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12

AUXILIARY ENGINES

A. GENERAL MOTORS 8-268 AND 8-268A ENGINES

12A1. General. The General Motors 8-268 or 8-268A engine is used on board

modern submarines as an auxiliary

engine. It is located in the lower flats ofthe after engine rooms, and may be

used for directly charging the batteries

or carrying the auxiliary load, andindirectly for ship propulsion. The GM

8-268 is an 8-cylinder, in-line, 2-cycle,

air started engine rated at 300 kwgenerator output at 1200 rpm. In

general, the individual parts of theengine are similar to, but smaller than

the corresponding parts in the GM 16-278A. For example, the camshafts,

exhaust valve and rocker lever

assemblies, injectors, pistons, cylinders,liners and connecting rods are almost

miniature replicas of the 16-278A parts.

The main differences between theengines appear in the construction and

design of the various systems such as

the scavenging air, exhaust, lubricatingoil, and fuel oil systems, as well as inthe fact that the 8-268 is an in-line

engine.

12A2. Engine stationary andmoving parts. a. Cylinderblock. The cylinder block is themain structural part of theengine. It is composed offorgings and steel plates

welded together, combiningstrength with light weight.

The upper and lower decks ofthe cylinder block are bored toreceive the cylinder liners. Thespace between the decks is thescavenging air chamber. The

access to the crankcase. Eight are locatedon one side and seven on the other. The

remaining handhole is covered by the air

maze which may be moved. Seven of thecovers are of the safety type, each having

four spring-loaded plates, which in an

emergency, relieve any undue pressure inthe crankcase.

The main bearings are lubricatedfrom the lubricating oil manifold

located in the crankcase.

b. Crankshaft. The crankshaft isa heat-treated steel forgingfinished all over, having eightconnecting rod throws orcrankpins 45 degrees apart. Thecrankshaft is held in the cylinderblock by nine main bearing caps.The bearing at the drive end ofthe engine acts as a combination

main and thrust bearing.Lubricating oil is supplied underpressure from a main manifoldlocated in the crankcase, and isforced through tubes to thecrankcase crossframes, where itflows through oil passages to themain bearings. From the mainbearings the oil flows throughdrilled holes, in the crankshaft tothe adjoining crankpin and

lubricates the connecting rodbearing. The combination mainand thrust bearing journal No. 9is not connected by drilled holesto a crankpin. There is a 1/4-in.diameter radial oil hole in thesurface of this journal into whicha capscrew, with the head

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bore in the lower deck isconstructed with a groovewhich serves as a cooling waterinlet for the liner. The cylinder

liners are located in thecylinder block by means ofdowel pins in the upper deck.

The camshaft bearing lowersupport is an integral part ofthe cylinder block located atthe extreme top of the block.The bearing cape and bearingsupports are match-markedand must be kept together.

The forged transversemembers in the bottom of thecylinder block form the maincrankshaft upper bearing seats.Again the bearing caps andbearing supports are match-marked and must be kepttogether.

Fifteen removable handhole

covers permit

ground off enough to clear thebearing seat, may be insertedfor rolling out the upper shell.

c. Elastic coupling. The powerfrom the engine crankshaft istransmitted through springpacks from the inner springholder of the elastic coupling, orflywheel, to the outer springholder, and from there throughthe driving disk to the generatorarmature shaft flange. A pilot onthe end of the crankshaft fitsinto a ball bearing in the

armature shaft. The turning gearpinion engages a ring gearshrunk on the rim of the outerspring holder.

The inner cover of the elasticcoupling, through which thecamshaft gear train is driven, isfastened to the outer springholder. A helical

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Figure 12-1. Blower end control side of GM 8-268 auxiliary engine.

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Figure 12-2. Blower end exhaust header side of GM 8-268 auxiliary engine.

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Figure 12-3. Longitudinal cross section of GM 8-268 auxiliary engine.

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Figure 12-4. Transverse cross section of GM 8-268 auxiliary engine.

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Figure 12-5. Cutaway of frame,GM 8-268.

internal gear, cut in the innerbore of the elastic couplingcover, meshes with thecrankshaft gear, forming asplined drive connection to thecrankshaft gear which has aloose mounting on thecrankshaft.

The bearing bore of thecrankshaft gear. hub receivesoil that flows from the adjacentmain bearing through passagesin the crankshaft. The parts ofthe elastic coupling arelubricated with the oil thatflows from the bearing bore ofthe crankshaft gear hub.

d. Main bearings. Each mainbearing consists of an upperand a lower double-flanged,bronze-backed, precisionbearing shell. The centrifugallycast lining is a high leadbearing metal called Satcowhich contains a special

Figure 12-6. Lubrication of main

bearings, GM 8-268

into full contact when the cap isfully tightened. A drilled hole inthe lower shell fits on a dowelpin in the cap. The dowel pinlocates the lower shell in thebearing cap and prevents boththe upper and lower shells fromrotating.

Each bearing shell is marked onthe edge of one flange. Forexample, 2-L-B.E. indicates thatthe shell so marked is for the No.2 main bearing, the lowerbearing shell, and the flange somarked must be toward theblower end of the engine. Themain bearing nearest the blowerend of the engine is the No. 1main bearing. Upper and lower

bearing shells are notinterchangeable.

Crankshaft thrust loads aretaken by the rear main bearing.The thrust bearing shells are thesame as the other main bearingshells except that the bearing

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hardener.

The lower shell is mounted inthe bearing cap and the upper

shell in its seat in the cylinderblock crossframe. The jointfaces of the upper and lowerbearing shells project a verysmall amount above the seatand cap. That is to insure thatthe backs of the shells will beforced

metal is extended to cover theflanges. Each main bearing capis marked with its bearingnumber and is marked Blower

Endon the side that should facethe blower end of the engine.

Lubricating oil enters the oilgroove in the upper shellthrough a hole in the top andthen

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flows to the lower shell. The bearing

surface of the lower shell has an oilgroove starting from the joint face at

each side and extending partially

around the inner surface of the shell.

e. Pistons. The pistons aremade of an alloy cast iron. Thebored holes in the piston pinhubs are fitted with bronzebushings. The outer ends of thebore for the full-floating alloy

steel piston pin are sealed withcast iron caps.

A cooling-oil chamber is formedby an integral baffle, and thepiston crown lubricating oilunder pressure flows from thetop of the connecting rod,through a sealing member, intothe cooling chamber. The oilseal is a spring-loaded shoe

which rides on the cylindricaltop of the connecting rod. Theheated oil overflows throughtwo drain passages.

Each piston is fitted with sixcast iron rings, fourcompression rings above the

of upper and lower bearing shells. The

bearing shells are lined with Satco metaland are of the precision type. Each

connecting rod bearing shell is marked

on the edge of one flange. For instance,1-L-B.E. indicates the shell is marked for

the No. 1 connecting rod, and lower

bearing shell, and the bearing flange somarked must be toward the blower end of

the engine. No shims are used between

the connecting rod and the bearing cap.The upper and lower bearing shells are

not interchangeable.

The lower shell is mounted in thebearing cap and the upper shellin its seat in the connecting rod.The joint faces of the upper andlower bearing shells project avery small amount above theseat and cap. This is to insurethat the backs of the shells willbe forced into full contact when

the cap is fully tightened. Adrilled hole in the lower shell fitson a dowel pin in the cap. Thedowel pin locates the lower shellin the bearing cap and preventsboth the upper and lower shellsfrom rotating.

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piston pin and two oil controlrings below. These rings are ofthe conventional one-piece,cut-joint type.

f. Connecting rods. Theconnecting rod is an alloy steelforging. The connecting rodbearing in the lower end of theconnecting rod consists

The piston pin is of the fullfloating type. The piston pinbronze bushing is a shrink fit in

Figure 12-7. Cross section of piston, GM 8-268.

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the upper hub of the connecting rod.The ends of the pin oscillate in the

bronze piston pin bushing hubs of the

piston.

g. Cylinder liner. The cylinderliner is a cylindrical alloy ironcasting with cored annularspaces between the inner andouter surfaces between theinner and outer surfaces

through which cooling water iscirculated. The liner isaccurately bored to a smoothfinish.

The cylinder liner is held in theengine block by the lowerdeckplate and a recess in the

Figure 12-8. GM 8-268 cylinder liner

cross section showing cooling water

passages.

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upper deckplate. The cylinderhead forces the liner againstthe cylinder block. The lowerdeckplate has a groove that

serves as the water inlet intothe passages in the cylinderliner. It is made watertight bytwo synthetic rubber ringgaskets, called seal rings. Thecooling water flows up throughthe cylinder liner and into thecylinder head through ferrulesmade watertight by syntheticrubber gaskets. The air intakeports, through which

scavenging air from the blowerenters to supply the cylinderwith fresh clean air, are locatedaround the circumference ofthe liner. When the pistonreaches the bottom of itsstroke, these ports arecompletely open and the airspace above the piston ischarged with fresh air.

The joint between the cylinderliner and the cylinder head ismade gastight by an innerbronze gasket while an outercopper gasket which hasnotches in it serves to seat thehead squarely against thecylinder liner. The drain plug inthe lower part of the jacket ofthe cylinder liner should beremoved for draining water

when freezing temperaturesare expected and an anti-freeze solution is not in use.

h. Cylinder heads. The enginecylinders are fitted withindividual cylinder heads whichare made of alloy cast iron.

Cooling water flows from thecylinder liner into the head andthen flows into the water jacketof the exhaust manifold.

Each cylinder head is fitted withfour exhaust valves, the unitinjector, rocker lever assemblies,air starter distributor valve, anover speed injector lock, the airstarter check valve, and thecylinder test and safety valves.

i. Rocker lever assembly. Eachcylinder head is equipped with

three rocker levers, two of whichoperate the two pairs of exhaustvalves, and the third operatesthe injector. The rocker leversare made of alloy steel forgings.Bushings are pressed into thelever hubs and are reamed for abearing fit on the rocker levershaft.

The three rocker levers rock on a

fixed shaft which is clamped in abearing support. They are fittedwith cam rollers, which operatein contact with the exhaust andinjector cams. Each of the threecam rollers turns on a bushingand the bushing turns on asleeve that has a loose mountingon the roller pin. Each of theexhaust valve rocker leversoperates two valves

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Studs in the cylinder block holdeach head against the cylinderliner flange. The joint betweenthe head and the liner is made

gastight with an inner bronzeand an outer copper gasket.The outer gasket serves to seatthe head squarely on the liner.The shallow milled groovesshow leakage of exhaust gas orwater.

The head is also fastened tothe vertical wall of the campocket with tap-bolts. The joint

is made oiltight with asynthetic rubber gasket.

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through a bridge. Each of the valverocker levers is fitted at the valve end

with a nutlocked adjusting screw,

which has a hardened ball end that fitsinto the ball socket in the valve bridge.

The injector rocker lever is fitted at the

injector end with a nut-locked adjusting

screw, which has a hardened ball at thelower end. This ball is fitted with a

hardened steel flexibly mounted shoe.

The shoe bears on the injector plungerfollower and transmits the rocker lever

motion to the injector plunger.

The rocker lever shaft is madeof alloy steel and is ground tosize. The shaft is clamped inthe bearing support by two

bearing caps and is held in itscorrect location by a dowel pinin one of the bearings. A rockershaft thrust plate is bolted toeach end of the shaft, and aplant fiber gasket is placed inthe joint between the thrustplate and the rocker lever

the sequence of events essential to theoperation of the engine will be in the

proper order. The forged steel crankshaft

gear, which is driven by, the crankshaftthrough the elastic coupling, is keyed on

a split collar and drives the camshaft gear

through the crankshaft and camshaft idler

gears. A spacer ring is doweled to thecrankshaft gear.

Steel-backed babbitt-linedbearing shells support the innerand outer hubs of the forgedsteel helical idler gears. Theinner and outer supports arebolted and doweled togetherbefore being mounted in thecamshaft drive housing. The fuel

oil pump and governor aredriven from a gear that mesheswith the lower idler gear. A pairof bevel gears drives the verticalgovernor shaft which is mountedin ball bearings.

The lower idler gear also drives

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shaft. The bearing support isfastened to the cylinder headwith two studs and positionedby two dowels, and is also held

against the head by two of thecylinder head hold-down studs.

The rocker lever assembly islubricated with oil receivedfrom one of the camshaftbearings. The oil flows from thetop of the camshaft bearingthrough a tube to the plateconnection that is fastened toone end of the rocker lever

shaft. From this connection, theoil flows through drilledpassages in the rocker levershaft to the three bearings inthe rocker lever hubs.

A drilled passage in each of therocker lever forgings conductsthe lubricating oil from a holein the hub bushing to thecamshaft end of the lever. The

rocker lever motion permits oilto flow intermittently underpressure from the hole in theshaft, through one hole in thebushing and rocker lever to thecam roller. The bearing in eachof the cam rollers receives oilthrough drilled holes in theroller pin and in the bearingbushings.

j. Camshaft drive. In 2-cycleengine operation the camshaftrotates at the same speed asthe crankshaft. The camshaftdrive gears are located at thepower takeoff end of theengine. They transmit therotation of the crankshaft to

the quill shaft gear, which issplined for the quill shaft thatdrives the blower and accessorygear trains. A splined coupling,

which rotates in the babbitt-linedcenter bearing, joins the twosections of the quill shaft.

The overspeed trip weightassembly and the camshaft gearare bolted and doweled to a hubthat also serves as a bearingjournal for this assembly. Thehub is splined to fit on the end ofthe camshaft.

Lubricating oil for the camshaftdrive gear train and bearings ispiped from the end of thelubricating oil manifold in thecylinder block. Oil is suppliedunder pressure to the hollowcamshaft through the camshaftgear bearing. Open jets spray oilon the gear teeth.

Complete dynamic balance ofthe engine is obtained bybalance weights mounted in acertain relation to each other onthe gears in the front and reargear trains.

k.Accessory drive. Theaccessory drive, locatedbetween the end of thecrankcase and the blower,

consists of a train of helicalgears driven from the camshaftdrive gear train through the quillshaft. The gears in the accessorydrive are match-marked with adefinite relationship to thematch-marks on the gears in thecamshaft drive gear train, to

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the camshaft. It is necessary tomaintain a fixed relationshipbetween the rotation of thecrankshaft and the rotation of

the camshaft so that

maintain the

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Figure 12-9. Cross section of camshaft, GM 8-268.

relationship between the balance

weights in both trains.

The accessory drive gear drivesthe upper idler gear. This upperidler gear drives the lower idlergear. A plate with a splined hubfor driving the lubricating oilpump is bolted to the hub of

the lower idler gear. The freshwater and sea water pumpdrive gears are driven from thelower idler gear. The hubs ofthe water pump drive gearshave a spline cut in the bore forthe fresh water and sea waterpump shafts. The hubs whichproject from each side of thelower idler and water pumpgears run in steel-backed

babbitt-lined bearings mountedin the inner and outer bearingsupports. These bearingsupports are bolted togetherand the assembly is fastened inplace on the inside of theaccessory drive housing.

steel backed and babbitt lined, are held

on their seats in the cam pocket withbearing caps.

There are four cams for eachcylinder. The two outer camsoperate the exhaust valves, andthe center cam operates theinjector. The fourth cam, which

is narrower than the other three,operates the air timing valve.

The camshaft drive end of thecamshaft is splined for a drivingconnection in the hub of thecamshaft gear which is drivenfrom the crankshaft gearthrough a train of idler gears.

Lubricating oil under pressure is

supplied to the camshaft borethrough the splined driveconnection. The oil is thendelivered to the camshaftbearings through radial holes inthe camshaft. Oil for lubricatingthe rocker lever mechanismsflows through tubes from the

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Lubricating oil is piped to theaccessory drive from the mainlubricating oil manifold in thecylinder block. Oil lines and

connecting pass ages in thebearing supports supply oil tothe bearings in the drive.

The accessory drive covershould be removed periodicallyand the gear train inspected forexcessive wear of any parts.Lubricating oil lines andpassages should be checkedperiodically to insure that they

are not broken or clogged. Allnuts and capscrews should betight.

1. Camshaft. The camshaft is ofthe one-piece type with integralcase-hardened cams andbearings. The bearingbushings, which are

camshaft bearing caps.

m. Engine control. The governor,which is located at the generator

end of the engine, controls theengine speed for any setting.

The movement of the governorpower mechanism is transmittedthrough lever and linkconnections to the injectorcontrol shaft in the cam pocket.Each fuel injector rack isconnected to a control shaftlever through a slipjoint link. A

micrometer adjusting screw onthis link increases or decreasesthe amount of fuel injected intothe combustion chamber.

A slip joint is connected to eachinjector rack so that in case thecontrol rack in one injectorbinds, the compression of thespring in

238the slip-joint link allows normal

operation of the other injectors. Eachspring is preloaded to limit the force

that can be applied by the governor to

move the injector control racks. Whenthe link is either shortened or

lengthened by a load greater than its

assembly load, the spring is

compressed.

The start and stop lever is usedfor manual control whenstarting or stopping the engine,and its movements aretransmitted through aconnection that provides forunrestricted governor controlwhen the start and stop lever is

filter on the cylinder head to a jumper

tube that supplies the injector. Theinjector inlet contains another filter to

further prevent solid matter from

reaching the spray valve.

The surplus fuel is bypassed inthe injector and flows throughanother filter in the injectoroutlet passage so that any

reverse flow of fuel cannot carrydirt into the injector. The surplusfuel passes from the injectorthrough a tube to a fuel bleedmanifold, which is the bottompipe in the multiple oil pipeassembly. The fuel from thisbleed manifold flows to the

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latched in the RUN position.The governor connections tothe injector control shaftinclude an extensible spring-

loaded link which permits theinjector control shaft to beturned manually withoutmoving the governor powerpiston.

When the governor or any partof the injector control system isrenewed, the governor powerpiston should be linked in thecorrect relation to the injector

rack.

n. Overspeed trip. Theoverspeed trip mechanismstops the injection of fuel oil tothe combustion chamberswhen the engine speedexceeds 112 percent of ratedspeed.

The overspeed trip weight

assembly, mounted on thecamshaft gear, is fitted with aspring-loaded flyweight. Thespring tension is adjusted sothat, at a predeterminedengine overspeed, thecentrifugal force moves theflyweight radially until it strikesa roller latch, releasing thespring-actuated injector lockshaft in the cam pocket at each

engine cylinder. The injectorlock carries a lever on the shaftthat moves a pawl engaging anotch on the injector rockerlever. The injection of fuelstops when the locked rockerlever holds the injector plungerat the lower end of its pumping

metering block, through themetering valve which sets upenough resistance to maintainthe required pressure in the fuel

supply manifold, and then flowsback to the clean fuel oil tank.

Fuel oil leakage from the injectorplunger and bushing is drainedthrough an injector body ferrule,through a cylinder head passageinto a manifold connectionclamped between the cylinderblock and cylinder head. Theinjector drainage is conducted

through this connection to thesecond manifold from the top inthe multiple oil pipe assemblyand then it flows through thedrain to the fuel oil tank or bilge.

b. The unit injector. On thisengine, the fuel pump and sprayvalve are combined into a singleand compact unit called a unitinjector, which meters the fuel

and also atomizes and sprays itinto the cylinder. This injector issimilar to that used in the GM16-278A and its operatingprinciple is identical. The unitinjector is held in position in awater-cooled jacket in the centerof the cylinder head: At thelower end, the injector forms agastight seal with the taperedseat in the cylinder head. All the

injectors in this engine are alikeand interchangeable. Fuel issupplied through jumper tubeswith spherical type gasketlessconnections.

The pumping function of theinjector is accomplished by the

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stroke.

The overspeed trip is manuallyreset with a hand lever on the

shaft which projects from thecamshaft drive housing.

12A3. Fuel oil system. a.Description. The fuel oil pumpdraws oil from the clean fuel oiltank and forces it through thefuel block and the fuel oilstrainer and filter. From thefilter, the oil flows to the fuelsupply manifold, which is the

third pipe from the top in themultiple oil pipe assembly, andthen through a small jet

reciprocating motion of theconstant stroke injector plungerwhich is actuated by the injectorcam on the engine camshaft,

through the injector rocker lever.

The position of the plunger, andthereby the timing, is adjustedby means of the ball stud andlock nut at the injector end ofthe rocker lever.

The quantity of fuel injected intoeach cylinder, and therefore thepower developed in

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that cylinder, is varied by rotating theplunger by means of the injector

control rack. A rack adjustment (called

the microadjustment) located on the

control linkage permits balancing theload of each cylinder while the engine

is running,

c. Fuel block. The fuel block islocated under the exhaustmanifold at the camshaft driveend of the engine and in frontof the fuel oil pump. The fuelblock contains a meteringvalve, a priming valve, and anadjustable pressure reliefvalve.

d.Jet filters. The cylinder headjet filters are located on eachhead, just above the exhaustmanifold connection. Theelement in each cylinder headis of the edgewise-wound metalribbon type. This filter is

Figure 12-10. Cross section of Northern

fuel oil pump used on GM 8-268 engine.

or both filtering units. In normaloperation both filtering units arein operation.

The arrows under the valvehandles show the positions of

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correctly assembled when thehelical spring and cap areplaced over the long end of thefiltering element to hold the

element flange against theshoulder at the inner end of thefilter wall.

e. Fuel pump. The fuel oil pumpis located under the exhaustmanifold at the camshaft driveend of the engine and is of thepositive displacement, spurgear, rotor type. Fuel entersthe pump through the top port

in the end of the pump and isdischarged from the lower porton the side of the pump. Eachpump gear is keyed to its shaftby a pin.

f. Fuel oil strainer. The fuel oilstrainer contains two strainingunits, each with an inner andouter winding. The spacebetween the windings on the

inner and outer elements is0.001 in.

Fuel oil enters the strainercase, flows through the outerand inner windings, throughthe center of the elements, andout through the strainer head.Provision is made for usingeither one or both strainerunits. When the handle on the

unit is shifted to the No. 1position, the oil is flowingthrough the No. 1 unit. Thisapplies also to the No. 2position. When the controlvalve is in the Both position, oilis flowing through both units.This is the position of the

the valve handles for usingeither one or both of the units.The flanges are also marked INand OUT indicating the direction

of flow of fuel oil through thefilter. When the valve handlesare between the two positionsindicated on the valve handlebase, or with the valve handlesdirectly above the inlet andoutlet flanges, fuel oil is passingthrough both units. If the valvehandle on the IN end of the filteris in one of the positionsindicated by the arrow on the

casting, the valve handle on theOUT end of the filter must be inthe corresponding position. Theflow of fuel oil to the engine willbe stopped if both valve handlesare not pointing in the samedirection when using only onefiltering unit.

12A4. Lubricating oil system.a. Description. The lubricating oil

pressure pump, mounteddirectly below the blower, drawshot oil from the oil pan through astrainer in the

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control valve for normaloperation. The positions of thecontrol valve and the numberof the corresponding straining

unit are cast into the strainerhead at the control valve.

g. Fuel oil filter. The fuel oilfilter is a duplex filter withprovisions for using either one

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pump suction line. A spring-loaded

pressure relief valve is built into the

discharge passage of the pump body,

which bypasses excess oil into theengine oil pan. The pump forces the oil

through the strainer and the cooler into

the engine lubricating oil system. Theengine inlet connection, on the blower

and pump drive housing, is fitted with a

spring-loaded relief valve. The springpressure is adjusted by means of a

regulating screw to maintain the correct

pressure. Any surplus oil is returned tothe oil pan.

Lubricating oil is supplied tothe lubricating oil manifold inthe cylinder block. From thismanifold, oil is forced throughtubes to the crankcasecrossframes, where it flowsthrough oil passages tolubricate the main bearings.The crankpin bearings arelubricated with oil received

from an adjacent main bearingthrough oil passages in thecrankshaft. Oil holes in the

upper connecting rod conduct lubricating

oil to the piston cooling chamber in the

top of the piston.

The camshaft drive gears arelubricated with oil from thegenerator end of the lubricatingoil supply manifold in the engineblock. Oil is piped from thismanifold to the camshaft drivegear bearing support and to thelubricating oil distribution blockin the camshaft drive housing.Lines from the distribution block

carry oil to the other gearbearings in the camshaft driveand the mating teeth of thegears in the camshaft drive. Thelubricating oil from the camshaftdrive housing is returned to theengine oil pan by the camshaftdrive housing scavenging pump.

Oil under pressure is supplied tothe camshaft bore through the

splined drive connection. The oilis then delivered to the camshaft

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Figure 12-11. Cutaway view of GM 8-268 lubricating oil pump.

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Figure 12-12. Lubricating oil suction

strainer, GM 8-268.

bearing through radial holes inthe camshaft. Oil for lubricatingthe rocker lever mechanismflows through tubes from thecamshaft bearing caps. This oilalso furnishes lubrication forthe valve assembly. The oil

Figure 12-13. Cutaway of

lubricating oil cooler GM 8-268.

draws the oil from the camshaftdrive housing and returns it tothe engine oil pan. Thegenerator bearing scavengingpump draws the excess oil fromthe generator bearing and

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then drains to the oil pan.

The blower and accessory drivegear bearings receive oil from

the blower end of thelubricating oil pressuremanifold in the engine block.Oil for the blower bearings andgears is received from the reliefvalve connection on the mainlubricating oil manifold, andthen is conducted through thetubes under the rotor housingto passages in the blowerendplates, and returned to the

oil pan.

b. Lubricating oil pump. Theattached lubricating oil pumpunit is mounted below theblower. The pump unit is of thepositive displacement, helicalgear type, and consists of alubricating oil pressure pump, acamshaft drive housingscavenging pump, and a

generator bearing scavengingpump. The lubricating oilpressure pump supplieslubricating oil to the engine.The camshaft drive housingscavenging pump

returns it to the engine oil pan.The pump housing is made infour separate parts: the bearingflange, the generator bearing

scavenging pump housing, thecamshaft drive housingscavenging pump housing, andthe lubricating oil pressure pumphousing. The driving gear shaftbearings are located in the pumphousing. The driven gears, fittedwith bronze bushings, rotate onthe stationary idler gear shaft.

c. Strainers. Two types of

strainers are used in thisinstallation. The lubricating oilsuction strainer is located in thepump intake line at the blowerend of the engine and strains theoil entering the pump from theengine lubricating oil pan. Thestraining element is made ofwire screen and is in the shapeof a cylinder. The pump draws oilthrough the open end of the

strainer element and sends it outthrough its side.

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Figure 12-14. SALT WATER COOLING SYSTEM, GM 8-268 AND 8-268A.

Figure 12-15. FRESH WATER COOLING SYSTEM, GM 8-268 AND 8-268A.

The other strainer in the system is the

supply line strainer which is similar to

the strainer found in GM 16-278A

engines. The strainer case contains acylindrical straining element of the

edgewise-wound metal ribbon type. A

handle on the top of the unit is used torevolve the straining element under

manifold and into the cylinder liners

through the lower deckplate in the engine

block. The water is then pumped upward

to the cylinder heads through the ferrulesin the top of the liner. From the cylinder

head the cooling water flows to the water

jacket around the exhaust manifold, tothe fresh water and lubricating oil

http://www.maritime.org/fleetsub/diesel/foldout/fig12-14.htmhttp://www.maritime.org/fleetsub/diesel/foldout/fig12-15.htmhttp://www.maritime.org/fleetsub/diesel/foldout/fig12-14.htmhttp://www.maritime.org/fleetsub/diesel/foldout/fig12-15.htm

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metal cleaning blades. The strainer

should be cleaned frequently when the

engine is running, by turning thecleaning handle one or more complete

revolutions.

The direction in which to rotatethe cleaning handle is indicatedby an arrow. The pressure dropthrough the strainer is anindication of the condition ofthe straining element.

The other lever on the straineroperates the bypass valve.When the lever is in the ON

position the lubricating oil isflowing through the strainer.When the lever is in theBYPASS position the oil isflowing directly through thehead of the unit, and thestrainer case and element canbe removed and cleaned. TheON and BYPASS positions areindicated on the strainer case.

d. Lubricating oil cooler. Thelubricating oil is cooled in aHarrison type cooler that ismade up of a core assemblyand an enclosing case. Theoblong tubes enclose a seriesof baffles which form a windingpassage for the flow of oil. Thetubes are fastened to headerplates at the ends. The coreassembly is permanently

attached to the casing.

12A5. Cooling system. a.General. The cooling system isof the closed type, employingfresh water to cool the engine,with salt water in the generatorair coolers and acting as the

coolers, and back to the pump. The fresh

water system is filled through the

expansion tank. Control of the freshwater temperature is by means of a

temperature regulator identical with that

found on 16-278A engines.

d. Fresh water and salt waterpumps. The fresh water and saltwater pumps are of the,centrifugal type. Water entersthe center of the impeller and isthrown outward through theimpeller vanes by the rotatingmotion of the pump.

The pump impeller is keyed tothe tapered end of the drivingshaft and rotates in the pumphousing on two pairs ofreplaceable bronze wear rings.

A packing sleeve is keyed to theshaft and butts against theimpeller. A watertight seal isprovided by three 1/8-in. squareplastic metallic packing rings

that fit in a recess of the packingsleeve. This packing is tightenedby rotating the locking sleevewith a spanner wrench, therebycompressing the packing. Thesleeve is locked in place with asetscrew. The packing glandmust be removed and thesetscrews loosened before thelocking sleeve can be tightened.

A finger, locked to the shift witha setscrew, throws off any waterthat may work its way along theshaft toward the ball bearing.The ball bearing is pressed onthe shaft and can be removedonly with the bearing pullerfurnished for this purpose. This

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cooling agent in the fresh watercooler.

b. Salt water system. The salt

water pump draws water fromthe sea chest through astrainer and forces it throughthe engine water cooler andout through the overboarddischarge. The pump alsoforces sea water through abranch line to the generatorcoolers. The valve controllingthe flow of salt water throughthe generator coolers should be

set to keep the temperature ofair in the generator at thetemperature specified in themanufacturer's instructionbook.

c. Fresh water system. Thefresh water pump forces thewater into the engine water

bearing is lubricated by splashfrom the accessory drive. Aleather seal prevents the oilfrom leaking out of the bearing

housing.

e. Fresh water cooler. Theengine water is cooled in aHarrison type cooler consistingof a core assembly and anenclosing case. The oblong tubesare baffled to form windingpassages for the flow of enginewater. The tubes are fastened toheader plates at the ends. The

core assembly is permanentlyattached to the casing.

12A6. Air intake and exhaustsystems. a. General. An airblower scavenges the engine

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Figure 12-16. GM 8-268 water pump disassembled.

cylinders by forcing air through the

intake ports in the liners as the pistons

approach the end of their power

From the manifold the water passes

through an elbow into the expansion

tank. (See Section 12A5.)

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strokes. This air forces out the burned

exhaust gases through the open exhaust

valves in the cylinder head.

Air is drawn by the blower

through an intake silencer andis discharged through adistributor manifold into the airbox surrounding the cylinders.Air is admitted to each cylinderwhen the piston uncovers theintake ports. These ports aredesigned to produce a swirlingflow of air upward through thecylinder toward the exhaustvalves which open for the

discharge of the exhaust gases.This results in completescavenging and filling of thecylinders with clean air.

The exhaust gases from eachcylinder are discharged into awater-jacketed manifold, whichin turn discharges the gasesinto one of the main engineexhaust pipes (usually No.

3ME) and thence to theatmosphere.

The cooling water flows fromeach cylinder head into thewater passages of themanifold.

Thermocouples for measuringthe temperature of the exhaustgases from each cylinder arelocated in the manifold.

b. Blower. The blower consists ofa pair of rotors revolvingtogether in a closely fittedhousing. Each rotor has threehelical lobes which produce acontinuous and uniformdisplacement of air. The rotorsdo not touch each other or thesurrounding housing. Air entersthe housing at one side and fills

the spaces between the rotorlobes as they roll apart. The airis carried around the cylindricalsides of the housing, into theclosed spaces between the lobesand the housing, and is forcedunder pressure to the dischargeside of the housing as the lobesroll together. Then the air passesthrough a distributor manifoldinto the air box around the

cylinder liners.

Each rotor is carried by a tubularserrated shaft. Endwisemovement is prevented by twotaper pins. No gaskets are usedbetween the

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Figure 12-17. Cutaway of fresh watercooler, GM 8-268.

endplates and the housing dueto the importance ofmaintaining the correct rotorend clearance. A fine silkthread around the housing,inside the stud line, togetherwith a very thin coat of non-hardening gasket compound,

provides an airtight seal.

Large babbitted bearings in theendplates accurately locate therotors in the two half-bores ofthe housing so that theclearances between the rotortips and the housing bores canbe held to a minimum. Bothends of the rotor bearings atthe gear end of the blower are

made with thrust surfaces thatlocate the rotor endwise andprevent contact between therotors and the endplates.

The power to drive the bloweris transmitted directly to therotor gear train by a drive shaft

hexagon head lockscrew, threaded in the

rotor shaft, holds a thrust collar as a

spacer between the gear hub and the endof the rotor, maintaining the clearance

between the rotors and the blower

endplate.

The blower rotor gears arebolted to the gear hub flangesand are located angularly byhardened dowel pins. Due to theimportance of having the rotorsroll together without touching,yet with the least possibleclearance, it is necessary tolocate the dowel pins during the

assembly for a given set of gearsand hubs. This is the onlyadjustment provided for timingthe gears with respect to therotors.

Oil passages in the endplatesconduct lubricating oil underpressure to the bearings. Oilseals are provided at eachbearing to prevent oil from

entering the rotor housing.

c.Air maze. A breather system isused to prevent contaminationof the engine room atmosphereby heated, fume-laden air thatotherwise would escape from theengine crankcase. Thisventilation of the crankcase alsoreduces the formation of sludgein the oil and prevents the

accumulation of combustiblegases in the crankcase and oilpan.

Atmospheric air for the breathersystem enters the enginethrough the cylinder head coverbreathers. The blower draws air

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that extends through a passagein the blower housing. Closelyfitted helical rotor gears arerigidly attached to both rotor

shafts to prevent the rotorsfrom touching each other asthey roll together. Each hub ispressed on the serrated rotorshaft. A

from the crankcase through theair maze which prevents oil mistfrom being drawn into theblower.

The air maze element consists ofa number of fine steel andcopper wire screens. Oil ladenair is drawn through the airmaze screens. The oil depositedon the screens, drains to thebottom of the air maze housing.This separated oil is returned tothe accessory drive coverthrough a drain tube.

12A7. Air starting system.High-pressure air is piped to alever-operated air starting valve.When the lever opens the valve,it allows the air to flow throughthe starting air manifold in thecam pocket of the crankcase tothe individual air distributorvalves or air timing valves in therocker lever bearing support at

each cylinder. The distributorvalve is of the poppet type andis operated from the narrow earnin each group of four on theengine camshaft. Starting airfrom each distributor or timingvalve is conducted

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through passages in the rocker lever

bearing support and cylinder head to

the air starter check valve. The jointbetween the rocker lever bearing

support and the cylinder head is made

airtight with a metal ferrule and a

neoprene gasket. The air starter checkvalve prevents exhaust gases from

entering the air starting passage. It

is opened by the high-pressure starting

air and closed by a spring when the

starting air from the timing valve is cutoff. From the check valve the starting air

flows into the space above the piston and

forces the piston downward until the air

distributor valves closes and the exhaustvalves open.

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B. FAIRBANKS-MORSE 38E 5 1/4 ENGINE

12B1. General. The F-M 38E 5 1/4 7-Cylinder engine is used as an auxiliary

engine on submarine whose main

propulsion engines are Model 38D 81/8 Fairbanks-Morse engines. Like the

GM 8-268 engine, it is located on the

lower deck level of the after engineroom and may be used to carry the

auxiliary load, to charge batteries and

indirectly for propulsion. The engine is

of the opposed piston type, with 7cylinders in line and air started, and is

rated at 300 kw generated output at

1200 rpm. It works on exactly the same

principle as the F-M 38D 8 1/8, andmost of the parts are identical in design,

the only difference being in the size anddimension of the parts.

12B2. Operation. The opposed pistonengine is of the solid injection, inlet and

exhaust port, scavenging blower type and

is designed to use a variety of fuels. Thetwo pistons in each cylinder work

vertically against each other, forming a

single combustion space between thepistons at the center of the cylinder. The

cross sections of the engine show the

relative positions of the blower,

crankshaft, pistons, and generator.

The engine operates on the two-cycle principle in which two

strokes of each piston and onecomplete revolution of eachcrankshaft are necessary tocomplete the cycle. The cyclebegins with the movement of thepistons from their outer deadcenters. As the pistons move

Figure 12-18. Control side of 7-cylinder F-M auxiliary engine.

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Figure 12-19. Longitudinal cross section of 7-cylinder F-M auxiliary engine.

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Figure 12-20. Transverse cross section of 7-cylinder F-M auxiliary engine.

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inward they cover the exhaust and inlet

ports and start to compress the air in the

cylinder. As the pistons approach

combustion dead center, fuel is injectedinto the combustion space in a fine

spray. The fuel immediately starts to

burn and expansion follows, forcing thepistons outward and delivering work to

the crankshafts. The shafts are

connected by a vertical gear drive.

Figure 12-20 shows a transverse cross

section of the working cylinder.

12B3. Engine main movingand stationary parts. a.Cylinder block. The cylinderblock is the main structural partof the engine and is designed togive it the necessary strengthand rigidity. It is constructed of

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Toward the end of theexpansion stroke, the lowerpistons uncover the exhaustports and allow the burned

gases to escape to theatmosphere through theexhaust system. Soonafterward, the upper pistonsuncover the air inlet ports. Atthis point the pressure in thecylinder is about atmospheric.As the inlet ports areuncovered, the scavenging airunder pressure in the airreceiver rushes into the

cylinder with a whirling motion,sweeping the cylinder clear ofany remaining exhaust gas andfilling it with fresh air for thenext compression stroke. Thewhirling motion or turbulenceof the air is obtained by thetangentially cast inlet ports.This turbulence persiststhroughout the injection periodand aids in the mixing of the air

and fuel.

With this arrangement of thepistons and crankshafts asdescribed above, the lowercrankshaft will lead the uppercrankshaft by approximately 12degrees. The difference in thecrankshaft setting is referred toas the lower crank lead. Thetwo pistons will be the nearest

together when the upper pistonis approximately 6 degreesahead of inner dead center andthe lower piston is 6 degreespast inner dead center. Thepoint midway between the twopistons when they are in thisposition is called thepiston

hot rolled steel plates of theproper dimensions welded into asingle unit, combiningcompactness and strength with

lightness of weight.

Transverse vertical memberstogether with horizontal decksform enclosures, housings, andfastenings for the operatingparts of the engine. The fourhorizontal decks are bored toreceive the cylinder liners alongthe centerline of the engine. Anextension of the block is

provided for attaching thescavenging air blower at thevertical drive end of the engine.

The cylinder block is separatedinto the following compartments:

1. The control end compartmentwhich forms an enclosure for thetiming chain, controls,overspeed and timing governors,

and drives for the regulatinggovernor and attached pumps.

2. The vertical drivecompartmentwhich houses thevertical gear drive thatinterconnects the upper andlower crankshafts. Used oil fromthe drive gears and uppercrankcase compartment drainsdown through this compartment

to the oil pan or engine sump.

3. The upper crankcasecompartmentwhich forms thebearing saddles for the uppercrankshaft bearings andbearings hubs for the camshaftbearings. The saddles and

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dead center.

From the foregoing it can beseen that when the upper

piston reaches inner deadcenter, the lower piston willhave completed 12 degrees ofthe expansion or power stroke.This causes the lower piston toreceive the greater part of theexpansion force with the resultthat at full load about 70percent of the total load isdelivered by the lowercrankshaft. The remaining

power is delivered to the uppercrankshaft where it is partiallyutilized in driving thescavenging blower. Anyresidual power is transmittedthrough the vertical drive gearto the lower crankshaft which isconnected to the generator.

bearing hubs are drilled forpassage of lubricating oil to thebearings from the upper oilheader. The used oil from these

parts collects on the floor of thiscompartment and drains wayfrom the center of the blocktoward each end where it passesthrough openings to the enginesump or oil pan.

4. The air receiver compartmentwhich extends the full length ofthe block and completelysurrounds the cylinder liners at

the air intake ports, forming apassage for scavenging air fromthe blower to the inlet ports ofthe cylinder liners.

5. The injection nozzlecompartments

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which form enclosures for the injection

nozzles, air start check valves, andcylinder relief valves. The injection

pump, which is cam actuated, is locatedat an angle in the underside of the

upper crankcase on the control side and

furnishes fuel under pressure to the

injection nozzle.

6. The exhaust compartmentwhich extends the full length ofthe block on each side. The

exhaust decks are bolted to theblock and surround the cylinderliner, forming water-cooledpassages for the exhaust gasesfrom the combustion spaces tothe exhaust manifolds. Themanifolds are water-cooledwelded steel units, bolted to

cylinder liner jackets which are pressed

on the outside of the liners. They extendfrom the bottom of the scavenging air

inlet ports to a short distance above theexhaust ports.

Openings for the air start checkvalve, cylinder relief valve, andinjection nozzle are located inthe liner and liner jacket at thepoint where the pistons arrive atinner dead center.

The channels directing thecooling water up and around thecylinder liner are cast inbetween the ribs on the liner.The heat of combustion thataccumulates in the cylinders, aswell as the heat conducted to

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the cylinder block and exhaustdecks.

7. The lower crankcase

compartmentwhich formsbearing saddles for the lowermain and thrust bearings.These saddles are drilled forthe passage of lubricating oil tothe bearings. The used oil fromthe engine collects in the oilpan or engine sump.

After welding, the block is sandblasted and stress relieved to

remove the internal strains atcertain vital points. It is thenmagnafluxed to check for thepresence of any constructionfaults. The variouscompartments are providedwith covers. The uppercrankcase compartment isclosed by a top cover bolted tothe block. The cover hasseveral inspection covers along

the top, one of which is anexplosion cover to relieve anyexcess pressure built up in theupper crankcase. An explosioncover on the control end of theblock above the exhaust nozzleprevents the possibility ofexcess pressure building up inthe lower crankcase.

The main and thrust bearing

saddles are machined togetherwith the forged steel bearingcaps. These are match-markedto show proper position. Whena replacement cylinder block isordered the bearing caps arealways furnished in place.

the air start check valve,cylinder relief valve, andinjection nozzle, is transferred tothe cooling water which flows

into these passages throughregular fittings from the waterjacket of the exhaust manifold.The water leaves the cylinderliner near the top of the jacketby means of an outlet pipe tothe water header.

c. Crankshafts and mainbearings. The crankshaft is aheat-treated, cast iron shaft with

an allover finish. It is held in thecylinder block by main bearingcaps. The bearing at the blowerend of the upper crankshaft andat the coupling end of the lowercrankshaft act as combinationmain and thrust bearings. Thecrankshaft is drilled from eachmain bearing journal to eachconnecting rod journal so thatoil, furnished to the main

bearing saddles from the oilheaders, flows into the crankand into each connecting rodjournal. The combination mainand thrust bearings are notconnected to any connecting rodjournal; accordingly they are notdrilled, but receive their oil fromseparate tubes direct from theoil headers.

d. Vertical drive assembly. Thepower developed by the uppercrankshaft is transmitted to thelower crankshaft by means of agear drive which is turned by thecrankshaft gear bolted to theblower end of each crankshaft.The drive assembly consists of

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b. Cylinders and cylinder liners.The cylinders are formed bycylindrical sleeves or linerslocated on the centerline of the

engine and spaced tocorrespond with the crankshaftthrows. The cast iron linershave specially designed airinlet and exhaust ports for thepassage of scavenging air to,and of exhaust gases from thecombustion space.

The liner cooling spaces areformed by

two tapered shafts with pinions,connected together by a flexiblecoupling with laminated ringsbetween the hubs, coupling

shaft, and adjusting flange. Theupper and lower housingscontain a large and a small setof thrust bearings.

e. Connecting rod andconnecting rod bearings. Theconnecting rod is an alloy steelforging with a closed eye at oneend and a removable

250

cap at the other end. The connecting

rod crankpin bearing is made up of a

cap bearing shell and a rod bearingshell. The bronze-backed bearing shells

are lined with a high lead bearing

composition containing a specialhardener and known under the trade

name of Satco metal. Each connecting

rod crankpin bearing shell is identified

by a mark stamped on the edge of theshell. New shells may be installed

without fitting or scraping. The piston

pin bearing consists of two rows ofhardened steel rollers or a bronze

bushing fitted in the space between the

piston pin and the connecting rodbushing.

f. Piston and piston pinassembly. The upper and lower

cast iron pistons are identicalexcept for the position of thefuel opening in the cup at thetop of the piston. The pistonsare marked and should beinstalled in their proper places,so that the fuel openings lineup correctly with the injection

are the bearings at the blower end of the

camshaft stub shaft, which are held in

place by a bearing nut. Oil is supplied tothe control end bearings by a pipe that

leads directly to the camshaft bearing

saddle from the upper oil header. The oilflows through the hollow shaft and

supplies oil to the rest of the bearings by

means of the radial holes drilled in the

shaft.

h. Timing chain. The timingchain is the means by which therotation of the upper crankshaftis conveyed to the camshafts,turning the camshafts at thesame rate of speed as thecrankshaft. Sprockets arefastened to the control end ofthe crankshaft, camshaft, and

stub shaft. The chain is guidedby special links over thecrankshaft sprocket, under atiming chain sprocket, and overthe camshaft sprocket. It thenpasses under a tightenersprocket, over the stub shaftsprocket, and under a second

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nozzle openings in the liners.

The pistons are connected totheir respective crankshafts by

the piston pin bracket, pistonpin, needle bearings or bronzebushing, and forged steelconnecting rods, and arecooled by lubricating oil asdescribed later.

Each piston is fitted with sevencast iron rings, four of whichare compression rings locatedabove the piston pin and three

of which are oil rings locatedbelow the piston pin. Of thesethree rings there is one oilscraper, one oil drain, and oneoil cutter ring.

The condition of the lowerpiston and rings may beobserved through the exhaustmanifold and ports after thethermocouple or plain covers

have been removed from themanifold.

g. Camshaft, camshaft stubshaft, and camshaft bearings.The camshaft is of the one-piece type with integral camson a case-hardened alloy steelshaft. There is one cam on thecamshaft for each cylinder.This cam actuates the injection

pump plunger. There is onlyone camshaft on this model F-M engine. On the other side ofthe engine from the camshaftis a camshaft stub shaft whichis used to drive variousgovernor auxiliaries and toform a part of the timing chain

timing chain sprocket to thecrankshaft.

The timing chain is a No. 766

Duplex 1/2 in. pitch, 2 in. wide,center guide, endless chain of116 pitches. It is assembled tooperate the links, to guide thechain on the camshaft andcrankshaft sprockets, and tooperate in slots in the tightenerand timing sprockets.

i. Hand control lever. The engineis started and stopped by means

of a hand-control lever. Thislever has three positions: START,STOP, and RUN. In the STOPposition, the fuel cutout cam onthe control shaft moves the fuelinjection pump control rod to theno fuel position. When the leveris in the START position, thecontrol shaft mechanism movesthe air control valve plunger andopens the control valve,

admitting air to the engine airheader and air distributor. In theRUN position, the engine isunder full governor control.

j. Emergency stop and resetlever. The engine is equippedwith a hand-operatedemergency stop device,consisting of a push button thatoperates against the overspeed

latch and releases the overspeedstop plunger, shutting off thedelivery of fuel to the injectionpumps. This emergency stopmay be connected to the ship'sair supply so that it can beoperated from the maneuveringroom by the use of a quick

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system. This stub shaft isextremely short, extending forthe length of one cylinder only.

The camshaft bearings are heldin place in the block by specialsetscrews. Exceptions to this

opening valve to stop theengine. When air pressure isadmitted to the emergency stophousing, the overspeed stop

latch is tripped and shuts off the

251

Figure 12-21. Engine controls, end view, F-M auxiliary engine.

supply of fuel as described in thepreceding paragraph.

k. Overspeed governor. Theoverspeed governormechanism automatically stopsthe engine when the maingovernor fails to hold theengine speed below the safemaximum of 1290 to 1370 rpm.This mechanism consists of a

weight on the end of, androtating with the camshaft.When an overspeed conditionoccurs, movement of thegovernor weights releases thespring-loaded stop device asdescribed below.

should be inspected to see that it isoperating at the correct speed.

In order to start the engine afterit has been stopped by either theoverspeed governor or theemergency stop, the plungermust be returned to its spring-loaded normal position. This isaccomplished by moving thereset lever which in turn moves

the reset shaft and pulls the stopplunger up, thus compressingthe spring to a position wherethe overspeed latch will bebrought up back of the head onthe plunger by the stop latchspring. The reset lever is then in

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When the predetermined safespeed of the engine is reached,the centrifugal force of thegovernor weight will overcome

the opposing pressure of aspring and allow the governorweight to swing outward andstrike the governor lever. Thistrips the overspeed stop latchand releases the overspeedstop plunger which moves fuelcutout lever and shaft, shuttingoff the supply of fuel to theinjection pumps. The speed atwhich the governor weight will

strike the governor lever canbe adjusted by the addition orremoval of shims. At regularintervals this governor

its normal position and theengine is ready to operate.

1. Flexible drive. The flexible

drive transmits power from thelower crankshaft to drive thegovernor, air start distributor,lubricating oil pump, and fuel oiland generator bearing drainpumps.

The pump drive hub is pressedon to the lower crankshaft, andthe pump drive gear is bolted toit.

The lower torsiongraph driveshaft is

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bolted to the end of the louder

crankshaft and aids in holding the hubon the shaft. The pump driven gear is

keyed to the pump drive shaft which is

located in the pump drive housing. The

housing is bolted to the engine blockand supported by the pump mounting

plate.

The power take-off for the airstart distributor and thegovernor is located in the pumpdrive housing and consists of agear keyed to the pump driveshaft and driving a final spiralgear.

The lubricating oil pump isbolted to the pump mountingplate and is connected to thepump drive shaft by a positivedrive coupling. At the end ofthe lubricating oil pumpimpeller driving shaft is a set of

and the housing, and between the

impellers and bearing plates are reducedto minimum. Under no circumstances

should oil be allowed to leak into the

blower housing or air receiver.

b. Oil separator. The enginecrankcases, vertical drive, andcontrol end compartments arevented by means of the suctionof the blower. A slight vacuum isproduced by suction through anoil separator located inside theblower end cover. This should beadjusted to 2 in. maximum watervacuum by the screw on top of

the oil separator in the blowerend cover. Passage to the oilseparator is through the hollowimpeller shafts.

The separator consists of ametal box, with small holesdrilled in the front piece, filled

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beveled gears that drive thefuel oil and generator bearingdrain pumps. These pumps arelocated on each end of the fuel

pump drive housing.

The fresh water and salt waterpumps are driven directly fromthe pump drive gear.

13B4. Scavenging systemand blower. a. Generaldescription. Scavenging air issupplied to the cylinders undera pressure of from 2 to 5 psi by

means of a positivedisplacement type blower. Theblower consists of a housingcontaining inlet and exhaustpassages enclosing two three-lobe spiral impellers. Timinggears, driven by a gear drivefrom the upper crankshaft,interconnect the impellers.

Air is drawn from the

atmosphere through the airsilencer and enters the inletpassage of the blower. It ismoved by the lobes along thewalls of the blower housing andforced through the outletpassages. Pipes conduct thescavenging air to the airreceiver compartments on eachside of the cylinder block.These receivers are the full

width of the cylinder block andextend to the control endcompartment. They completelysurround the cylinder liners atthe air inlet ports. Thescavenging air enters thecylinder under pressure, andsweeps the exhaust gases out

with copper gimp upon whichthe oil collects as the air passesthrough it. The accumulated oilis drained off each end of the

separator, collecting in the lowercompartments of the blower anddraining back into thecrankcase.

The separator should beremoved and cleaned inkerosene at regular intervals.The excess oil should be blownfrom the copper gimp beforeplacing the separator back into

service. If for any reason theseparator is neglected, theseepage of oil from the lowercrankcase side cover or apossible smoky condition of theexhaust will indicate that itshould be cleaned.

12B5. Fuel system. a.Description. The fuel oil supplysystem is composed of a

standby and priming pump, anattached fuel oil pump, and afuel oil strainer-filter with thenecessary relief valves andpiping.

The standby and priming pumpis used to fill the complete fuelsystem prior to first starting theengine or after the engine hasbeen over hauled. As the engine

starts to turn, the attached fueloil pump takes over the task ofsupplying fuel to the engine andforces the fuel past a reliefbypass valve through the fuel oilstrainer-filter to the engineheader where each individualinjection pump is supplied. The

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through the exhaust ports,producing completescavenging. A quantity ofscavenging air is trapped in the

cylinder by the pistons, thusproviding fresh air for the nextcompression stroke.

The scavenging air isdischarged from the blowerwith a uniform velocity due tothe design of the impellerlobes. For greatest efficiencythe clearances between theimpellers, the impellers

overflow from this header isdirected, via a relief valve, to theclean fuel oil tank. Dirty oil fromthe injection nozzle

compartment flows back to theleakage tank or to the bilgesdepending on the particularinstallation.

The capacity of the supply pumpis such

253

Figure 12-22. Fuel oil piping, F-M auxiliary engine.

that a sufficient velocity of fuel is

obtained in the fuel oil header to insurerapid replacement of fuel as it is used

by each individual injection pump atfull speed.

b. Fuel pump. The attached fueloil supply pump is a positivedisplacement pump. It shouldrequire no attention other thanan occasional inspection. The

stroke, lapped plunger, cam-actuated type

and is identical in principle to the pumpused on the Model 38D 8 1/8 engine. The

pump measures the correct amount offuel and delivers it at the correct momentto the injection nozzle from which it is

injected into the combustion space

between the pistons.

The injection pumps areenclosed in the cylinder block in

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packing gland should betightened or repacked as foundnecessary. It is very importantwhen installing pump packing

that the rings be cut to theexact lengths. The joints of thepacking should be alternatedso that they do not come in linewith each other. Leakageshould be permitted throughthe gland after the packing isfirst installed. The gland shouldthen be set up in smallincrements with severalminutes between tightening in

order to permit the packing toadjust itself to the shaftgradually.

c. Injection system. Theinjection system for eachcylinder is made up of theinjection pump, injectionnozzle, and the tubingconnecting the two units.

1. The injection pump is of theconstant

an inverted position on thecontrol side of the engine belowthe camshaft. The camshaft isdriven through a silent chain by

a sprocket on the control end ofthe upper crankshaft. Eachpump consists of a housing,plunger, barrel, control rack,plunger spring, delivery valve,delivery valve seat, and deliveryvalve spring. The push rodassembly transforms the rotarymotion of the camshaft intolinear up-and-down motion ofthe plunger.

The injection pump plungermoves in the plunger barrel witha constant stroke and deliversfuel through the delivery valveand injection tubing to theinjection nozzle and on to thecombustion space in the cylinderliners. The

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plunger stroke remains constant, and

the amount of fuel is varied by rotating

the plunger in the barrel by means of

the serrated control rack acting uponand meshing with the pump plunger

control sleeve.

When the plunger is in itshighest position, the fuel inletport is uncovered and thepump barrel fills with fuel. Asthe plunger moves down, theport is covered and fuel isdelivered to the combustionspace. Delivery of fuel

discharge tubing, no oil can drain out of

the tubing. The seating of the delivery

valve causes the injection nozzle to close

sharply and prevents a dribbling of oilfrom the nozzle.

2. The fuel injection nozzle

consists primarily of a nozzlebody, nozzle spring housing,needle sleeve, needle, push rod,spring, filter, shim and nozzletip. On the down stroke of theinjection pump plunger, fuelenters the injection nozzlethrough the injection tube and is

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continues until the helical edgeof the plunger uncovers thebypass port. Fuel not requiredfor combustion is discharged

through the bypass port to thesuction header. (See Figure 5-23.)

The exact position in theplunger stroke at which thehelical edge uncovers thebypass port depends on therotary position of the plunger.When the plunger is in the stopor no fuel position the vertical

groove and the helical edge ofthe plunger keep the bypassport uncovered during theentire plunger stroke,bypassing all the fuel.

Rotary position of the plungeris controlled by the regulatinggovernor through its linkagewith the fuel control rod andinjection pump control rack.

The control rack is connectedto the fuel control rod of thegovernor linkage at the shiftersleeve and to the injectionpump at the plunger controlsleeve. The sleeve is toothed atone end and slotted at theother end. Lugs on one end ofthe pump plunger fit into theslots of the control sleeve.

For an increase in fuel, theshifter sleeve moves thecontrol rack through the shiftersleeve key. For a decrease infuel, the control rack is movedby the control rod shifter sleevespring. This flexible design isused to actuate the control

forced through the nozzle filter.The nozzle filter removes anyforeign matter which may havegone through the main filters.

The filter built into this nozzle isextremely simple. It is a close fitin the nozzle body with aclearance of .0015 in. to .0022in. for fuel to pass from onegroove to another. Thelongitudinal grooves areconnected alternately with theannual grooves so that fuelentering the annular groove is

forced through the spacebetween the filter and the nozzlebody into the annular grooveconnected to the opposite end ofthe filter. The filtered fuel isforced into the chamber throughthe flutes and holes, into theoutside of the needle sleevewhere it enters the chamber atthe face of the needle seat.

The fuel under pressure actsagainst the face of the needlelifting it from its seat. Thepressure of the oil iscounteracted by the springthrough the nozzle push rod.This permits the pressure of thefuel to build up to about 3000 lb.When it reaches this point, thenozzle needle opens, allowingfuel to escape through the three

small holes in the nozzle tip intothe combustion space of thecylinder in a fine spray. The fastaction of the needle caused bythe fuel, acting on the face ofthe needle, and the springcounteracting this pressure,insures quick opening and

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racks so that if any of the rackssticks while the engine isrunning, the remaining pumpscan be operated to decrease

the fuel injected.

In order to cut out anyindividual pump while theengine is in operation, theshifter sleeve should be rotateduntil the slot in the sleeve canpass over the sleeve key of thefuel control rod. This will permitthe movement of the individualcontrol rack to the stop or no

fuel position.

The delivery valve seats whenthe pressure of oil in the pumpchamber is relieved. Becauseof the spring and the high oilpressure in the

closing of the needle andeliminates dribbling or leaking.

12B6. Lubricating oil system.

a. Description. Lubricating oil issupplied to the system underpressure to insure a continuousflow of oil to all surfacesrequiring lubrication and to thepistons for cooling. The systemis comprised of the attachedlubricating oil pump, oil pan,strainer, oil separator, filter andcooler with the necessary valvesand piping.

An oil gage connection to thegage board

255

is provided from the discharge of the

lubricating oil pump and upper oil

header. A marked oil gage stick islocated at the control end of the oil panfor checking the level of the oil in the

engine.

The lubricating oil pump,located on the control end ofthe engine, draws oil from theoil pan through a strainer anddischarges it through the filterand cooler to the lower and

upper oil headers. Throughbranches from these headers,oil is supplied to each mainbearing and to the thrustbearing. From the mainbearings, oil passes throughholes drilled in the crankshaftand through tubes swedged

circulating water pump, lubricating oil

pump, fuel oil and generator bearing

drain pumps. A tube from the upperheader supplies oil to the automatictiming governor for the operation of that

unit.

The camshaft and stub shaftbearings are lubricated by pipesfrom the upper oil header to thefirst bearing of each shaft. Oilenters the hollow shafts andlubricates the rest of the

bearings through openingsdrilled radially in the camshaft.

Used oil from the bearings,tappet housing, and pistonscollects in the upper crankcasecompartment where it drainseither toward the control end or

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into the crankshaft to eachcrankpin bearing. Oil is thenforced through the passagesdrilled the length of the

connecting rod to the pistonpin needle bearings or bronzebushing and to the piston oilpockets for cooling the pistons.An opening through the uppercrankshaft lubricates the timingchain.

The cooling oil from each lowerpiston is discharged throughthe piston cooling bracket

outlet pipe into the sump or oilpan. Oil from each upper pistonis discharged through thepiston cooling bracket outletpipe into the upper crankcasecompartment where it candrain toward either end of theengine and flow back to theengine sump.

Branches from the lower oil

header supply oil to the thrustbearing, crankshaft verticaldrive gears, and main bearings.The bushings of the flexiblepump drive located on thecontrol end of the lowercrankshaft, receive lubricationthrough an opening in thelower crankshaft from thecontrol end main bearing. Thesurfaces of the lower thrust

bearing shell and thecrankshaft flange arelubricated by openings in thebearing shell.

Connections from the upper oilheader supply lubricating oil tothe vertical drive gears and

toward the blower end of theblock and flows back to the oilpan. Used oil from the blowergears and bearings collects at

the bottom of the blower innerbearing plate and at the bottomof the blower end cover. An oiltube connects the blower endcover compartment to the innerbearing plate compartmentallowing oil to drain from theseareas to the oil pan, via thevertical drive compartment.

An oil separator is fastened

inside the blower end cover andvents the crankcase of fumes.

b. Lubricating oil pump. Thelubricating oil pump is attachedto the pump mounting plate onthe control end of the enginebelow the exhaust nozzle. It is ofthe positive displacement type,driven by a pump driveshaftthrough the flexible coupling. A

built-in relief valve is set tooperate at 60 pounds' pressureto relieve the pump when excesspressure is built up. Oil from therelief valve flows directly into theoil pan.

The pump should require verylittle attention except forperiodic removal for inspectionand the cleaning and grinding of

the seat of the relief valve withthe tool furnished for thatpurpose. When reassembling thepump, carefully adjust the valveto open at the proper pressure.

Special pullers are furnishedamong the tools for removing

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bearings, to the blower flexibledrive wear rings, to the innerand outer blower impellerbearings, and to the injection

pump tappet housing. Theblower drive gears arelubricated by a splash systemobtained from a special fittingthat directs a spray of oil to thegears.

Fittings at the control end ofthe upper oil header supplylubrication to the timing chainand control mechanism. This oil

drains down and also lubricatesthe governor drive and gears,

the drive gear, the timing gear,and drive coupling. Spannerwrenches are provided forremoving the locknuts on the

drive gear, the timing gear, andcoupling.

c. Generator bearing drainpump. A small gear type drainpump, mounted on the front ofthe attached lubricating oilpump at one end of

256

Figure 12-23. Lubricating oil piping, F-M auxiliary engine.

257

the fuel pump housing, is driven by a are identical they are discussed together

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beveled gear on the extension of the

upper impeller shaft of the lubricating

oil pump. This pump takes the warmused oil from the closed generator

bearings and returns it to the engine oil

pan. Cool filtered oil is furnished to thegenerator bearings by the lubricating oil

pump.

d. Suction strainer. Thelubricating oil suction straineris located in the pump intakeline. All oil from the oil panpasses through the strainerbefore entering the pump. Thestrainer consists of a piece of

screen supported by acylindrical shell which isfastened in the enlargement inthe oil piping. This strainershould be removed andcleaned frequently to insure anadequate supply of clean oil tothe pump.

12B7. Cooling system. a.General. An adequate supply of

cool, clean, soft, fresh water,free of scale-formingingredients, is essential forproper operation of the engine.The sodium dichromate watertreatment should be used. Saltwater should not be used forcooling the engine.

The cooling system is of theclosed type in which fresh

water is circulated through theengine and fresh water cooler.Salt water is circulated throughthe fresh water cooler andthrough the generator aircooling system. For moredetailed discussion, the twosystems are discussed

under the fresh water system.

c. Fresh water system. Theattached fresh water pump isdriven through the flexible pump

drive from the lower crankshaftand draws water from the freshwater cooler and forces it intothe engine at the base of theexhaust nozzle. From theexhaust nozzle, water flowsaround the jacketed outside ofthe exhaust manifold, thencethrough fittings into the spacebetween the cylinder liner andjacket on each cylinder. The heat

of combustion is transferred tothe cooling water as it travels upand around the cylinder liner,injection nozzle, air start checkvalve, and cylinder relief valve.The water leaves the jacketedspace of the liner by means ofoutlet pipes connected to thewater header on the sideopposite the control side of theengine. The water flows past a

mercury bulb thermometerwhere the outlet watertemperature of the engine isregistered.

Adjustments are possible so thatpart of the water can bebypassed around the cooler bymeans of a temperatureregulator similar to that used onthe Model 38D 8 1/8 engine. All

of the cooling passages of theengine can be drained at theexhaust nozzle. The systemshould be drained if the engineis to be left in freezingtemperature with no protection.

d. Circulating water pumps. The

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separately. In olderinstallations, salt water is usedas the cooling agent in thelubricating oil cooler, but in

later installations, fresh wateris used.

b. Salt water system. The saltwater system consists of anattached salt water pumpwhich is driven through theflexible drive from the lowercrankshaft. It draws water fromthe suction sea chest andstrainer, forces it through the

generator cooling system, thefresh water and sometimes thelubricating oil coolers, anddischarges it overboard. Thenecessary piping, fittings, andvalves complete the system. Ahand-operated three-waybypass valve is installed in thedischarge piping from thepump to the cooler, controllingthe amount of salt water

passing through the coolersand thereby, to some extent,the temperature of the freshwater and lubricating oil to theengine.

Since the salt water and freshwater pumps

pumps are of the centrifugaltype with the water entering atthe center of the impeller andbeing forced outward by the

rotating motion of the impellervanes to the pump discharge.

These pumps require very littleservicing beyond the tighteningor replacing of the packing andthe oil retainer ring. The packingshould be tightened occasionallyto keep the gland from leaking.If it must be replaced, thespecial packing hook should be

used to remove the old packing.The new packing should be cutto the correct length and thejoints alternated so they do notcome in line. The gland nutshould then be tightened insmall increments to allow thepacking to adjust itself graduallyto the shaft. The bearings ofthese pumps are lubricated fromthe gear drive case.

12B8. Air starting system.The air starting system isfurnished with air from the ship'shigh-pressure air line or from airbottles. A reducing

258

valve (3000 to 250 psi), a relief valve,

gages, and necessary valves are in thepiping leading to the engine. On the

engine the control valve, the air startdistributor, engine starting air header,

pilot air tubing, and air start check

valves, complete the system.

Engine starting is accomplished

the valve spring and high-pressure air.

The valve is opened when the handcontrol lever is moved from STOP to

START position. The clearance betweenthe valve plunger and the valve stem

should be 1/16 in. This clearance can be

adjusted by adding or removing shimsbetween the valve body and plunger

body.

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by the action of thecompressed air on the pistonsin their proper firing order. Theoperation is identical with that

described in Chapter 4 for aModel 38D 8 1/8 F-M engine.When the hand control lever ofthe fuel and governor controlrod is moved from STOP toSTART position, the machinedportion of the control valveplunger acts as a cam, forcingthe control valve open,allowing high-pressure air toenter the engine starting air

header and the air startdistributor. The air chamber ofthe distributor housing the pilotvalves is under pressure whenthe control valve is open. Thispressure is greater than theforce exerted by the valvesprings and accordingly itforces the pilot valves downagainst the air start cam.

The cam is designed so thatthe pilot valves on high camare closed and vented to theatmosphere. The pilot valveson low cam are open, allowingpilot air to enter the pilottubing from the distributor airchamber. The rotation of thecam, which is driven throughthe flexible pump drive fromthe lower crankshaft, causes

the pilot valves to open in timewith the engine firing order,admitting pilot air up to the airstart check valves. The actionof this valve allows a fullcharge of air from the mainengine starting air header toenter the combustion space in

The valve will require littleservicing beyond its removal,and reseating of the valve seatwith the tools furnished for this

purpose. After the valve seat hasbeen refaced, the valve shouldbe lapped to make a positiveseat and prevent leakage of airfrom the air inlet piping.

The air start distributor, locatedon the side opposite the controlside of the engine below theexhaust manifold at the controlend, is properly timed and

marked at the factory. Thedistributor directs a flow of airinto the combustion chamber ofthe engine in time with theengine firing order. Undernormal circumstances it will notneed to be timed again;however, should a new cam beinstalled, it must be retimed.

The air start check valve is

located in the cylinder liner, atthe injection nozzle level, on theside opposite the control side ofthe engine. It is actuated by asupply of pilot air from the airstart distributor which actsagainst the pressure of the valvespring forcing the operatingpiston to open. When the pistonopens, it releases a charge of airfrom the engine starting air

header to the combustion spacebetween the pistons in thecylinder liner, forcing the pistonsapart and causing thecrankshafts to rotate.

When the air start distributorshuts off the supply of pilot air to

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the cylinder liner, forcing thepistons apart and rotating thecrankshafts.

When the engine begins to fire,the hand control lever is movedfrom START to RUN position.This raises the control valvespring to close the valve,shutting off the air to theengine header. The enginestarting air header and air startdistributor are vented to theatmosphere through anopening in the control valve.

When the pressure is relievedon the air chamber, the valvesprings raise the pilot valvesfree of the cam, therebyventing all pilot tubing to theatmosphere.

The control valve located in theengine header is held closed bythe combined action of

the valve, the spring closes theoperating piston. The air fromthe engine starting air headerpresses against the balancing

piston with greater force than itdoes against the check valve sothat at no time is there enoughpressure to open the valve.

The valve is vented to theatmosphere through two holes inthe valve body. Water from thecylinder liner jacket enters thespace between the check valvesleeve and the sleeve water

jacket to cool the valve andvalve body.

12B9. Exhaust system. Theexhaust system conducts thegases from the enginecombustion space through theexhaust ports to the

259atmosphere. The hot gases are forced

out of the cylinder liner when the upperand lower pistons uncover the exhaust

and inlet ports The gases enter

individual exhaust decks connected tothe exhaust manifolds mounted in the

cylinder block on each side of the

engine. The gases pass on through the

combined exhaust nozzle at the controlend of the engine to the exhaust pipe

and on to the atmosphere, usuallythrough one of the main engine exhaustvalves. The exhaust deck castings and

welded exhaust manifolds contain

water jackets far the passage of coolingwater from the welded exhaust nozzle,

through which the water enters the

engine. A drain plug is provided in the

line. All of the cooling water passages of

the engine can be drained through aplugged hole in the exhaust manifold.

The exhaust decks and manifolds are

doweled in place so that they will line upwith other parts after removal or

replacement. The exhaust manifolds are

provided with openings at each cylinder

for inspection and cleaning purposes.Plain flange covers are furnished for

those openings for the side opposite tothe control side of the engine. The coverson the control side are quipped with

pyrometers. These instruments indicate

the temperature of the exhaust gasesleaving the exhaust ports of each cylinder

on a single selector indicator on the

control board.

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exhaust nozzle for draining any

condensation in the nozzle, manifold,

or exhaust

260

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