Question Set 134

· During the design of a friction clutch what are the considerations that should be made?

In order to design a friction clutch the following points must be kept in mind:
> The material for the contact surfaces must be carefully selected.
> For high speed devices to minimize the inertia load of the clutch, low weight moving parts must be selected.
> The contact of the friction surfaces must be maintained at all the times without the application of any external forces.
> Provisions for the facilitation of repairs must be there.
> In order to increase safety the projecting parts of a clutch must be covered.
> A provision to take up the wearing of the contact surfaces must be present.
> Heat dissipaters to take away the heat from the point of contacting surfaces must be there.

· What are the different types of brakes and explain them briefly?

Brakes can be classified on the basis of their medium used to brake, they are as follows:
> Hydraulic Brakes: These brakes as their name suggest use a fluid medium to push or repel the brake pads for braking.
> Electric Brakes: These brakes use electrical energy to deplete or create a braking force.
Both the above types of breaks are used primarily for applications where a large amount of energy is to be transformed.
> Mechanical Brakes: They can be further classified on the basis of the direction of their acting force: Radial Brakes: As their names suggests the force that acts on the brakes is of radial direction. They can further be classified into internal and external blades. Axial Brakes: In these types of brakes the braking force is acting in an axial direction as compared to radial brakes.

· On what basis can sliding contact bearings be classified? Explain?

Sliding contact bearings can be classified on the basis of the thickness of the lubricating agent layer between the bearing and the journal. They can be classified as follows:
> Thick film bearings: These type of bearings have their working surface separated by a layer of the lubricant. They are also known as hydrodynamic lubricated bearings.
> Thin film bearings: In this type of bearings the surfaces are partially in direct contact with each other even after the presence of a lubricant. The other name for such type of bearings is boundary lubricated bearings.
> Zero Film Bearings: These type of bearings as their name suggests have no lubricant present between the contact layers.
> Externally or hydrostatically pressurized lubricated bearings: These bearings are able to without any relative motion support steady loads