TECH TALK

How does an F1 car’s brak­ing sys­tems work? The brake-by-wire sys­tem is com­plex and has been rein­vented with the hy­brid era

Motor (Australia) - - POWER. PERFORMANCE. PASSION. | CONTENTS -

Brake-by-wire is now a thing, here’s how it works in the rigours of For­mula 1

“BRAKE-BY-WIRE AL­LOWS A GREATER LEVEL OF CON­TROL OVER BRAK­ING PRES­SURE FOR MORE BAL­ANCE AND STA­BIL­ITY”

WHEN YOU THINK ABOUT the abil­i­ties of a For­mula 1 car, its ac­cel­er­a­tion and down­force are usu­ally what come to mind. But in the last few years the brak­ing sys­tems in F1 have be­come ar­guably just as im­pres­sive. Be­fore we dive into how they work, let’s look at the ba­sics of brak­ing and how the pre­vi­ous con­ven­tional sys­tem worked. Much like the brakes in the vast ma­jor­ity of road cars, the sys­tem used pre-2014 in F1 cars had di­rect phys­i­cal con­nec­tion from the pedal to the caliper. To sim­plify it some­what, pres­sure from the pedal trans­fers through the mas­ter cylin­der and pres­surises the fluid in the brake lines, which acts on the calipers. The calipers then, as we all know, clamp and ap­ply fric­tion to the disks, slow­ing the car. Rather dra­mat­i­cally, in the case of F1. In 2009, the Ki­netic En­ergy Re­cov­ery Sys­tem (KERS) was in­tro­duced to F1, and this changed the brak­ing game some­what. As KERS har­vests power un­der brak­ing, it also cre­ates fric­tion and re­sults in more dra­matic de­cel­er­a­tion. In 2009 this wasn’t a huge is­sue for driv­ers, as KERS was lim­ited to har­vest a max­i­mum of just un­der 60kW. Un­til 2014, rear brakes were still hy­draulic. Now, F1 uses a sim­i­lar sys­tem called En­ergy Re­cov­ery Sys­tem (ERS) which ap­plies more fric­tion and is al­lowed to gather more en­ergy – around 120kW. Be­cause of this, teams were al­lowed to use a far more ad­justable elec­tronic brak­ing sys­tem to bet­ter con­trol the pres­sure ap­plied to the rear brakes for more bal­ance and sta­bil­ity. Front brakes re­main hy­draulic. So how does this sys­tem work? When a driver brakes, the pedal still pres­surises the mas­ter cylin­der for the rear brakes hy­drauli­cally, but the phys­i­cal con­nec­tion ends there. A com­puter mea­sures the driver’s pedal pres­sure, and then takes into ac­count both the front brake ef­fec­tive­ness and how much en­ergy the Ki­netic Mo­tor Gen­er­a­tor Unit (MGU-K) is able to har­vest be­fore reach­ing the 120kW stor­age ca­pac­ity. The front/rear brake bias cho­sen by the driver via steer­ing­wheel con­trols is also taken into ac­count by the ECU. While en­ergy is be­ing col­lected, the brakes will ease off to coun­ter­bal­ance the amount of re­tar­da­tion caused by the fric­tion of the ERS. If the MGU-K is un­able to gather any more en­ergy, the rear brakes ap­ply max­i­mum pos­si­ble pres­sure. If the ECU which con­trols the rear brakes fails, there’s a backup line to the brakes, though its ef­fec­tive­ness is lim­ited and un­able to ad­just it­self. This did ac­tu­ally oc­cur in the Cana­dian GP in 2014, when both Mercedes’ ERS failed and driv­ers were left us­ing the backup hy­draulics – de­liv­er­ing Daniel Ric­cia­rdo his first F1 GP vic­tory. The lower re­liance on rear brakes has now meant en­gi­neers can use smaller (and there­fore lighter) brakes at the rears, with some teams us­ing four-pis­ton calipers in­stead of six. For ex­am­ple, in 2014 Red Bull, Mercedes, Sauber and McLaren all down­sized their brakes in an ef­fort to make the ever-valu­able weight sav­ing, though Mercedes would later swap back to us­ing six-pis­ton calipers. Though brake-by-wire re­mains pri­mar­ily the realm of F1 en­gi­neer­ing, Alfa Romeo has taken it to the road with its Guilia’s brak­ing sys­tem, known as In­te­grated Brak­ing Sys­tem (IBS). Though it numbs the driver’s sense of what’s happening at the cor­ners of the car, like the pul­sat­ing ef­fects of ABS for ex­am­ple, it also al­lows a more im­me­di­ate re­ac­tion. Mercedes also gave it a try in the early 2000s with Sen­sotronic, though it didn’t last long, and many Sen­sotronic equipped cars were re­called.

COM­PUTER BRAINS

Rather than a driver need­ing to mod­u­late brak­ing dif­fer­ently each time due to the En­ergy Re­cov­ery Sys­tem hav­ing an in­con­sis­tent ef­fect on slow­ing, a com­puter ad­justs brake pres­sure based on each fac­tor.

RE­LI­ABLE

F1 cars still run con­ven­tional hy­draulic sys­tems for their front brakes, and can ad­just front/rear bias ac­cord­ing to the driver’s needs, al­though the sys­tem is still a few grades above the hy­draulic brakes found in road cars.

BACKUP PLAN

If any­thing goes wrong with the brake-by-wire sys­tem, there’s still a hy­draulic line to the rear brakes, though the driver has to work a lot harder to brake prop­erly with­out a com­puter ad­just­ing brak­ing pres­sure for them.

ADDING LIGHT­NESS

Though it may seem like a step back­wards to use smaller brakes with fewer calipers, the ex­tra slow­ing force ap­plied by ERS means un­nec­es­sar­ily large brakes are just ex­tra weight that could be shed to go faster.

ABOVE That’s not meant to hap­pen... rear brakes can still see sky-high temps and will of­ten smoke dur­ing pit stops

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