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Second Year Millwright > Belts And Chains > Flashcards

Belts And Chains Flashcards

0
Q

What are the limitations of v belts

A

Most designs operate with fixed center distance only, they have a minimum 120. ° arc of contact, they are unsuitable for positive drive requirements such as timing

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1
Q

What are the advantages of v belts?

A

They are cost-effective, there are highly reliable, no lubrication is required, they absorbs shock, they are quiet, and they can slip on overload to protect other components

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2
Q

What is the name of the part of the V-belt that carries the load?

A

The tensile members

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3
Q

How does the V-belt transmit power?

A

Friction between the sides of the belt and the sides of the sheave groove, the tensile members from the driver to the driven pulley

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4
Q

What things determine the amount of power that A belt can transmit?

A

The strength of the tensile members, the grip of the belt on the pulley

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5
Q

What is the minimum area of contact for a v belt?

A

120°

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6
Q

What is the pitch line?

A

The pitch line runs through the load carrying zone of the belt with the tensile members are located

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7
Q

What is belt creep?

A

Creep means 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

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8
Q

What is belt slip?

A

When you have increased the load sufficiently the arc of creep extends all the way around the pulley and slip occurs

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9
Q

What problems does slip produce?

A

Power loss between the driver and driven pulleys, increase in belt and sheave groove wear, extra heat which degrades the belt material, the vibration transmitted to the bearings and seals results in a short life for the belts components.

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10
Q

What three things affect the grip between the belt in the pulley?

A

The coefficient of friction and, the arc of contact, the tension of the belt.

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11
Q

Where must a vbelt never touch?

A

The v belt should never touch the bottom of the groove in the shiv

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12
Q

What is the designation for a classical series of vbelts?

A

A,B,C,D, or E

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13
Q

What are the features of a classical series of v belt?

A

They have the highest tolerance for poor operating conditions, the most reliability where maintenance is infrequent, the most reliability for unusual drives such as Reverse bend, clutching, and quarter turn, and the whitest choice of belt and sheave sizes

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14
Q

What is the designation for a cog raw edge belt?

A

AX, BX, CX

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15
Q

What is the designation for a fractional horsepower belt?

A

2L,3L, 4L, 5L

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16
Q

What are the advantages of a called raw edge belt

A

They have greater flexibility and enhanced airflow which results in cooler operation. The cogs allow the belt to bend around sheaves with the smaller radius. The raw edges have no covers on the sides and bottom. Raw edge belts fit the sheaves more accurately than wrapped belts.

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17
Q

What are some limitations of cogged raw edge belts

A

They cannot be subjected to reverse bending, and they cannot be used on clutching drives, shock loads, or drives with changing center distances

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18
Q

What is another name for a banded belt?

A

Joined classical belts

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19
Q

How are banded belts constructed?

A

They are constructed by joining two or more standard belts with a common backing

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20
Q

What issues are solved by using a banded belt?

A

Belt vibration, whip, and turnover

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21
Q

How is alignment affected when using a banded belt?

A

Alignment is critical because these belts have less ability to flex sideways than individual belts

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22
Q

What is another name for a double v belt?

A

Hexagonal belts

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23
Q

What is the designation for double v belt?

A

AA, BB, CC

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24
Q

What type of drive our fractional horsepower belts used for?

A

Generally used for drives of less than 1 HP

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25
Q

What are fractional horsepower belts good for?

A

They are good for high speed

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26
Q

What is another name for a high capacity belt?

A

Narrow vbelts

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27
Q

Describe a high capacity vbelt

A

They are narrower and therefore have a larger area of contact on the sheave. They provide more support for the tensile members than classical v belts

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28
Q

What are the advantages of a high capacity v belt?

A

They are compact, which allows for use of a smaller diameter sheave, they have a higher power capacity than classical belts

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29
Q

What are some disadvantages of high capacity vbelts?

A

They require higher tension, therefore higher bearing loads, the higher side wall loading accelerates sheave wear in dirty or abrasive environments

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30
Q

What is the widths in a 3V, 5V. And 8V high capacity belt?

A

3/8”, 5/8”, and 1”

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31
Q

What is another name for a poly v belt?

A

Micro b

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32
Q

What is the designation for poly v belts?

A

J, K, L, M. H is also available for small sheaves and micro drives

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33
Q

What are some advantages of poly v belts?

A

They perform well on small diameter sheaves, ideal for high speed ratios, they can be used for reverse bends on serpentine belts, compact

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34
Q

What are the disadvantages of poly v belts?

A

They require special sheaves, high tension, and the alignment is more critical than for poly v belts

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35
Q

What are variable speed belts?

A

They run in sheaves with specially designed sides called flanges

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36
Q

Which variable speed setup has a changing center distance?

A

The single variable sheave. One flange is mechanically moved apart to permanently change the speed

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37
Q

Describe this code for a variable speed belt.

12 28 V 255

A

Top width is 12/16(3/4), 28 is the groove angle, cross section is a v shape, and the pitch length is 25.5”

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38
Q

When can you adjust a variable speed drive?

A

You can only adjust the speed while the drive is running never when it is not turning

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39
Q

What is the use of open ended belting?

A

It is used as emergency replacements on the exact length of endless belt is not available.

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40
Q

What is the load capacity of a open ended belt?

A

They can only carry about one third of the loan of the corresponding endless belt.

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41
Q

What is a link belt, and what is it good for?

A

It can be used in situations where it is difficult or impossible to install an endless belt. It can also be used as an emergency replacement for an endless belt. It has the same power rating as a classic v belt from the same cross-section

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42
Q

What are some limitations of link belts?

A

They generate more vibration and endless belts, they cannot be used with back idlers, and they cannot be used with endless belts

43
Q

Describe round belts

A

They have a round cross section, and multiple layers of tensile members through the center.

44
Q

What are round belts generally used for?

A

They’re suitable for quarter turn drives, serpentine drives, and are used for light duty fractional horsepower applications

45
Q

What are the two ways to tell if a sheave is worn?

A

Use a sheave groove guard, or try a new belt in the sheave groove

46
Q

What should you always do before installing a new belt?

A

Always back off the tension before you install it. Do not force any belt on to a sheave or pulley with a prybar or screwdriver

47
Q

Why should you not use an impact wrench for tightening bolts?

A

She runs much straighter if the hub bolts are tight and evenly and alternately by hand

48
Q

What is the purpose of idler pulley’s?

A

The main reason is to increase the arc of contact. Increasing belt tension and preventing belt whip are two other reasons

49
Q

Where can you not use idlers?

A

On reversing drives

50
Q

What size and what location should be idler pulley be used

A

It should be at least 1.5 times the diameter of the smaller pulley and positioned as close as possible to the smaller sheave

51
Q

What is another name for a contact idler

A

Kiss idler

52
Q

When should you recheck tension of a belt after installation?

A

After 24 to 48 hours of operation

53
Q

What is the maximum speed of a quarter turn drive?

A

2.5:1

54
Q

How much is the horsepower rating De-rated in the quarter turn drive

A

It is De-rated by 90% of the normal rating

55
Q

What does belt dressing do to a belt?

A

It degrades a belt material and shortens the belt life however it can be used in an emergency situation to avoid a machine outage at a critical time

56
Q

What does belt whip mean?

A

It usually means that you should try increasing the tension of the belt. It can also mean that a belt is overloaded

57
Q

At what temperature should you consider a belt that is heat treated?

A

Belts that reveal a temperature over 60°C

58
Q

How should belts be stored?

A

They should be protected from moisture and temperature extremes, stored in their original package and out of direct sunlight, do not bend the belt or hang it on anything with the diameter of less than the smallest recommended pulley

59
Q

What is a synchronous belt also called?

A

Timing belt, or positive drive belt

60
Q

What are advantages of a synchronous belt drive?

A
  • they last 3X as long as chain drive
  • less tension than classic belt
  • require no retensioning
  • no lubrication
  • wide speed range
  • virtually maintenance free
61
Q

What are the disadvantages of a synchronous belt drive

A

They are more expensive than classic v belts, they do not provide overload protection by slipping, they require more accurate alignment then b belts

62
Q

What are the tensile members made from in the synchronous belt?

A

They are twisted from fiberglass cords and sometimes aramid fiber is used

63
Q

What is the arc of contact for a synchronous belt?

A

It must be a minimum angle of 60° or a minimum of six teeth engaged

64
Q

Name some types of synchronous belts

A

Trapezoidal teeth, rounded tooth profile, twin tooth belt, helical offset tooth

65
Q

What is another name for a twin toothed belt

A

A serpentine belt

66
Q

Which belt is the highest power rating and the lowest noise rating in their belt line?

A

The helical offset to the design. It is also known as the Goodyear Eagle belt

67
Q

225 L 075 belt. What does it indicate?

A

Pitch length 22.5”
Tooth pitch L
Width 0.75” or 3/4”

68
Q

How much tension needs to be applied to a synchronous belt?

A

It requires just enough tension to remove any slack from the unloaded span

69
Q

When do synchronous belts need to be retensioned?

A

Because the fiberglass 10 sound members do not stretch you never need to re-tension it

70
Q

What must at least one sprocket have on it in a synchronous drive?

A

Flanges to guide the belt

71
Q

What are the three types of hubs?

A

QD hub, taper bushing hub, taper lock hub

72
Q

When you mount the hub with a keyless taper, how much contact area do you need between the tapered surfaces?

A

At least 85%

73
Q

What kind of drive is a chain considered?

A

Positive drive

74
Q

How efficient are chains?

A

98% or better

75
Q

What are the three types of chains?

A

Roller chain silent chain and leaf chain

76
Q

What are the two types of fits on master links?

A

Slip fit or pressfit. Slip fit reduces strength by 30%

77
Q

What is different about heavy duty chain?

A

It has thicker sidebars to increase its resistance to fatigue, but does not have a higher load capacity

78
Q

What are the two types of pre-lubricated chains

A

Sintered bushing, and O-ring chain

79
Q

How are roller list chains designated?

A

There is a number five on the right-hand part of the chain number

80
Q

What is another name for silent chain

A

Timing chain

81
Q

What is another name for a serpentine drive chain?

A

Duplex

82
Q

What must the straight edge touch when aligning sprockets?

A

Must touch at all four points of contact

83
Q

How much sag is acceptable in slow to medium, and high speed drives.

A

Slow to medium drives is 4-6% on the non tensioned side and 2-3% on a higher speed drive

84
Q

When should a chain be inspected for sag, after installation

A

After 8 hours of operation

85
Q

What is the most important factor in controlling a chains wear?

A

Proper lubrication

86
Q

Where should oil be put on a chain?

A

Between the plates on the unloaded side

87
Q

What are the three methods of chain lubrication?

A

Manual or drip feed (low speed), bath lubrication (600-1500 fpm), forced lubrication (above 1500 fpm or heavily loaded drives)

88
Q

When should a chain be replaced?

A

When it is elongated by 3% or more

89
Q

What are the specs on these 2 chains?

70
25

A
  1. =7/8 pitch roller chain

25 = 2/8 pitch roller less chain

90
Q

What must be specified when ordering a new sprocket?

A

Chain pitch, number of strands, hub style

91
Q

What is recommended chain wrap angle?

A

120° however it can go as low as 90° can carry the full design load if proper chain tension is closely maintain

92
Q

What are two ways to improve the wrap angle?

A

Increase the center distance, use a jack shaft to obtain the final ratio

93
Q

What is a sprocket with an odd number of teeth

A

Hunting tooth sprocket

94
Q

What are the three types of hub style sprockets?

A

Type A-mounts on any type of hub large hole
Type B- hub one one side,
Type C- hubs on both side for support
Type D- split design. Allows you to replace sprocket without removing bearings

95
Q

What are the attachments available for type a B and C sprockets?

A

Shear pin hubs, tapered for hubs, street for hubs, and keyless adapter also known as ring fetter

96
Q

What does a Pratt and Whitney key look like?

A

An oval. It’s like a square key with the corners rounded

97
Q

What is the taper on a gib head key.

A

1/8” taper per foot

98
Q

How is a woodruff key identified?

A

The first 2 numbers is width in 1/32” and second two is diameter in 1/8”

99
Q

How is a QD hub recognizable?

A

They have an axial split through the barrel to the flange

100
Q

What should key clearance not exceed?

A

.002-.005”

101
Q

What is rule of thumb for key width??

A

1/4 the diameter of shaft

102
Q

When should a gib head key not be used?

A

On a cast iron hub, as it could crack

103
Q

When should you use a chamfered key and seat?

A

Large keys, high horsepower. Heavy shock loads

104
Q

What are two types of links on a roller chain?

A

Roller link, pin link

105
Q

Double strand chain is approx how much stronger than a single strand?

A

1.7 times

Second Year Millwright (8 decks)

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