Braking that makes cents

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.

TEXT: ALEXANDER FARNSWORTH

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 downchanging 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.

Scania Retarder pays for itself

Moreover, the cost of downtime, materials and work for changing the linings and brake pads on a tractor and semitrailer means that investing in a Scania Retarder pays for itself within a couple of years.

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 is about distributing the braking power in a vehicle to as many different systems as possible so that the brake pads remain as cool as possible and in an emergency can deliver as much as possible,” says Selling.

An automatic braking system

In a Scania truck, the driver has the choice of using the Retarder 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, and this action automatically alleviates the disc brakes.

But there is a funny thing that happens when using Scania 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 a truck only equipped with an exhaust brake,” says Selling.

The technology behind

Scania Retarder is a hydraulic braking 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 the engine brake delivers. The lever on the steering column controls Retarder braking in five steps with 20 percent increments.