Mechanical Engg Simple Notes ,Solved problems and Videos

Limitations of knife edge follower are:

1. Excessive wear due to small area of contact between cam & follower surfaces.

2. In this follower a considerable thrust exists between the follower and guide.

Methods to reduce the slip in belt and pulley:

1. Vertical belt drive should be avoided.

2. In horizontal belt drive the upper side should be kept as loose side.

Law of Gearing: The law of gearing states that the angular velocity ratio of all gears of a meshed gear system must remain constant also the common normal at the point of contact must pass through the pitch point.

Self energizing & Self Locking brake

Rn x X = PL + μaRn

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

In the above equation when frictional force adds to the breaking torque. In other words, the frictional torque and braking torque are in the same direction its a self locking brake.

In the above equation when X < μa, P becomes negative

Limitations of a shoe brake :

1. Heavy side thrust causes bending of the shaft.

2. More wear & tear as the contact surface is large.

Uniform Wear theory:

When the product of pressure and area of the contacting surface transmitting load is taken as constant to determine the axial force & torque, it is termed as uniform wear theory as it is assumed that wear along the surface is uniform.

Effects of imbalance in machine

1. Imbalance imparts vibratory motion to the frame of the machine.

2. Produces noise which leads to human discomfort.

3. Detrimental effects on the machine performance & structural integrity of the machine foundation.