Cooperation between KONI and URE
University Racing Eindhoven has been participating in the electric class of the formula student for several years already. KONI has been our sponsor for over 10 years and has constantly supplied the team with high-performance dampers. The past years the team has been driving around with dampers that are as light as possible, even using ex Formula 1 designs. Also the damping characteristics have been set to URE-specific curves.
To realise better setups on the car, which will lead to better performance at the competitions, it is desired to have dampers with different damping profiles. Together with KONI the decision was made to drive with low speed adjustable dampers on our car. Initiated by KONI, the decision was made to add low speed adjustment to the dampers, while maintaining the very low weight. The new adjustable dampers have the same weight and stroke as the previous dampers, while the length has only increased with just 2 cm.
To get to the damping profile URE looks into which damping is required for the car. At KONI the damper is then valved and produced as close to the desired damping profile as possible. In figure 1 and 2 the damping characteristic from this year’s car are visualized in a force-velocity graph. During the development process URE can count on the experience and expertise of KONI. After the dampers are delivered it is up to our team to come to good setups via extensive testing and get the most out of the custom KONI dampers!
Technical
For the damper settings the focus is at achieving the most mechanical grip instead of being as stiff as possible for aerodynamics. This is also of importance to our car, however the mechanical grip has priority, because the velocities reached during the events ensure the aerodynamic forces do not become very large. At URE different studies have been made into optimizing mechanical grip via the dampers in the past. These studies have made use of combinations of testing and simulations to find optimal damping characteristics for our cars.
The mechanical grip has been evaluated by studying the fluctuation in vertical force on the tyre. By minimizing this fluctuation the tyre can better transfer forces to the road. The vertical force has been studied for several different situations. Firstly, a simulation has been done in which one corner of the car, consisting of the tyre, suspension geometry and shocks, is driven over an uneven asphalt track. With this simulation damping at high damping velocities is simulated. Next to this simulation dynamic situations are also evaluated by a vehicle simulation model and testing. The dynamic situations studied are driving at constant velocity over bumps, a constant radius turn and handling of the car when a sudden large steering input is given. By simulating these situations damping at low damping velocities is evaluated. The settling time and damping ratio of the vehicle are taken as indicators with these simulations.
The results from these studies are the desired damping constants and also the transition point from low to high damping velocities. Because not all of the studies have been done on the latest car, the damping constants are converted into damping ratios. This can be done via the spring constants and the sprung mass of the car. Therefore, simulations and tests done on older cars can be used. The damping ratios are then converted to damping constants for the latest car, the URE12. KONI then produces the dampers as close to the desired constants as possible. Figure 1 and 2 show the damping characteristics for the URE12 dampers. As can be seen KONI produced dampers closely to the desired characteristics.
For more information about University Racing Eindhoven, check their
website.