Braking a heavy truck at any speed generates a huge amount of heat. Over time this can damage brake discs, pads and linings and compromise safety. The solution: Scania Retarder.
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.
Moreover, the saved costs of downtime, materials and work for changing the linings and brake pads on a tractor and semitrailer mean that a Scania Retarder may pay for itself within a few years.
Launched 20 years ago
Scania Retarder was launched in 1993. Together with Scania Opticruise (automated gearchanging), 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.
“Scania Retarder distributes the braking power in a vehicle to as many different systems as possible, keeping the brake pads as cool as possible. In an emergency, the pads can then deliver as much braking as possible,” says Selling.
Automatic or manual mode
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.
How Scania Retarder works
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.