How can I calculate forces on a vehicle frame?

[7055]

I am working on an SAE Baja vehicle for a competition as part of my coursework requirements. Right now I am trying to come up with a method to estimate the forces that the frame will be subjected to. I need help doing this. I know that the top speed will be 30mph and that the vehicle will weigh 500lbs. To calculate the force of an impact I would also need to know the impulse or time of impact. I'm kind of stumped on where to start.

 

[Simon Bridge]

Impulse time depends on the type of collisions and where it strikes - you presumably have bumpers and shock absorbers at strategic places?

A back-of-envelope approach would model the impact as a spring contact ... if you have actual springs then this should be easy otherwise you have to work something for the rigid frame bending/flexing. If the idea is to figure out what sort of shock-absorbers to include then you can just put in the spring constant (or however the absorbers get rated) as a variable in the calculation.

The kinetic energy of the impact has to be absorbed by the springs.