Historical development of vehicle brakes:
The development of braking systems was synonymous with the invention of the wheel. It is assumed that some primitive methods of slowing and stoping the first vehicles and carts was to deploy a log attached by rope off the vehicle and allow it to drag along behind. Another assumed method may have been to deploy an anchor of wedge that could be stuck into the ground. As the development of brakes was becoming more of an important issue, the dragged systems adapted into onboard more efficient devices such as a wedge to jam against one wheel causing a skid. Although this method was easier and more efficient, it was also quite dangerous as the vehicle would often turn and in some cases cause it to overturn. The first effective braking system was introduced in 1838, the spoon brake. This system consisted of a wooden block that pressed against the iron wheel of the vehicle when a lever of foot pedal was mechanically applied by the operator. On heavier vehicles another adaptation of this brake was used where the friction block of the spoon brake was applied to one of the pullies in the transmission. The next developed braking system invented was the external contracting band brake. This system was largely more effective than the spoon brake. The band brake consisted of a drum attached to the axle of the rear wheels or the drive shaft under the vehicle, that was accompanied by a band with a friction lining that wrapped around the drum and was applied by a hand lever that acted on a number of solid rods that pulled and in turn contracted the band around the drum. This system became popular and widely used by manufactures by 1904. In 1898 the early disc brake was developed, these brakes made a large amount of noise and were highly inefficient, and as a result soon forgotten. In there replacement was the invention of the drum brake or the internally expanding shoe brake. This development was considered to be the most effective method of braking at the time. In 1907 disc brakes were brought back out on the market with the discovery of asbestos lined brake pads. This eliminated the nose factor of the previous make and also increased the margin enormously for service intervals. The mechanically operated drum and disc brakes were the two most competitive braking systems of this time, until in 1918 the development of the hydraulically operated braking systems was introduced. This system not only allowed a more even and smooth brake distribution to be applied but also increased the strength and the flexibility of the fluid and tubes allowed the brake lines to be weaved around components or the undercarriage and reach all four wheels without disturbance or overcrowding.
The Modern Hydraulic Drum Brake:
This brake system was developed after the external strap brake. It is a modification based on the strap brake, which has many areas that have been improved. The drum brake is a servo-assistant system which aids the performance and braking force dramatically. Like the disc brake the modern drum brake is operated by a series of compression cylinders and a number of flexible and corrosive resistant tubing. From the master cylinder the brake fluid (high temperature liquid) is equally distributed into four metal tubes which direct the fluid into the four slave cylinders located nearby the braking system at each of the wheels. As the operator compresses the brake pedal the brake fluid is forced into the slave cylinder from the master cylinder and squeezes the piston inside the drum to push the brake shoes apart to contact the inside of the drum and activate the friction linings. The shoes when in contact with the drum wedge and further compress against the pan as a natural self actuating function of these brakes. Because of this, when the brake pedal is released and the slave cylinders pistons retract, the shoes remain in contact, this is why a series of springs are attached to the shoes to restore the...
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