Mumbai University > MECH > Sem 5 > Theory Of Machines 2

Marks: 5 M

Year: May 2015

Rn = PL/(X-μa)

Rn = Normal reaction

P = Applied force

L = lever length

X = Distance of block from hinge

μ= coefficient of friction

a = distance of drum from hinge

• Self energizing effect:

  It occurs when frictional force adds to the breaking torque. In other words, the frictional torque and braking torque are in the same direction

  Rn = PL/(X-μa)

  Rn x X = PL + μaRn

  Where PL is braking torque and μaRn is the frictional torque.

• Self Locking effect

  It occurs when brake gets applied on its own.

  Rn = PL/(X-μa)

  P = R(X-μa)/L

  When X < μa, P becomes negative

  Hence, P is not required for braking and brake gets applied on its own.