ENERGY STORING ELEMENTS AND ENGINE COMPONENTS Springs – Design of helical springs – Design of Leaf, Belleville springs and Torsion springs – Flywheels considering stresses in rims and arms for engines and punching machines. Design of Crankshaft.

1. Unit-4
Springs

2. Introduction
Spring is an elastic member which deflects
under the action of load and it regains its
original shape after the load is removed.

3. Application
• Automobiles
• Railway wagons
• Valves
• Watches

4. Functions of springs
• To provide cushioning effect
• Reduce the effect of shock or impact load
• To measure forces in spring balance
• To store energy such as in clocks, toys
• To apply forces and to control the motions as in brakes
and clutches.
• To control motions by maintaining contact between two
elements as in cam and followers

5. Types of Spring
• 1. Helical springs.
The helical springs are made up of a wire coiled in the
form of a helix and is primarily intended for
compressive or tensile loads.
The cross-section of the wire from which the spring is
made may be circular, square or rectangular. The two
forms of helical springs are compression helical spring
and tension helical spring.

6. Types of Helical spring
Helix angle more
than 10 degree
Helix angle less
than 10 degree
1)Closed coil helical or Tension spring
2)Open coil helical or Compression spring

7. Advantages of helical spring
The helical springs have the following advantages:
(a) These are easy to manufacture.
(b) These are available in wide range.
(c) These are reliable.
(d) These have constant spring rate.
(e) Their performance can be predicted more accurately.
(f) Their characteristics can be varied by changing
dimensions.

8. Spiral Spring

9. Leaf Spring

10. Disc or Belleville Spring

11. Conical Spring

12. Design of Helical Compression Spring

13. 1)Free length
2)Pitch
3)Endurance limit
4)Slenderness ratio
5)Pitch
6)Active coils
7)Solid length
8)Pitch angle
TERMINOLOGIES IN A COMPRESSION HELICAL SPRING
9)Hysterisis
10)Initial tension
11)Permanent set
12)Set
13)Spring rate
14)Spring index

18. Stresses in Helical Spring

19. Subjected to Axial Load

20. formulas
Torque, T = F X R
But , Torque =

21. Shear & Transverse Stresses

22. Transverse shear stress
Resultant
shear
stress

23. Wahl’s Stress Concentration Factor
• C should not be less than 3
• The value of C should be 5-12
• For industrial spring C= 6 -10

24. Deflection of the spring
C= D/d

25. Stiffness of the spring
C= D/d

26. Strain Energy Stored in Spring (U)
Also

27. Spring Under Impact Load
Energy Absorbed in Spring

28. End Conditions of Spring = Active coil + inactive coils
Poor Seating
Space
Better Seating
Space than
Plain
Better than
other types in
Seating Space
Its for high stress
model spring
application

29. Design Procedure of Helical Spring

30. The designers should find the
following basic things
• Pitch
• Diameter of the coil , D
• Wire Diameter, d
• Number of turns , n
• Free Length , Lf
• Solid Length, Ls
• Spring Stiffness, q
• Type of Ends

36. Condition of Natural Frequency

37. Stiffness – Springs in Series

38. Stiffness – Springs in Parallel

39. Helical Spring Subjected to
Variable Loading
Formulas
P 7.100 PSGDB

40. Helical Spring Subjected to
Variable Loading
• Spring subjected to fluctuating stresses are
designed on the basis of modified Soderberg
equation

41. Design of Belleville Spring

42. S.
NO
Springs in parallel Springs in Series
1
They have high load
capacity, this depends on
number of discs
The deflection is
proportional to the
number of discs

43. Formulas Axial Deflection

44. Constant

45. Maximum Stresses occurring at the edges

46. C1 & C2 - Constants

47. Constants finding graph
In general the ratio
of do / di should
be 1.5 - 5

48. Belleville Spring
Material
Chrome Vanadium Alloy
Steel
Allowable stress 1500 N/mm2
Young’s Modulus 2 x 105 N/mm2
Poisson’s Ratio 0.3
Thickness of spring 1 – 2 mm
Dia of disc at base 28 – 300 mm
h / t 0.4 – 0.75 for stiffness

49. t / do 0.03 – 0.06
Cone Angle 4 – 7 degree
Best value 6.5
Degree

50. INTRODUCTION

51. Formulas
7.131-PSGDB
7.131-PSGDB

52. LEAF SPRING

53. LEAF SPRING or FLAT SPRING
• The spring used not only for absorbing load ,
its also used to carry
• Lateral Loads
• Braque Torque
•Driving Torque

54. Arrangement of leaf Spring
• The design may be of cantilever type or simply
supported type.

55. Limitations in Leaf spring
They are stressed more at one specific location
and the other parts are stressed lightly
So some design considerations needed in this type.
So they increase the width of the plate and keep the
thickness as same

56. Material

57. Design Procedure

60. Check for Pin

61. Check for Pin

62. FLY WHEEL

63. INTRODUCTION
Fly wheel is a heavy rotating member
placed between power source and
driving unit.
It act as a reservoir – for storing energy
(its an energy accumulator)

64. Functions of fly wheel
• It will absorb energy when the demand is less
than supply of energy.
• It will release it when the demand is more
than the supply of energy.

65. Two distinct Applications of Fly wheel

66. Types of fly wheels

67. Fly wheel effect and
co-efficient of fluctuation of speed

68. Cont…

69. Maximum Fluctuation of speed
Co-Efficient of fluctuation of speed
The difference between maximum speed and
minimum speed during the cycle is called
maximum fluctuation of speed.

70. Value of Co-efficient of Fluctuation of
speed (Ks)
7.121-PSGDB

71. Mass of the fly wheel (m)

72. Co-efficient of fluctuation of energy (Ke)
The difference between maximum and minimum
energy during the cycle is called fluctuation of
energy

73. Formulas

74. Values of Co-Efficient of Fluctuation of
Energy (Ke)

75. Stresses in Fly Wheel rim

76. Cont..
Tensile Stress
Due to Centrifugal Force

77. Cont..
Bending Stress
Due to Straining Effect of Arms

78. Cont..
Resultant Stress
In rim with the junctions of arms

79. Stresses in Rims
Tensile Stress
Due to Centrifugal Force

80. Cont..
Bending Stress
Due to Torque

81. Cont..
Belt Stress
Stress Due to Belt Tension

82. Design of flywheel shaft, Hub and Key
Shaft
Hub
di = d

83. Design of flywheel shaft, Hub and Key
Key

84. CONNECTING ROD

86. Stresses in Connecting Rod

87. Formulas
7.122 - PSGDB
7.122 - PSGDB
7.122 - PSGDB

88. Formulas
7.122 - PSGDB

89. Formulas
7.122 - PSGDB

90. Formulas
7.122 - PSGDB
7.122 - PSGDB
7.122 - PSGDB

91. Whipping Stress

92. CRANK SHAFT

93. Introduction
• It’s a shaft used to convert a reciprocation
motion of piston into rotary motion

94. Types of crank shaft

95. Material of crank shaft
The crank shaft subjected to shock and fatigue loads.
so its should have more tough and fatigue strength

96. Stresses in Crank Shaft

97. Failure Cause
The crank shaft failures are caused by a
progressive fracture due to bending or reversed
torsional stresses .
Thus the crank shaft is under fatigue loading, so
the design is based on the endurance limit of the
material of the crank shaft