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Millwright Level 2 > Belts & Chain Drives > Flashcards

Belts & Chain Drives Flashcards

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1
Q

The grip of a belt depends on these 3 things

A

Area of contact, materials of belt and pulley, tension in belt

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2
Q

The most common belt materials

A

Cotton, leather, rubber, nylon

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3
Q

Most common pulley materials

A

Cast iron, pressed steel, die-cast alloys

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4
Q

How is installed belt tension expressed

A

Percent elongation or percent tension

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5
Q

The tension needed on the belt to transmit power without slipping

A

Effective tension

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6
Q

What is the run in time of a new belt

A

12 to 24 hours before re-tension

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7
Q

How can you check belt deflection

A

Halfway between the two shafts apply force so for 1/64” for each inch of distance.
Ex. Center distance = 32” = 32/64 = 1/2”

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8
Q

Formula for belt length

A

((D+d) / 2) x π + (2C)

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9
Q

How can you control belt slip

A

Use smaller pulley ratios

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10
Q

What causes creep

A

The elasticity of the belt

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11
Q

In this belt, the drive members (power plies) carry the forces to transmit power

A

Flat belts

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12
Q

This belting contains a single row of cords

A

Compass

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13
Q

Name the 3 types of ways to join a belt

A

Chemical - Use adhesives
Vulcanized - Use heat and pressure (strongest)
Mechanical - Hinges, lacing, plate

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14
Q

V-belt efficiency

A

93%

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15
Q

Velt construction (four sections)

A

Top section - extension section
Bottom section - compression section
Neutral section - give belt it’s tensile strength
Cover section - protect inner parts from wear, only part that touches the sheave

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16
Q

Cord construction for long, heavy drives

A

Multi-layer

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17
Q

Belt with two ropes that have high load capacity and great flexibility

A

Grommet

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18
Q

How are conventional V-belts classified

A 
A - 0.50"
B - 0.66"
C - 0.88"
D - 1.25"
E - 1.50"
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19
Q

How are high-capacity V-belts classified

A

3V - 3/8”
5V - 5/8”
8V - 8/8” (1”)

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20
Q

How much more horsepower can High capacity V belts transmit

A

3 times

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21
Q

What does 3V250 and 8V500 mean

A 
3V250 = 3/8 width and 25" pitch line 
8V500 = 5/8 width and 50" pitch line
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22
Q

Light duty belts are also called this

A

Fractional horsepower belts

ex. 3L, 4L, 5L

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23
Q

Type of V-belt where both halves absorb compression and tension

A

Double-angle V-belt

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24
Q

Another name for positive drive belts

A

Timing or gear belts (have teeth)

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25
Q

What does 390 L 100 mean

A

Pitch length = 39” (390 / 10)
Pitch of drive = light
Belt width = 1” (100 / 10)

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26
Q

Also referred to as multi-ribbed or V-ribbed belts

A

Poly V-belts (rib spacing of 3/32, 3/16, and 3/8)

Pitch line above the sheave

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27
Q

Operate at high ratios, retain contact under extreme conditions of misalignment and tension

A

Poly V-belts

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28
Q

Referred to as joined V-belts, group V-belts or grip-bands

A

Power band V-belts

29
Q

Whats the most efficient rim speed

A

4000-6000 ft/min (3500 says Rob)

30
Q

When are drives needed to be dynamically balanced

A

over 5000 ft/min

31
Q

Surface speed formula

A

SS = .262 x RPM x D

32
Q

Why are idler pulleys used

A

increase arc of contact

act as take up (cause a reverse bend in belt, shortens life)

33
Q

How big should a outside idler be

A

One third larger than smallest drive pulley

34
Q

How big should an inside idler be

A

As large or slightly smaller than the smallest drive pulley

35
Q

How do you determine the width of a flat belt

A

Pulley face is one inch wider than the belt for pulleys up to 6 inches wide
Two inches wider than the belt for pulleys over 6 inches wide

36
Q

The higher the belt speed, the ______ the required crown

A

smaller

37
Q

What is the groove angle of the sheave

A

Between 34 and 42 degrees

38
Q

How should a proper belt fit on a sheave

A

Flush or slightly above outside diameter of the sheave

39
Q

The two types of variable speed drives

A

Adjustable centres and Fixed centres (adjust while running)

40
Q

Offset link designed for high speed or heavy service

A

Two-pitch

41
Q

Chain roller dimensions

A 
Pitch = 120 = 12/8
Width = 5/8 x pitch
Roller diameter =5/8 x pitch
Pin diameter = 5/16 x pitch
Link plate thickness = 1/8 x pitch
42
Q

Multi-strand chains are up to this many wide

A

8

43
Q

What does 100-2H chain mean

A

1-1/4” pitch, regular, 2 strand, heavy series
0 = regular
1 = lightweight
5 = rollerless bushing

44
Q

What does the letters C and A mean for chain

A 
C = Rollerless
A = Standard
45
Q

Chain used for maximum power with the smallest pitch size

A

Multiple strand roller chain

46
Q

Chain that consists of a series of toothed link-plates assembled on pin connectors. For high speed drives

A

Silent chain

47
Q

What does a D 40 B 15 sprocket mean

A 
D = Double - indicates number of strands in the chain
40 = chain number
B = Hub type
15 = Number of teeth on sprocket
48
Q

When can a sprocket be used with double pitch chain

A

With 36 teeth or more (less than 36 are cut specifically for double pitch chains)

49
Q

Efficiency of roller chain drive assemblies

A

98% - 99%

50
Q

How much centre distance of chain is adequate

A

30 to 50 pitches (20 for pulsating loads)

At least one third of teeth should engage chain (120 degree wrap)

51
Q

The driven sprocket should not exceed this many teeth

A

120

52
Q

Speed ratio formula

A

Speed ratio = N teeth on driven / n teeth on drive

53
Q

Sprocket ratios that are allowed

A

12:1 for low speed (100 rpm max)
Up to 7:1 for single chain
Use a double reduction drive or countershaft for over 5:1

54
Q

Recommended amount of slack for horizontal chain drives and vertical

A

2% (less for reversing or shock loaded)

Vertical chain one-quarter the chain pitch

55
Q

On chain drives where should an outside idler go

A

towards the smaller sprocket

56
Q

On chain drives where should an inside idler go

A

Middle, slightly towards the larger sprocket

57
Q

When can chain guide rails be used

A

speeds less than 300 ft per minute

58
Q

When should chain be replaced

A

When the extension is 1% to 2%

59
Q

How much of a load can an open-ended belt carry compared to an endless belt

A

1/3 of the load

60
Q

Maximum misalignment of the sheaves must not exceed this

A

1/16” per foot of distance

61
Q

Should you use idlers on reverse drives

A

No

62
Q

When transmitting power from a horizontal shaft to a vertical shaft use this

A

Quarter-turn drive (maximum speed ratio 2.5:1)

63
Q

What temperatures are belts cured to operate at

A

60 C (Can use heat treated belts over that temp)

64
Q

What is the minimum arc of contact for a synchronus belt

A

60 degrees (6 teeth must be engaged)

65
Q

The strongest and most energy efficient belt tooth design

A

Rounded tooth

66
Q

Double strand chain is approx this much stronger than single

A

1.7 times

67
Q

The offset link of a silent chain is called

A

hunting link

68
Q

Slip fit master links reduce the working capacity by this much

A

30%

69
Q

The name of sprockets with an odd number of teeth

A

Hunting tooth

Millwright Level 2 (10 decks)

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