Design of Helical Spring

 Introduction (What is springs ?)
 Spring material
 Applications of springs
 Disadvantages 0f springs
 Types of springs
 Design of helical spring
 Conclusion
2

Spring is : a device used to store energy,
so that when the energy is needed, it is
released.
They can return to their original shape
when the force is released.
It is defined as elastic bodies.
3

 The mainly used material for manufacturing the
springs are as follows:
1) Hard drawn high carbon steel 06) Inconel
2) Oil tempered high carbon steel 07) Monel
3) Stainless steel 08) Titanium
4) Copper or nickel based alloys 09) Chrome vanadium
5) Phosphor bronze 10) Chrome silicon
4

1) To apply forces and controlling motion, as in brakes
and clutches.
2) Measuring forces, as in the case of a spring balance.
3) Storing energy, as in the case of springs used in
watches and toys.
4) Reducing the effect of shocks and vibrations in
vehicles and machine foundations.
5

 If the deflection of the spring exceeds
some critical value than the spring will
buckle .
 It is difficult to replace the spring
 Ones the spring is damaged it is difficult to
repair
6

Helical springs
Leaf springs
Volute springs
Beam springs
Belleville springs
7

 Helical spring is a spiral wound wire with a
constant coil diameter and uniform pitch.
FUNCTION OF HELICAL SPRING
 Used to store energy and subsequently
release it
 To absorb shock
 To maintain a force between contacting
surfaces
8

9
Tensional springs
Compressional springs
Spiral springs
Torsional springs

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1. It has some means of transferring the load
from the support to the body.
It stretches apart to create load.
2. The gap between the successive coils is small.
3. The wire is coiled in a sequence that the turn is at right
angles to the axis of the spring.
4. The spring is loaded along the axis.
5. By applying load the spring elongates in action

Among the four types, the plain end type is
less expensive to manufacture. It tends to
bow sideways when applying a
compressive load.
11

 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.
12

1. It is made of a band of steel wrapped around itself
a number of times to create a geometric shape.
2. Its inner end is attached to an arbor and outer end
is attached to a retaining drum.
3. It has a few rotations and also contains a thicker
band of steel.
4. It releases power when it unwinds.
13

• Sometimes it is also called as a semi-elliptical spring, as
it takes the form of a slender arc shaped length of spring
steel of rectangular cross section.
• The center of the arc provides the location for the
axle,while the tie holes are provided at either end for
attaching to the vehicle body.
• Heavy vehicles leaves are stacked one upon the other to
ensure rigidity and strenth.
• It provides dampness and springing function.
14

The beam spring is the name commonly
given to an IBM key switch mechanism
which was formally referred to in some
documents as the combination beam
spring and fly spring or beam/fly spring
interlock. It was used in almost all of the
keyboards that IBM designed during the
1970s
15

A Belleville washer, also known as a
coned-disc spring, conical spring washer,
disc spring, Belleville spring is a type of
spring shaped like a washer. It has a
frusto-conical shape which gives the
washer a spring characteristic.
16

A volute spring is a compression spring in
the form of a cone (a volute).
17

 The design of new helical involves the following
consideration.
• Space into which the spring must fit and operate
• Values of working forces and deflections
• Accuracy and reliability needed.
• Tolerances and permissible variations in
specifications.
• Environmental conditions such as temperature,
pressure of corrosive atmosphere.
• Cost and qualities needed
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 C = Spring Index D/d
d = wire diameter (m)
D = Spring diameter (m)
Di = Spring inside diameter (m)
E = Young's Modulus (N/m2)
F = Axial Force (N)
G = Modulus of Rigidity (N/m2)
L 0 = Free Length (m)
L s = Solid Length (m)
n t = Total number of coils
n = Number of active coils
p = pitch (m)
τ = shear stress (N/m2)
τ max = Max shear stress (N/m2)
θ = Deflection (radians)
20

 A round wire helical compression is subjected to
axial force.
 The effect of axial force is equivalent to:
1. Torsional T=FD/2, acting on the wire cross section
2. Direct shear force F acting on wire cross section
 So stresses induced in spring wire are,
1. Torsional shear stress
2. Direct shear stress
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1. Torsional Shear Stress:
- The torsional shear stress induced in a spring
wire, due to torsional moment T=FD/2 is given by,
2. Direct Shear Stress:
- The direct shear stress induced in a
springwire,due to direct shear force F is given by,
22
33
816
d
FD
d
T
t

 
  22
4
4
d
F
d
F
d

 

3. Resultant Shear Stress:
- Hence, the maximum resultant shear stress in the spring
wire is given by,
dt  
23
48
d
F
d
FD







D
d
d
FD
2
1
8
3






Cd
FD 5.0
1
8
3







 2
8
d
FC
Ks



 Spring is made of an elastic material that
changes in shape, or deforms when
 a force is applied to it.
There are a number of other spring shapes
used in engineering .
24

Design of Helical Spring

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