cylinder engine has two crankshafts, each having nine cranks. Main bearing and connecting rod journals are stone ground to a smooth finish. Weight and bearing loads are reduced by hollow casting the shaft and crankpins. Oil passages are drilled so as to permit lubricating oil to be forced from each main bearing journal to the adjacent crankpin journals.

The crankshaft sprocket for the timing chain drive is keyed to the upper crankshaft at its control end. The air start distributor camshaft is also fastened to the upper crankshaft at the control end. At the opposite or blower end, the blower flexible drive gear is keyed and held with a retainer plate to the crankshaft.

The torsional damper is keyed to the control end of the lower crankshaft and secured by means of a key and a damper hub nut. The flexible pump drive gear for driving the governor and attached pumps is keyed to the torsional damper spider. The flexible crankshaft coupling driving gear is bolted to a flange on the blower end of the lower crankshaft.

b. Main bearings. Main bearings in the upper and lower crankcase support the upper and lower crankshafts. Each main bearing consists of an upper and lower precision made bearing shell that is lined with Satco metal. The upper and lower shells fit into the enclosures formed by the saddles or bearing seats in the cylinder block and the bearing caps. The bearing caps are made of forged steel. They are assembled with the bearing saddles in the cylinder

Both upper and lower bearing shells have oil grooves around the center of the inside surface. The bearings are lubricated by oil under pressure from the engine pressure system. The oil is piped to the bearing caps through lines from the main oil header and fed through holes into the grooves where it lubricates the bearing surface. Oil is conducted through oil passages in the crankshaft to the connecting rod journals and bearings. Crankshaft thrust is taken by a

c. Torsional damper. Every crankshaft with attached rotating parts has a natural period of torsional vibration, the frequency of which depends upon the mass and elasticity of the shaft and of the parts attached to it. If turning impulses are applied to the shaft at regular intervals, and if their frequency of application is a multiple of the natural frequency of the shaft, a condition of synchronous torsional vibration is produced. This condition is not usually found in the F-M 9-cylinder engine but is definitely present in the F-M 10-cylinder engine. The points at which it occurs are known as the critical speeds.

If the engine is to be permitted to run at one or more of these critical speeds, a means of damping the torsional vibration is advisable.

The torsional damper is mounted on the lower crankshaft at the control end of the F-M 10-cylinder engine. This unit consists of a spider fitted with eight damper weights. These are installed in two rows in slots in the spider. Each weight is located and free to move in or out on the two weight pins, according to the speed of rotation of the crankshaft. Lubrication is furnished to the moving parts of the damper from the engine pressure system by means of grooves and holes in the spider hub.

In addition to the torsional damper, it is necessary to devise a method of preventing torsional vibrations between the crankshafts and the various auxiliary drives. This is usually done by means of flexible drive gears in each auxiliary gear train and by a flexible spring coupling in the vertical drive shaft.

d. Pistons and piston rings. The upper and lower pistons of the F-M diesel engines are

e. Piston pin assembly. Connection between the piston and connecting rod is made by the piston pin and the piston pin bracket. The latter is bolted inside the piston, clamping the piston pin tightly and forming an enclosure for the piston cooling oil.

There are two types of piston pin bearings. The sleeve bearing, or bushing type of piston pin bearing, consists of a cast bronze lining pressed into the steel bushing in the connecting rod eye. Lubrication is supplied by oil holes in the steel bushing which line up with the drilled oil hole in the connecting rod. Grooves on the surface of the lining distribute oil over the bearing surface.

The F-M 9-cylinder diesel engines were originally equipped with a needle roller type piston pin bearing instead of the bushing type of bearing. However, replacements for this assembly are of the plain bushing type. In the roller bearing type the inner race is formed by

f. Connecting rods and connecting rod bearings. The construction of the upper and lower connecting rods is basically the same except that the lower connecting rod is longer than the upper connecting rod. The connecting rods are made of alloy steel forgings. The rods are forged in an I-section with a closed eye at the piston end to receive the piston pin bearing and a removable cap at the crank end which encloses the connecting rod bearing shells. The cap is secured to the rod by two bolts, castle nuts, and cotter pins.

The connecting rod bearing is made up of upper and lower bearing shells. These are bimetal precision type bearings with machined bronze or steel backs and with a centrifugally cast soft lining of Satco metal, a high lead bearing metal. Both bearing shells are kept from rotating by dowel pins in the cap and bearing

g. Vertical drive. On Fairbanks-Morse

The 9- and 10-cylinder engine vertical drives differ in construction. In the 10-cylinder engines, helical bevel gears or ring gears are bolted to flanges on both the upper and the lower crankshafts. Each of the ring gears meshes with a helical bevel pinion. Each of the pinions is fitted and keyed to a vertical pinion drive shaft. The two pinion shafts rotate in roller and thrust bearings located in the upper and lower drive housings. These housings are bolted to the horizontal decks of the cylinder block.

The inner ends of the pinion drive shafts are keyed to coupling hubs. The upper and lower pinion shaft coupling hubs are connected together by means of a flexible coil spring coupling unit having an upper and lower coupling hub and an adjusting flange, or cone coupling as it is sometimes called. The upper pinion shaft coupling hub bolts directly to the flexible spring coupling upper hub. The lower pinion shaft coupling hub is connected to the lower flexible spring coupling hub through the adjusting flange. Thus the upper and lower pinion shafts are connected by a spring-loaded flexible coupling which consists of upper and lower members between which are housed 16 coil springs held by retainers. Torque on the upper hub of the flexible coupling is passed to the coil springs which in turn apply torque to the lower hub of the flexible coupling. Thus the coupling has torsional flexibility which permits it to absorb crankshaft torsional vibrations.

The flexible spring coupling also has a certain amount of vertical flexibility to allow for expansion due to operating temperatures. It has sufficient flexibility to account for a small amount of misalignment between the upper and lower pinion shafts.

The adjusting flange serves as a means of disconnecting the vertical drive so that the crankshafts may be turned separately for servicing. It is clamped to a tight fit over the tapered lower pinion shaft coupling hub by means of a clamp ring and retains a fixed relation between

The 9-cylinder Fairbanks-Morse vertical drive and the 10-cylinder vertical drive use a flexible coupling, which consists of a coupling shaft with upper and lower collar, and which has a set of laminated saw steel rings at each end. Each laminated group consists of 30 to 40 rings, each .019 inch thick. The set, when installed and compressed, is about 5/8 inch thick. The upper pinion shaft coupling hub and the upper collar of the coupling shaft are bolted to the laminated rings at different points. The lower collar of the coupling shaft and the upper collar of the adjusting flange are bolted to the lower set of laminated rings at different points. The vertical flexibility of the coupling through the laminated rings allows variations due to expansion of the engine. In addition some of the Fairbanks-Morse 10-cylinder engines use a coil spring type of flexible coupling.

h. Flexible drive far auxiliaries. The fresh water and sea water circulating pumps, the attached fuel oil and lube oil pumps, and the Woodward governor are all driven from the lower crankshaft through a flexible gear drive at the control end.

In this drive, power is transmitted through springs which absorb shocks inherent in the engine and transmitted by the lower crankshaft. The two circulating water pumps are driven directly from the flexible gear through their driven gears. The fuel oil pump drive gear and idler gear in turn rotate the fuel oil pump driven gear. The lubricating oil pump driven, gear and drive shaft drive the pump by means of a coupling meshing with slots in the end of the shaft.

A bevel gear, mounted on the lubricating oil pump drive shaft, meshing with a mating gear on the governor drive shaft, drives the governor through the governor coupling shaft The ball bearings and gears of the governor drive are lubricated with oil thrown off from the

Figure 3-52. Camshaft lubrication, F-M.

3D4. Valves and valve actuating gear. a. Camshaft. The Fairbanks-Morse engine has two camshafts which are located in the upper crankshaft compartment. The function of the camshafts is to actuate the two fuel injection pumps at each cylinder in exact unison and at the proper time.

Both camshafts are made of steel and each consists of three or four sections flanged and bolted together. The cams are forged integral with the camshaft and then ground to a master camshaft. The sections are match-marked so that they may be connected in proper relationship to each other. The camshafts may be removed a section at a time or in one unit. There is one cam for each cylinder on each camshaft. Each camshaft is operated by a sprocket bolted to a flange on the control end of the camshaft. Both camshaft sprockets are driven by one timing chain so that proper timing between the two camshafts is maintained.

The camshaft bearings are lubricated by oil from the upper lubricating oil header. The oil is led through oil tubes to the control end bearing of each camshaft. Oil enters the bearing cap, is forced through a hole in the bearing shell and camshaft journal to the hollow bore of the camshaft. It is then forced through radial drilled holes to each of the bearings along the entire camshaft. Oil holes in the hubs at the driving ends of the camshafts connected with the holes in the camshaft sprockets provide oil for the timing chain. The overspeed governor is mounted at the control end of the left-hand camshaft in the left-hand rotation engines and on the right-hand camshaft in right-hand rotation engines.

Figure 3-54. Timing chain details, F-M.

Figure 3-55. Timing chain link, F-M.

The endless timing chain passes over the crankshaft sprocket, under two opposed timing sprockets, over the two camshaft drive sprockets, and under a chain tightener sprocket. The two timing sprockets are mounted on a timing bracket. The timing bracket has an 8-degree pitch adjustment. Moving the timing bracket arm moves both timing sprockets on the chain at once, changing the camshaft relation to the crankshaft. Thus the chain is tightened in operation between the crankshaft sprocket and one camshaft drive sprocket, and given more slack between the crankshaft sprocket and the other camshaft drive sprocket. This provides a precision adjustment for securing the exact phase relation desired between the crankshaft and two camshafts. The tightener sprocket is adjustable to secure the proper slack in the chain.

The timing chain is assembled as shown in Figure 3-53. The guide links for guiding the chain on the timing sprockets and tightener sprocket ride in slots in the crankshaft and camshaft drive sprockets.

c. Cylinder relief and indicator valves. Each cylinder in the engine is fitted with a water-cooled, automatic relief valve for the out let of excessive pressures in the combustion space. The relief valves are normally set to open at about 2,000 psi, and to close as soon as the pressure has dropped below this setting.

The relief valve is threaded into the adapter valve which also has a tapped opening for an indicator valve. The complete assembly is attached to a cylinder liner valve adapter sleeve by means of a threaded collar and stud nuts.

The relief and indicator valve adapter sleeve is cooled by water which is admitted to the adapter water jacket through a groove machined on the outside of the cylinder liner.

The indicator valves are threaded and screwed permanently into the cylinder relief valve adapters. When a pressure reading is to be

Figure 3-57. Cylinder relief valve and adapter, F-M.

As the indicator valve is closed, the beveled collar is forced against the other seat in the inlet port, and the pressure in the indicator is free to escape through the vent holes in the valve body.

ENGINE DATA, RATINGS, AND CLEARANCES