chain-drives-02.pdf

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MA3001 Chain Drives July 2019
Machine Element Design (Nanyang Technological University)
Studocu is not sponsored or endorsed by any college or university
MA3001 Chain Drives July 2019
Machine Element Design (Nanyang Technological University)
Downloaded by Jordan Moses (mosesjordan24@gmail.com)
lOMoARcPSD|21319694

1
PART 2
Chain Drives
Tutorial 2 Chain Drives
Appendix B
Dr Hoon Kay Hiang
Tel: 6790 5523
Office: N3-02c-94
Email: mkhhoon@ntu.edu.sg
July 2019
MA3 0 0 1
MACHI NE ELEMENT DESI GN
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In this lecture, you will learn:
• Identify the basic features of a chain drive system.
• Describe the standard roller chain and its classification.
• Identify the types of chain sprockets
• Use guidelines for design of chain drive
• Select roller chains from basis of strength for static or very slow
speed applications
• Select roller chains and sprockets from basis of power transmission
for high speed applications
• Analyse forces on sprocket and shaft
Learning objectives
CHAI N DRI VE DESI GN
2
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3
I NTRODUCTI ON
• The modern power transmission chain is in part, an American invention
growing out of a need for mechanized farm machinery. The roller
chain, however, was invented by Renold (England) in 1880.
• A chain is a power transmission element made as a series of pin-
connected links.
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4
• One side of the strand is always slack with zero tension and power is
transmitted solely by the tight side tension, which explains why chain drives
generate a smaller shaft load than belt drives.
• Consequently, chain drives require smaller, less costly bearings and shaft.
• Chain drives are thus more compact, powerful and efficient than belt drives.
BASI C LAYOUT OF CHAI N DRI VES
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5
• Besides the major use of chains for power transmission, chains are also used to
- convey materials
- raising and lowering loads on a forklift.
https://www.youtube.com/watc
h?v=grMBzq0YHH0
APPLI CATI ONS OF CHAI N DRI VES
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6
- as devices for synchronization of movements such as valve timing in engines
Roller
Chain
http://www.atlprorepair.
com/uploads/5/3/9/6/53
965149/1033208.gif
APPLI CATI ONS OF CHAI N DRI VES
• Timing belt being made of rubber is susceptible to breakage and should be replaced timely
to avoid damages to the engine valves and pistons.
• Timing chain does not break easily and would be preferred to prevent such damages
http://www.samarins.com/
glossary/ohv_engine.gif
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• Roller chain is the most widely used type in which the roller on each pin
provides exceptionally low friction between the chain and the sprockets.
• Of its diverse applications, the most familiar is the roller chain drive on a
bicycle.
• The parts and assembly of a single
roller chain are shown here.
• Chains are endless and this is a
major advantage over V-belts
and gears.
• One link is always detachable,
so that the chain can be mounted and
dismounted at will.
Typical roller chain assembly
BASI C FEATURES OF ROLLER CHAI N
7
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8
https://www.youtube.com/watch?v=aekApCg_MYQ
MANUFACTURI NG OF ROLLER CHAI N ( REF: TSUBAKI )
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EVEN AND ODD NUMBER OF LI NKS OR PI TCHES
• Since each roller link requires a pin link for assembly, a chain normally has
an even number of links.
• What if the number of links is odd?
• If an odd number of links is required, it is necessary to use an offset link.
• Offset links wear faster than straight links and should be avoided whenever
necessary.
Pitch
9 links - Odd number of pitches
9 links - Odd number of pitches
Offset Link
8 links - Even number of pitches
6 links
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• A roller chain is generally made of hardened steel and sprockets of steel or
cast iron.
• Roller chains have a high efficiency of 97 to 99% and can be used for heavy
loads at speeds up to 20 m/s.
• All chains are classified according to the pitch.
p - pitch
ROLLER CHAI N
Single Strand Chain
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• The dimensions of standard sizes for a single strand chain specified by American
National Standards Institute (ANSI) is shown in Table 1.
Eg. No 40 chain has a
pitch of 12.70 mm
ROLLER CHAI N CLASSI FI CATI ON
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• Multi-strand such as double-, triple- and quadruple-strand roller chain and
sprockets are also stocked in most standard sizes according to size by the
American National Standards Institute (ANSI).
• Multi-strand roller chain consists of two or more parallel strands of chain
assembled on common pins.
• Figure shows a chain drive with double strands. In some cases, up to 10-
strand chain width is available.
common pin
MULTI -STRAND ROLLER CHAI NS
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• Roller chains seldom fail because they lack tensile strength; they more often
fail because they have been subjected to a great many hours of service.
• Actual failure may be due either to wear of rollers on the pins or fatigue of
the surfaces of the rollers.
• At lower speeds, the power capacity of roller chain systems is determined by
the fatigue life of the link plates.
• At higher speeds, the power capacity is determined by the roller bushing
fatigue life
• At very high speeds, it is determined by galling or a phenomenon of
localized cold weld on the bearing surface between a roller and its bushing
that resulted in surface roughening as the weld is broken.
FAI LURE MODES OF ROLLER CHAI NS
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• Roller chains drive and are driven by sprockets, which are
toothed wheels machined to fit the chain rollers.
• Proportions of sprockets are standardized and are
available in manufacturers’ catalogues.
• Roller chain and sprocket MUST have the SAME ANSI
No.
• Single strand chain only works with single strand
sprocket, double strand chain with double strand sprocket,
and so on.
• Sprockets are generally made from cast iron and cast
steel.
CHAI N DRI VE SPROCKETS
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− Type A has no hub
− Type B has a hub on one side
− Type C has a hub on both sides
− Type D has a detachable hub
FOUR TYPES OF SPROCKETS
A B C
D
C B
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Sprocket
( )
( )
mm
/
180
sin
mm
/
180
sin
2
2
1
1
N
p
D
N
p
D
°
=
°
=
Pitch diameter of a sprocket
where p = pitch in mm
CHAI N DRI VE GEOMETRY
c
N1 N2
D1
D2
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Chain Length
= 2 arcs + 2 straight tangents over pitch circles
pitches
in
4
)
(
2
2 2
1
2
1
2
2
C
N
N
N
N
C
L
π
−
+
+
+
=
where
N1 = number of teeth in
the driver sprocket
N2 = number of teeth in
the driven sprocket
N1
N2
CHAI N PI TCH LENGTH
17
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• Centre Distance, in pitches
• Angle of contact - on small sheave,
2
sin
2
180 1
2
1
1 




 −
−
= −
C
D
D
o
θ
pitches
4
)
(
8
2
)
(
2
4
1
2
1
2
1
2
1
2
2
2









 −
−





 +
−
+
+
−
=
π
N
N
N
N
L
N
N
L
C
CENTRE DI STANCE & ANGLE OF CONTACT
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• Speed ratio =
The DRIVER can be the smaller sprocket for speed step-down or the
bigger sprocket for speed step-up.
• Direction of rotation
- Same direction
• Chain velocity V = r ω m/s
1
2
2
1
Speed
Output
Speed
Input
N
N
=
=
η
η
N1
N2
SPEED AND DI RECTI ON OF ROTATI ON
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• The recommended type shown in the power rating tables is influenced
by chain speed and the amount of power transmitted.
• Proper lubrication of roller chains is highly important to their design
performance.
• With proper lubrication and proper alignment, a sprocket and roller
chain system should be capable of 15,000 hours of service at full load.
• Usually a medium or light mineral oil is used as the lubricant. Heavy
oils and greases are not recommended because they are too viscous to
enter the small clearances in the chain parts.
• Three basic types of lubrication for chain drives are as follows:
CHAI N LUBRI CATI ON
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~ For manual lubrication, oil is applied with a brush or spout at
least once every 8 hours of operation.
~ For drip lubrication, oil is fed directly onto the link plate edges.
It is generally used for low rpm application.
TYPE A – MANUAL OR DRI P LUBRI CATI ON
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~ For bath lubrication, the lowest portion of the chain pitch line is
immersed in an oil sump in the chain housing.
~For disc lubrication, the chain operates above the oil level. The disc
picks up oil from the sump and deposits it onto the chain by means of a
collector plate and a trough or gutter. This type of lubrication is often
found on chain drives operating at intermediate speed and power.
TYPE B – BATH OR DI SC LUBRI CATI ON
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~ The lubricant is usually supplied by a circulating pump capable of
delivering continuous stream of oil.
~ The oil should be directed at the slack strand and applied inside the
chain loop and evenly across the chain width.
TYPE C – OI L STREAM LUBRI CATI ON
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Power Transmission Applications (greater than 100rpm)
• For smooth operation, it is considered good practice to use a sprocket
with at least 17 teeth.
• Where space limitations are severe, smaller tooth numbers (lesser
than 17) may be used by sacrificing the life expectancy of the chain.
(Note: this is quite often encountered in real applications). However,
care must be taken to prevent the chain from lifting off and jumping
out of the sprocket teeth due to chordal acceleration at high chain
speed. Eg. using idler sprocket can prevent this.
• Optimum range for centre distance is between 30 and 50 chain
pitches. However, centre distances greater than 50 pitches are often
used but 80 pitches and over are not recommended.
GUI DELI NES – FOR POW ER TRANSMI SSI ON
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• Speed ratio should be about 7:1. If a higher speed ratio is required,
a multi stage reduction drive should be proposed.
• The calculated chain length should be rounded off to a whole
number, preferably an EVEN one to avoid specification of a weaker
offset link
• It is recommended that no more than 4 strands be used because of
the loads placed on the shaft and the corresponding reduction in the
load rating of additional strands.
GUI DELI NES – FOR POW ER TRANSMI SSI ON
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• For power transmission, chain is selected by Power Rating provided by
manufacturer.
• Power ratings, however, do not increase proportionately.
• The power ratings of a multi–strand roller chain is obtained by multiplying the power
rating of a single-strand chain by the multiple strand factors which is given in Table 2.
• These factors are not a direct multiple of the number of strands because of non-
uniform loading among the parallel strands.
Table 2 Multiple Strand Factors
Number of Strands Multiple Strand Factor
1 1.0
2 1.7
3 2.5
4 3.3
5 3.9
6 4.6
For power transmission,
One strand can transmit 1.0 kW
Two strands can only transmit
1.7 x 1.0 = 1.7 kW
Three strands can only transmit
2.5 x 1.0 = 2.5 kW
and so on..
MULTI STRAND FACTOR FOR POW ER
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DESI GN DATA
27
• Most roller chain manufacturers provide data tables to aid the
engineer in choosing the roller chains and determining their power
capacity. The tables in Appendix B are a sample of what could be
found in catalogues.
• Power ratings are given for ONE STRAND and based on very
smooth driving conditions (a service factor of 1), a chain length of
100 pitches, use of recommended lubrication, a two-sprocket drive
and sprockets aligned in the same plane, mounted on parallel
horizontal shafts and a service life of about 15,000 hours.
~ The power ratings relate to the speed of the smaller sprocket and
drive selections are made on this basis, whether the drive is speed
reducing or speed increasing.
~ Ratings for intermediate numbers of sprocket teeth or speed
(rpm) are obtained by interpolation.
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• Select smallest roller chain using
• To select chain, Rated power/strand ≥ Design Power/strand
• Rated power per strand is the power that can be transmitted by a
chain is given in the manufacturer’s power rating table for:
a) small sprocket speed (interpolate speed when needed)
b) small sprocket teeth
• Select standard driving and driven sprocket sizes (no. of teeth) to
satisfy speed and size requirements
- NOTE: for tutorials and examination, choice of number of teeth in
larger sprocket is not restricted to Table B-4 of Appendix B.
• Specify chain pitch length
(kW)
Factor
Strand
Multiple
Factor
Service
x
ed
transmitt
be
Power to
strand
per
Power
Design =
SELECTI ON OF CHAI NS AND SPROCKETS
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Eg. No.40 chain
(kW)
Factor
Strand
Multiple
Factor
Service
x
ed
transmitt
be
Power to
strand
per
Power
Design =
Power
ratings in
Table are for
ONE strand.
Table B-4 of Appendix B
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30
Design a chain drive for an agitator to be driven by an electric motor.
The input speed is 900 rpm, and the desired speed is 245 to 255 rpm.
The agitator requires 11 kW, and the distance between the driving and
driven shafts is limited to approximately 760 mm. The pitch diameter
of the sprockets should not exceed 400mm.
EXAMPLE 1 – DESI GN FOR POW ER
TRANSMI SSI ON ( > 1 0 0 rpm )
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31
1. Determine the Design Power
a)
b) from Table B-2, service factor (motor and agitator) = 1.0
c) let’s decide on a single strand ⇒ multiple strand factor = 1.0
d) Design Power per strand = (11.0 x 1.0)/1.0 = 11.0 kW
(kW)
Factor
Strand
Multiple
Factor
Service
x
ed
transmitt
be
Power to
strand
per
Power
Design =
EXAMPLE 1 SOLUTI ON
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2. Select the chain size and also the number of teeth on the smaller sprocket
a) using the rpm of the smaller sprocket, 900rpm and design power 11.0 kW,
look for matching power rating (given by manufacturer) in Table B-4, Appendix
B, that is equal to or greater than 11.0 kW. Starting from the smallest available
chain (No. 25 in our case); the idea is to select as small a chain as possible
32
Look for manfacturer’s power rating > ( DP = 11.0kW)
Table B-4
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Look for manufacturer’s power rating > ( DP = 11.0kW)
33
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Selected N1=40
34
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2. b) a match is found for No. 40 roller chain with N1=40 teeth which has a
rating of 11.2 kW.
The pitch for No. 40 from Table B-1 is 12.70 mm.
Check: D1 = p / sin (180°/N1) = 12.7/ sin (180°/40) = 161.9 mm
i.e. less than the max pitch diameter of 400mm, hence is suitable!
35
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36
3. Determine the number of teeth N2 for the larger sprocket (the
driven sprocket)
a) Driven speed = 245 to 255 rpm; use average or nominal driven
speed for η2 ie η2 = (245+255)/2 = 250 rpm
b) Speed Ratio, η1/ η2= 900/250 = 3.6
c) N2 = N1(η1/η2) = (40)(3.6) = 144 (for tutorial and examination,
choice of number of larger sprocket teeth is not restricted to Table
B-1 of Appendix B)
(is N2 = 144 suitable?)
d) Check: D2 = p / sin (180°/N2) = 12.7/ sin (180°/144) = 582.2 mm
e) since D2 exceed the max pitch diameter of 400mm, therefore this
No. 40 chain is NOT suitable
f) go back to step 2 and select a larger chain size until requirements
are met
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37
4. Repeat Step 2 and 3 to reselect chain
a) Reselect No. 50 chain with N1= 20 giving a power rating of 11.0 kW.
Selected N1=20
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4. Check if reselected chain yields suitable sprocket sizes
From Table B-1, No. 50 chain pitch, p = 15.875mm
Check: D1 = 15.875/sin (180°/20) = 101.5 mm
i.e. less than the max pitch diameter of 400mm, hence is suitable!
b) N2 = (20)(3.6) = 72
c) so for tutorial and examination, choice of number of larger sprocket teeth is not
restricted to Table B-1 of Appendix B
select whole number, N2 = 72
Check: D2 = 15.875/sin (180°/72) = 363.9 mm;
Suitable, since < max pitch diameter of 400 mm
d) Compute actual output speed (IMPORTANT to check if it is within the specified
range),
η2= 900 (20/72) = 250 rpm
(within range of 245 to 255rpm - OK!)
e) hence, N1 = 20, N2 = 72
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39
5. Centre Distance and Chain Pitch Length
a) given that the centre distance is limited to approx 760 mm,
then let Tentative Centre Dist (TCD) = 760/p in pitches
= 760/15.875
= 47.9 pitches
b) calculate the Tentative Chain Length, TCL in pitches
c) adjust TCL to the closest even number of pitches to obtain the
standard chain length, L = 142 pitches (so as not to exceed c=760mm)
pitches
2
.
143
)
9
.
47
(
4
)
20
72
(
2
20
72
)
9
.
47
(
2
)
(
4
)
(
2
2
2
2
1
2
1
2
2
2
=
−
+
+
+
=
−
+
+
+
=
π
π
TCL
TCD
N
N
N
N
TCD
TCL
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40
6. Calculate the Actual Centre Distance
mm
4
.
750
875
.
15
x
27
.
47
pitches
27
.
47
4
)
20
72
(
8
2
)
20
72
(
142
2
20
72
142
4
1
4
)
(
8
2
)
(
2
4
1
2
2
1
2
1
2
1
2
2
2
2
2
=
=
=









 −
−





 +
−
+
+
−
=









 −
−





 +
−
+
+
−
=
C
C
N
N
N
N
L
N
N
L
C
π
π
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41
7. Select an appropriate type of lubrication
The No. 50 rating table shows that Type B lubrication is required for this
drive.
Suggested Chain Drive
Single strand No. 50 roller chain, pitch = 15.875, N1=20, N2=72,
L = 142 pitches, C = 750.4 mm, Type B lubrication
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42
GUI DELI NES – DESI GN FOR STRENGTH
Static or Very Slow Speed Applications (less than 100 rpm)
• Strength is the design criterion for such applications.
• The average tensile strengths and maximum allowable loads for the various
chain sizes are also listed in the catalogue.
• These allowable loads can be used for very slow speed drives or for
applications in which the function of the chain is to apply a tensile force or
support a load.
Apply tensile force -
Chain Pipe Wrench
Very slow speed - Fork lift
lOMoARcPSD|21319694

43
If maximum allowable load is not
given in some catalogues, then use
10% of Average Tensile Strength
• A sample of a manufacturer’s catalogue is given in Appendix B, Table B-1. It is
recommended that only 10% of the average tensile strength be used as the
maximum allowable load if the maximum allowable load is not given.
We use these
values for our
course
GUI DELI NES – DESI GN FOR STRENGTH
Table B-1 of Appendix B
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44
• The tensile strength of a multi-strand chain is a direct multiple of the
number of strands multiply with the tensile strength of a single-
strand chain of the same pitch.
Eg.
A single strand ANSI No. 40 chain has an allowable tensile strength of 370 x g = 3,630 N.
A double strand ANSI No. 40 chain will have an allowable tensile strength of
= 2 x 3630 = 7,260 N
A triple strand ANS! No. 40 chain will have an allowable tensile strength of
= 3 x 3630 = 10,890 N
ALLOW ABLE TENSI LE STRENGTH
lOMoARcPSD|21319694

Roller chain is used in a fork lift truck to elevate the forks. If two
strands support the load equally, which size would you specify for a
design load of 44,000 N.
44,000N
2 strand
EXAMPLE 2 – DESI GN BY STRENGTH CRI TERI ON
45
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46
This is an example of selection of roller chains for Very Slow Speed
Applications (ie. less than 100 rpm)
In forklift trucks, load is typically lifted very slowly, hence the application of the
load on the chains is almost static or at very slow speed. So, the selection of the
roller chain is based on strength requirement.
Design Load – the maximum operating load that the forklift can lift.
Hence the maximum operating load on the two strands of roller chain is 44,000N.
Therefore maximum operating load supported by each strand = 44,000 / 2
= 22,000 N
maximum operating load ≤ allowable load
Now refer to Table B-1 (next page) to find a chain that has an allowable
load/strand that is equal or greater than 22,000 N (or 22,000/9.81= 2,242 kg).
EXAMPLE 2 SOLUTI ON
lOMoARcPSD|21319694

47
Looking for allowable
load > 2242kg
EXAMPLE 1 SOLUTI ON
Chain No. 100 has an allowable load of 2,300kg.
Hence it is suitable for this application!
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48
QUICK REFERENCE
The reference is appended at the end of these slides for
quick referral (for your reading).
FULL PROCEDURE
Design for Power Transmission (>100rpm)
lOMoARcPSD|21319694

• Equations are similar to belt drives except that F2 = 0
• Transmitted Power,
P = T1ω1 = T2ω2
• Torque, T1= (F1- F2) D1/2,
T2= (F1- F2) D2/2
where P = power (W)
ω = shaft angular velocity (rad/s) [ω = 2πη/60 and η in rpm]
T1, T2 = Torque on sprockets 1 and 2 resp (Nm)
D1, D2 = pitch diameter of sprockets 1 and 2 resp (m)
F1 = tension on tight side (N)
F2 = 0 – ZERO tension on slack side 49
POW ER, TORQUE, CHAI N TENSI ON
lOMoARcPSD|21319694

DRIVER SPROCKET:
Input Torque SAME direction
as rotational direction
50
T2
DRIVEN SPROCKET:
Output/Resisting Torque
OPPOSITE direction as
rotational direction
Torque and Direction of Rotation (similar to belt)
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51
• How to determine which side is tight? (similar to belt)
– Look at rotation of driven sprocket - tight side gives direction of
rotation to driven sheave
The Tighter side F1
gives direction of η2
rotation to DRIVEN
sprocket
TI GHT TENSI ON SI DE
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52
Shaft Load
is determined in the same way as belt drives, ie.
tension is assumed parallel (normal practice adopted in this course and
industry)
F2 = 0 – ZERO tension on slack side
Driver Shaft Forces
η1
TS= (F1)D1/2
T1
η1
Driver Sprocket Forces
Fx = F1
SHAFT LOAD
lOMoARcPSD|21319694

53
• Select smallest roller chain using
• To select chain, Rated power ≥ Design Power
• Rated power per strand is the power that can be transmitted by a
chain is given in the manufacturer’s catalogue for:
a) small sprocket speed (interpolate speed when needed)
b) small sprocket teeth
SUMMARY
(kW)
Factor
Strand
Multiple
Factor
Service
x
ed
transmitt
be
Power to
strand
per
Power
Design =
lOMoARcPSD|21319694

54
Eg. No.40 chain
(kW)
Factor
Strand
Multiple
Factor
Service
x
ed
transmitt
be
Power to
strand
per
Power
Design =
SUMMARY
Power
ratings in
Table are for
one strand.
lOMoARcPSD|21319694

55
• Standard driving and driven sprocket sizes
- for tutorial and examination, choice of number of larger sprocket
teeth is not restricted to Table B-1 of Appendix B.
- Maximum speed ratio for a single reduction, N2/N1 = 7.0; If higher
reduction is required, use multi-stage reduction.
- IMPORTANT! check if the two sprockets, N1 & N2 combination
or multi-stage combination gives the required speed ratio or
within driven speed range:
η1/ η2 = N2/N1
SUMMARY
lOMoARcPSD|21319694

DRIVER SPROCKET:
Input Torque SAME direction
as rotational direction
56
T2
DRIVEN SPRCOKET:
Output/Resisting Torque
OPPOSITE direction as
rotational direction
Torque and Direction of Rotation
SUMMARY
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57
• Rotation of driven sprocket - tight side gives direction of rotation to
driven sheave
The Tighter side F1
gives direction of η2
rotation to DRIVEN
sprocket
SUMMARY
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58
Shaft Load
Tension is assumed parallel (normal practice adopted in this course)
Driver Shaft Forces
η1
TS= (F1)D1/2
T1
η1
Driver Sprocket Forces
Fx = F1
SUMMARY
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59
TUTORI AL 2 – CHAI N DRI VES
1. The layout of the drive of an internal combustion engine-driven machine is shown in Figure 1. The
engine drives a small V-belt sheave A which drives a large sheave B. On the same shaft as B is
mounted a small chain sprocket C which drives the large sprocket E with a single-strand No. 40 roller
chain. The engine is rated 6.0 kW at 2750 rpm at the shaft J. The machine is of the moderate load
type and is driven at 800 ± 10 rpm at shaft L.
a) Determine the number of teeth for sprocket C and E, and the actual speed and direction of rotation
at shaft L.
Ans: NC=21, NE=47
b) Determine and show the forces acting on sprocket E.
Ans: F1=748.4 N, F2=0
Figure 1
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60
QUICK REFERENCE PROCEDURE
Design for Power Transmission (>100rpm)
• In a much similar way as in belt drives, chain selection for drives
depends upon the rated power of the driver, the specified speed ratio,
the centre distance, the shaft diameters and the service conditions.
• Usually the chain selection process is iterative.
• A procedure for establishing the elements of a good roller chain
configuration is listed below.
FOR YOUR READI NG!
lOMoARcPSD|21319694

1. Determine the Design Power
a) select service factor from Table B-2, Appendix B
~ determine the classification of the load according to its shock characteristics as
guided by List 2 of Table B-2 and then determining the service factor from List 1
of Table B-2 which is dependent upon the characteristics of the input power
b) drive power - actual power requirement of the driven machine
c) Tentatively select the number of strands. You can start with one strand first and
then check later if space requirements are met. If necessary iterate until
requirement is met).
(kW)
Factor
Strand
Multiple
Factor
Service
x
ed
transmitt
be
Power to
strand
per
Power
Design =
61
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62
2. Select the chain size and also the number of teeth on the smaller
sprocket
a) Starting with the available smallest chain size ie No. 25 chain in Table
B-4 with the design power and at the required rpm of the smaller sprocket,
determine the minimum size sprocket ie number of teeth, N1 needed to
provide a power rating (given by manufacturer) equal to or greater than
the design power. The idea is to select as small a chain as possible
b) Use preferred minimum of 17 teeth if space is not an issue
3. Determine the number of teeth N2 for the driven sprocket
a) Speed Ratio, η1/ η2=N2/N1
b) Speed ratio should be about 7:1. If a higher speed ratio is required, a
multi stage reduction drive should be proposed.
c) Select a standard N2 nearest to the calculated value
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63
4. Calculate the pitch diameters of the sprockets
to get an idea of the size of the sprockets
D1 = p / sin (180°/N1) mm,
D2 = p / sin (180°/N2) mm
5. Centre Distance and Chain Pitch Length
a) if an approximate centre distance is not known, use recommended
centre distance of 30 to 50 pitches and decide on a Tentative Centre Dist
(TCD) in pitches.
Eg. choose a smaller centre distance of 33p for compactness.
b) find the Tentative Chain Length, TCL in pitches
c) specify an even number of pitches for the chain length, L, closest to
the TCL, that satisfies design requirements.
pitches
4
)
(
2
2 2
1
2
1
2
2
TCD
N
N
N
N
TCD
TCL
π
−
+
+
+
=
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64
6. Calculate the Actual Centre Distance
7. Select an appropriate type of lubrication
~ read off the type of lubrication recommended in the power
rating table for the selected chain.
pitches
4
)
(
8
2
)
(
2
4
1
2
1
2
1
2
1
2
2
2









 −
−





 +
−
+
+
−
=
π
N
N
N
N
L
N
N
L
C
lOMoARcPSD|21319694

chain-drives-02.pdf

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