Lammers’ Hydro-Pneumatic Suspension
Or Rather Josep Fontdecaba’s Hydro-Pneumatic Suspension

Racing for Holland didn’t use the clever, new suspension system after qualifying on Wednesday night at Le Mans 2005, but the system is still of interest. Alan Lis caught up with Josep Fontdecaba, the proprietor and engineering director of Creuat Suspension Technology, based in Barcelona, Spain and the creator of the hydro-pneumatic suspension system – at the test day weekend.

How did you come up this suspension system?
About 10 years ago I bought a road car with very, very soft suspension, which made it very unstable, so I started thinking how it could be improved. I came up with some ideas that are more or less what you see now on the Racing For Holland Dome. After we proved the theory with mathematical modeling, we started building mechanical prototypes for road cars. When we saw the results we started thinking that it could be applied to any kind of car and in 1999 we filed a patent on the basic system of all these prototypes. In 2003 we talked with a few racing teams and they showed some interest, when we explained that in theory this could be applied to racing as well.

Is this the first time this system has been on a racing car?
No, in 2004 we did some tests on a Dodge Viper and it was very promising, but the team did not race their car with the system. It is also on a Ford Puma rallycross car and that team is racing with the system and recently finished third in a round of the Belgian championship.

The first car it was fitted to was my Citroen, then we had a Range Rover with the mechanical version, then a Range Rover with hydraulic. After that we put the system on the rally cross car, then the Viper and now this car. We also made some prototypes for a Yamaha Grizzly quad bike.

Could you explain how the system works?
Yes. It is very simple. In a normal suspension system a shock absorber and a spring takes care of all the motion of one wheel. In our system we effectively have springs that are separately handling pitch, roll and vertical movement. This means that with our system you can adjust every movement of the body of the car separately. This is very useful on cars that have a lot of roll inertia because you can put more damping into the roll making it more stable without losing the ability to adjust the vertical stiffness. Our system allows the coupling of the front and rear axles so they can they can cross freely if you want them to or the system can be adjusted so they do not cross if that is what you want. In a car with a conventional suspension system when you go over a surface that is not flat and you have different loads on the wheels this can be very bad because the more roll stiffness you have the more difficulty the car will have over irregular surfaces. With our system what we try to do is to make the roll as stiff as we want but keep the weight on the wheels equal. This has several advantages, not only because you have more grip but also when you hit a bump it is absorbed reducing the effect of the bumps on the steering.

The suspension is described as a hydropneumatic suspension. What is the hydraulic element?
We use oil. There are two versions of the system, you can make it mechanical or hydraulic but for competition we always use hydraulic because you have more of the spring and the damping effect.

So there are actually no coil springs in the system?
No coil springs, no anti-roll bars, everything is done with cylinders that control the movement of the wheels. The system displaces fluid as in a conventional damper but this fluid is not only used for the damping, it also transmits forces to a central device that has gas chambers that act as springs. So in effect the fluid is both the damper and the spring.

Is the system easy to fit to a car, is it necessary to make any particular modifications?
The central device is fitted in the passenger seat area alongside the driver, you remove the springs and the dampers and put in hydraulic cylinders in place of the springs and fixed length metal rods in the place of the normal dampers, which can be done very quickly. So if the team wants to compare the results of normal dampers with this system, they only have to block the cylinders of our system and re-fit their normal dampers on the car.

How adjustable is this system?
You can adjust every movement separately.

How do you make those adjustments?
The spring rates can be adjusted by changing the gas pressure or the volume of the gas chambers and the damping rates you can be changed with adjusters that are in the system circuit.

Are they like the adjusters that you would click on a conventional damper?
Yes and you have also separate high speed and lower speed. But in total you have more adjustments, because in theory you could adjust low speed and high speed for every movement separately.

Is this system available to buy?
Not yet.

Is this something you are looking at?
We are studying this. The only problem we have with this is for the initial production we need to find a way where we can build enough units to make it commercially viable.

Is it an expensive thing to produce in small volume at the moment?
For small volumes it is of course more expensive then normal shock absorbers and it could be comparable to competition shock absorbers.

What is the meaning of your company’s name?
Creuat is located near Barcelona and the name in Catalan means crossed, because the first idea was to have a crossed link between the front and rear axles.