Design a various type springs and flywheels basic concepts.

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ME 6503 : DESIGN OF MACHINE ELEMENTS
UNIT -4 : DESIGN OF ENERGY STORING ELEMENTS AND ENGINE COMPONENTS
By
Mr. B.Balavairavan
Assistant Professor
Mechanical Engineering
Kamaraj College of Engg and Tech
Virudhunagar

2. SPRING
Spring is an elastic body whose function is
to distort when loaded and to recover its
original shape when the load is removed.
Mechanical springs are
used in machines and other
applications mainly
• to exert force,
• to provide flexibility
• to store or absorb energy.
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3. APPLICATION OF SPRINGS
1. To apply forces as in brakes, clutches
and spring loaded valves.
2. To store energy as in watches, toys.
3. To measure forces as in spring balance
and engine indicators.
4. To cushion, absorb or control energy
due to either shock or vibration as in
car.
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4. APPLICATIONS OF SPRINGS
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Springs in railway wagon

5. The most common types of springs are as follows
1. Helical Spring
2. Leaf Spring
3. Disc Spring or Belleville Spring
TYPES OF SPRING
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6. TYPES OF SPRING – HELICAL
SPRING
The helical springs are made up of a wire coiled in the
form of helix and are primarily intended for tensile or
compressive loads. The cross section of the wire from which
the spring made may be circular, square or rectangular. The
two forms of helical springs are compression spring and
helical tension springs.
Helical springs - Classification
a) Open coiled or Compression helical spring
b) Closed coiled or Tension helical spring
c) Torsion spring
d) Spiral spring
e) Concentric spring
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7. TYPES OF SPRING – HELICAL
SPRING
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(a) Open coiled or Compression helical spring
The springs which are sustain compressive force along the
axis are called compression helical or open coil springs. These
springs have helix angle more than 100
(b) Closed coiled or Tension helical spring
The springs which are sustain tensile force along the axis
are called tension helical or closed coil springs. These springs
have helix angle less than 100.

8. HELICAL COMPRESSION SPRING
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9. HELICAL TENSION SPRING
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10. (c) Torsion Spring
It is also a form of helical spring, but it rotates about an
axis to create load. It releases the load in an arc around the
axis. Mainly used for torque transmission. The ends of the
spring are attached to other application objects, so that if the
object rotates around the center of the spring, it tends to push
the spring to retrieve its normal position.
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11. TORSION SPRINGS
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12. (d) Spiral Spring
It is made of a band of steel wrapped around itself a
number of times to create a geometric shape. Its inner end is
attached to an arbor and outer end is attached to a retaining
drum. It has a few rotations and also contains a thicker band of
steel. It releases power when it unwinds.
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13. TYPES OF SPRING –
CONCENTRIC SPRING
• Concentric helical springs are
used to obtain a greater spring
force in a given space and to
ensure the operation of a
mechanism in the event that one
spring will break.
• To obtain the above conditions,
either a two- spring nest or a
three-spring nest may be used.
• Fig. Shows the two concentric
springs have the same free
length and arc compressed
equally. Such springs are used
for automobile clutches and
railway clutches.
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Concentric springs in Two wheeler and Railway
Suspension

14. TERMINOLOGIES USED IN
HELICAL SPRING
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15. Terminologies used in Helical spring
• Coil Diameter (D)
The mean diameter of the helix.
D = (D outer + Dinner)/2.
• Wire Diameter (d)
The diameter of the wire that is wound into a helix.
• Spring Index (C)
The ratio of mean coil diameter to wire diameter.
C = D/d
• Spring Stiffness or Spring rate (q)
The ratio of load required per unit deflection.
q = P/y
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16. TERMINOLOGIES USED IN
HELICAL SPRING
• Active Coils (Na or n)
The number of coils which actually deform when the
spring is loaded.
• Inactive Coils
The coils which do not take part in deflection of the
spring are known as inactive coils.
• Total Coils (Nt)
The number of coils or turns in the spring.
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17. TERMINOLOGIES USED IN
HELICAL SPRING
• Solid Length (Ls)
When the compression spring is compressed until the coils come in
contact with each other the spring is said to be solid. The solid length of a
spring is the product of total number of coils and the diameter of the wire.
• Free Length (Lf)
It is the length of the spring in the free or unloaded condition. It is
equal to the solid length plus the maximum deflection or compression of
the spring and the clearance between the adjacent coils.
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18. TERMINOLOGIES USED IN
HELICAL SPRING
• Pitch (p)
The pitch of the coil is defined as the axial distance
between any two adjacent coil in uncompressed state.
• Helix angle or Coil angle or pitch angle (α)
The angle between the coils and the base of the spring.
The pitch angle is calculated from the equation
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19. TERMINOLOGIES USED IN
HELICAL SPRING
• Wahl’s Stress Concentration factor
A factor to correct stress in helical springs effects of
curvatures and direct shear.
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20. END CONDITIONS OF HELICAL
SPRING
Generally, the following four end conditions are used.
1. Plain end
2. Plain and Ground
3. Squared end
4. Squared and Ground end
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21. DEFORMATION OF TENSILE AND
COMPRESSION HELICAL SPRINGS
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Deformation of compression Spring Deformation of Tension Spring

22. ENERGY STORED IN SPRINGS
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23. SURGE IN SPRINGS
• When one end of a helical spring is resting on a rigid support
and the other end is loaded suddenly, then all the coils of the
spring will not suddenly deflect equally, because some time is
required for the propagation of stress along the spring wire.
• If the applied load is of fluctuating type as in the case of valve
spring in internal combustion engines and if the time interval
between the load applications is equal to the time required for
the wave to travel from one end to the other end, then
resonance will occur.
• This results in very large deflections of the coils and
correspondingly very high stresses. Under these conditions, it
is just possible that the spring may fail. This phenomenon is
called surge. D.M.E - B.B 23

24. SURGE IN SPRINGS
The surge in springs may be eliminated by using the following
methods :
1. By using friction dampers on the centre coils so that the wave
propagation dies out.
2. By using springs of high natural frequency.
3. By using springs having pitch of the coils near the ends
different than at the centre to have different natural
frequencies.
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25. BUCKLING OF
SPRINGS
The helical
compression spring
behaves like a
column and buckles
at a comparative
small load when the
length of the spring
is more than 4 times
the mean coil
diameter.
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26. SPRINGS IN SERIES AND PARALLEL
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27. The laminated or leaf spring consists of a number of flat
plates of varying lengths held together by means of clamps and
bolts. These are mostly used in automobiles.
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TYPES OF SPRING – LEAF
SPRING

28. NIPPING IN LEAF SPRING
Stress in the full length leaves is 50% greater than the
stress in the graduated leaves. When the load is gradually
applied to the spring, the full length leaf is relieved of the
initial stress and then stressed in opposite direction. Such a pre
stressing obtained by a difference of radii of curvature is
known as nipping.
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29. MATERIALS FOR LEAF SPRINGS
The material used for leaf springs is usually a plain carbon
steel having 0.90 to 1.0% carbon. The leaves are heat treated
after the forming process. The heat treatment of spring steel
produces greater strength and therefore greater load capacity,
greater range of deflection and better fatigue properties.
According to Indian standards, the recommended materials are
• 1. For automobiles : 50 Cr 1, 50 Cr 1 V 23, and 55 Si 2 Mn 90
all used in hardened and tempered state.
• 2. For rail road springs : C 55 (water-hardened), C 75 (oil-
hardened), 40 Si 2 Mn 90 (waterhardened) and 55 Si 2 Mn 90
(oil-hardened).
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30. TYPES OF SPRING –
BELLEVILLE SPRING
• Belleville springs or Disc springs are used where space
limitations require high capacity units i.e. Applications
requiring high spring stiffness and compact spring units. This
is obtained at the expense of thickly non-uniform stress
distribution across the section. High Stresses are used in the
design of Belleville springs. Each spring consists of several
annular discs that arc dished to a conical shape as in fig (a).
There are staked up one on top of another as in fig. (b) In order
to increase the deflection.
• The unit may be held in alignment by a central bolt or a tube.
The springs placed in series as shown in fig. (c) and the
deflection is proportional to the number of discs.
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31. TYPES OF SPRING –
BELLEVILLE SPRING
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32. RUBBER SPRING
• A rubber or an Elastomers is a material which
has approximately 100% extension and it will
return to its original length when the load is
removed.
• Rubber springs have high energy absorbing
capacity.
• High damping properties hence they are used
for resilient mounting in application requiring
vibration isolation.
• Rubber spring are very cost effective as
compared to coil springs.
• Rubber springs have ability to resist oil,
chemical, heat, dust , corrosion etc.
• Maximum deflection of these spring is 35%
• These springs have high buckling resistance.
• As the deflection of these spring is large , the
free length is approximately half of the coil
spring.
• These springs have high bucking resistance.
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34. FLYWHEEL
A flywheel used in machines serves as a
reservoir, which stores energy during the period
when the supply of energy is more than the
requirement, and releases it during the period
when the requirement of energy is more than the
supply.
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35. COEFFICIENT OF
FLUCTUATION OF SPEED
The difference between the maximum and
minimum speeds during a cycle is called the
maximum fluctuation of speed. The ratio of the
maximum fluctuation of speed to the mean speed is
called the coefficient of fluctuation of speed.
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36. TURNING MOMENT DIAGRAM
The turning moment diagram (also known
as crank effort diagram) is the graphical
representation of the turning moment or crank-
effort for various positions of the crank. It is
plotted on cartesian co-ordinates, in which the
turning moment is taken as the ordinate and
crank angle as abscissa.
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37. TURNING MOMENT DIAGRAM –
SINGLE CYLINDER ENGINE
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38. TURNING MOMENT DIAGRAM –
MULTI CYLINDER ENGINE
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39. TURNING MOMENT DIAGRAM –
IC ENGINE
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40. FLUCTUATION OF ENERGY
The variations of energy above and below the
mean resisting torque line are called fluctuations of
energy.
The difference between the maximum and the
minimum energies is known as maximum fluctuation
of energy.
Maximum fluctuation of energy, E =
Maximum energy – Minimum energy
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41. COEFFICIENT OF
FLUCTUATION OF ENERGY
It may be defined as the ratio of the
maximum fluctuation of energy to the work
done per cycle.
CE= Maximum fluctuation of energy /
Work done per cycle
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42. WORK DONE PER CYCLE
The work done per cycle (in N-m or joules)
may be obtained by using the following two
relations :
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43. WORK DONE PER CYCLE
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44. ENERGY STORED IN A
FLYWHEEL
Energy stored, E = mk2ω2CS = mv2CS
m = Mass of the flywheel in kg,
k = Radius of gyration of the flywheel in metres
ω = angular speed in rad/s2
Cs = Coefficient of Fluctuation of Speed
v = Mean linear velocity
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45. DIMENSIONS OF THE
FLYWHEEL RIM
Tensile stress or hoop stress,σ = ρR2ω2 = ρv2
ρ = Density of rim material in kg/m3,
N = Speed of the flywheel in r.p.m.,
ω = Angular velocity of the flywheel in rad/s,
v = Linear velocity at the mean radius in m/s
= ω R = DN/60
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46. Mass of the rim, m = Volume × density = ρ DA
If the cross-section of the rim is a
rectangular, then
A = b × t
where b = Width of the rim, and
t = Thickness of the rim.
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DIMENSIONS OF THE
FLYWHEEL RIM

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