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Millwright Level 2 > Gear Drives > Flashcards

Gear Drives Flashcards

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
A primary worm and worm gear combined with a secondary worm and worm gear can have ratios of this
25:1 to 4900:1
26
A triple reduction consisting of all worm and worm gears have have ratios of
1000:1 to 180 000:1
27
When replacing gears in a reduction unit a good rule of thumb is to do this
Fit the largest gear first, intermediate gear second and pinion last
28
Bevel, mitre, and hypoid reduction units have ratios of this
1: 1 to 10:1 1: 1 are called mitre gear boxes
29
Planetary gear reduction units have ratios of
1.1 :1 to 50 000:1
30
A reducer and power source can be joined in these two ways
Direct drive and indirect drive
31
Lubrication of most reduction units is by way of
Splash method
32
Gears manufactured together and intended to mate with each other are called
Gear sets (hypoid and bevel gears)
33
When two or more gears mesh or work together as a unit it is called a
Gear train
34
In bevel and hypoid sets the smaller gear is called the _____ and the larger gear is called the ____ _____
Pinion and Crown gear (ring gear)
35
This drive is when the input speed of the gearbox is the same as the output speed
Direct drive
36
This is when a bearing supports only one side of the load
Overhung gear or overhung load (common for bevel and hypoid gears)
37
These gears are mounted between two bearings
Straddle-mounted
38
When the gear or shaft is allowed to move axially
End play
39
The centreline around which a gear or parts revolve
Axis of rotation
40
The side of the gear that is in contact with the other gear teeth
Drive side (other side is coast side)
41
Steeper helix angled lead to ______ operation but have more of this type of friction
Smoother and sliding
42
The more starts a worm has the ______ the worm wheel advances in one turn
Faster
43
The radius across the flank and the face of the tooth, makes meshing quieter and smoother
Involute
44
The pattern of areas of the tooth that are in contact when the gears are meshed together
Contact pattern
45
The ratio between the number of teeth and the pitch diameter is called this
Diametrical pitch (larger the number the larger the teeth)
46
Name the types of friction as gear teeth mesh
1. Sliding, 2. Rolling, 3.Sliding
47
Same the three types of shaft positions
Parallel Intersecting Crossing over at 90 degrees
48
The correct centre to centre distance between spur gears
Half the sum of the pitch diameters of the two gears
49
Bevel gears develop these types of loads
Axial thrust and radial (exception is Zerol which don't have axial)
50
The two positions bevel gears can be mounted
Straddle and overhung
51
Spiral bevel gears have curved teeth that are _______ to the shaft axis
oblique (angular)
52
Type of bevel gear that forms a drive between two shafts that cross over and are at 90 degrees
Hypoid gears
53
Are the worm and worm wheel of the same or opposite hand?
Same
54
If a worm only has a few starts it tend to be this
Self-locking
55
In a worm gearbox which is harder, the worm or worm wheel
Worm, usually hardened steel
56
How do you determine the lead of a worm
pitch x number of starts
57
Worm gear ratio formula
Number of teeth / Starts
58
How should a worm tooth contact be set up
The contact between the teeth is slightly toward the leaving side of the worm wheel
59
What is the preferred material for gears that mesh with non metallic gears
Cast iron
60
The three parts of a Planetary gear
Sun gear, carrier with planet gears, ring gear
61
The part that is held in a planetary gear set
Reaction member (if two are locked it produces a direct drive)
62
Double or multiple reduction units have at least this many shafts and this many gears
3 shafts and 4 gears
63
When the gearbox input shaft and output shaft are on different planes it's called
Offset reducers (on the same plane is concentric reducers)
64
The rotational arc clearance between a pair of mounted gears
Backlash
65
When is minimal backlash required?
Applications involving frequent starting and stopping, reverse rotation or load reversals
66
How can you check backlash in a gearbox
Dial indicator, lead wire, feeler gauges
67
How can you adjust bearing position on the shafts and within the bearing housings
Machining or shims
68
When installing a gearbox you should place these under all feet of the gearbox
1/8 inch thick shims
69
What is the hidden danger with high-ratio planetary drives
Reverse torque lockup
70
How often should you change the oil
Every 20 000 hours, or 4 years | Bearings cleaned and repacked every 10 000 hours
71
How can you check for residual magnetism
A compass
72
What is the proper positioning of a torque arm?
90 degrees from a line running from the output shaft to point of attachment
73
The point at which the cones pivot on bevel gears
The apex
74
Common gears and shaft arrangements
``` Spur - Parallel Single helical - Parallel or crossing Double helical and Herringbone - Parallel Bevel and Mitre - Intersecting Hypoid, Worm & Wheel - Crossing ```
75
Formula for Center Distance
(N+n) / (2 x DP)
76
What can you use to hand-dress the teeth
``` Tapered oilstones (abrasive files) 2800 grit aluminum oxide stone after ```
77
The finish on a shaft should be
10 to 20 micro inch finish by plunge grinding
78
The most common helix angle
7 degrees to 23 degrees
79
What is the typical gear ratio for each reduction
6:1
80
Which way is more ideal in a spiral bevel gear, right hand cw or left hand ccw
left hand ccw, away from the apex

Millwright Level 2 (10 decks)

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