[DeTomaso] Activ suspension.

[Göran Malmberg]

Some month ago we where talking Corvette and its avtive suspension.
With regards to my Racing Corvette build. I found it useful to
write a few words about the issue to put in my book. Anf why not 
let you folks read it here. Any komments, please let me know.

Active suspension. 

Today we can build an advanced active suspension system, but the passive system will still appears the most, especially in amateur racing. One can of course imagine a hybrid solution in which an active system intervenes in certain parts of a passive system. But in practice there will be no purely active or passive systems, but there is always a more or less an integrated function. The active system has the advantage in that we can program such as spring constants, which decreases with increasing compression of the spring system, in contrast with the normal physical laws of spring. This is of course to achieve with mechanical gear ratios as well, but the difference is that with the active system, we can program the circumstances under which suspension shall be in one way or another. Like to eat the cake but still have it. However, it is not as easy as it looks, that you only acquire an active system you will have mastered the road maintenance problem. We know how it is only uising an advanced shock absorbers, which frightens many in terms of attitude. Even assuming a "closed loop" active system, it is those who understand how it works that may prevail and thus can make their own settings. Another factor that must be taken into consideration is that an active system is not detached from the mechanical geometry. We will, therefore, have a system that is both active and geometric. If we are in a hybrid system that uses 50% anti-dive so this puts an end to the forward momentum of the active system in that area because 50% is cut off from the suspension movement. This makes it necessary to be clear about what kind of basic geometry an active-sprung car should be equipped with. It is not just to buy an active system and put it on the car. 

In general, then we must be careful with the geometric debauchery. Despite this, we hear often on cars that are fast despite their rigid rear axle, Mc Person, Jaguar rear end, or any less good geometry, which would legitimize the solution in question. Or prove that it is "right". So it is not. Sure, it can go awfully quickly with really weird solution, but it is also about people who do not understand why the effects of an adjustment will not be as expected. If one is to adjust the car's balance, it is the cause of the imbalance they must give themselves to. Is the tire pressure fault so we should not adjust the swaybars. Is the whole construction weird you should replace the entire car on a track where it does not work. 

On an ordinary car, it's geometric relationships towards a linear slipp angle that gives a good balance, while the downforce racing car has a nonlinear slipp angle. Since the aero load changes with the speed as amended μ tire grip as a direct consequence thereof. Front tire dimensions are determined by the braking force, making them oversized for anything but high speed turns. In the slowest curves is sufficient almost to the dimension of a tire. One can exploit this by adding a large part of the roll stiffness in the front to thereby increase the acceleration grip on the rear wheels, which are needed for high-powered cars. Now there is a limit to how much the roll stiffness can be present, set by the lateral stability of the tires. It is about 200-300N/mm, if we look at some different tires, so having a car without suspension, the role of the balance to be determined by this meaning that maximum roll distribution ports around 65%. Swaybars is limited in the same way as the active suspension system, by a limitation set by other elements of its operating range. 

With an active suspension system, so need the springs as already mentioned,  not need follow the normal spring-laws, but may, for example, deliver higher constant with reduced burden. You can have the outer wheel to carry 99,9% of the roll, while still leaving the inner wheel at the ground.
At the rear, we have a different mode, the tires are not enough for a high-output engine. We therefore need to even out the load between the tires, but since the acceleration moves weight to the rear wheels the situation deteriorates. When braking the opposite happen, the rear springs of the car is under rebound and up front compression, which moves the centre of aero forward which impairs the rear grip, but we can take advantage of the relief of rear grip, which will result. 
Balance in high speed corners are determined by the mass position and aerodynamics, and we see that the normal suspension system will provide situations that are sometimes right and sometimes counter to the need. We can not just mount stiffer suspension system then, to take care of the car's downforce, which increases for these inconsistencies.
Goran