Download for anticlockwise rotation of the brake drum.

GUJARAT TECHNOLOGICAL UNIVERSITY
BIRLA VISHVAKARMA MAHAVIDYALAYA
(ENGINEERING COLLEGE)
VALLABH VIDYANAGAR
MECHANICAL ENGINEERING DEPARTMENT
SUBJECT: THEORY OF MACHINE
BE Third Level Fifth Semester
‘‘Band Brake’’
Submitted by:
Hardik Patel(130070119030)
Rajesh Hirani(130070119031)
Jaykishan Jadav(130070119032)
GUIDED BY: V.D.Chauhan
Simple band brake
• A band brake consists of a flexible band of leather,
one or more ropes, or a steel lined with friction
material, which embraces a part of the
circumferences of the drum.
• In a simple band brake one end of the band is
attached to a fix pin or fulcrum of the liver while the
other end is attached to the lever at distance b from
the fulcrum
The operating principle of this type of brake is
following:
• Frictional torque is generated when tension is
applied to the band. It is known that the tensions in
the two ends of the band are unequal because of
friction and bear the following relationship:
• If the band is wound around a drum of radius R, then
the braking torque is
• In simple band brake one end of the band is attached
to the fulcrum of the lever arm. The required force to
be applied to the lever is
for clockwise rotation of the brake drum and
for anticlockwise rotation of the brake drum,
where l = length of the lever arm
b = perpendicular distance from the fulcrum to
the point of attachment of other end of the
band.
• Notes :
– If the permissible tensile stress t for the material of the
band is known, then maximum tension in the band is given
by
T1 = t wt
Where w = width of the band
t = thickness of the band
– The width of the band should not exceed 150 mm for drum
diameter (d) greater than 1 meter and 100 mm for drum
diameter less than 1 meter. The band thickness (t) may also
be obtained by using the empirical relation i.e. t= 0.005
For brakes of the hand operated winches, the steel bands
of the following sizes are usually used
Differential band brake:
• In this type of band brake, two ends of the band are
attached to two points on the lever arm other than
fulcrum.
• The breaking torque on the drum may be obtained in
the similar way as discussed in the simple band brake
• Drawing the free body diagram of the lever arm and
taking moment about the fulcrum it is found that
for clockwise rotation of the brake drum and
for anticlockwise rotation of the brake drum.
• Hence, P is negative if
for clockwise rotation of the brake drum
for counterclockwise rotation of the brake drum
• In these cases the force is to be applied on the lever
arm in opposite direction to maintain equilibrium. The
brakes are then self locking.