Mechanical four-wheel drive steering system with gearbox
Apex Dynamics BV sponsors the 21 students who participate in the Bridgestone World Solar Challenge on behalf of the University of Leuven as the team Punch Power Train Solar Team. The engineering students have worked for 13 months to get the Punch 2 ready to start on the 8th of October for the 3,000 km long journey from Darwin to Adelaide. The Punch 2 will prove itself in an enormously competitive playing field of more than 50 teams. Everyone tries to drive the route as fast as possible!
This year, there are a lot of novelties in the solar car. The Punch 2 features a unique mechanical four wheel steering system. This system allows the wheel caps (the housing around the wheels) to be even narrower without affecting the regulated turning circle. The result is an aerodynamic improvement of more than 1%.
The system consists of a mechanical decoupling of the front and rear wheel steering. This means that the front wheels rotate at the first 90 ° of the steering displacement. When the driver rotates the steering wheel further, the rear wheel steering gets activated. As a result, the pilot only uses the four-wheel drive at low speeds. With the help of steel cables and pulleys, the steering movement is transferred to the 4 wheels.
Because this is a new and challenging concept, the team decided to completely retrofit and test the steering system first before building it into the car. A brushless DC servomotor was used in combination with Apex Dynamics gearbox. This combination was mounted to the steering wheel of the test setup and simulated the steering movements that we can expect during a race of 3000 km.
The steering system was loaded with strong springs, which required a gearbox to provide the necessary force or torque. Many cycles are tested to validate the steering system for durability. During the tests, some of the steering system weaknesses were also identified, such as cable clips, which reduced the clamping force after many cycles. The tests were very useful and gave a lot of confidence in the steering system. The Punch 2 has now driven 2,000 km on circuits with the new four-wheel drive system.
Apex Dynamics wishes the KU-Leuven team good luck in Australia !