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Millwright Block 2 (harmonized) NS > Gears > Flashcards

Gears Flashcards

1
Q

If speed is increased what happens to torque in a gear train?

A

Decreased

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2
Q

What are the speed ranges (ratios) in a single reduction gear box?

A

5:1 - 70:1

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3
Q

What are the speed ranges (ratios) in a double reduction helical and worm gear box?

A

20:1 - 280:1

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4
Q

What are the speed ranges (ratios) in a double reduction 2 worm gear box?

A

25:1 -4900:1

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5
Q

What are the speed ranges (ratios) in a triple reduction 3 worm gear box?

A

1000:1 - 180 000:1

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6
Q

How much efficiency is lost in every gear configuration?

A

2%

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7
Q

How does speed affect cooling of a gear box?

A

Less speed typically equates to less cooling

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8
Q

What direction(s) do helical or herringbone gears have their shafts?

A

Parallel

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9
Q

Single Helical gears require what bearings?

A

Tapered roller bearings

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10
Q

Do single helical gears create thrust (y/n)

A

Yes

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11
Q

What type of bearings do herringbone gears require?

A

Radial bearings

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12
Q

Do herringbone gears create thrust? (Y/n)

A

No

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13
Q

What bearings do double opposed helical gears require?

A

Radial bearings

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14
Q

Why do double opposed helical gears not create thrust?

A

They push against each other opposed to one direction

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15
Q

When fitting gears what order should you follow?

A

Largest first
Pinion last

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16
Q

When/what are bevel gears used for?

A

Right angle drives typically with helical gears

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17
Q

What are the ratios of bevel gears?

A

1:1 - 10:1

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18
Q

What is the ratio of a mitre gear box?

A

1:1

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19
Q

What direction are the shafts in a hypoid gear?

A

Cross

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20
Q

What are the ratios of a hypoid gear?

A

2:1-8:1

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21
Q

What bearing are to be used with bevel, mitre, and hypoid gears?

A

Tapered roller bearings

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22
Q

Do bevel gears create thrust? (Y/n)

A

Yes

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23
Q

Do mitre gears create thrust (y/n)

A

Yes

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24
Q

Do hypoid gears create thrust (y/n)

A

Yes

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25
Q

Where are shafts located in a planetary gear?

A

In line

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26
Q

What are the 4 uses for planetary gear boxes?

A

Reduction
Overdrive
Reversing
Direct

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27
Q

What are the ratios for planetary gears?

A

1.1:1 - 50 000:1

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28
Q

What are the 3 main members to a planetary gear?

A

Ring
Sun
Pinions

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29
Q

What are the 2 type of ways a reducer is joined to a power source?

A

Direct
In direct

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30
Q

What are the two types of direct attachments between a reducer and a power source?

A

Flexible
Flanged

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31
Q

What type of base does a flexible connection between a reducer and power source require?

A

Strong / rigid

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32
Q

What is an in direct way of connecting a reducer to a power source?

A

V belts

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33
Q

What are the two main types of mounting styles of a gear box?

A

Base mounted
Shaft mounted

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34
Q

What is important to remember when mounting a base mounted gear box?

A

The orientation in reference to the oil level/lubrication method

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35
Q

What is the purpose of a torque arm?

A

To hold a unit in position preventing rotation

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36
Q

Where should a torque arm be mounted?

A

Right angle from the output shaft to point of attachment

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37
Q

What is the two main benefit of using V belts to power a gear box?

A

-Extra variation in speed by using different sized sheaves
-overload protection

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38
Q

Where should V belts be mounted on a gear system?

A

Right angle to a line between output and input shaft

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39
Q

What are the 4 methods for lubrication of a reducer?

A

Splash
Wipers
Pump
Provisions

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40
Q

What lubrication method does worm gears typically have?

A

Wipers

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41
Q

What lubrication method does vertically mounted units typically have?

A

Provisions to the bearings

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42
Q

What does chordal mean?

A

Engagement

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43
Q

Where is the pitch point on a gear?

A

Where the teeth make contact

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44
Q

How do you find the ratio of a worm gear?

A

of teeth on the wheel : # of starts on the worm

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45
Q

What are the 3 typical pressure angles?

A

14.5 degrees
20 degrees
25 degrees

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46
Q

In pressure angles what is strongest?

A

The largest one (25)

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47
Q

What is the pressure angle on a gear?

A

The angle the teeth are cut at

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48
Q

What must gears that mesh have?

A

The same pressure angle

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49
Q

What are the 2 types of teeth profile on a gear?

A

Involute
Straight

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50
Q

What does an involute gear tooth look like?

A

Curved

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51
Q

Where is the pitch circle on a gear?

A

Middle of the teeth

52
Q

Where is the root diameter on a gear?

A

Bottom of the tooth

53
Q

If a gear train has clockwise (cw) drive gear at the start and an even number of gears what direction will the last gear rotate?

A

The opposite direction as the drive (counterclockwise ccw)

54
Q

If a gear train has clockwise (cw) drive gear at the start and an ODD number of gears what direction will the last gear rotate?

A

Same as the first gear (clockwise)

55
Q

If you have a gear train where the drive gear has 10 teeth and the driven gear has 30 teeth what is the ratio?

A

3:1

56
Q

If a drive gear has 20 teeth and the driven gear has 30 what is being obtained?

A

Reduction of speed
Increase of torque

57
Q

When calculating ratios in a gear train with only a 1 drive and driven do the middle gears matter?

A

No. Just the drive and driven

58
Q

What is an open gear drive?

A

Heard exposed to the outside environment

59
Q

What is a gear set?

A

Matched pair of gears manufactured together with the intent to mate together

60
Q

What is classified as a gear train?

A

Two or more gears working together as a unit

61
Q

When two gears that have a different number of teeth mesh together, what is the gear with fewer teeth called?

A

Pinion

62
Q

In bevel and hypoid gear sets, the smaller gear is called a pinion but the larger gear can be called what?

A

Crown gear
Or
Ring gear

63
Q

When the input speed of the gearbox is the same as the output speed what is it called?

A

Direct drive

64
Q

A gear train with a SLOWER output speed than input speed is called what?

A

A reducer

65
Q

A gear train with a faster output speed than input speed is called what?

A

Speed increaser

66
Q

If a gear train has a large gear driving a small gear what is it called?

A

Speed increaser

67
Q

If a gear train has a smaller gear driving a larger gear what is it called?

A

Speed reducer

68
Q

What two things does a reducer do?

A

Reduce speed
Increase torque

69
Q

What are the two purposes of overdrives?

A

Increase speed
Reduce torque

70
Q

What can direct drives change?

A

Direction or angle

71
Q

How can you tell the hand of a gearbox unit?

A

Seen from the input shaft view
(Looking at the input, the direction the output comes from tells you the hand)

72
Q

What direction of rotation are MOST gearbox units, clockwise or counterclockwise?

A

Clockwise

73
Q

What the minimum units of reduction in a reducer?

A

2 or more

74
Q

How do you find your gear ratio on a spur gear?

A

Driven gear / driving gear
(Driven divided by driving)

OR

Output / input

75
Q

What is a compound gear?

A

A number of gears fixed together
(NOTE: not fixed by teeth)

76
Q

What is the difference between helical gears vs spurs gears?

A

Spur gear teeth are straight
Helical gear teeth are at an angle

77
Q

What is backlash?

A

The clearance between the gear teeth

78
Q

What is a gear that only has bearing support on one side called?

A

Overhung

79
Q

Gears that are supported between two bearings are called what?

A

Straddle mounted gears

80
Q

Are work gears typically self locking? (Y/n)

A

Yes

81
Q

What is the difference between opposed double helical gears and herringbone gears?

A

Herringbone comes to a point
Double helical have a space or gap

82
Q

What is the module in terms of gear teeth?

A

The thickness
The bigger the number the bigger the thickness

83
Q

If two members of a planetary gear are locked what does it do?

A

It acts as a direct drive

84
Q

Where do we ideally want a worm gear contact set up in terms of the worm wheel?

A

SLIGHTLY towards the leaving side of the worm wheel

85
Q

What does the term throated mean in terms of gears?

A

Beveled to increase tooth contact

86
Q

Why would we permanently stamp numbers into gears?

A

To accurately take future measurements
Timing to ensure gears are assembled the same

87
Q

What does the term toe refer to in bevel and hypoid gears?

A

The smallest part of the gear tooth

88
Q

What does heel refer to in terms of bevel and hypoid gears?

A

The largest part of the gear tooth

89
Q

Describe residual magnetism

A

Gears and bearings become magnetized attracting small particles

90
Q

What is the purpose of the oil scraper?

A

Direct oil where needed

91
Q

What are gears for?

A

Transmit power and motion

92
Q

Why would we select a double throated work gear drive for a power train reduction?

A

Smooth operation and deep reduction ratios

93
Q

What must a pair of gears have to mesh?

A

Same pressure angle and diametrical pitch

94
Q

What is backlash

A

Space between the teeth of meshing gears

95
Q

What is a gear train that converts linear to rotary motion?

A

Rack and pinion

96
Q

What worm and gear drive has the most critical bearing adjustment setup?

A

Double throated

97
Q

What is an overhung gear?

A

Supported by bearings on one side only

98
Q

In a gear train what are the gears having no effect on ratio called?

A

Idler gears

99
Q

What are two common tooth pressure angles of spur gears?

A

14.5
20

100
Q

Why would we select spur gear drive for a power train reduction?

A

Economical to purchase, operate and maintain

101
Q

What is the space between the top land of one gear and the root of a meshing gear tooth called?

A

Clearance

102
Q

What are backlash measurements used to keep track of?

A

Gear wear

103
Q

What is used for checking for cracks in gear teeth?

A

Penetrant dye and developer

104
Q

What are broken gear teeth a sign of?

A

Shock or over loading

105
Q

What is tolerance stack up?

A

Slight variations in machining that add up to a sum total

106
Q

Gears and power transmission devices are used where you want ___________________

A

Positive positioning and ratio

107
Q

What gear is typically the smallest in a two gear train?

A

Pinion gear

108
Q

A good mesh pattern between two mated gears is indicated by what?

A

A central pattern not contacting the tooth edge

109
Q

What is the MA of a 160T worm wheel being rotated by a four start worm?

A

40:1

110
Q

What is the bottom half of a gear tooth called?

A

Dedendum

111
Q

What are the three methods for checking hearing backlash?

A

Dial
Lead wire
Feeler gauges

112
Q

What is the purpose of an oil dam in a gearbox?

A

Gathers and directs oil over the gears and bearings

113
Q

What components are in a planetary gear assembly?

A

Sun gear
Ring gear
Planet gears
Carrier

114
Q

If gear (driver) has 10T, turning at 125rpm, meshes with gear B (driven), having 250T, what is the mechanical advantage (ratio) of this reduction gear box?

A

25:1

115
Q

A double reduction helical gearbox gearbox has a 12/60 input gear set and a 16/80 output gear set. What is the gearbox’s reduction ratio?

A

25:1

116
Q

Damaged hardened gear teeth may be hand worked to remove burrs and high points with what tool?

A

Abrasive file

117
Q

What is the main reason for selecting the use of a hypoid gear?

A

Smooth and quiet operation

118
Q

A gear train has 9 gears meshing together the input gear is rotating clockwise what direction is the 9th gear turning?

A

Clockwise

119
Q

In a planetary gear set if the sun is held what will the carriers output be?

A

Same direction speed reduction

120
Q

When removing an old gasket from a flange or gearbox what must you ensure?

A

Old pieces of gasket do not fall into the system

121
Q

When removing old O rings during a rebuild what is the best practice to follow?

A

Always replace the O rings

122
Q

What must a pair of gears have to mesh?

A

Same pressure angle and diametrical pitch

123
Q

What worm and gear drive has the most critical bearing adjustment setup?

A

Double throated

124
Q

In a planetary gear set if the sun is held what will the carriers output be?

A

Same direction speed reduction

125
Q

A double reduction helical gearbox has a 12/60 input gear set and a 16/80 output gear set. What is the gearbox reduction ratio?

A

25:1

126
Q

What do you shim to get the correct rotational torque on a hypoid input gear?

A

Pinion preload

Millwright Block 2 (harmonized) NS (17 decks)

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