ASC Paper Notes
...
| Expand | ||
|---|---|---|
| ||
The distance of the NSP from the front axle is determined by the following equation   Assuming the tires in the front and back are the same model, and thus the cornering stiffness values are the same, the equation simplifies down to 1/3WB. |
The location of the CG relative to the NSP determines the characteristic of the yaw response. This can be summarized in variables known as the static margin and the understeer coefficient
...
3-Wheel Design Considerations
When looking at 3 wheels, a slight modification needs to be made to the understeer gradient and static margin equations. Instead of using C_f bar and C_r bar, they are instead replaced with C_f and C_r.
...
This is simply modifying the values present in the bicycle model and does not change the underlying performance metrics. This means that the same conditions for under/oversteer are the same for 3 wheels and 4 wheels; with the only difference being in the formula.
With only 2 wheels at the front and 1 wheel in the back, it is important to note that only lateral weight transfer between tires can occur at the front. This means, that due to load sensitivity, the front stiffness would decrease, which can increase the K value as lateral acceleration increases (assuming steering angle stays constant).
...
This means that the K value CAN be negative at the start but quickly become positive given increasing lateral acceleration. This is still indicative of a stable vehicle.
This means that, in theory, the maximum weight on the rear axle can be increased from 33.33% up to 36% while maintaining the same stability.
Tipping of 3-Wheel Vehicle - Tipping Test
The diagram that will be used for reference here is as follows.
...
Braking Weight Transfer
Reading List
...