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Millwright Block 2 (harmonized) NS > Belts > Flashcards

Belts Flashcards

1
Q

What type of drive are belt drives?

A

Friction drives

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2
Q

What is a tensile members in terms of belts?

A

Cords that carry the load

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3
Q

In terms of belts what transmits the power between the sheave and tensile member and support cords?

A

Compression material

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4
Q

What is the purpose of the cover in terms of belts?

A

To protect the core of the belt

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5
Q

How does a V belt transmit power? (2)

A
  • friction between the sides of the belt and the sides of the sheave groove
  • tensile members from the driver to the driven pulley
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6
Q

What does the amount of power a belt can transmit depend on? (2)

A

-Strength of tensile member
-Grip of the belt on the pulley

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7
Q

What does the amount of grip a belt has on a pulley depend on? (3)

A

-Arc of contact
-Tension applied to the belt
-Coefficient of friction

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8
Q

Where is the pitch line located in terms of belts?

A

Through the load carrying zone

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9
Q

Where should the pitch line of a belt be located on a sheave by industry standard during set up?

A

As close as possible to the outside diameter of the sheave

So the widest cross section of the belt Carries the load

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10
Q

Define stretch in belts

A

The increase in length of a belt during its time in service

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11
Q

In belt terminology the loss of driving speed due to the lengthening and shortening of the belt as it cycles from the slack side to the tight side is defined as what?

A

Creep

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12
Q

What takes place if creep extends all the way around a pulley?

A

Slip

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13
Q

What is the arc of contact in belt terminology?

A

The number of degrees that a belt wraps around a pulley

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14
Q

In belt terminology what is the number of degrees that a belt wraps around a pulley called?

A

Arc of contact

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15
Q

What determines the tension on the belt?

A

The force between the belt and the pulley

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16
Q

The gripping action on a V belt is entirely on the _______ of the belt and the ________ of the sheave groove

A

Sides

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17
Q

In V belts the belt must NOT touch what part of the sheave?

A

The bottom

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18
Q

What is the most widely used series of V belts?

A

Classical / standard series

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19
Q

If a V belt is designated as A, B, C, D, or E what type of belt series does this indicate?

A

Classical / standard series

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20
Q

Classical or standard series belts are designated with what?

A

A, B, C, D, or E

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21
Q

What are A and B series belts commonly used for?

A

Single and multiple belt drives

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22
Q

What are C, D, and E belts used in?

A

ONLY multiple belt drives

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23
Q

What are the 5 main advantages of using a standard (classical) series belts

A

-High tolerance in poor conditions
-Reliability with infrequent maintenance
-reliability with unusual drive systems
-widest choices
-cover wraps around the entire belt

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24
Q

What are the 4 variations of classical (standard) series belts?

A

-coffee raw edge
-banded (joined)
-double V
-fractional horsepower

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25
Q

How are cogged raw edged belts designated on labels?

A

AX, BC, CX

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26
Q

What are the 5 benefits of a cogged raw edged belt?

A
  • greater flexibility
  • enhanced airflow
  • no covers on side and bottom
  • fit sheaves more accurately
  • higher friction
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27
Q

What is crucial with cogged edged belts? (2)

A

Cleanliness and sheave alignment

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28
Q

What is another name for banded belts?

A

Joined classical

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29
Q

What is another name for Double V belts?

A

Hexagonal belts

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30
Q

What type of belt is pictured?

A

Double V belt

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31
Q

What type of belt is pictured?

A

Banded belt

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32
Q

What type of belt is pictured?

A

Cogged raw edge belt

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33
Q

What are double V belts uniquely capable of?

A

Transmitting power on either side of serpentine drives

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34
Q

How are double V belts designated?

A

AA, BB, CC

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35
Q

What is another name for fractional horsepower belts?

A

Light duty belts

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36
Q

How are fractional horsepower belts designated?

A

2L, 3L, 4L, 5L

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37
Q

The first number in a classical belt designations is the number over fraction?

A

/8ths

Ex

4L2550
= 4/8 Light duty 25.5”

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38
Q

What is another name for high capacity V belts?

A

Narrow V belts

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39
Q

How are Narrow V belts designated?

A

3V, 5V, 8V

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40
Q

Why are narrow belts high capacity?

A

Due to their narrow wedge design it provides more support for the tensile members compared to classical

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41
Q

When tensioning high capacity V belts what should you keep in mind?

A

They require more tension than regular V belts

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42
Q

What is another name for Poly V belts?

A

V ribbed belts

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43
Q

How are Poly V belts designated?

A

J, K, L, and M

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44
Q

A belt designated as J, K, L, or M is what type of belt?

A

Poly V belt

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45
Q

What does the code for poly V belts provide? (3)

A

Length
Section
Number of ribs

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46
Q

What does belt 180J6 mean?

A

Poly V belt
180 inches
J size
6 ribs

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47
Q

When are variable speed belts used?

A

When speed changes are needed

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48
Q

What are the sides of variable speed belts called?

A

Flanges

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49
Q

What information is given in variable speed belt codes?

A

Top width
Groove angle
Cross section
Pitch length

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50
Q

What fractions are the first digits in a variable speed belt code out of?

A

/16th

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51
Q

What does the V belt code 1228V255 mean?

A

12/16
28 degrees
V shape
25.5”

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52
Q

What does a variable speed belt require?

A

Special sheaves

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53
Q

Where are link belts used?

A

In places/situations where it is difficult or impossible to install an endless belt

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54
Q

In round belt codes what does the first numbers indicate?

A

Diameter

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55
Q

What fraction is the round belts diameter given in?

A

/16ths

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56
Q

How do you check for wear on a sheave?

A

Sheave groove gauge

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57
Q

What is the MAXIMUM misalignment of a sheave?

A

1/16 inch per foot

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58
Q

What is the MAXIMUM runout of a sheave?

A

0.005 inches

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59
Q

Where is the slack side of a pulley system?

A

The side coming directly from the driver

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60
Q

Where should you NOT use idlers?

A

On reversing drives

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61
Q

What are outside idlers mainly used for?

A

Means of tensioning a belt

62
Q

When using an outside idler what the MINIMUM size you should use?

A

1/3 larger than the smallest drive

63
Q

Would you ever use a crowned outside idler?

A

No

64
Q

Where should an outside idler be IDEALLY placed?

A

Slack side near the drive

65
Q

What is the MAXIMUM speed of a cast iron sheave?

A

6500 feet/min

66
Q

What is the MAXIMUM speed of a ductile Iron sheave?

A

9500 feet/min

67
Q

What is the minimum speed a V belt can go?

A

1500 feet/min

68
Q

What is the maximum speed a V belt can go?

A

9000 feet/min

69
Q

What is the ideal speed of a V belt?

A

6500 feet/min

70
Q

What is the formula for rim speed?

A

(Diameter x 3.14 x rpm) divided by 12

71
Q

What is the MINIMUM centre of a drive and driven pulley?

A

The diameter of the largest sheave

72
Q

What is the Maximum centre distance of a driven and drive pulley?

A

3 x the sum of both sheaves
OR
5 x the largest diameter

73
Q

What is the max ratio of a V belt?

A

6:1

74
Q

What is the maximum ratio for a cogged or small section belts?

A

7:1

75
Q

Under ideal conditions what is the average belt life?

A

5000-7000 hours

76
Q

Under ideal conditions what is the average life of a sheave?

A

25,000 hours

77
Q

As a rule of thumb how often are belts replaced compared to sheaves?

A

Belts are replaced 4 x to one sheave replacement

78
Q

If there is a larger and smaller sheave under the exact same conditions which one would wear first?

A

The smaller one

79
Q

What is the MINIMUM arc of contact on the smallest (driven) pulley?

A

120 degrees

80
Q

How is proper deflection calculated in a belt?

A

1/64” to every inch between centres

81
Q

If you have a 40 inch centre distance what is the deflection for tensioning?

A

40/64

82
Q

if you excessively tension a belt what will occur?

A

Wear in belt and bearings

83
Q

After tensioning a belt when should you re check it?

A

12-24 hours

84
Q

If you tighten a belt too loose what can occur?

A

Slip
Loss of power
Wear

85
Q

What does it mean if the bottom of a sheaves groove is shinny?

A

Excessive wear needs to be replaced

86
Q

What are the angles available for sheave grooves?

A

34-42 degrees

87
Q

How much wear requires a sheave to be changed?

A

1/32 of an inch

88
Q

What is the formula for calculating belt length between two pulleys?

A

[ Diameter (a) + diameter (b) ] x 3.14 +(2 x shaft centres)

89
Q

If a smaller pulley is slipping what can you do?

A

Change to a smaller ratio ( 3:1 or 4:1)

90
Q

What are the 3 constructions of a sheave?

A

Block
Webbed
Arm

91
Q

What do notched belts provide compared to regular V or flat belts? (2)

A

Flexibility
Cooling

92
Q

I’m wide V belts what do the ribs also provide?

A

Reinforcement

93
Q

What is important when installing matched belts

A

That they are ALL new and ALL match

94
Q

How much slippage is normal with V belts?

A

5%

95
Q

How does the rigidity of a belt affect creep?

A

The more rigid the less creep

96
Q

What is the typical angle of a V belt?

A

40 degrees

97
Q

Where should you IDEALLY align sheaves?

A

From the inner edge

98
Q

How should a V belt fit into a sheave?

A

Flush or a bit above the top, not touching the bottom

99
Q

How are classic V belt lengths measured?

A

At the inside diameter

100
Q

What does a V belt depend on to develop the proper friction?

A

The sides of the belt to grip the sides of the sheave

101
Q

What type of belt is best when timing is important?

A

Toothed belt

102
Q

What is an advantage of a friction belt drive over chain drives?

A

Belts are cheaper and require less maintenance

103
Q

Which section of a V belt protects the belt from rust, weather, and harmful chemicals?

A

Cover

104
Q

What is the most likely cause if a belt is slipping only under heavy load?

A

Not enough tension on belt

105
Q

What 3 factors does a V belt depend on for grip?

A

Area of contact
Tension
Material of belt and pulley

106
Q

Why is perforated or expanded metal popular in the fabrication of guards on a V belt drive?

A

To allow air circulation

107
Q

What is the reason for a crowned pulley?

A

To centre the belt on a sheave

108
Q

One of the purpose of an idler pulley is to ______________

A

Act as a belt take up adjustment

109
Q

What is the typical crown on a 12 inch wide pulley?

A

1/8 inch

110
Q

A standard or multiple belt series is also called ____________

A

Classical

111
Q

A Belt coded 3L200 is what type of belt?

A

Fractional HP

112
Q

What is an advantage of the cogged belt?

A

More flexible and provide better heat dissipation

113
Q

A belt that is coded 3L200 is how many inches wide?

A

3/8

114
Q

A belt having the code designation of 5V380 is how many inches wide?

A

5/8

115
Q

A V belt has a centre distance of 96 inches, how much deflection must be in the belt?

A

1.5 inches

116
Q

Which part of the V belt takes the load from one pulley to the other?

A

The tensile member

117
Q

What is the minimal amount of arc contact for friction belt drives?

A

120 degrees

118
Q

A new belt should be run how long before it is re tensioned?

A

12-24 hours

119
Q

When will a double able V belt be used?

A

Sheaves are to be driven by the top and bottom of the belt

120
Q

What belt has more tensile capacity in a given width?

A

Narrow V belt

121
Q

Why would we use mechanical flat belt connectors?

A

Fast and cheap

122
Q

What is the minimal amount of arc contact for a positive belt drive

A

60 degrees or 6 teeth

123
Q

What is a main advantage of using V belts over chains?

A

Dampens vibrations

124
Q

Where is the pitch line located in a power transmission belt?

A

Through the tensile members

125
Q

What is the advantage of a vulcanized flat belt?

A

Gives the strongest joint

126
Q

Variable speed drives typically use what belt?

A

Wide V belt

127
Q

What type of belt is a 240L100

A

Positive drive type belt

128
Q

What type of belt is a 650L4

A

Poly V belt

129
Q

What is the most tolerant belt for misalignment?

A

Standard V belts

130
Q

Why are standard V belts the best for misalignment?

A

Least loaded

131
Q

What type of belt is a 3V450

A

High capacity

132
Q

What is the ideal surface speed to run a V belt for optimal power transfer?

A

4500sfpm

133
Q

How long is a rubber V belt in storage good for?

A

8 years and then it’s service life is expected to reduce

134
Q

What type of belt is a 800-8M-30

A

Metric positive drive belt

135
Q

How often should you re tension positive drive belts in service?

A

Only if noticeable slack, backlash, or ratcheting occurs

136
Q

Why are we banding multiple series belt drive belts together?

A

Keeps them all at the same speed and wear rate

This also increases the strength and torque capacity of the belt

137
Q

Where can a belt labeled A20(4L220) be used?

A

As a 20 inch standard or a 22 inch fractional hp belt

138
Q

How do you get the correct deflection when you tension a belt?

A

Consult a chart for what pressure to apply to a belt and proper calculated deflection

139
Q

How should a V belt properly fit into a sheave?

A

Almost flush or above the top not touching the bottom

140
Q

How are classic V belts lengths measured?

A

At the inside diameter

141
Q

A standard or multiple belt series is also called what?

A

Classical

142
Q

A belt that is coded 3L200 is how many inches wide?

A

3/8

143
Q

What belt has the most tensile capacity in a given width

A

Narrow V belt

144
Q

What type of belt is a 800-8M-30

A

Positive drive type belt

145
Q

Why are we banding multiple series belt drive belts together?

A

This keeps them all the same speed and wear rate

146
Q

Besides keeping fingers out why is perforated sheet metal popular in fabrication of belt guards?

A

To keep them cooler

147
Q

Variable speed drives typically use what belt?

A

Wide V belt

148
Q

What type of belt is a 240L100

A

Positive drive type belt

149
Q

What type of belt is a 650L4

A

Poly V belt

150
Q

A 3V450 is what type of belt?

A

High capacity

151
Q

Where can a belt labeled A20(4L220) be used?

A

As a 20 inch standard or 22 inch fractional hp belt

152
Q

How do you get the correct deflection when you tension a belt?

A

Consult chart for pressure value to apply until proper deflection achieved

Millwright Block 2 (harmonized) NS (17 decks)

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