ME‐205 : Element of machine dynamics and design
Machine dynamics : Chain Drives
Dr. Muhammad Wasif
Assistant Professor – I.M.D.
Ph.D. (CAD/CAM – Canada), M.Engg. (Mfg. Engg. – NEDUET),
B.E. (Mech. Engg. – NED UET). Member ASME and PEC
Room : 1st on LHS of main corridor, ground floor – IM Building
1
Chain Drives
•
Roller chain is mostly used to transmit power.
•
A chain is a power transmission element made
as a series of pin‐connected links.
•
Load is applied by the driving sprocket on the
chain, the load is transmitted to a bushing, pin,
and pair of link plates, pins and link plates push
the driven sprocket to run.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives ‐ Advantages
• Due to no slippage, constant velocity is obtained.
• Less width is occupied, due to metal strength.
• Can be used for short as well as long center distances.
• High transmission efficiency (97‐99%).
• One chain can transfer power to multiple shafts.
• Can be operated at high temperature.
• Permits high speed ratio of 8 to 10.
• Multiple reduction stages are made, for high reduction ratio.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives ‐ Limitations
• Installation and component cost is higher.
• Require maintenance and lubrication.
• Velocity fluctuation occurs, when mounted inaccurately.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives – Roller chains
Roller dia (d)
b1
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives ‐ Nomenclature
• Pitch
Is the distance between the centers of two adjacent pins.
• Pitch circle radius (rc)
Distance between the pin
center and the center of
sprocket, when the hinge
is
meshed
with
that
sprocket.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives ‐ Classification
• Hoisting and hauling
(or crane) chains
‐ Can be used up to 0.25m/s
‐ Two types : Oval and square links
• Conveyor Chains
‐ Used for elevating and conveying
within 0.8 to 3m/s.
‐ Two types : Detachable or hook
joint, closed joint type.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives ‐ Classification
• Power Transmitting Chains
‐
‐
‐
‐
‐
Used for short center distance.
Three types :
Block or bush chain
Bush roller chain
Silent chain
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives – Lubrication
• The performance of chain assembly is improved by
proper lubrication. It reduces the friction and act as
a coolant.
• Improper lubrication produces premature chain
failure.
• Lubrication types depend upon the
speed and
environment.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives – Lubrication
• Manual lubrication : Lube is applied periodically
using brush or oil can. e.g. cycle or bike chain.
• Drip lubrication : oil drips with sufficient flow is
directed on the chain. e.g. Conveyor chains, engine.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives – Lubrication
• Bath or Disc lubrication : chain runs
through an oil sump or bath in the drive
housing. In disc lubrication, a disc picks
up the oil and deposit on chain. Oil
level is to be maintained in these cases.
• Stream lubrication : Some nozzles
attached with supply of oil, are set on
chain to spray the oil on chain near
sprocket engagement.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Chain Drives – Roller chains
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Recommendations
•
17,
,
120
= No. of teeth on small, large sprocket
• Velocity Ratio (V.R.) = n1⁄n
2
7
• 30 pitches center distance (C)
50 pitches
• Pitch (p) should be even.
• Chain length (L)=2C
∙
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains – problem solving steps
1. Specify a service factor and compute the design power.
Ks=K1.K2.K3 ;
Pt=Ks x P
Multiple strand factor (1,2,3) ‐ Km=1.7, 2.5, 3.3 – Pt/Km
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
2. Compute the velocity ratio.
V.R. = n1/n2
3. Select the chain pitch, and rpm of smaller sprocket.
16
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
Roller chains ‐ Calculation
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
4. Number of teeth of small sprocket.
5. Pitch of the chain
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Roller chains ‐ Calculation
Roller dia (d)
b1
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
6. Compute number of teeth of larger sprocket.
T2 = T1 V.R (check in catalogue)
7. Compute the actual expected output speed
n2= n1 (T1/T2)
8. Compute the pitch diameters of the sprockets.
°⁄
°⁄
9. Compute the length of the chain (L).
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
10. Corrected center distance.
1
∙
4
2
8∙
2
2
11. Compute the angle of wrap of the chain for each
sprocket
180 °
2.
−
/2
180 °
2.
−
/2
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
Design a chain drive for a heavily loaded coal conveyor
to be driven by a gasoline engine through a mechanical
drive. The input speed will be 900 rpm, and the
desired output speed is 230 to 240 rpm. The conveyor
requires 15.0 hp. (variable load with mild shock, 20 hr)
1. Ks=1.25(.8)(1.4)=1.4;
Pt=Ks x P = 1.4 x 15 = 21hp
2. V.R. = n1/n2 = 900/235 = 3.83
3. Pt = 15hp = 21hp x 0.7456 kW/hp = 15.6576kW
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
3. Select the chain pitch, and rpm of smaller sprocket.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
4. Number of teeth on sprockets.
5. Pitch
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Roller chains ‐ Calculation
6. T2= T1 x V.R = 23 x 3.83 = 88.09 89
7. n2= n1x(T1/T2) = 900(23/89) = 232.58 rpm
Range given 230‐240 – OK
8.
°⁄
°⁄
=
=
.
°⁄
.
°⁄
139.902mm
539.790mm
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
9. Length of the chain
C = 40pitch
(30 to 50 is recommended)
L
2C
L
L
138.757pitch 140 pitches (even recommended)
140(19.05) 2667 mm
∙
Corrected center distance
C
C
∙
8∙
40.64 pitch
C = 40.64(19.05) = 774.248mm
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
10. Angle of wrap
180 °
2.
−
/2
= 175.114°
180 °
2.
−
/2
184.885°
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Design summary
 539.790mm
 139.902mm
175.114
184.885°
°
774.240mm
Chain
Pitch
: No. 12B, 19.05mm
Length
: 140pitches = 2667mm
Center distance
: 774.24mm maximum
Sprockets
: Single strand, No. 12B, 19.05mm pitch
Small
: 23 teeth, D = 139.902mm
Large
: 89 teeth, D = 539.790mm
Lubrication
Bath lubrication is recommended due to 1000 rpm, large sprocket dip in bath.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Compact Redesign
1. Transmitted power (design for 3 strands) Km=3.3
Pt = 15.6576/3.3 = 4.745kW
2. V.R. = 3.83
3. Chain selection
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Roller chains ‐ Calculation
4. Number of teeth on sprockets.
5. Pitch
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Roller chains ‐ Calculation
6. T2= T1 x V.R = 23 x 3.83 = 88.09 89
7. n2= n1x(T1/T2) = 900(23/89) = 232.58 rpm
Range given 230‐240 – OK
8.
°⁄
°⁄
=
=
.
°⁄
.
°⁄
93.268mm
359.860mm
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
9. Length of the chain
C = 35pitch
(30 to 50 is recommended)
L
2C
L
L
129.151pitch 130 pitches (even recommended)
130(12.7) 1651mm
∙
Corrected center distance
C
C
∙
8∙
35.443 pitch
C = 35.443(12.7) = 450.137mm
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Roller chains ‐ Calculation
10. Angle of wrap
180 °
2.
−
/2
= 171.592°
180 °
2.
−
/2
188.408°
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Design summary
 359.860mm
 93.268mm
171.592
188.408°
°
450.137mm
Chain
Pitch
: No. 08B, 12.7mm
Length
: 130pitches = 1651mm
Center distance
: 450.137mm maximum
(41.86% reduced)
Sprockets
: three strand, No. 08B, 12.75mm pitch
Small
: 23 teeth, D = 93.268mm
(33.33% reduced)
Large
: 89 teeth, D = 359.860mm (33.33% reduced)
Lubrication
Bath lubrication is recommended due to 1000 rpm, large sprocket dip in bath.
ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)
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Refernces
•
•
•
•
•
•
•
R.S. Khurmi, G.K. Gupta, 2005, A text book of machine design, New Dehli‐ India,
EURASIA PUBLISHING HOUSE.
R. G. Budynass, J.K. Nisbett, 2005, Shigley’s Mechanical Engineering Deisgn, New
York –USA, McGraw Hill.
R. L. Mott, 2004, Machine Elements in Mechanical Design, USA, Pearson Prentice‐
Hall.
R. L. Norton, 1996, Machine design an integrated approach, NJ USA, Prentice‐Hall.
B. J. Hamrock, B. O. Jacobson, S. R. Schmid, 1999, Fundamental of Machine
Elements, New York –USA, McGraw‐Hill.
U. C. Jinbal, 2010, Machine Design, India, Pearson .
R. O. Parmley, 2005, Machine devices and components, USA, McGraw‐Hill.
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