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4th year HET > clutch fundamentals and service > Flashcards

clutch fundamentals and service Flashcards

1
Q

what do spring loaded clutches allow

A

a drive unit to be connected to a driven unit

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2
Q

besides connecting two components together what do clutches also provide

A

a means of smoothly transmitting power during the engagement process and providing a means of temporarily disengaging an engine from a transmission

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3
Q

how is the clutch engaged or disengaged

A

through some sort of mechanical linkage or partial mechanical with hydraulic or an air/hydraulic pressure assist

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4
Q

how are spring loaded clutches applied and engaged

A

with some sort of spring located within the clutch assembly

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5
Q

the pressure springs can be what type of design

A

diaphragm, angled or perpendicular coil spring design

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6
Q

where are the pressure springs usually located

A

between the clutch cover and the pressure plate

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7
Q

what are the two types of spring clutches

A

push style and pull style

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8
Q

when the spring loaded clutch is engaged it is tightly between the

A

pressure plate and flywheel friction surfaces

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9
Q

when the clutch is engaged all three components ( engine, clutch and transmission ) will

A

rotate together at the same speed

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10
Q

what happens during the disengagement process

A

pressure springs are slightly compressed - clamping force is eliminated and the clutch disc is able to move freely of the flywheel and pressure plate friction surface -

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11
Q

what happens when the clutch is disengaged

A

the flywheel and clutch cover/pressure plate assembly will rotate at engine speed while the clutch disc remains stationary or rotates at transmission input shaft speed

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12
Q

where are push type clutches used

A

light to medium duty vehicles

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13
Q

how are push type clutches disengaged

A

as the operator moves the clutch pedal towards the floor a mechanical linkage system within the clutch continues the disengagement process

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14
Q

clutch release levers used in push-type clutches are attached to and located

A

within the clutch cover/pressure plate assembly

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15
Q

where are pull-type clutches used

A

in medium to heavy duty vehicles

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16
Q

when a pull type clutch assembly is disengaged the release bearing sleeve will

A

be pulled away from the flywheel

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17
Q

when is mechanical clutch actuation linkage usually used

A

when the engine, clutch, transmission and cab are in reasonably close proximity with space available

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18
Q

what are the benefits of mechanical linkage

A

relatively inexpensive, can operate with a certain amount of wear or damage and is fairly simple to repair and adjust

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19
Q

what are disadvantages of mechanical linkage

A

numerous wear points lubrication may be limited to major wear points pin and yokes may be exposed to road dirt and water causing accelerated wear

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20
Q

how are hydraulically activated clutches actuated

A

operator pushed the clutch pedal connected to a push rod connected to a single reservoir clutch master cylinder connected to a single piston slave cylinder by steel lines and flex lines

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21
Q

what are disadvantages to hydraulically actuated clutches

A

if a line breaks or there is air in the system clutch function will be lost

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22
Q

what are advantages to hydraulically actuated clutches

A

mounting versatility . ease of force application . easy access to the slave cylinder and master cylinder

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23
Q

why would air over hydraulic assist assembly be used when releasing a clutch

A

because the spring pressure in the clutch may be to great for operator foot pressure to overcome

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24
Q

how can clutch size be determined

A

diameter of the disc - outside diameter of the clutch shaft - number of splines in the hub - number of dampening springs

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25
Q

what are the main functions of the flywheel

A

to provide a flat smooth friction surface for one side of the clutch disc to work against and provide a bore with a bearing to pilot the transmission input shaft

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26
Q

why is the piloting feature in a flywheel or crankshaft critical to a clutch

A

because the inputshaft of the transmission that is piloted into the bore is used to center the clutch disc in relation to the pressure plate

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27
Q

what are the two types of flywheels

A

flat and countersunk

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28
Q

flat flywheels

A

combines two surfaces. the machined surface area where the clutch cover is fastened and the friction surface where the clutch disc will be positioned

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29
Q

flat fly wheels are suitable for

A

both single and double clutch disc assemblies

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30
Q

countersunk flywheels have

A

a recessed friction surface

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31
Q

the countersunk design allows for

A

a double clutch assembly to be used

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32
Q

what will having a double clutch assembly allow for

A

the handling of increased torque loads due to the increased friction surface

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33
Q

what is used to separate the clutch discs in a double clutch design

A

an intermediate plate that is driven by the flywheel or clutch cover between the two discs

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34
Q

what are the two types of clutch cover construction

A

cast iron and stamped steel

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35
Q

what are the advantages of cast iron clutch covers

A

can handle high heat and due to the ridged construction high torque loads

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36
Q

what are advantages of the stamped steel clutch covers

A

lighter design and allow for higher engine speeds to develop

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37
Q

pressure plates are typically constructed from

A

cast iron

38
Q

where is the pressure plate located

A

in the clutch cover and is driven by the clutch cover during operation

39
Q

perpendicular coil springs are

A

a series of coil springs standing at 90 degrees to the pressure plate

40
Q

the springs keep the pressure plate in the

A

engaged position

41
Q

angled coil springs are

A

a series of coiled springs at an angle to the pressure plate

42
Q

diaphragm spring

A

created from flat spring steel in a dish shape

43
Q

what are the clutch driven members

A

the clutch discs and transmission inputshaft

44
Q

what are the clutch drive members

A

the flywheel and the clutch cover/pressure plate assembly also if equipped the intermediate plate is a drive member

45
Q 
name the drive / driven members 
pressure plate =
clutch disc = 
intermediate plate = 
clutch disc = 
flywheel =
A 
pressure plate = drive 
clutch disc = driven 
intermediate plate = drive 
clutch disc = driven 
flywheel = drive
46
Q

two types of clutch discs

A

ridged clutch discs and dampened clutch discs

47
Q

rigid clutch discs

A

solid with some sort of lining either bonded or riveted to both sides of the outer diameter - often riveted to central splined hub that slides on the transmission input shaft splines - used where limited amount of engagement and disengagement occur

48
Q

dampened clutch discs

A

may be some what flexible - the central splined hub may be attached to the disc through a spring loaded limited movement mechanism design to absorb torsional shock loads

49
Q

what type of clutch disc design will extend service life of clutches that are disengaged and engaged very frequently

A

dampened clutch disc type

50
Q

what are the types of disc lining construction

A

organic and ceramic

51
Q

organic disc lining

A

also called NOA ( non-asbestos organic ) made from various binders, resins and fillers . metallic particles may be added to improve service life where high heat is encountered

52
Q

ceramic disc lining

A

used when high heat and heavy loads are encountered . provide very good resistance to slippage during the engagement process

53
Q

intermediate plates

A

are used when two clutch discs are used

54
Q

why must the intermediate plate not be fastened tightly to the flywheel or clutch cover

A

because one or both of the clutch discs will remain in contact when disengaged

55
Q

what can be used to reduce noise in the intermediate plate

A

anti-rattle springs between the drive pins and intermediate plate drive slots or between the drive lugs and drive slots

56
Q

clutch release levers are used to

A

move the pressure plate closer to the clutch cover during the disengagement process

57
Q

release bearing and bearing sleeve assembly

A

are used to move the clutch release levers

58
Q

on a push type the release bearing and sleeve will be

A

rotating all the time the engine is running but will only be under load when the clutch is disengaged and engaged

59
Q

on a pull type the release bearing and sleeve will be

A

only rotating when disengaged and engaged

60
Q

how do manual clutches adjust

A

push type have a threaded pushrod that moves the release bearing yoke shaft - pull type clutches have an internal threaded ring that must be first unlocked from the clutch cover and then turn to adjust

61
Q

how do self adjusting clutches self adjust

A

every time the clutch is disengaged and engaged the self adjusting mechanisim will try to adjust only when it is worn will it self adjust

62
Q

what is the purpose of clutch breaks

A

to stop rotation of the clutch disc and transmission input shaft to prevent gear teeth clash when shifting from neutral to first or reverse

63
Q

clutch brakes that are constructed as a one piece assembly are often called

A

torque limiting clutch brakes

64
Q

torque limiting clutch brakes are designed to

A

slip above a pre determined torque load

65
Q

why will depressing the clutch pedal to the floor every time a gear selection is made cause premature failure

A

over works the clutch brake and can cause early failure

66
Q

what type of brake assembly eliminates the need to remove the transmission for service

A

a two piece clutch brake assembly

67
Q

what is one cause of slippage in a clutch

A

oil spray from leaking seals

68
Q

if clutch slippage is extreme or occurs often

A

heat build up is excessive

69
Q

what will heat build up cause on the clutch springs

A

loss of spring tension causing less clamping force and more slippage

70
Q

what causes a dragging clutch

A

when it is not quickly freed from the flywheel or pressure plate

71
Q

what damage will a dragging clutch cause

A

gear clash and gear tooth damage as well as difficulty shifting

72
Q

what can cause clutch drag

A

improper adjustment ( excessive free play )

73
Q

what would happen if the free play was to little

A

the release bearing and levers could be in constant contact and cause premature failure

74
Q

what would excessive free play cause

A

the operator to move the clutch pedal much further before release and causing drag

75
Q

what must also be kept in mind when checking clutch pedal free play

A

wear in the connecting linkage

76
Q

when checking for a dragging clutch what should be kept in mind

A

flywheel, intermediate plate and the pressure plate may be in contact due to warpage from excessive heat

77
Q

what would cause chattering in a clutch

A

loose engine mounts or drivetrain components may be worn or damaged - clutch splines may also be worn

78
Q

how would oil contamination or grease contamination cause chattering clutch

A

the disc surface would become glazed and worn creating and unusual wear pattern

79
Q

what might cause clutch vibration

A

an imbalance in the clutch assembly -linings could separate and individual sections could be torn off the disc . also dirt or mud build up

80
Q

prior to removing a clutch from a vehicle you should

A

disconnect the battery ground cable to prevent engine turnover

81
Q

when removing the clutch assembly from the engine what should be installed to help you slowly and evenly slide the clutch away

A

two long guide studs in the clutch cover pressure plate assembly mounting fastener holes

82
Q

why should you remove the clutch cover in the manufacture pattern

A

to prevent warpage of the assembly

83
Q

what should be remembered when removing clutch material

A

the clutch dust may contain asbestos so breathing protection should be considered

84
Q

what would you use to check for warpage on the intermediate plate and pressure plate

A

straight edge and a feeler gauge

85
Q

when checking the springs you should check for

A

all the springs are the same height and use a spring gauge to make sure tension is within speck

86
Q

when cleaning or handling clutch components you should make sure

A

no oil or grease gets onto the clutch friction surface . clean all parts with steam or water or a brake cleaning solution

87
Q

after reassembly what should be checked

A

crankshaft end play

88
Q

how can the alignment of the re assembled components be checked

A

with a flywheel runout check

89
Q

why are crankshaft, flywheel and clutch bore housing checks conducted

A

to ensure the centerlines of the crankshaft and transmission input shaft are in line with each other

90
Q

when is the centrifugal clutch in the locked state

A

at full load speed

91
Q

what are the common connections when a centrifugal clutch is used

A

belt - close coupled - flex couples

4th year HET (31 decks)

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