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Millwright Level 2 > Gear Drives > Flashcards

Gear Drives Flashcards

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1
Q

These are used to transmit force and motion

A

Gear drives

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2
Q

The circumference of the cylinder represents this part of the gear

A

Pitch circle

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3
Q

The line of contact between the two cylinders is called this

A

Pitch line

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4
Q

Formula for Addendum

A

1 / DP

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5
Q

Formula for Dedendum

A

1.157 / DP

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6
Q

Formula for Clearance

A

0.157 / DP

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7
Q

Formula for OD

A

(N+2) / DP

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8
Q

Formula for DP

A

N / PD

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9
Q

Formula for Pitch Diameter

A

N / DP

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10
Q

Formula for Working Depth

A

2 x ADD

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11
Q

Formula for Whole Depth

A

ADD + DED

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12
Q

Proper mesh is achieved by these three things

A

Same diametrical pitch, pressure angle, tooth profile

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13
Q

Most spur gears have these pressure angles

A

14.5 or 20 degrees (20 preferred)

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14
Q

Type of gear where teeth are cut parallel to it’s bore, do not generate axial thrust

A

Spur gears

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15
Q

Like spur gears but have the gear teeth at an angle to the bore

A

Helical gears (standard 45 degree helix angle)

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16
Q

Difference between helical gears connecting parallel shafts and crossed shafts

A

Parallel gears are of the opposite hands, cross shafts are of the same hand

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17
Q

Two helical gears are abutted, to act as a single unit

A

Herringbone gears

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18
Q

Type of gear where the teeth are cut on the surface of a cone, connect shafts that intersect at right angles

A

Bevel gears

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19
Q

If a bevel gear has a pitch cone angle of 90 degrees it’s called this

A

Crown gear

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20
Q

Bevel gear with a pitch cone angle of 45 degrees and a 1:1 ratio, used to change shaft direction

A

Mitre gear

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21
Q

Gear used for transmitting power between shafts that do not intersect

A

Hypoid gear

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22
Q

Unit that increases speed and decreases torque

A

Overdrive

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23
Q

Single reduction units have a speed range of this

A

5:1 to 70:1

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24
Q

A primary helical reduction combined with a worm and worm gear can have ratios of this

A

20:1 to 280:1

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25
Q

A primary worm and worm gear combined with a secondary worm and worm gear can have ratios of this

A

25:1 to 4900:1

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26
Q

A triple reduction consisting of all worm and worm gears have have ratios of

A

1000:1 to 180 000:1

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27
Q

When replacing gears in a reduction unit a good rule of thumb is to do this

A

Fit the largest gear first, intermediate gear second and pinion last

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28
Q

Bevel, mitre, and hypoid reduction units have ratios of this

A

1: 1 to 10:1
1: 1 are called mitre gear boxes

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29
Q

Planetary gear reduction units have ratios of

A

1.1 :1 to 50 000:1

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30
Q

A reducer and power source can be joined in these two ways

A

Direct drive and indirect drive

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31
Q

Lubrication of most reduction units is by way of

A

Splash method

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32
Q

Gears manufactured together and intended to mate with each other are called

A

Gear sets (hypoid and bevel gears)

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33
Q

When two or more gears mesh or work together as a unit it is called a

A

Gear train

34
Q

In bevel and hypoid sets the smaller gear is called the _____ and the larger gear is called the ____ _____

A

Pinion and Crown gear (ring gear)

35
Q

This drive is when the input speed of the gearbox is the same as the output speed

A

Direct drive

36
Q

This is when a bearing supports only one side of the load

A

Overhung gear or overhung load (common for bevel and hypoid gears)

37
Q

These gears are mounted between two bearings

A

Straddle-mounted

38
Q

When the gear or shaft is allowed to move axially

A

End play

39
Q

The centreline around which a gear or parts revolve

A

Axis of rotation

40
Q

The side of the gear that is in contact with the other gear teeth

A

Drive side (other side is coast side)

41
Q

Steeper helix angled lead to ______ operation but have more of this type of friction

A

Smoother and sliding

42
Q

The more starts a worm has the ______ the worm wheel advances in one turn

A

Faster

43
Q

The radius across the flank and the face of the tooth, makes meshing quieter and smoother

A

Involute

44
Q

The pattern of areas of the tooth that are in contact when the gears are meshed together

A

Contact pattern

45
Q

The ratio between the number of teeth and the pitch diameter is called this

A

Diametrical pitch (larger the number the larger the teeth)

46
Q

Name the types of friction as gear teeth mesh

A
  1. Sliding, 2. Rolling, 3.Sliding
47
Q

Same the three types of shaft positions

A

Parallel
Intersecting
Crossing over at 90 degrees

48
Q

The correct centre to centre distance between spur gears

A

Half the sum of the pitch diameters of the two gears

49
Q

Bevel gears develop these types of loads

A

Axial thrust and radial (exception is Zerol which don’t have axial)

50
Q

The two positions bevel gears can be mounted

A

Straddle and overhung

51
Q

Spiral bevel gears have curved teeth that are _______ to the shaft axis

A

oblique (angular)

52
Q

Type of bevel gear that forms a drive between two shafts that cross over and are at 90 degrees

A

Hypoid gears

53
Q

Are the worm and worm wheel of the same or opposite hand?

A

Same

54
Q

If a worm only has a few starts it tend to be this

A

Self-locking

55
Q

In a worm gearbox which is harder, the worm or worm wheel

A

Worm, usually hardened steel

56
Q

How do you determine the lead of a worm

A

pitch x number of starts

57
Q

Worm gear ratio formula

A

Number of teeth / Starts

58
Q

How should a worm tooth contact be set up

A

The contact between the teeth is slightly toward the leaving side of the worm wheel

59
Q

What is the preferred material for gears that mesh with non metallic gears

A

Cast iron

60
Q

The three parts of a Planetary gear

A

Sun gear, carrier with planet gears, ring gear

61
Q

The part that is held in a planetary gear set

A

Reaction member (if two are locked it produces a direct drive)

62
Q

Double or multiple reduction units have at least this many shafts and this many gears

A

3 shafts and 4 gears

63
Q

When the gearbox input shaft and output shaft are on different planes it’s called

A

Offset reducers (on the same plane is concentric reducers)

64
Q

The rotational arc clearance between a pair of mounted gears

A

Backlash

65
Q

When is minimal backlash required?

A

Applications involving frequent starting and stopping, reverse rotation or load reversals

66
Q

How can you check backlash in a gearbox

A

Dial indicator, lead wire, feeler gauges

67
Q

How can you adjust bearing position on the shafts and within the bearing housings

A

Machining or shims

68
Q

When installing a gearbox you should place these under all feet of the gearbox

A

1/8 inch thick shims

69
Q

What is the hidden danger with high-ratio planetary drives

A

Reverse torque lockup

70
Q

How often should you change the oil

A

Every 20 000 hours, or 4 years

Bearings cleaned and repacked every 10 000 hours

71
Q

How can you check for residual magnetism

A

A compass

72
Q

What is the proper positioning of a torque arm?

A

90 degrees from a line running from the output shaft to point of attachment

73
Q

The point at which the cones pivot on bevel gears

A

The apex

74
Q

Common gears and shaft arrangements

A 
Spur - Parallel
Single helical - Parallel or crossing
Double helical and Herringbone - Parallel 
Bevel and Mitre - Intersecting 
Hypoid, Worm & Wheel - Crossing
75
Q

Formula for Center Distance

A

(N+n) / (2 x DP)

76
Q

What can you use to hand-dress the teeth

A 
Tapered oilstones (abrasive files)
2800 grit aluminum oxide stone after
77
Q

The finish on a shaft should be

A

10 to 20 micro inch finish by plunge grinding

78
Q

The most common helix angle

A

7 degrees to 23 degrees

79
Q

What is the typical gear ratio for each reduction

A

6:1

80
Q

Which way is more ideal in a spiral bevel gear, right hand cw or left hand ccw

A

left hand ccw, away from the apex

Millwright Level 2 (10 decks)

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