Brake discs information. The disc brake or disk brake has a brake, which slows down rotation of the wheel by the friction caused by pressing brake pads against a brake disc with a set of calipers. The brake disc (or rotor in American English) is usually made of cast iron, but in some cases be made of composite materials such as reinforced carbon-carbon or ceramic matrix composites. This is connected with the wheel and / or the shaft. To the wheel, the friction material in the form of brake pads mounted on an apparatus said magnet bow stop mechanically forced hydraulically, pneumatically or electromagnetically from both sides of the disc.Friction causes the brake discs and attached wheels to slow or stop. Brakes transform motion and heat to warm the brakes less effective, a phenomenon that is fading.
Brake Discs – History
Disc-style brakes development and use began in England in the 1890s. The first disc brake caliper-type car was patented by Frederick William Lanchester in his Birmingham, Great Britain in the factory in 1902 and used successfully on Lanchester cars. However, the limited choice of metals in this period, meant he had to use copper as the medium on the disc brakes. The poor state of the roads at this time, no more than a dusty, rough tracks, meant that the buyer quickly wore the disc brake system non-viable (as defined in the Lanchester Legacy) make. It took another half century for his innovation to be widely adopted.
The 1950 Crosley Hot Shot is often given credit for the first American production disc brakes, but the Chrysler Imperial Crown actually had them first as standard equipment at the beginning of the 1949 model year. The drive was a Crosley Goodyear development, with a thickness type with ventilated rotor, originally designed for aircraft applications. Only the Hot Shot featured it. Lack of adequate research caused enormous problems with the reliability, especially in regions that use of salt on winter roads, such as paste and corrosion. Drum brake conversions for Hot Shots were very popular.
The Chrysler four-wheel disc brake system was complex and expensive than Crosley, but much more efficient and reliable. It was built by Auto Specialties Manufacturing Company (Ausco) of St. Joseph, Michigan, under patents of inventor HL Lambert, and was first tested on a 1939 Plymouth. In contrast to the caliper disc, Ausco-Lambert uses two disks that are growing rubbing the inner surface of a cast iron brake drum, which is used as the rembehuizing. The discs from each other to cut the friction against the inner drum surface to create by the action of the standard wheel cylinders.
Chrysler drives were “self-energy,” in that part of the braking itself contributed to the stopping power. This was achieved by small balls placed in the oval holes which leads to the brake surface. When the disc first contact with the friction surface is made, the balls are forced holes through which the discs farther apart and increase the braking energy. This made for lighter than brake calipers, avoid fading, promoted cooler and has a third more friction surface than standard Chrysler twelve inch drums. But because of cost, the brakes were standard on the Chrysler Imperial Crown through 1954 and the Town and Country Newport in 1950. They were optional on other Chryslers, priced around $ 400 at a time when a whole Crosley Hot Shot at retail for $ 935. The current owners consider Ausco Lambert very reliable and powerful, but admit that the grabbiness and sensitivity.
Reliable caliper-type disc brakes were developed in the UK by Dunlop and first appeared in 1953 on the Jaguar C-Type racing car. The 1955 Citroën DS with powered inboard front disc brakes was the first French application of this technology, while the 1956 Triumph TR3 was the first English production car equipped with modern disc brakes. The first production car with brake discs on all 4 wheels, the Austin-Healey 100S in 1954. The first British company with a production sedan (U.S.: sedan) on the market equipped with disc brakes on all four wheels was Jensen Motors with the introduction of a Deluxe version of the Jensen 541 with Dunlop disc brakes. The first German production car with disc brakes was the 1961 Mercedes-Benz 220SE coupe with British-built Girling units at the front. The next American production car with a caliper-type disc brakes was the 1963 model year Studebaker Avanti (the Bendix system optional on some of the other Studebaker models). For disc brakes became standard in 1965, the Rambler Marlin (the Bendix units were optional on all American Motors “senior” platform models), Ford Thunderbird and Lincoln Continental. A four-wheel disc brake system was also introduced in 1965 on the Chevrolet Corvette Stingray.
In comparison with drum brakes, disc brakes offer better stopping performance, because the brake disc is cooled faster. As a result brake discs are less susceptible to the “fading” caused when overheated brake components, disc brakes and recover more quickly from immersion (wet brakes are less effective). Most of the drum brake designs have at least a leading shoe, which has a servo-effect, such as above / drum. However, a disc brake has no self-servo effect and the braking force is always proportional to the pressure on the brake pads by using a brake servo, brake pedal or lever, this tends to give the driver a better “feel” threatened to to avoid jamming. Drums are also prone to “bell mouth stabbing” and fall worn lining material in the assembly, both the causes of different brake problems.
Many early implementations for automobiles located the brakes on the inner side of the shaft, near the differential, but most brakes today are located in the wheels.(An inboard location reduces the unsprung weight and eliminates a source of heat transfer to the tires.)
Disc brakes were most popular on sports cars when they were first introduced, since these vehicles are more demanding about brake performance. Brake discs are now the most common form in most passenger cars, although many (particularly light weight vehicles) use drum brakes on the rear wheels to the cost and weight down and to the provisions for parking easier. If the brakes for most of the braking, this can be a reasonable compromise.
The first motorcycles to use disc brakes were racing vehicles. The first mass-produced road motorcycle on a disc-brake sport was the 1969 Honda CB750.Disc brakes are now often on motorcycles, mopeds and even mountain bikes.
In the past, discs manufactured worldwide with a strong concentration in Europe and America. Between 1989 and 2005, the production of discs headed mainly to China.
The disc is the disc of a competent disc, against which the pads are applied. The design of the brake disc will vary slightly. Some of ordinary cast iron, but other hollow with fins or vanes assembly of two contact surfaces of the disc (usually as part of a molding process). The weight and power of the vehicle determines the need for vented discs. The “ventilated” disc design helps to dissipate the heat generated and is often used on the more-heavily loaded rotors.
Much better performance brakes have holes drilled through them. This is known as cross-drilling and was originally done in the 1960s on racing cars. For heat dissipation purposes, cross drilling is still used in some brake components, but is not favored for racing or other hard use as the holes are a source of stress cracks under severe conditions.
Brake discs can also be slotted, where shallow channels are machined into the disk to assist in removing dust and gas. Stabbing is the best method in most racing environments to remove water and gas and brake fires. Some brake discs are both drilled and slotted. Slotted brake discs are generally not used on standard cars because they quickly wear pads, but this removal of material is good for racing vehicles since it keeps the pads soft and avoids vitrification of their surfaces.
As a way to prevent thermal stress cracking and warping, the disc sometimes mounted in a semi-loose way to the hub with coarse splines. This allows the disc to extend symmetrically in a controlled and less unwanted heat transfer to the hub.
On the road, drilled or slotted discs still have a positive effect in wet conditions, because the holes or slots prevent a film of water to build up between the disc and the pads. Cross-drilled discs can eventually break into the holes due to metal fatigue. Cross-drilled brakes are poorly manufactured or subjected to high stresses will crack much faster and harder.
Brake Discs – Racing
In the racing and high performance road cars have different disk materials are applied. Reinforced carbon brake discs and pads inspired by aircraft braking systems like those used on the Concorde were introduced in Formula One for Brabham in collaboration with Dunlop in 1976.  of carbon-carbon brake is now used in most of motor sport in the world top-level, reducing the unsprung weight, better performance of friction and improved structural properties at high temperatures, compared to cast iron. Carbon brakes have occasionally been applied to road cars, by the French Venturi sports car manufacturer in the mid-1990s, for example, but have a very high temperature before it can get really effective and are therefore not suitable for use on the road. The extreme heat produced in these systems is easily visible at night driving, especially at shorter tracks. It is not uncommon to be able to look at the cars, either in person or on television to life and the rotors glowing red during the application to see.
Brake Discs – Ceramic composites
Ceramic brake discs are used in some high-performance cars and heavy vehicles.
The early development of the modern ceramic brake was made by the British engineers working in the industry for TGV applications in 1988. The aim was to reduce weight, the number of brakes per axle and provide stable friction from very high speeds and all temperatures. The result was a carbon fiber reinforced ceramic process which is now used in various forms for the automotive, railroad, and aircraft brakes.
The requirement for a large portion of the ceramic composite material with a very high heat tolerance and mechanical strength often relegates ceramic discs to exotic vehicles where the cost is not prohibitive to the application, and industrial use, where the ceramic brake disc and lightweight maintenance properties justify the cost compared to alternatives. Composite brakes can withstand temperatures that would make steel discs bendable.
Composite Ceramic Porsche brakes (PCCB) are siliconized carbon fiber, with a very high temperature capability, a 50% weight reduction on iron discs (thus reducing the unsprung weight of the vehicle), a significant reduction of dust, greatly increased maintenance intervals and improved durability in a corrosive environment compared to conventional cast iron discs. Found on some of their more expensive models, it is also an optional brake all street Porsches at extra cost. It is widely recognized by the bright yellow paint on the aluminum six-piston calipers that are tailored to the disks. The discs are internally ventilated like iron ones, and cross-drilled.
Brake Discs – Disc damage modes
Brake discs are usually damaged in one of four ways: scarring, cracking, warping or excessive rust. Supermarkets will sometimes respond to a disc problem by changing the discs is complete, this is done primarily when the cost of a new disc can even be lower than the cost of the labor to resurface the original disc. Mechanically, this is not necessary unless the discs have reached the manufacturer’s recommended minimum thickness, making it unsafe to use them, or vane rusting is severe (vented discs). Most major car manufacturers recommend brake disc skimming (U.S.: run) as a solution for lateral run-out, vibration issues and brake noises. The brake operation is performed in a lathe, that a very thin layer of the disk surface clean from small to repair damage uniform thickness removed. Editing the disc if necessary will maximize the mileage from the current drives on the vehicle.
Brake Discs – Too much lateral run-out
The measurement of this is effected by means of a dial indicator to a fixed solid surface, with the tip at right angles to the face of the brake disc’s. It is usually measured approximately 1/2 “(12 mm) of the outer diameter of the disc. The disc is spun. The difference between the minimum and maximum value on the clock face is called lateral runout. Typical hub / CD assembly runout specifications for passenger vehicles are about 0.0020 “, or 50 micrometers. Sway can be caused by deformation of the disk itself, or by play in the wheel hub underlying face, or contamination of the plate surface and the underlying hub mounting surface.Determining the cause of the indicator displacement (lateral runout) requires disassembly of the disc from the hub. Disc face runout due to hub face runout or contamination will usually have a period of a minimum and a maximum per revolution of the rotor.
Drives can be edited to the thickness variation and eliminate lateral runout.Processing can be in situ (on the car) or out of the car (lathe). Both methods eliminate the thickness variation. Operation on the car with the right equipment can also eliminate lateral runout due to hub-face non-squareness.
Incorrect assembly can deform (warp) discs, the disc mounting bolts (or wheel / wheel nuts, when the disc is simply sandwiched in place of the wheel, like on many cars) should gradually and evenly tightened. The use of air tools to wheel nuts is extremely bad habit, unless a torque tube is also used. The vehicle manual will indicate the correct pattern for fixing, and a torque to the bolts. Wheel nuts should never be tightened in a circle. Some vehicles are sensitive to the force the bolts apply and down should be done with a torque wrench.
Often uneven pad transfer is confused for disc warping. In reality, the majority of the discs that are diagnosed as “deformed” are really just the product of uneven transfer of pad material. Unequal transmission path will often lead to a variation in thickness of the disc. If the thicker portion of the disc passes between the pads, the pads will move apart, and the brake light will increase, this pedal is pulsing. The thickness variation can be felt by the driver when it is about 0.17 mm or more (on car drives).
This type of thickness variation has many causes, but there are three primary mechanisms that contribute most to the spread of disc thickness variations connected to uneven pad transfer. The first is incorrect selection of brake pads for a given application. Pads which are effective at low temperatures, such as the brakes for the first time in cold weather, are often made of materials that are dissimilar decompose at higher temperatures. This inequality of decomposition resulting in irregular deposition of material on the brake disc. Another cause of uneven material transfer is incorrect break in a path / drive combination. For a good break, to the disk surface to be refreshed (by processing the contact surface, or by replacement of the disk as a whole), each time the electrodes are changed on a vehicle. Once this is done, the brakes are applied heavily several times in succession. This ensures a smooth, even interface between the pad and the disc. If not just the pads sees an uneven distribution of stress and heat, resulting in an uneven, seemingly random, deposition of pad material. The third primary mechanism of uneven pad material transfer is known as “imprinting path.”This happens when the pads are heated to the point that the material begins to degradation and wear of the disc. In a well broken in brake system (with properly chosen pads), this transfer is natural and actually it is an important contribution to the braking force between the pads. If the vehicle is stationary and the driver’s braking continues, the electrodes of depositing a layer of material in the shape of the pad. This small variation in thickness can begin the cycle of unequal transmission path.
When the brake disc is a certain degree of variation in thickness, uneven deposition path acceleration, at times to changes in the crystal structure of the metal that the wheel in extreme situations assemble it. Because the brakes, the pads slide over the different disc surface. Since the pads along the thicker portion of the disc, they are forced to the outside. The foot of the driver arranged on the brake pedal resistance, of course, this change, so that more force is applied to the electrodes.The result is that the thicker parts to see higher voltage. This causes an uneven heating of the surface of the disc, which are two major problems. If the disc heats unevenly It also expands unevenly. The thicker sections of the disc expand more than the thinner see through more heat, and thus the difference in thickness is increased. Also, the uneven distribution of the heat transfer leads to further path of dissimilar material. The result is that the thicker parts is warmer than the path of material thinner portions cooler received contributes to a further increase of the variation in thickness of the disk. In extreme cases this may even result in uneven heating of the crystal structure of the disc material to change. When the hotter parts of the discs is very hot (1200-1300 degrees), the carbon in the cast iron of the disk will react with said iron carbide molecules cementite forms. This iron carbide is very different from the cast iron of the remainder of the disc is composed of. It is very difficult, is very brittle and do not absorb heat well. After cementite is formed, the integrity of the damaged disc. Even if the disc surface is edited, the cementite at the disk does not carry or absorb heat at the same speed as the cast around it, so that the uneven thickness and uneven heating characteristics of the disk drive.
Brake Discs – Scars
Scarring (U.S.: Scoring) can occur if brake pads are not easily changed when they are at the end of their useful life and are considered worn. Once enough of the friction material is worn, the path of the steel back plate (for glued pads) or the pad holder rivets (for riveted pads) is directly bear on the wear of the disk surface, causing the brake power and making scratches on the disc. Generally a moderately marked / scored disc, which satisfactorily with existing brake pads, will be equally useful with new pads. If the deeper scars, but not excessive, it can be repaired by processing a layer of the surface of the disc. This is only a limited number of times the disk has a minimum rated safe thickness. The minimum thickness value is usually poured into the disk drive during the manufacture of the hub and the rim of the brake disc. In Pennsylvania, where one of the most rigorous vehicle safety inspection programs in North America, an auto-drive not safety inspection possible score is deeper than 0.015 inch (0.38 mm), and must be replaced if operation will drive under reduce the minimum safe thickness.
To prevent scarring, it is wise to regularly check the brake pads for wear. A band is a logical rotation time for the inspection, because the rotation should be regularly carried out on the basis of operation of the vehicle and time, all the wheels have to be removed, allowing ready visual access to the pads. Some types of light-alloy wheels, and brake arrangements are provided for sufficient open space for the pads to be viewed without removing the wheel. When practical, pads that are near the wear-out point must be replaced immediately as complete wear leads to scarring damage and unsafe brakes. Many disc brake pads, a type of soft steel spring or drag tab as part of the pad assembly which is designed to start dragging on the disk when the path is almost worn out. The result is a moderately hard metallic squeaking sound, alerting the user of the vehicle requires service, and this will not normally scar the disc when the brakes are immediately repaired. A plurality of electrodes may be considered for replacement, if the thickness of the pad material is equal to or smaller than the thickness of the support steel. In Pennsylvania the standard 1/32 “.
Brake Discs – Cracking
Cracking is usually limited to the drilled brake discs, so that small cracks may be formed around the edges of holes drilled in the neighborhood at the edge of the disc as a result of unequal to the disc, the degree of expansion in a very heavy work environments. Manufacturers that use drilled brake discs as OEM usually do for two reasons: the appearance, if they find that the average owner of the vehicle model will look better but not too much emphasis on the hardware, or as a function of reducing the unsprung weight of the brake assembly, with the engineering assumed that enough brake rotor mass remains to be racing temperatures and stresses. A disc is a heat sink, but the loss of heat sink mass can be compensated by the increased surface area to radiate heat away. Small cracks are shown in cross perforated metal disc as a normal wear mechanism, but the severe case the disc catastrophic failure. Nr. repair the cracks and crack as serious, the disk must be replaced.
Brake Discs – Rust
The brake discs are generally made from cast iron, and a certain amount of so-called “rest surface” normal. The brake disc contact area for the pad is kept clean by regular use, but a vehicle is stored for a longer period may be significant rust to develop in the contact area that the braking force can be reduced for a time until the rusted layer is worn again. Over time, can be ventilated brake discs of severe rust corrosion inside the ventilation openings, detracting from the strength of the structure, and must be replaced.
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