|Modern F1 cars are an interesting extreme contradiction in what should be correct geometry. They have an ultra high front roll center and a backwards sloping roll axis. The front suspension geometry and roll couple distribution are both totally sacrificed for aerodynamics. An F1 car probably pushes in super low speed turns, but then again I guess F1 cars hardly ever corner at super low speeds.|
The mass and roll center locations can be used to predict the car’s natural handling characteristics. If the front and rear roll centers are plotted and a line is drawn between them, that line will represent the roll axis of the car. The roll axis is the axis that the car rolls around in a turn. The mass axis of the car can be plotted roughly by drawing a line through the front and rear masses of the car used for plotting the roll centers.
|Can you guess what the terminal handling characteristics of this Porsche with a heavy rear weight bias and a low rear roll moment is going to be?|
The mass axis will henceforth be called the Mike axis since I could not find a preexisting engineering term for it! When the roll axis and the Mike axis are plotted next to each other, the distance and slope between the two will give you what the car’s natural handling tendencies will be.
|Ahhh, Sport Compact car called the roll axis the Mike Axis!|
If the space between the two lines is less in the front of the car, with an upward sloping Mike axis, the car will tend to understeer due to greater weight transfer to the outside wheels at the front of the car due to a greater amount of geometric anti roll. If the distance between the lines is greater at the front and less in the rear, the car will understeer less due to the greater amount of rear geometric anti roll giving more rear outside weight transfer.
Front engine RWD cars typicaly exhibit the latter trait can can oversteer a lot despite a front weight bias. Rear heavy rear and mid engine cars also exhibit this trait, partially due to a larger rear polar moment of inertia and a smaller rear than front roll couple. A front wheel drive car is typically so nose heavy that it is pretty hard to overcome the tenancy to understeer. It takes pretty high rear roll stiffness and a bit of geometric antiroll to get these cars to rotate with reasonable wheel rates.
|I have shit named after me yo!|