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UpdateBraking that makes centsBrakingaheavytruckatanyspeedgeneratesahugeamountofheat.Overtimethiscandamagebrakediscs,padsandliningsandcompromisesafety.Thesolution:ScaniaRetarder.Text: Alexander Farnsworth Illustration: Semcon Informatic Graphic Solutions Photo: Carl-Erik Anderssonthe Way to sLoW DoWn a movingstandard truck in addition to applying thewheel brakes is to shift down and use theengine brake. All trucks have an enginebrake, but they are often noisy and thereforeless suitable in urban areas.But Scania trucks also have theScania Retarder, which together withdownchanging can be considered a thirdauxiliary braking system.“Scania Retarder is capable of dealing with90 percent of all braking on long-haul work,so it substantially increases the service lifeof the wheel brakes,” says Tomas Selling,a control system development engineer atScania. Moreover, the cost of downtime,materials and work for changing the liningsand brake pads on a tractor and semitrailermeans that investing in a Scania Retarderpays for itself within a couple of years.Scania Retarder was launched in 1993.Together with Scania Opticruise (automatedgearchanging), the Scania Retarder is ableto automatically choose the gear that needsto be engaged in line with the cooling andbraking performance required. Both share thesame control lever on the steering column.“Scania Retarder is about distributingthe braking power in a vehicle to as manydifferent systems as possible so that thebrake pads remain as cool as possible andin an emergency can deliver as much aspossible,” says Selling.In a Scania truck, the driver has the choiceof using the Retarder in fully automatic mode(actuated by the brake pedal) or in a manualmode (actuated by the lever on the steeringcolumn). In automatic mode, the brakepedal activates the Retarder, and this actionautomatically alleviates the disc brakes.But there is a funny thing that happenswhen using Scania Retarder.“Because a higher safe downhill speedcan be maintained, trucks fi tted with ScaniaRetarder can achieve a higher averagespeed on undulating roads, compared witha truck only equipped with an exhaust brake,”says Selling.“Scania retarder is capable of dealing with 90percent of all braking on long-haul work...”Tomas Selling, Powertrain Control System Development, ScaniaHow ScaniaRetarder worksScania Retarder is a hydraulic systemthat is integrated into the output endof a truck’s gearbox and uses highpressureoil as a braking medium. Viaa gear transmission, the Retarder actson the output shaft of the gearbox andthus directly on the propeller shaft.Scania GR875R 8-speed gearbox.Scania Retarder is partof Scania’s integrated powertrain inwhich ScaniaOpticruise also playsan important role.Once the Retarder is applied, it generatesa braking force on the propeller shaftcorresponding to up to 500 kW,depending on the propeller shaft speedand the applied braking torque. This isabout two to three times more brakingpower than the engine brake delivers.The lever on the steering columncontrols Retarder braking in five stepswith 20 percent increments.www.scania.com N o 3/2009 • SCANIA REVOLUTIONS 1