vehicle dynamics week 3 set 1
1, Can you change the total lateral load transfer that occurs during cornering? If yes, how?
2, Does the spring contribute to roll stiffness or is it responsible only for vertical stiffness?
3, Why do we want the load transfer on the front axle to be higher than the load transfer on the rear axle?
4, Assume you have a solid anti-roll bar (ID=0). If you want to double the torsional stiffness, by what factor do you have to increase the OD? What can you conclude from this?
5, With reference to an anti-roll bar, if the ID is half the OD, how much torsional stiffness do you lose when compared to a solid bar? What can you conclude from this?
6, What are the disadvantages of a solid rear axle over an independent suspension?
7, Why does the Mustang have a split lower control arm with two lower ball joints? Why won’t one ball joint serve the purpose?
Answers:
Answers:
1-Total lateral load transfer can be changed by adding wheel spacers to change track width or changing the ride height, but this is hard and seldom done ,instead optimizing the coupling between the elastic and kinematic components is usually done and this can be done by changing roll center and optimizing anti roll bar and spring stiffness.
2- yes, the springs contribute to the roll stiffness as it forms the primary roll stiffness source while the Anti rollbars are considered the auxiliary roll stiffness source
3-because increasing the load transfer on the front axle will make it lose its grip first which will result in understeer which is desirable as it is easier to control (for ex. by just releasing the foot from the accelerator) as opposed to oversteer which is harder and requires high skill and fast reflexes
4-increasing the OD by approximately 20%(19%) will give us double the stiffness, and because of that we can conclude that any small change whether it is increase or decrease of the OD can have drastic effects on the torsional stiffness of the antiroll bar
5-approximately 6%,so we can conclude that mainly the torsional stiffness is controlled by the outer diameter and it is the dominant factor, and only the inner diameter can be used for fine tuning the final stiffness.
6-Since the wheels are connected, a bump on one side effects the wheel on the other side, leading to loss of grip
Unsprung mass of axle and differential leads to slower suspension response to road changes ,therefore compromising grip
7-inorder to form virtual steering axis which will reduce the scrub radius and it won’t have any clearance issues ,and we can’t do it with one ball joint because it can hit the brake rotor because of the tight packaging space.