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crankshaft bearings and related components > crankshaft and bearings > Flashcards

crankshaft and bearings Flashcards

1
Q

Function of a crankshaft

A

converts reciprocating motion into rotary and rotary motion into reciprocating motion
also drives the camshaft

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2
Q

cast crankshafts

A

mostly used in gas engines

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3
Q

Forged alloy crankshafts

A

mostly used in diesel engines

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4
Q

most common crankshaft rotation

A

clockwise as viewed from the front of the engine

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5
Q

do 2 stroke engines have mating pairs

A

no because all cylinders must fire in one rotation

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6
Q

three components that contribute to engine balance

A

rotating balance weights (counter weights) vibration damper and fly wheel

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7
Q

how many counter balance weights will a 4 stroke engine use

A

2 driven at twice the speed of the crankshaft to cancel inertia from the pistons and con rods

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8
Q

rubber element damper

A

damper hub and inertia mass bonded together with a rubber compound
rubber flexes allowing small amount of movement between hub and inertia mass

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9
Q

viscous damper

A

inertia mass is contained in the hub suspended in a thick silicone fluid
fluid provides resistance to mass

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10
Q

most common front and rear main seals used in diesel engines

A

one piece lip type seal

may ride directly on the crankshaft or on a wear sleeve

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11
Q

if the flywheel must be installed in a certain position

A

can be accomplished by using dowels or offset bolt circle

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12
Q

flywheel timing marks are used for

A

checking and adjusting fuel injection timing

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13
Q

three types of bearings

A

full round / seamed
shell type
thrust

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14
Q

two types of bearing construction

A

single metal

multi-layered

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15
Q

press fit bearings

A

sleeve type pressed into the bore with an interference fit

creates crush to retain and provide good heat transfer

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16
Q

Bearing oil supply

A

pumped through a system of passage ways in the block and crankshaft
Must maintain the proper volume and pressure to maintain oil film between the bearing and the shaft

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17
Q

hydrodynamic lubrication

A

rotating crankshaft acts as a pump and forces oil between the bearing and the shaft
position of the shaft in the bore depend on engine speed / load and oil pressure

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18
Q

An unbalanced engine would have

A

Reduced mechanical efficiency

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19
Q

The balance weights in some 4 stroke engines

A

counter balance inertia forces created by the pistons and rod assemblies

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20
Q

crankshafts used in diesel engines are usually hardened to increase wear characteristics of

A

the journals

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21
Q

Locating lugs and dowels are used for

A

positioning bearing shells in the main bores

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22
Q

when removing a vibration damper

A

Never pry or hammer on them

Use appropriate puller

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23
Q

front gear covers

A

usually made of stamped metal or cast and can be easily damaged

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24
Q

All components removed during disassembly should be

A

stored in a safe and secure position to prevent component damage and personal injury

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25
when removing crankshaft
lift as straight as possible make sure counterweights and throws do not catch on main bearing webs no binding between the shaft and the thrust bearing
26
when removing bearing shells
mark upper shell for positioning and tape upper and lower together normally replaced but should be kept for further diagnosis if needed
27
if more than half the bolt holes on a crankshaft are damaged it should be
replaced | a loosed damper or flywheel could cause major engine damage
28
crankshaft seal surface wear grooves les than .010"
can usually be polished out for reuse | if not a wear sleeve can be installed
29
three main measurements done on a crankshaft
main and connection rod journals -out of round taper and max wear thrust surface-located on either side of the middle or rear main bearing journal measure distance between the thrust surfaces Straightness - use a dial indicator and rotate crankshaft in a v block
30
Straightening a crankshaft
some can be straightened if within manufacture specs | should be recheck for cracks after
31
when regrinding journals
reground and polished to undersize dimensions new size stamped on front counter weight always compare with manufacture specs to verify dimensions all respective journals must be reground to same size
32
bearings can be commonly identified by
stamped markings on the back of the shell
33
when removing burs on the crankshaft nose
use a smooth cut file or a honing stone then polish with fine sandpaper
34
when installing crankshaft gear
check for gear direction (chamfered teeth and timing marks) Alignment of gear keyway with crankshaft keys ensure gear is fully seated allow gear to cool at room temp do not quench
35
pilot bearing in the fly wheel
retained with a press fit | if loose bore can be machined and repair sleeve can be installed
36
When installing a new ring gear on the fly wheel
make sure chamfered teeth face proper direction to engage the starter
37
when removing a ring gear off the fly wheel
use heat and a hammer and chisel | do not heat with cutting torch as the fly wheel may get damaged
38
installing a new ring gear on the fly wheel
ring gear has a shrink fit gear must be heated evenly to a specific temp after install allow gear to cool at room temp do not cool ring gear with water this can cause distortion
39
when checking the fillet radius of a reground crankshaft
some manufactures supply a radius gauge | if the fillet radius is to small or ground incorrectly it may break in this area
40
rough reground journals can cause
rapid bearing wear
41
Minimum journal dimension
do not undersize less than .030" this can cause removal of hardened surface and weakens the journals
42
diesel fuel in the engine oil can result from
internal leakage of fuel system excessive idle time incomplete combustion
43
Diesel fuel in engine oil will cause
reduced viscosity causing journal to come into contact with bearing surface under load causing wiping and produces a greenish brown discoloration
44
corrosion damage can be eliminated by
controlling operating conditions and monitoring oil change intervals
45
coolant contamination effect on bearings
destroys bearing overlay and leads to fatigue failure of inner layer shows up as black discoloration
46
improper bearing assembly
can cause spot loading witch will lead to fatigue failure of bearing surface caused by misaligned tangs or foreign body between bearing and bore
47
when preforming a bearing roll in
use a bearing removal pin in the journal oil hole
48
when installing bearings during a roll in
do not lubricate the back side of bearing this can effect seating and heat transfer
49
the accuracy of torqueing depends on
thread condition and cleanliness condition of mating surface type of thread lubricant used accuracy of torque wrench
50
after torqueing main bearing caps
check crankshaft for free rotation | if binding occurs work backward through torque procedure and loosen cap bolts to locate binding
51
one method to adjust misaligned thrust bearing
loosen thrust bearing main cap bolts one turn push crankshaft firmly to front then rear retorque main cap bolts and re measure
52
when installing gasket on front covers you should check for
alignment of passageways to prevent blockage
53
What should be double checked before removing front or rear housing
bolts still holding the housing part of the pan still attached are there specific pry points
54
Why is the annular grove in a bearing shell usually placed in the block side of the main bearing bore
to give the loaded side more surface area | to ensure oil can flow from the hole in the block to the hole In the crank
55
when a journal is machined what type of bearing size would be required
Undersized
56
if one crankshaft main journal needed to be repaired
machine all main journals and install undersized bearing
57
what type of seal is most often used on a crankshaft
a one piece lip type
58
what is the best method to install s main seal
press it in from the front with an installation tool
59
why would there be numbered markings on a flywheel
used as a crankshaft position reference
60
what is a friction type bearing
has no moving parts uses a film of oil
61
where would bushings usually be
to support in block camshaft
62
what is the purpose of a thrust bearing
controls axial movement
63
how are the main journals and connecting rod journals connected
by the webs
64
when is a crankshaft ground and polished
after induction hardening
65
how many main bearings support each connecting rod assembly in an inline engine
two mains for every one rod assembly
66
what speed and what direction do 4 stroke counter balance shafts turn at
twice crank speed in opposite directions
67
what type of construction is most common for a shell type bearing
two piece multi layer construction
68
if a bearing fails due to heavy loading what type of damage would be seen
spalling
69
what is the purpose of lateral grooves in a bearing
to supply oil to the thrust face of the bearing
70
what areas of the crankshaft are considered critical loading areas
oil holes webs and fillets
71
what would cause a crankshaft to break at the main journals
misaligned main bearing bores
72
what would cause a crankshaft to brake at the rod journals
excessive torsional loads
73
what would cause wiping of a bearing surface
loss of oil film
74
when preforming a bearing roll in what should be done before removing bearing caps
loosen drive belts

crankshaft bearings and related components (3 decks)

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