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20 years of safer braking by the Scania Retarder

The Scania Retarder has been holding heavy loads back for 20 years, using a dedicated piece of mechanical wizardry attached to the rear of the gearbox.

The Scania Retarder not only reduces braking system wear and tear, but critically importantly, boosts safety by keeping the service brakes cold for full emergency performance when a driver needs it most.

The way to slow down a moving standard truck – in addition to applying the wheel brakes – is to shift down and use the engine brake. All trucks have an engine brake, but they are often noisy and therefore less suitable in urban areas. But Scania trucks also have the Scania Retarder, which together with downshifting can be considered a third auxiliary braking system.“Scania Retarder is capable of dealing with 90 percent of all braking on long-haul work, so it substantially increases the service life of the wheel brakes,” says Tomas Selling, a control system development engineer at Scania.In addition, the saved costs of downtime, materials and work for changing the linings and brake pads on a prime mover and semitrailer mean that a Scania Retarder may pay for itself within a few years. And that’s before the additional safety feature of keeping the service brakes cold is considered.The Scania Retarder was launched in 1993. Together with Scania Opticruise (automated gear changing), the Scania Retarder is able to automatically choose the gear that needs to be engaged in line with the cooling and braking performance required.Both share the same control lever on the steering column.“The Scania Retarder distributes the braking power in a vehicle to as many different systems as possible, keeping the brake pads and linings as cool as possible. In an emergency, the pads can then deliver as much braking as possible,” says Selling.In a Scania truck, the driver can use the Retarder either in fully automatic mode (actuated by the brake pedal) or in a manual mode (actuated by the lever on the steering column). In automatic mode, the brake pedal activates the Retarder, automatically alleviating the disc brakes. But there is a surprising additional benefit to the Retarder:“Because a higher safe downhill speed can be maintained, trucks fitted with Scania Retarder can achieve a higher average speed on undulating roads, compared with trucks only equipped with exhaust brakes,” says Selling.Scania Retarder is a hydraulic system that is integrated into the output end of a truck’s gearbox and uses high-pressure oil as a braking medium. Via a gear transmission, the Retarder acts on the output shaft of the gearbox and thus directly on the propeller shaft.Once the Retarder is applied, it generates a braking force on the propeller shaft corresponding to up to 500 kW, depending on the propeller shaft speed and the applied braking torque. This is about two to three times more braking power than can be delivered by the engine brake.The lever on the steering column controls Retarder braking in five steps of increasing brake power. Depending on the position of the automatic exhaust brake switch, the automatic exhaust brake is also activated with increasing brake power to achieve the highest possible performance.“In Australia, we have demonstrated frequently the value of the Scania Retarder,” says Ian Butler, Scania Product and Application Support, New Trucks.“For instance, a highly competent driver heading into Adelaide should be able to run down the Mount Lofty Road quite safely using only the Scania Retarder, leaving the service brakes untouched and ready for emergency activation.“The same could be said for the run down the Toowoomba Ranges and many of the other steep descents typically found on Australia’s main highways. We often hear reports from drivers that they are amazed at the Scania Retarder’s performance on first acquaintance, and they quickly become committed to using it to assist their safe driving on a daily basis,” Ian says.