Hydraulic Reactive Ride Suspension System
Prior Art Department
Way back in 1999 on the way back from a mission in Scotland I stopped at a castle and wrote down an idea that I had had thanks to the boredom of the M6.
It is a dynamic reactive ride suspension system primarily for use on supercars and what are now called Hypercars. The problem it solves is;
an aerodynamic car needs to have close control of the height of the bodywork off the ground, but at the same time, when travelling at sub
aero speeds, it still needs “mechanical grip”. Spring rate is critical to achieve grip, in fact the parameter that is critical
is actually wheel frequency. But if you use soft enough springs to have a wheel frequency low enough to give good tyre compliance to the road
surface (grip) as soon as the aero kicks in the bodywork will hit the ground. So race car thinking uses stiff springs to get the aero stability
and compromises low speed grip, relying only on the flex in the tyre itself to keep the tread on the ground most of the time. If you use a
stiffening strategy that works in parallel with the spring, during the stiff phase the car ends up being supported on just the dampers really.
The wheel frequency goes through the roof, but you get away with it because there is enough downforce. The transition between the two phases
is a proper nightmare, so why not have no transition?
All the (misnamed) “active” ride systems that I have come across use some form of pressurising or stiffening of the dampers to
control body attitude; roll, pitch, heave etc. Like a hydraulic anti-roll bar not just in roll. All these increase wheel rate when they do this.
Increasing wheel rate and thereby wheel frequency damages the tyres ability to maintain a uniform pressure across the contact patch and a uniform or at least gently modulating net pressure in the contact patch. All this unhooks the tyre from the road surface, just like hitting the bump stops.
For more information about Hydraulic Reactive Ride Suspension Systems contact David Wedge on +44 (0)1865 407726