Steer by Brake: Simplifying the steering operation

In order to simplify the steering operation in trailers with more than three axles used in heavy and abnormal goods transportation, Kässbohrer in partnership with Knorr-Bremse has developed the Steer by Brake (SBB) System to reduce the operational complexity for efficiency and safety by eliminating the need for self-steering axles, and therefore reducing costs.

Trailers with more than three axles for heavy and abnormal goods transportation are equipped with self-steering axles, to fulfil the turning radius requirements as defined in the ECE-Regulation 79 and legislations according to the country of registration. However, the use of self-steering axles brings a complex steering operation and higher material costs.

Kässbohrer has developed the Steer By Brake (SBB) System to reduce the operational complexity for higher efficiency and safety by eliminating the need for self-steering axles.

Kässbohrer engineered the Steer by Brake technology in partnership with Knorr-Bremse, to eliminate the complex self-steering operation while fulfilling the turning radius requirements without self-steering axles. Furthermore, because the SBB is built on the existing trailer electronic brake system (TEBS) architecture, the use of the SBB reduces the total cost of ownership, in terms of initial investment, tire wear and maintenance.

Kässbohrer engineers first initiated the concept development phase to define project objectives, which is followed by the development of the breaking system infrastructure by Knorr Bremse. The Kässbohrer R&D team then applied the system into the vehicle. Two parties ran the test phase together.

The main challenge in the project was to keep tire wear as low as possible. Since the SBB idea simply suggests that the steering operation can be carried out by selective breaking of rear wheels individually, the first expected result was increased tire wear as a consequence of higher usage of breaks. Kässbohrer and Knorr Bremse engineers overcame this challenge by optimizing the system architecture after extensive tests.

The Steer by Brake (SBB) system replaces the self-steering axle(s) with standard (non-steering/rigid) axle(s).  The system builds on the existing TEBS architecture to provide control over the steering of the trailer. Consequently, during cornering, the air suspension of the axles is controlled by the trailer’s TEBS system. Furthermore, the system assists cornering by selectively breaking the inner rear wheel of the last axle, thus transferring the effective wheel base forward. Steer by Brake assists the cornering by allowing the rearmost axles to slip sideways through the corner.

The TEBS system automatically configures the suspension and braking systems to achieve the desired cornering radius when the trailer enters a tight turn at low speed.  As the axles are fixed, there is no need for the user to lock the axle for alignment while reversing as in the case of a self-steering system. There is also no need to lock the axles at high speed thus stability is maintained even in the case of a failure in the electrical system.