In the automotive sector electronic brake force dis tribution for the front and rear wheels has existed since 1994 In 1995 stability programs are added that automat ically slow individual wheels when the driver seems to be losing control Since 1996 brake assist has been in stalled as standard equipment which assists the driver in emergency braking events Electronics enable Hill De scent Control HDC as well which supports engine brak ing The latter describes the mechanical resistance of the engine against torque forced upon it externally Eventually not only the size of automotive disc brakes changed the largest ones at the moment are Bentley Bentayga s family pizza sized front 17 3 inch 440 mm rotors but so have the materials they re made of Today ceramic brakes are regarded as the gold stan dard The high tech brake discs of carbon fiber rein forced silicon carbide do not corrode are insensitive to salt heat resistant which among other things avoids brake fading and lightweight hardly emit any fine dust particles and are able to last for 350 000 kilome ters 217 480 miles The best systems by now manage to bring a 1 5 ton sports car to a halt from 100 km h 62 mph in just 30 meters 98 feet Making sensible use of braking energy The most recent as well as most energetically effi cient method to decelerate cars is recuperation On hy brid and all electric automobiles and on other electric vehicles such as electric locomotives excess kinetic en ergy is recuperated as electrical energy for charging the traction or electrical system battery The electric decel eration can account for up to a fifth of the disc or drum brake capacity As a result the charging current generat ed by the technology may amount to as much as 30 per cent of the vehicle s range Electric cars such as the BMW i3 recuperate so intensively that a driver using a predictive driving style may be able to travel nearly exclu sively without depressing the brake pedal Here the tech nology is becoming increasingly advanced as well The new Audi e tron for instance decelerates with a seam less transition between electric and hydraulic braking Race driver Daniel Abt from the Audi Sport ABT Schaeffler Formula E team was obviously thrilled about the electric SUV following a road test The e tron decelerates by as much as 0 3 g strictly via the electric motors this is the case in more than 90 percent of all braking events so the degraded kinetic energy is nearly always converted into charging power As a driver you don t notice any dif ference in the effect of the brake that s operating at the moment The transition is seamless That s clearly more comfortable than on our Formula E race cars On the race cars recuperation only takes place on the driven rear axle whereas a conventional braking system acts on the front wheels Abt This requires a perfect setup of brake THE AUTHOR Motor editor Roland Löwisch has plenty of personal experiences with brakes and braking The de celeration technology saved his butt on numerous occasions so researching the cultural history of the brake for this article was huge fun balance in order to be able to act with precision down to a few centimeters on the narrow circuits By the way Nicolas Cugnot the unlucky technology pioneer mentioned at the beginning of this article ulti mately went down in world history even without brakes as the inventor of the first self propelled vehicle and the person to have caused the first ever traffic accident with an automobile Like playing chess at 200 km h 124 mph Not only Lucas di Grassi from Team Audi Sport ABT Schaeffler knows that perfectly timed energy use and recuperation are the keys to success in Formula E year a one family home could be supplied with the electric power that Schaeffler s partner Porsche recuperated during its 2015 and 2016 Le Mans wins some 900 kWh on each occasion in motion 53

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