Tháo dời, thay thế và lắp ráp các thành phần cơ khí của ô tô (disassemble replace assemble engineering components)

Skills Tech Australia
School of Engineering Technology
Fitting and Machining

Student Resource Book
MEM18055
Disassemble replace assemble engineering components

MEM18006
Disassemble Repair Replace Assemble Fit Replace Assemble Engineering Components

Student Name:

.


Contents
Section 1: Power Transmission Systems .........................................5
Flexible Belt Drives ............................................................................................................................................ 5
Key factors enabling belt drives to transmit power....................................................................................................... 5
Advantages of belt drives (compared with chains) ....................................................................................................... 5
Disadvantages of belt drives (compared with chains)................................................................................................... 5
Types of belts................................................................................................................................................................ 5
Flat Belts ....................................................................................................................................................................... 6
V-Belts .......................................................................................................................................................................... 6
Timing belts ................................................................................................................................................................ 10
Pulleys or Sheaves .......................................................................................................................................... 12
Types of Pulleys.......................................................................................................................................................... 12
Pulley Faults................................................................................................................................................................ 12
Pulley alignment ......................................................................................................................................................... 13
Belt adjustment ........................................................................................................................................................... 14

Belt maintenance......................................................................................................................................................... 15
Variable speed drives .................................................................................................................................................. 15
Summary of Belt Drives ............................................................................................................................................. 16
Chain Drives .................................................................................................................................................... 17
Chains ......................................................................................................................................................................... 17
Advantages of chains (compared to belts) .................................................................................................................. 17
Disadvantages of chains (compared to belts) .............................................................................................................. 17
Uses of chain drives .................................................................................................................................................... 17
Types of chains used in chain drives........................................................................................................................... 17
Chain Classification .................................................................................................................................................... 20
Chain Drive Maintenance ........................................................................................................................................... 21
Sprocket Alignment .................................................................................................................................................... 24
Installing and Removing Chains ................................................................................................................................. 25
Chain Wear ................................................................................................................................................................. 26
Sprocket Wear............................................................................................................................................................. 27
Hunting Tooth Sprockets ............................................................................................................................................ 28
Troubleshooting Chain Drive Systems ....................................................................................................................... 28
Shaft Couplings ............................................................................................................................................... 28
Principles of Operation ............................................................................................................................................... 28
Types of Coupling....................................................................................................................................................... 30
Maintenance Practices................................................................................................................................................. 32
Failure Patterns of Couplings...................................................................................................................................... 33
Shaft Alignment .......................................................................................................................................................... 34
Principles of Alignment .............................................................................................................................................. 35
Methods of Alignment ................................................................................................................................................ 37
Review Questions – Section 1......................................................................................................................... 45

Section 2: Fastening and Locking Devices.....................................46
Types of Fasteners .......................................................................................................................................... 46
Bolts and Nuts ................................................................................................................................................. 50

Thread Form................................................................................................................................................................ 50
Tensile Strength .......................................................................................................................................................... 51
Bolt Identification ....................................................................................................................................................... 53
Nuts............................................................................................................................................................................. 53
Problems encountered when fastening nuts and bolts:................................................................................................ 54
Machine, Set and Cap screws...................................................................................................................................... 55
Screws ............................................................................................................................................................. 56
Self-tapping and Drive Screws.................................................................................................................................... 56
Locking Devices............................................................................................................................................... 60
Lock wire .................................................................................................................................................................... 60
Liquid Locking Materials (Anaerobic resins) ............................................................................................................. 61


Pins.............................................................................................................................................................................. 62
Retaining Rings and Circlips ..................................................................................................................................... 64
Washers....................................................................................................................................................................... 65
Rivets .......................................................................................................................................................................... 65
Review Questions – Section 2......................................................................................................................... 67

Section 3 – Plain & Anti-friction Bearings .......................................68
Overview of Bearings ................................................................................................................................................. 68
Purpose of Bearings .................................................................................................................................................... 68
Principle Classes of Bearings...................................................................................................................................... 68
Types of Loads that can be applied to Bearings.......................................................................................................... 68
Design of Bearings...................................................................................................................................................... 69
Bearing Material Requirements .................................................................................................................................. 70
Specific qualities of bearing materials ........................................................................................................................ 70
Bearing materials ........................................................................................................................................................ 71
Bearing materials – suited to heavy loading. .............................................................................................................. 71
Lubrication of Heavy Duty Bearings. ......................................................................................................................... 71

Friction ............................................................................................................................................................. 73
Nature of Friction........................................................................................................................................................ 73
Factors affecting friction............................................................................................................................................. 74
Plain Bearings.................................................................................................................................................. 75
Sliding Contact Bearings ............................................................................................................................................ 75
Bushes......................................................................................................................................................................... 75
Types of Plain Bearings .............................................................................................................................................. 76
Installation of Bushes.................................................................................................................................................. 77
Removal of Bushes ..................................................................................................................................................... 77
Anti-friction bearings ........................................................................................................................................ 78
Bearing designations ................................................................................................................................................... 79
Parts of an anti-friction bearing................................................................................................................................... 81
Types of anti-friction bearing...................................................................................................................................... 82
Fitting anti-friction bearings ............................................................................................................................. 88
Inspection of bearing journals and housing bores ....................................................................................................... 90
Installation Methods - Force fitting............................................................................................................................. 93
Installation Methods - Shrink fitting ........................................................................................................................... 96
Installation Methods - Freeze fitting ........................................................................................................................... 98
Advantages and Disadvantages of Shrink and Freezing Methods .............................................................................. 98
Other installation methods .......................................................................................................................................... 99
Setting of bearings – Preloading and Endplay .......................................................................................................... 101
Methods of measuring preload.................................................................................................................................. 102
Preloading of duplex bearings................................................................................................................................... 104
Removal of Bearings ..................................................................................................................................... 105
Do’s and Don’ts when working with bearings?.............................................................................................. 108
Review Questions – Section 3....................................................................................................................... 109

Section 4: Lubrication ...................................................................112
Lubrication in General.................................................................................................................................... 112
Fluid Lubrication: ..................................................................................................................................................... 112

Types of Lubricants ....................................................................................................................................... 113
Oils............................................................................................................................................................................ 113
Greases ......................................................................................................................................................... 113
Types of Greases....................................................................................................................................................... 114
Lubrication delivery systems ......................................................................................................................... 115
Oil-Bath Lubrication ................................................................................................................................................. 115
Wick-Feed Lubrication ............................................................................................................................................. 116
Drip-Feed Lubrication............................................................................................................................................... 116
Oil-Splash Lubrication.............................................................................................................................................. 116
Circulating-Oil Lubrication....................................................................................................................................... 117

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Oil-Jet Lubrication .................................................................................................................................................... 117
Oil-Mist Lubrication ................................................................................................................................................. 117
Pressure and Pressure Spray...................................................................................................................................... 118
Grease Lubrication.................................................................................................................................................... 118
Grease packing of Bearings ...................................................................................................................................... 118
Lubricant selection......................................................................................................................................... 119
Viscosity ................................................................................................................................................................... 119
Viscosity Index ......................................................................................................................................................... 119
Pour Point.................................................................................................................................................................. 119
Lubricant additives......................................................................................................................................... 121
Review Questions – Section 4....................................................................................................................... 122

Section 5: Sealing Mechanisms ...................................................123
Introduction .................................................................................................................................................... 123
Static sealing mechanisms ............................................................................................................................ 124
Types of static seals .................................................................................................................................................. 124

Gaskets...................................................................................................................................................................... 124
Desirable characteristics of gaskets........................................................................................................................... 125
Gasket materials........................................................................................................................................................ 125
Metallic Gasket Designs ........................................................................................................................................... 126
Metallic O-rings ........................................................................................................................................................ 128
Working with Gaskets............................................................................................................................................... 129
Sealing compounds with gaskets .............................................................................................................................. 132
Gasket failures .......................................................................................................................................................... 132
Static sealing with O-rings ........................................................................................................................................ 134
Sealants ..................................................................................................................................................................... 135
Dynamic sealing mechanisms ....................................................................................................................... 136
Dynamic O-rings....................................................................................................................................................... 136
Radial Lip Dynamic Seals......................................................................................................................................... 137
Exclusion Type Dynamic Seals ................................................................................................................................ 141
Clearance Type Dynamic Seals ................................................................................................................................ 144
Compression Packing Type Dynamic Seals.............................................................................................................. 146
Molded Packing Type Dynamic Seals ...................................................................................................................... 147
Face Type Dynamic Seals......................................................................................................................................... 149
Diaphragm Type DynamicSeals ............................................................................................................................... 151
Diaphragm Type DynamicSeals ............................................................................................................................... 152
Review Questions – Section 5....................................................................................................................... 154

Section 6: Gearing Systems ........................................................156
Definitions................................................................................................................................................................. 156
Types of Gears .......................................................................................................................................................... 162
Enclosed Gear Systems - Fixed Ratios ..................................................................................................................... 166
Enclosed Gear Systems – Selectable Ratios.............................................................................................................. 172
Gearbox Installation.................................................................................................................................................. 176
Maintaining and Rebuilding a Gearbox .................................................................................................................... 176
Review Questions – Section 6....................................................................................................................... 178

Section 7: Pumps ........................................................................180
Introduction............................................................................................................................................................... 180
Centrifugal Pumps .................................................................................................................................................... 181
Concepts For Centrifugal Pumps .............................................................................................................................. 184
Trouble shooting a pump .......................................................................................................................................... 189
Preventative maintenance.......................................................................................................................................... 190
Other types of pumps .................................................................................................................................... 197
Review Questions – Section 7....................................................................................................................... 200

Section 8: Maintaining Mechanical Equipment.............................202
Introduction: ................................................................................................................................................... 202

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Methods of Performing the Maintenance Function........................................................................................ 202
Prevention of Breakdown: ........................................................................................................................................ 203
Evaluating Mechanical System Problems: ................................................................................................................ 205
System Disassembly ..................................................................................................................................... 208
Disassembly Procedures ........................................................................................................................................... 208
Examples of Specialised Tools ................................................................................................................................. 209
System Reassembly ...................................................................................................................................... 211
Tasks for System Reassembly................................................................................................................................... 211
Review Questions – Section 8....................................................................................................................... 214

Section 9: Repairing Mechanical Components.............................215
Mechanical Component Failure..................................................................................................................... 215
Types of Failure ........................................................................................................................................................ 215
Modification of Components .......................................................................................................................... 215

Repairing Mechanical Components............................................................................................................... 216
Keyway Damage ....................................................................................................................................................... 216
Seal Damage ............................................................................................................................................................. 217
Bearing Location Damage - Shaft............................................................................................................................ 217
Bearing Location Damage - Housing....................................................................................................................... 218
Shaft Centre Damage ................................................................................................................................................ 219
Shaft Sealing Surface Damage.................................................................................................................................. 219
Damage to end of an otherwise serviceable Shaft..................................................................................................... 219
Broken gear teeth ...................................................................................................................................................... 220
Broken casting .......................................................................................................................................................... 220
Cracks in casting ....................................................................................................................................................... 221
Broken bolts or studs................................................................................................................................................. 221
Broken taps ............................................................................................................................................................... 222
Damaged threaded holes ........................................................................................................................................... 222

Section 10: Risk Assessment .......................................................224
Hazard Identification, Risk Assessment And Control Procedure.............................................................................. 224

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Section 1: Power Transmission
Systems
Flexible Belt Drives

Key factors enabling belt drives to transmit power
Flexible Belt drives transmit power by contact between the belt and the driving and driven pulleys by
friction. The design of belt drives is usually arranged to enable the transmission of power between two
parallel shafts. The ability of belts to transmit power depends on:
1. The tension holding the belt to the pulleys

2. The friction between the belt and pulleys
3. The arc of contact or “wrap” of the belt on the pulleys
4. The speed of the belt

Advantages of belt drives (compared with chains)
1. Do not require lubrication
2. Generally operate with less noise
3. Flat belt drives can be used where extremely long centre distances make chain drives
impractical.
4. Flat belts are advantageous for extremely high speeds
5. Single belt drives will accept more misalignment than chain drives
6. Many belt drives are less expensive for low power and lower ratio applications

Disadvantages of belt drives (compared with chains)
1. Belts are more easily damaged by oil, grease and heat
2. Belts cannot be used where exact timing or speed is required (Unless a special toothed belt is
used)
3. Belts are not suitable for very high load, low speed applications

Types of belts
There are six major types of belts used in modern heavy machinery.
1.

Flat belts

4.

Linked V-belt

5

2.
3.

V-belts
Banded V-belts

5.
6.

Timing belt
Ribbed V-belt

Flat Belts
Use of flat belts has decreased because most machines today have gear drives or use V-belts. A
common use is where high power is needed to drive a separate machine eg. Agricultural tractor
auxiliary drive to a saw bench, irrigation pumps etc. In this example where high speed is required, the
pulley has a crown in the centre to keep the belt from slipping off. Ref. Fig 1(b).

A more common use of flat belts is as a conveyor (medium speed) where the belt itself does the work
eg. Combine harvester grain conveyor, trencher soil conveyor. Ref. Fig 1(a).
Flat belts are usually made from fabric or cord impregnated with natural or synthetic rubber. Ref. Fig
1(a). Some types use cotton or synthetic fibre fabric without rubber impregnation.
Disadvantages of flat belts:
1.
They need larger pulleys and so take up more space
2.
They are also less flexible than some other belts.
Advantages of flat belts:

1.
Simplicity of operation
2.
Strength – larger cross section, often reinforced
3.
Low initial cost
Resistance to extreme dust.

V-Belts
V-belts are the most common way of driving loads between short-range pulleys. Their uses in heavy
equipment apply to water pump, generator/alternator, fan and accessory drives on engines, as a
transmission on smaller machines, and in combine harvesters, industrial sweepers, etc. They may be
used in single or multiple belt drives.
They have power ratings from fractions of a kW for the smaller belts, up to 35-40 kW per belt for the
larger belts.
The simple wedging action of the belt against the sides of the pulley groove is the outstanding feature
of V-belts. A greater pull or load merely results in a tighter belt grip. “Pulleys” used with V-belt
drives are often called “sheaves”. Either term is correct.

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Disadvantages of V-belt drives compared to flat belt drives:
The only disadvantage with V-belts and V-pulleys is that they cost more than flat belts and pulleys.
Advantages of V-belts drives compared to flat belt drives:
1.
Wedging action permits a shorter arc of contact on small pulleys and hence greater speed
ratios.
2.
Shorter centre distances can be used for a compact drive and use of streamlined belt guards.

3.
Absorb shocks to cushion motors and bearings against load fluctuations.
4.
Vibration and noise levels are low.
5.
Maintenance and replacements are quick and easy.
6.
Power transmission efficiency is as high as 95%.

V-belt Construction
V-belts are made in several types (Fig. 2), but each one is made up of four sections.
1.
2.
3.
4.

The top section of the belt is known as the tension section. (Fig. 2). It is rubber and stretches
as the belt forms around the sheave.
The bottom section is called the compression section because it compresses when wedged into
and shaped around the sheave. (Fig. 2).
The centre section is known as the strength section. These cords give the belt its tensile
strength. (Fig. 2).
The complete belt is covered by a cover section of tough fabric and rubber that protects the
inner parts. Some belts (called “raw edge”) have no fabric cover.
Note that the heavy-duty belt has more strength cords and a heavier fabric cover than the
standard-duty type.

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Double-angle V-belts are used for drives where both the top and the bottom of the belt must contact the
sheaves as in a serpentine drive. The strength cords are in the centre. Tension or compression forces
exist on either side of the strength cords while the belt bends either way.
Some V-belts also have corrugated under sides for greater flexibility.

Operation of V-belt
drives
Due to the wedging action
of their angled sides, V
belts pull well even when
wet. The section going
around a pulley tends to
bulge as it bends, hugging
the flanges tightly. See
Fig. 3.
The angle between
standard belt sides is 40
degrees. The angle
between the two sides of
the pulley groove is
somewhat less to ensure
full wedging contact.
The groove is much deeper
than the belt, for a standard
V-belt must never ride the bottom of the groove. If it does, it loses almost all grip, no
matter how tight.

Banded V-belts
Banded V-belts are multiple belts, which
have been permanently vulcanised to a tie

band. See Fig. 4. This reduces problems on
drives where belts may whip, turn over or
jump off. Other than the tie band they are the
same as
conventional V-belts.
Fig. 4

Construction of a banded V-Belt

8


Linked V-belts
Link type V-belts simplify assembly of multiple belt drives
where it would be difficult to match the length of each belt or
where replacement of a standard belt would be very
troublesome. Links can be added or removed to lengthen or
shorten the belt. See Fig. 5.
The flexible links are laminated to tough fabric and rubber and
are held together by metal studs secured with washers. The
links are shaped so that the sides of the complete belt fit a
standard sheave groove.

Fig. 5

Linked V-Belt

V-Ribbed Belts
V-ribbed belts combine the simplicity of the flat belt with the
positive tracking of V-belts. They eliminate the matching problem

in multi-V-belts, although the pulleys must be grooved to mate
precisely with the belt. The pulleys must also be precisely aligned.
V-ribbed belts are made of moulded rubber. A ply of strength
cords run along the “flat” section of the belt. See Fig. 7. Most of
these belts are oil and heat resistant.
Unlike V-belts, which depend on wedging action to transmit
power, V-ribbed belts depend entirely on friction between pulley
and belt. Tension is somewhat greater than for conventional Vbelts. These belts are suitable for very high speeds with power
ratings up to 7.5kW (10 H.P.).

V-belt sizes and selection
There are many different types and sizes of V-belts used in heavy equipment. We will look at
common sizes for standard V-belts that are shown in Figure 8. They range from 10mm wide
up to 32mm wide.

9


Figure 8

When ordering replacement V-belts, it is important to select the correct size, length and duty. The Vbelt must sit in the pulley groove as shown in fig. 9. If the V-belt is too large or too small a section, it
will not give adequate grip, and start slipping as a result.

When checking the length of the old belt, remember that used belts always stretch, so make allowance
for it. If the old belt was the right part you may be able to find the part number still on it. This will
save problems when ordering the new belt.
After the right section size and length has been found it is important to select the right duty belt. Light
duty belts will not stand up to the temperatures and loads of the heavy-duty belts used in heavy
equipment.
Never buy a belt so tight that is has to be pried hard over the pulleys as this may break the pulling cords

inside.

Timing belts

10


Timing belts combine chain and sprocket action with the simplicity of flat belts. They are essentially
flat belts with teeth, equally spaced on the surface, in contact with a toothed pulley.
Continuous, helically wound steel cables are embedded in the belt as the
load-carrying element. See Fig. 6. Neoprene backing and teeth are
bonded to the steel cables to provide shear resistance and protection from
dust, oil and moisture.
Like gear and chain drives, those belts require precise alignment of
pulleys and must be made endless. They are used for high power compact
drives and also where accurate timing between two drives is required.
Advantages of timing belts:
1.
No slippage or speed variation.
2.
Little maintenance is required.
3.
Wide range of load and speed up to 45kW (60 H.P.)
4.
Lowest bearing loads of any belt drive because of positive tooth action.
5.
Compact because of small pulleys, short centres, narrow belts and high capacity.
6.
Good mechanical efficiency because of low friction reduced initial tension, and thin
construction.

7.
High power to weight ratio.
8.
No lubrication required.
There are no significant disadvantages with timing belts.

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Pulleys or Sheaves

Types of Pulleys
The pulleys used in heavy equipment are usually made from cast iron, formed steel or aluminium.
Typical examples are shown in Fig. 10.

Pulley Faults
The pulley grooves must be in good condition and the sides must not be ‘dished’ from wear. See Fig.
11. The flanges of the pulley must not be chipped or bent as this will damage the belt.

12


The pulley must sit true on the shaft and not ‘wobble’ when running. Check and repair or replace as
necessary.

Pulley alignment
Misalignment of pulleys is a common cause of short belt life. The driving and driven shafts must be
parallel, and the faces of the pulleys must be in line. If either of these is incorrect, adjustment must be
carried out to rectify the problem.

To check for misalignment use a straight edge along the pulley faces (Fig. 2(b)). The straight edge
should touch the pulleys at the four arrows. Then rotate each pulley and note whether the contact of
either pulley with the straight edge is disturbed. If so, a shaft is bent or a pulley is wobbling.
To do a quick check on pulley alignment, sight along the pulley faces, and any obvious misalignment
will be noticed.

13


Belt adjustment
If the belt tension is too slack it will cause slippage and wear the belt prematurely. Too tight an
adjustment causes excessive stretch and overloads the bearings on the pulley shafts.
Belts are usually adjusted in one of three ways, namely:

1.

2.

By moving one pulley away from the other: This method
of adjustment is found on engines where the
generator/alternator or fan pulleys can be moved away
from the driving pulley on the crankshaft. In this and
other examples the method of adjustment is the same.
Move the adjustable pulley until the amount of slack is to
the manufacturer’s specifications. See Fig 13.

By adjusting the two halves of one pulley: This type is used where the centres of both pulleys
can only remain in set locations. The two halves of one pulley can be moved in or out by shim
or screw adjustment. See Fig 14.

Fig. 14 V-Belt tension
adjustment by split pulleys

3.

By adjusting an idler pulley: Simply move the idler pulley in or out until the specified belt
tension is obtained. See Fig 15. Check tension as in Fig 13.

14


Belt maintenance
When one V-belt in a multiple belt drive requires replacing the whole set must be replaced. If not they
will be mismatched with one new belt taking more drive than the remaining older stretched and worn
belts.
Keep an eye out for cracks, splitting, tears etc. and replace if these are evident. Any oil or grease must
be removed immediately otherwise it will cause slippage and rot the rubber.

Variable speed drives
Variable speed is obtained by changing the effective diameter of the driving and driven sheaves during
operation. This is accomplished by moving the two halves of each pulley in or out, as shown by the
pulleys in Fig 16.

15


Let’s assume we start off in low ration (Fig 16). It may be noted that the driving pulley has a small
effective radius while the driven pulley a large effective radius. This will result in a low ratio or under
drive.
As the control lever is moved towards the ‘high’ position it causes an increase in the effective diameter

of the driving pulley. As a result the V-belt increases in tension and pulls itself further into the driven
pulleys, compressing the spring. This results in a reduced effective radius on the driving pulley and the
smaller effective radius on the driven pulley results in a higher ratio.
Continued movement of the control lever towards the ‘high’ position will result in the drive ratio
changing from an under drive (low ratio) through direct drive (1:1) to an overdrive (or high ratio).

Summary of Belt Drives
A Belt Drive System provides a reliable, highly efficient method of transferring power between shafts.
Its build in flexibility even allows for coupling two shafts that rotate in different planes. Timing
between shafts can be achieved by use of toother belts and pulley, and a variable ratio drive can be
obtained by using split expanding pulleys.
Maintenance needs are minimal and are mainly concerned with periodic visual examination for wear,
adjustment to maintain belt tension, cleanliness, and replacing of belts when worn.

16


Chain Drives

Chains
Chain drives are a form of flexible gearing. They are similar to belt drives except they are less flexible
but are able to withstand greater loads. While belts may tend to slip, chains do not. Like belts, chains
are used to transmit drive between two or more parallel shafts.

Advantages of chains (compared to belts)
(a)
(b)
(c)
(d)
(e)

(f)
(g)
(h)

Chain drives do not slip
They maintain synchronisation of shafts
They maintain a positive speed between the two connected shafts
More compact for a given capacity
They can operate at higher temperatures than belts
Superior at low speeds
Chains require less adjustment periods than belts
Chains do not deteriorate due to age, oil, grease or sunlight.

Disadvantages of chains (compared to belts)
(a)
(b)
(c)
(d)

Chain drives are noisy
Chains require frequent lubrication and adjustment
Most chains will accept very little misalignment
Chains cannot normally be used where the drive must slip.

Uses of chain drives
There are three basic uses for chains. These are:
1.
2.
3.

Transmitting power from one rotating shaft to another shaft or shafts.
Converting motion (from rotary to linear, as in a conveyor system or track chains).
Timing or synchronising the rotation or motion of two or more shafts.

Types of chains used in chain drives
Six main types of chains are in general use. These are:
1)
2)
3)

Roller chain
Roller less chain
Silent chain

17


4)
5)
6)

Detachable link chain
Pintle chain
Block chain

Standard Roller Chain
Used for general purposes under moderate to heavy loads. Chain speed should not exceed 23m/s (4500
ft/min).

Roller less Chain

A general-purpose chain used for lower speeds and where chain pitch accuracy is not critical. In
operation there is no rolling action between chain and sprocket so rate of wear is generally higher than
roller type chain.

In operation there is no rolling action between
chain and sprocket so rate of wear is generally
higher than roller type chain.

Figure 2. Roller less chain

Silent Chain
As its name suggests, is designed for quiet operation.
Operating speeds in excess of 23 m/s (4500 ft/min) are
possible with little noise or vibration. This type of chain is
often used as timing chain in engines, especially overhead
camshaft designs. The chain consists of a series of flat metal
links with specially shaped ends that form a series of teeth on
the inner surface. These teeth engage with the teeth of the
sprockets, which in appearance are similar to gearwheels.
The sprocket teeth do not project through the chain so the
effect is like a toothed belt running on toothed
sprockets.

Figure 4. Silent chain engaging
with its sprocket.

18


A disadvantage of silent chain is the requirement of some form of guide flange either on the chain, or

the sprockets, to retain the chain.

Figure 5. silent chain
retaining methods.

Detachable Link Chain
This type of chain is very cheap and simple, suitable for use at low
speeds and light loads.
The links are of medium carbon steel or cast iron and have a hook
at one end and a bar at the other end. The chain can be opened by
unhooking the bar and hook of any adjoining links, this allows for
adjustment of length or replacement of links as required.
This type of chain is often found on agricultural machinery and
some conveyors.
Note: This chain must operate so that the links travel with their
hook ends leading.

Figure 6. Detachable link chain
(arrow shows direction of travel).

Pintel Chain
Is suitable for use at slow speeds where the chain is exposed to abrasive materials and weather. Often
used on conveyor systems.
Cast Malleable Iron Link (one piece).

The chain is made up of malleable iron links with steel pins,
which are prevented from turning in the sidebars, so that hinging
action takes place between the pin and barrel as the chain forms
around the sprocket. Note: This chain should only be used with
one direction of travel.

Figure 7. Pintle Chain (arrow
shows direction of travel).

Block Chain
Consists of a series of cast iron blocks joined with side links; the coupling pins are prevented from
turning in the side links so that hinging action is between the pins and the blocks.

19


This type of chain is used mainly for conveyors and the blocks may be fitted with pusher bars. Used
with special sprockets that have double pitch tooth spacing.

Figure 8. Block Chain.

Chain Classification
A chain is classified by its type, pitch, width and roller diameter.
Pitch: Is the distance between the centres of adjacent rollers or pins of a chain.
Width: Is the distance across the chain between the sidebars or links.
Roller Diameter: Is the diameter of the roller or pivot part of the chain that engages the sprocket
teeth.

Figure 9. Chain classification dimensions

Strand Chain

20


Where necessary to transmit the required torque a chain may have more than one strand as show below.

Figure 10. Duplex roller chain.

Figure 11. Four strand (Quadruplex) roller chain

Chain Drive Maintenance
The arrangement and position of sprockets, chain tensioners and methods of lubrication are carefully
planned to get maximum life from the drive. However, neglect of routine maintenance can cause rapid
wear to chain and sprockets, leading to consequent failure and possible damage to other parts of a
machine. Routine maintenance will normally be concerned with chain tension or lubrications:

Chain Tension
Chain drives must be kept correctly tensioned otherwise rapid wear and/or mis-engagement between
chain and sprocket can occur, causing damage.

Figure 12. Effects of chain tension

Chain Tension Adjusters
These may be classified into two general types as follows:
(a)
(b)

Manually operated adjusters. Used where periodic manual adjustment only is
required.
Automatic adjusters. Used where constant adjustment to take up chain slack due to
chain wear is required.

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Any adjuster system must have sufficient movement to allow for fitting a new chain, and to take up the
maximum chain stretch that can occur in service.

Manual Adjusters
These may consist of a screw thread or a simple hydraulic cylinder used to move one sprocket in
relation to the other.

Figure 13. Chain drive with manual screw tension adjustment

Manual
Tension Adjustment
When adjusting chain tension the drive must be rotated until the position of
minimum slack if found – the stretch in the chain may not be equal over its whole
length, or one or both of the sprockets may not run truly concentric with its shaft!
Place a straight edge over the slack of the chain and pull the chain down. Measure
the amount of slack from the top of the chain to the underside of the straight edge
at the centre of the span between the sprockets.
If necessary, take up the adjustment to allow the recommended amount of slack. If
manufacturers specification is not available, allow a slackness of 2% of the distance between
sprocket centres.

Fig. 14. Measuring chain
tension

Turn the chain drive manually and check the slack at several positions, if satisfactory replace all guards
or covers before running the chain drive under power.

Automatic Adjusters:

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These can be in the form of a simple hydraulic cylinder operated by oil pressure to push an idler
sprocket, or a rubber block, against the chain to automatically take up slack as it develops.

Fig. 15 Automatic hydraulic
Fig. 16 Timing chain layout
timing chain tensioner.
with hydraulic tensioner.

Spring Adjuster:
Another form of automatic adjuster uses a spring to push an idler, or jockey
wheel, against the chain too take up the slack. This idler may be a small
sprocket that fits the chain pitch, or a plain wheel that runs only on the side
links of the chain.
This type of adjuster is not completely automatic and does require periodic
manual adjustment to maintain sufficient spring tension to allow for
maximum normal chain wear.
Adjustment is made by slackening mounting bolt and rotating spring anchor
collar in the direction of the arrow, to increase spring tension.

Fig. 17 Spring loaded chain tension adjuster.

Lubrication
Correct lubrication is vital to obtain the maximum service life of a chain drive. Typical chain
lubrication systems are shown below, in semi-automatic and automatic systems it is only necessary to
check the oil reservoir level and that oil is actually reaching the chain.

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Method of
Lubrication

Manual

Brush can

SemiAutomatic

Pressure
Lubrication

Automatic

Drip Cup
Contact brush,
direct dip

Oil Bath
Chain dips into
oil

Oil Disk
Oil disk
throws lube
up on chain

Oil Stream
Pump sprays oil

on chain

Conveyors and
Elevators.
Drives in low
horsepower and
speed range

Drives – low to
moderate
horsepower and
speed

Drives –
moderate to
high
horsepower
and speed

Drives – high
horsepower and
speed

Application
of
Lubricant

Kind of
Equipment

Conveyors,
Elevators,
Simple
Drives

Conveyors

X

Sprocket Alignment
Rapid wear and mis-engagement of the chain can occur
due to the chain rubbing against the sides of sprocket
teeth if the sprockets and shafts are not correctly aligned.
Shafts must be parallel and aligned in the same plane.
Alignment appears correct with a straight edge between
faces of the sprockets, but the two shafts are not aligned
in the horizontal plane.
This could cause rapid wear and the chain may jump the
sprockets during load variations.
Fig. 19. Sprocket alignment

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