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Weight Transfer

Most racing cars are driven by their rear wheels. As the car accelerates, more of the weight is supported on the rear wheels. This process is called `weight transfer'.

  
Figure 6: The forces acting on the front and rear wheels of an accelerating car.

We first need to introduce the `Center of Gravity', or CoG. This is a useful point of reference. It is defined so that: any force that acts through the CoG has no tendency to make the car rotate. If you apply the force in a direction that does not pass through the CoG, it will make the car rotate unless it is balanced by another force (Tipler, p. 278).

For a racing car, the CoG is located between the wheels and as close to the ground as physically possible.

When the car is at rest (), the up and down forces must balance:

 

and the torque on the car's body due to the reaction forces must also be zero (since the reaction forces do not act through the center of gravity.)

 

Figure 6 shows the forces acting on the car as it accelerates. To make it general, I've sketched in a propelling force at the front wheel, although this is zero for a rear wheel drive car, like F1. As before, the weight of the car is balanced by the front and rear reaction forces (eq 10), but equation 11 must be modified to allow for the driving force at the rear wheels, which creates an additional torque about the CoG.

 

Equations 10 and 12 are a pair of simultaneous equations that can be solved to determine the reaction forces

 

 

where is the `wheelbase' of the car.



next up previous
Next: Maximum Acceleration Up: The Straights Previous: A Simple Model



Richard Bower
Thursday October 8 16:09:30 BST 1998