# Chassis Design 3g bump applied diagonally

1. Jun 20, 2011

### Jas1159

Ok well to many this is going to seem like a really stupid question im sure :/

I need to calculate Maximum Torsion in a chassis, to start with i want to look at collisions or rough terrain;

Assumed 3g bump applied diagonally
Assumed bump 150mm high

Overall factor applied 1.5

Giving an upward acceleration of 4.5g at the wheels

Opposite pair of wheels assumed to be 1g

As i understand this if a car hits a bump 150mm high I am assuming a 3g force is applied. I assume it is applied diagonally due to the impact location on the wheel? or the acceleration of the car?

I am unsure how the overall factor of 1.5 is decided? what is the 'overall factor'?

I assume by opposite pair of wheels it refers to the rear? but could this also be the passenger side if the impact was on the drivers side?

I apologies if this is like asking you guys to suck eggs however, I am comfortable designing and building to specified parameters and have an ambition to understand the stress calculations involved in creating these parameters. I would greatly appreciate any help explaining what is happening here in a dummy's guide?

2. Jun 20, 2011

### jack action

My understanding of what your are saying is as follow:

A bump of 150 mm high gives an upward acceleration of 3 g to a wheel. Applying a safety factor of 1.5, assume 4.5 g for the calculations.

Since it is applied to one wheel, say left front wheel, the «applied diagonally» means that it is the right rear wheel that will react (i.e. chassis torsion). The opposite pair of wheels are the right front and left rear wheels, which are both assumed to be under 1 g acceleration.

This is how I understand it.

3. Jun 21, 2011

### Jas1159

Thanks very much jack, that has confirmed many of my assumptions, the book still seems to refer to the opposite wheels as front - rear but i assume this will depend on whether it is a single wheel impact or twin.

Your help is much appreciated thanks