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Braking: Materials and development

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In the world of brakes, the day of the drum is done, even though the drum brakes of today are more efficient than the discs of the 70s. There aren’t many (if any) automakers that still use drums on the front wheels, where more efficient disc brakes are usually employed to do the lion’s share of braking.

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Braking: Materials and development

  1. 1. Automotive Braking: Materials and DevelopmentThe nectar of internal combustive invention is generally milked from the dangerous swaggerof pace, not the pedestrian commute to curtail it.It often seems braking technology is accelerations unwelcome side project, attracting scantconcern from automotive engineers who appear infinitely more interested in the rakishtransfer of sheer horse power to physical momentum. And who could blame them? Speed isElvis, after all, and braking is for squares, man.One only has to examine the development of the technology involved in these diametricendeavours to understand where the historical impetus of automotive R&D lay. In thezealous quest for speed, stopping is apparently an afterthought, as if lifes dowdy, fastidiousadministrator stubbornly tugged the automotive manufacturers sleeve and tiresomelyasked: "I know you dont care if you die in a squealing high-speed crash, but what about meand the kids?!"(This would, I imagine, inspire a Doh! moment Homer Simpson could justly pursue tocopyright litigation. Thereafter the sheepish gearheads would reluctantly shoehorn in acouple of extra seats and, muttering, bolt on a brake or two.)As the technology that drove cars to go faster progressed, advances dwindled from greatlunges to micrometric increments: refinement sharpens the cutting edge that shaves itselfever thinner. Especially in motor sports, where mere hundredths of a second can so easilydescribe first place from, well, death. By comparison, brake technology advanced inversely,with little change occurring in the early days of motoring to increasingly rapid improvementsover the last thirty or forty years. One only has to drive a sports car from the 50s or 60s intoa corner at anything approaching an athletic velocity to experience the difference betweenthen and now: every bodily orifice startlingly puckers uncontrollably the first time you stampon the relatively useless brake pedal. This vigorous full-body alarm viscerally demonstrateshow urgently brake systems have evolved in more recent years. 1------------------------------------------------------------------------------------------------------------------------------ IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  2. 2. Ye Olde Drum BrakesIn the world of brakes, the day of the drum is done, even though the drum brakes of todayare more efficient than the discs of the 70s. There aren’t many (if any) automakers that stilluse drums on the front wheels, where more efficient disc brakes are usually employed to dothe lion’s share of braking. The main reason they are still used on rear wheels is a result ofcost: drum brakes are much cheaper and easier to implement as a parking brake (rear discsrequire a separate parking brake facility to be installed). Although cheaper to produce, theirmain failing is their comparatively inadequate heat dissipation, which is essentially whatbrakes are designed to do: convert kinetic energy into heat energy and disperse it asefficiently as possible.DiscsIn order to aid heat dissipation, disc designs have for years incorporated cross-drilled holes(increasing surface area), especially in performance designs where regular replacement dueto wear isnt such an issue, and have moved from being solid cast iron units with opposingcontact surfaces to two relatively thin contact discs separated by fins or vanes (often still asingle piece of cast iron). This allows air to flow magnanimously around the unit, vastlyincreasing the cooling efficiency.Racing DiscsRacing applications often include slotting the contact surface, where shallow channels aremachined into the disc at an angle to the direction of motion that aid in removal of debris,gas and water. This technique is not often used for road cars as the wear on the pads isobviously quite rapid. Air ducting is often introduced (usually to the underside of the car) tochannel airflow to the centre of the disc in further effort to increase cooling, as is theaddition of dedicated electric brake disc fans.Brake PadsA brake pads effectiveness is measured by the dynamic friction coefficient " ", which is theratio of the friction force compared to the force pressing the two surfaces together. Moststandard automobile brake pads range from 0.35 to 0.42, while high performance brakesystems can reach up to 0.62. The best materials have a coefficient that remains fairlyconstant as temperatures change. If the materials coefficient changes too much when hot or 2------------------------------------------------------------------------------------------------------------------------------ IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  3. 3. cold, the brakes may fade or grab: both undesirable results when either travelling at speedand/or sipping a hot cup of coffee.The dissipating of heat, therefore, is the primary impetus behind brake development, both indesign and materials technology. The main evolution has been in brake pad and discmaterials and configurations, primarily driven by the racing industry, where efficiencytranslates directly into dollars.The higher the coefficient of dynamic friction rating for the material, the better brake pad itmakes, which led to asbestos being used extensively for decades, largely because of itstoughness and heat-resistant properties. As the health dangers of asbestos dust becameapparent, however, aramid began to replace it; a synthetic fibre asbestos substitute oftenused in ballistic body armour. Kevlar or fibreglass can also be used.CompositesComposite brake pads generally consist of a material, such as aramid, infused with copperor iron fibres/dust to provide increased heat dissipation and increased friction for greaterbraking power. This does tend to make braking louder, however, and is more abrasive oniron discs. Want to learn more about current technologies and developments in braking systems? Visit our download centre for more articles, whitepapers and interviews: http://bit.ly/braking-articlesAbout IQPC:IQPC provides tailored conferences, large events, seminars and internal training programmes formanagers around the world. Topics include current information on industry trends, technicaldevelopments and regulatory rules and guidelines. IQPCs conferences are market leading events,highly regarded for their opportunity to exchange knowledge and ideas for professionals from variousindustries.IQPC has offices in major cities across six continents including: Berlin, Dubai, London, New York, SaoPaulo, Singapore, Johannesburg, Sydney and Toronto. IQPC leverages a global research base of bestpractices to produce an unrivaled portfolio of problem-solving conferences. Each year IQPC offersapproximately 2,000 worldwide conferences, seminars, and related learning programs. 3------------------------------------------------------------------------------------------------------------------------------ IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de

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