This document discusses torsion, springs, and helical springs. It defines torsion as the twisting deformation of a shaft under a torque. Springs are elastic bodies that absorb and release energy. The two main types are laminated/leaf springs and helical springs. Helical springs come in two varieties: close-coiled springs which experience pure torsion, and open-coiled springs which can undergo both compression and extension due to their larger pitch. Key spring parameters are the spring index relating coil diameter to wire diameter, and solid length measuring the distance between coils with no gaps.

1. UNIT-II
TORSION AND SPRINGS

2. TORSION
• Torsion of shafts refers to the twisting or rotational
deformation experienced by a long, slender cylindrical
component known as a shaft when subjected to a torque or
twisting force.
• This twisting results in the shaft's cross-sectional elements
undergoing angular displacement relative to each other.

3. TORSION EQUATION

12. POWER TRANSMITTED BY SHAFT

15. SPRINGS
Springs are the elastic bodies which absorb energy due to
resilience. The absorbed energy may be released as and when
required. A spring which is capable of absorbing the greatest
amount of energy for the given stress, without getting
permanently distorted, is known as
the best spring. The two important types of springs are:
1.Laminatedor leaf springs and
2. Helical springs.
Laminated or leaf spring. The laminated springs are used to absorb
shocks in railway wagons, coaches and road vehicles (such as
cars, lorries etc.).

16. HELICAL SPRINGS
• Helical springs are the thick spring wires coiled into a helix.
They are of two types:
1. Close-coiled helical springs and
2. Open coiled helical springs.
• Close-coiled helical springs. Close-coiled helical springs are the springs in
which helix angle is very small or in other words the pitch between two
adjacent turns is small. A close-coiled helical spring carrying an axial load
is shown in Fig. As the helix angle in case of close-coiled helical springs are
small, hence the bending effect on the spring is ignored and we assume that
the coils of a close-coiled helical springs are to stand purely torsional
stresses.

17. Helical springs

19. Closed coil helical spring Open coil helical spring
Wire of the close coiled helical spring is wound
tightly providing no gap between two adjacent
coils of the spring.
Wire of the open coiled helical spring is wound
not so tightly and thus sufficient space or gap
exists between two adjacent coils.
Pitch of spring wire is smaller due to small helix
angle.
Pitch of spring wire is comparatively larger as a
result of larger helix angle
Close coiled springs cannot undergo axial
compression. It is designed to resist stretching
and twisting.
Open coiled springs are designed to undergo
extension and compression; and deflect its length
accordingly under the action of axial load.
The close-coiled spring is a torsion spring and the
bending stress is negligible.
open-coiled helical springs belong to the
categories of torsion and bending springs

22. The spring index is defined as the ratio of the mean diameter of
the coil to the diameter of the wire
c=D/d

23. The solid length of the spring means the distance between the coils when
the coils are touching each other. There is no gap between the coils.
The solid length is given by
Solid length =Number of coils x Dia. of wire = nx d