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HET Third Year Powertrain SAIT > 190303A > Flashcards

190303A Flashcards

Gearing Principles

1
Q

On a gear tooth, what is the line dividing the tooth lengthwise?

A

pitch line

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2
Q

what is the upper portion of a gear tooth that’s been divided lengthwise?

A

face

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3
Q

what is the lower portion of a gear tooth that’s been divided lengthwise?

A

flank

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4
Q

when a gear tooth has a larger and narrower end, what is the smaller end called?

A

toe

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5
Q

when a gear tooth has a larger and narrower end, what is the larger end called?

A

heel

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6
Q

when describing wider gear sections, what is common regarding the heel and toe sections?

A

to separate them using a centre section

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7
Q

what is tooth profile?

A

the shape of the tooth

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8
Q

what is the root fillet on a gear tooth?

A

the lowest point between two teeth

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9
Q

why is the root fillet area slightly rounded?

A

gives gear tooth strength and reduce chances of cracking at that area

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10
Q

what is a drive side of a tooth?

A

convex side, the side that gears contact when being driven

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11
Q

what is the coast side of a tooth?

A

the concave side, the side that gears contact when the loaded vehicle is pushing the powertrain

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12
Q

what is path of power?

A

the power flow from engine flywheel to drive axles.

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13
Q

what can the path of power be used to determine?

A

which gears are actually in use and delivering power

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14
Q

what pitch circle diameter is the shortest?

A

the root diameter (root circle)

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15
Q

what pitch circle diameter is the greatest?

A

the outside diameter (outside circle)

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16
Q

where is the pitch diameter in relation to the face and flank?

A

on the centreline that divides the face and flank. (pitch circle)

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17
Q

where do teeth mesh at?

A

the pitch line

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18
Q

How do you find circular gear pitch?

A

find pitch circle, then find the exact centre of each gear tooth

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19
Q

what is gear pitch?

A

the distance between the gear tooth centrelines

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20
Q

why must the circular gear tooth pitch be the same on each gear?

A

provide great gear strength and max force can be delivered through the gears

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21
Q

What is clearance?

A

when gear teeth mesh, a small clearance exists between tip of one tooth and root between 2 teeth on the opposite gear

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22
Q

why is clearance needed?

A

help maintain a lubrication film

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23
Q

What is backlash?

A

clearance on the side of the gear tooth

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24
Q

why is backlash needed?

A

for expansion of gear teeth and lubrication

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25
Q

what should you be aware of when measuring or adjusting backlash?

A

changes in gear tooth profile as the gears wear during operation

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26
Q

how can you measure gear tooth backlash?

A

with a dial indicator

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27
Q

Why would you time a gear set?

A

to ensure they always operate in a specific relationship with one another. creates a specific wear pattern. gears have been lapped in their pattern and need to operate in that specific pattern

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28
Q

what is an example of a timed gear set from the book?

A

engine crank and cam

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29
Q

are gear teeth timed in an angle drive gear set?

A

yes

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30
Q

on an angle drive gear set, what is the smaller gear and larger gear called?

A

smaller: pinion
larger: crown

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31
Q

What are non-hunting gears?

A

gear set that develops a specific tooth contact wear pattern. will always contact the same tooth every revolution

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32
Q

do non-hunting gear sets need to be timed?

A

yes

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33
Q

How will the number of pinion teeth divide into the number of crown gear teeth on a non-hunting gear set?

A

equally, ex. 3:1, 5:1. ratio expressed as a whole number

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34
Q

What are partial non-hunting gears?

A

gear set that develops a unique wear pattern. will contact the same few teeth, but in 2-3 revolutions of the crown gear before the first pinion tooth returns to original point

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35
Q

do partial non-hunting gears need to be timed?

A

yes

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36
Q

how will the number of pinion teeth divide into the number of crown teeth on a partial non-hunting gear set?

A

of pinion teeth divides into crown teeth unequally, completes in one or 2 decimal places. ex: 4.45:1, 2.50:1

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37
Q

What are hunting gears?

A

no special wear pattern, every pinion tooth comes into mesh with every crown tooth at some point in operation

38
Q

does a hunting gear set need to be timed?

A

no

39
Q

how will the pinion teeth divide into the crown teeth on a hunting gear set?

A

pinion teeth divides into the crown teeth unequally, in a weird continuous number. ex: 3.333:1

40
Q

what is direct drive?

A

when 2 gears in identical size are in mesh with one another. no speed/torque change. input= output

41
Q

what ratio is direct drive?

A

1:1

42
Q

How do you calculate gear ratio?

A

driven over drive

43
Q

what is reduction?

A

when a smaller gear drives a bigger gear. output speed=1/2 input speed. low speed, high torque.

44
Q

in gear ratios, how is a reduction usually seen?

A

reduction is always greater than 1. ex: 2:1, 3:1, 4:1

45
Q

What is overdrive?

A

input gear is bigger than output gear. low torque, high speed. output speed= 2x input speed

46
Q

where are overdrive gear sets often found?

A

in on highway vehicles to reduce input gear speed while keeping output gear speed

47
Q

in gear ratios, how is overdrive usually seen?

A

less than 1. ex: 0.5:1, 0.25:1, 0.99:1

48
Q

how can you change direction of rotation?

A

with an idler gear

49
Q

is an idler gear involved in ratio calculations?

A

no, only input and output

50
Q

what is one objective when adjusting gear mesh?

A

achieve a wear pattern that will provide maximum gear set service life

51
Q

what conditions could two gears on two different parallel shafts but in mesh with each other operate?

A

direct drive, reduction, overdrive.

52
Q

how could you create a reverse gear with 2 gears on 2 parallel shafts?

A

install a third shaft with an idler between the two gears

53
Q

characteristics of straight cut spur gears?

A

most basic, tooth identical on all sides, cheap

54
Q

where do straight cut gears contact?

A

across the entire pitch line

55
Q

where are the main power transmission loads exerted on straight cut gears?

A

on the two meshing teeth at any one time

56
Q

what is a benefit of using straight cut gears?

A

no axial thrust loadsw

57
Q

what are disadvantages of straight cut gears?

A

not high strength, noisyw

58
Q

where can straight cut gears be found?

A

in transmissions as main gears, or PTO’s

59
Q

can internal gears mesh with other internal gears?

A

fuck no

60
Q

what is needed to transmit power when using an internal gear?

A

an external gear in mesh

61
Q

benefits of internal gears?

A

high load handling

62
Q

what are single helical gears?

A

gears that are cut at an angle to the shaft

63
Q

benefits of helical gears?

A

good strength and less noise.

64
Q

what lengthens the time it takes for single helical gears to fully mesh?

A

the leading and trailing edges. ensures multiple teeth are involved in transmitting power

65
Q

what is a disadvantage of single helical gears?

A

axial thrust loads. use thrust washers

66
Q

what direction are axial thrust loads against a single helical gear?

A

both directions

67
Q

where are single helical gears common?

A

transmissions or anywhere that you can control axial thrust loads

68
Q

what are double helical gears?

A

single helical gears but two of them. separated by a line, line helps out with lubricating the gears

69
Q

what is another name for double helical gears according to the book?

A

herringbone

70
Q

benefits of double helical gears?

A

handles heavy torque loads, handle thrust loads like a breeze

71
Q

why doesn’t the double helical gears have thrust loads?

A

the double design helps offset the axial thrust loads at opposite ends of the gears.

72
Q

disadvantage of double helical gears?

A

expensive

73
Q

What are rack and pinion gears?

A

change rotary motion to linear motion. mostly straight cut spur gears, the rack is like someone cut open a spur gear and laid it flat

74
Q

what are angle drives?

A

used when needing to make a directional change, up to 90 degrees

75
Q

what are straight cut bevel gears?

A

may use straight cut gear teeth. can be noisy and only for small load applications. changes direction of power

76
Q

how can you gain strength in the design of angle drive sets?

A

use spiral gears

77
Q

where does the pinion gear and shaft sit in relation with the crown gear on a spiral bevel gear set?

A

at the centreline of the crown gear

78
Q

what does the short stub shaft on the pinion gear help with?

A

keeps pinion and crown in close contact during sudden high-torque shock loads

79
Q

where does pinion sit in relation to centreline of crown gear on a hypoid angle gear set?

A

centreline of drive pinion and shaft is below centre of crown gear

80
Q

benefit of hypoid angle gears?

A

good for high torque loads. has more tooth contact during meshing

81
Q

why must you use special extreme pressure EP lubricant with hypoid gear sets?

A

these gear sets have a lot of sliding contact and pressure when meshing

82
Q

Where doe the pinion sit in relation to the centre of the crown gear in an ambit gear set?

A

sits above the centreline. allows for higher driveline position (good for off-road clearance)

83
Q

benefit of worm and wheel gear sets?

A

very strong, good for high torque loads. load will not overrun

84
Q

where are planetary gear sets used?

A

where input and output shaft must operate on same plane

85
Q

3 components of planetarium?

A

sun, ring, planets (on a carrier)

86
Q

what is needed for a planetary to operate?

A

drive, driven, reactionary

87
Q

if no member is held stationary on a planetary, what condition is it in?

A

neutral

88
Q

if 2 members are held on a planetary, what condition is it in?

A

direct drive

89
Q

if the carrier is held in a planetary, what condition is it in?

A

reverse

90
Q

if the carrier is the driven component, what condition is it in?

A

reduction

91
Q

if the carrier is driving, what condition is it in?

A

overdrive

HET Third Year Powertrain SAIT (8 decks)

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