Originally Posted by claude
Many confuse the 'roll center' with 'center of gravity' (CoG). The center of gravity to put it as simple as possible rotates around the roll center .
For example When watching a nascar race you will may hear them say " they came in and raised the track bar'. In essence they raised to roll center.
With a low roll center and a high center of gravity the weight transfer in a turn is in a large arc. This translates into body roll. In most cases it is desrable to lower the center of gravity but there are definatly limits. If we are stuck on the possiblity to lowering the CoG then raising the roll center is a means to get rid of some body roll and allow the weight transfer to be in more of a lateral motion than 'up and over' so to speak.
When we determine the roll center locations at each suspension point then from there we can establish how they work together. This, in basic terms, is called 'roll couple'.
Hope that made some sense.
I have to admit I DO confuse the two myself sometimes
But in the NASCAR situation, when the track bar is raised or lowered, it only moves the roll centre miniscule amounts in order to slightly change a handling situation. In the'build' of the car, the aim is always to get the roll centre (and CoG) low in the frame.
But I think I've got my head around what you're saying about roll couples.