Brake blocks are integral mechanical components of any breaking system in that they apply pressure to the brake disc or spinning surface of a wheel to reduce speed as a result of increased friction. A broad term, brake blocks refer to one brake component, the pad, or both the pad and the brake shoe which are fitted to the contour of a wheel or drum.
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Brake blocks are used in automotive, railway, transit coach and bicycle industries to help control speed and stop vehicles. As railway braking systems are vastly different from bicycle brakes, brake blocks differ significantly in size and material composition to meet the specific needs of each industry. While originally made of wood, cast iron became a popular material. Technological advances, however, now allow for a great deal of variety in brake block manufacturing. Health hazards related to the use of random fiber asbestos limit its use making semi-metallic and ceramic composites more common. Mineral fibers, cellulose, aramid fibers, chopped glass, steel, copper and ceramic compounds are used in a variety of combinations. These composites are sintered together in precise measurements to allow for optimal braking. It is important to consider wear rates, performance, longevity and material handling when selecting a brake block. Spark-free materials, for example, are necessary in environments where wheels and brakes might encounter oil or other flammable substances as cast iron brake blocks can produce hot iron dust when rubbed against the wheel or disc.
There are two main types of brake block, the "L" block and the "K" block. These designations were given as the shape of each resembles the corresponding English alphabet letter. The "L" brake block is used predominantly in freight wagon settings whereas the "K" block is more commonly applied to passenger trains, trolleys and transit coaches. The basic process of braking remains the same for either situation. When a lever or pedal is pressed, it releases brake fluid which is put under pressure and delivered to the braking mechanism for each wheel simultaneously. A small hydraulic pump engages the brake shoe. This block component is usually metal or durable ceramic and the rigid rubberized pad is attached with rivets or strong adhesives. The shoe presses the pad, or brake lining, into the spinning wheel or disc. The friction created by contact between the two materials causes the wheel to slow in proportion to the amount of pressure applied. Because this process gives off a great deal of heat, brake blocks must be able to account for thermal expansion of all components. Field experience as well as chemical and material engineering allow constant advancements in brake block design and the friction materials used to produce them. These advancements result in reduced maintenance and operating costs, longer wear life, better functionality and overall consumer satisfaction.
