My manufacturing partner came up with the idea of combine reservoirs for packaging reasons. Instead of having individual reservoirs for each damper, he wanted a 'front' reservoir and a 'rear' reservoir on the basis that it's easier to route pipes around an engine bay than to find homes for two large reservoirs.
Now this idea has a couple of distinct advantages. The first is that if we keep the combined reservoir vertical and large enough, we won't need to gas pressurise the fluid at all which will make life inordinately easier for the end user, although there would be an increased risk of cavitation. If you do decide to pressurise, it'll be a lot easier to bleed air out of the system with a single reservoir at the highest point of the hydraulic circuit.
The second advantage came to me a little later. When the car rolls there will be effectively no change in the working volume of the dampers as what goes down on one side will go up on the other. Only when the suspension pitches or heaves will there be a change in the volume. Now, if we replace the gas spring with a stack of belleville washers, then we're effectively adding an extra spring which only works in heave. If we restrict the flow into the reservoir we also have extra controllable damping of that heave motion.
So the rendering above is a revised system that does just that... those out there who like lateral thinking might like to consider what would happen if we connected the dampers diagonally rather than side-to-side. And if you're really interested check out this link for some Spaniards who've been doing pretty much the same thing.
