Determining spring constant of a tire

thijsdb

1. The problem statement, all variables and given/known data

We are modeling the behavior of a sack truck when driven over a small step. Afterwords we will do some tests with an actual sack truck to verify the model. The movement will be modeled simply like a spring-damping system only having one spring and one damper, thereby ignoring horizontal movement. The occurence of the step will be modeled as a step-function: the ground will move upwards 2 cm for just .02 seconds.

mass of truck
mass of load
angles
measurements of truck
tire measurements
tire pressure
NEEDED: spring and damping coefficient





2. Relevant equations

How can we calculate, or reasonably estimate the spring and damping constant of the tire, given its measurements and pressure?


3. The attempt at a solution

First I thought about the surface touching the ground, given the pressure a force can be obtained by deviding the pressure by the area. This force then corresponds to a vertical position of the tire. Several measurements will give us different forces and different lengths, making the calculation of the spring constant possible. However this would involve measuring the pressure at each different position, as well as surface and position itself. this is very difficult since compressing the tire requires a lot of force and is only moves about .05 cm.. making acurate measurements difficult.
>Therefore we would like to know a way to calculate it or estimate the values, given the measurements & pressure