Drum brake is a brake in which the friction is caused by a set of brake pads or shoes that push against the inner surface of a rotating drum. The drum is coupled to a rotating wheel. The drum brake was invented by Louis Renault in 1902. In drum brakes, the shoes were mechanically functioning with levers and rods or cables. From 1930 the shoes are working with oil pressure in a small wheel cylinder and pistons, though some vehicles are sustained with pure mechanical systems for decades. Some of the brakes have two wheel cylinders.

Design

The brake drum is commonly produced on cast iron. Few automobiles contain aluminum drums, mostly for front wheel braking. Aluminum conducts the heat better than cast iron, which enhances heat dissipation and decreases fade. Aluminum drums are lighter than iron drums, which decreases the load. The aluminum wears easily than iron, aluminum drums will often have an iron or steel liner on the internal surface of the drum, connected or bolted to the aluminum external shield.

Drum brakes are generally illustrated as trailing or leading or dual leading. The brakes in the rear drum are for leading or trailing design. The shoes are moved by a dual performing hydraulic cylinder and centered at the same point. In drum brake, the brake shoes will always experience the self-applying effect, if the automobile is running front or reverse. This is mainly helpful on rear brakes, where the footbrake must apply adequate power to stop the automobile from moving back and grasp it on slope. The contact part of the brake shoes is big. The self-applying effect can safely hold a vehicle when the load is relocated to the rear brakes due to the slope. The benefit of using a one hydraulic cylinder on the rear is the differing pivot prepared in the form of a double lobed cam that is revolved by the action of the parking brake system.

The front drum brakes are designed in practice, but the dual leading design is more efficient. This design uses two activating cylinders arranged so that both shoes will utilize the self-applying characteristic when the automobile is moving forwards. The brake shoes pivot at opposite points to each other. This provides the highest probable braking when vehicle is moving frontward hence it is not efficient when the vehicle is traveling in reverse.

The finest arrangement of dual leading front brakes with trailing or leading brakes on the rear permits for added braking force to be set at the front of the vehicle when it is moving forwards, with fewer at the rear. This helps to prevent the rear wheels from locking up, but it gives sufficient braking at the rear when it is required.

Drum brakes are yet used in recent cars because of various manufacturing and cost benefits. Drum brakes let easy integration of a parking brake. They are frequently practical to the rear as mainly the stoppings occur in the front of the vehicle and therefore the heat produced in the rear is significantly less. Drum brakes are also rarely fitted as the parking and emergency brake even when the rear wheels use disk brakes as the chief brakes. In this situation, a little drum is generally fixed within or as part of the brake disk known as a banksia brake. In hybrid vehicles wear on braking system is significantly decreased by energy recovering motor generators, so few hybrid vehicles use drum brakes.

History

The automobile drum brake was invented in 1902 by Louis Renault. However a less sophisticated drum brake was used by Maybach a year before the invention of Louis Renault. In the first drum brakes, the shoes were mechanically activated with levers and cables. In the middle of 1930s the shoes were controlled by oil pressure in a small wheel cylinder and pistons, while few vehicles continued with olden mechanical systems itself for decades. Few brakes are designed with two wheel cylinders.

The brake shoes in drum brakes are subject to wear and the brakes required to be altered frequently. After the invention of self altering drum brakes in 1950s there is no alteration is needed. In the 1960s and 1970s the brake drums on front wheels are swapped with disc brakes and currently all automobiles use disc brakes on front wheels, with several disc brakes on every wheel. Still the drum brakes are frequently used for handbrakes as it was very complicated to design a disc brake for grasping an automobile while it is not in use. In addition it is very simple to equip the drum handbrake within a disc brake so that one unit provides service brake and handbrake together.

Old type brake shoes have asbestos. When driving on brake system of older automobiles care must be taken for not to gasp any dust present in the brake system parts. The United States Federal Government started to control asbestos manufacture, and brake manufacturers are changed to non-asbestos coatings. Automobile holders are at first complained of poor braking due to the change of asbestos. Later the technology is ultimately sophisticated to balance. Many every day running older automobiles are equipped with non-asbestos coatings. Several other countries too control the use of asbestos in brakes.

See also

Air Brake
Antilock Brake System
Disc Brake
Hydraulic Brake System