# Coefficient of Restitution for pneumatic wheels

• semion
In summary, Semionsemion estimates the coefficient of restitution to be 0.70. Skrambles says that the change of momentum for the whole robot will be different than the change of momentum for just a wheel, because the wheel is not independent of other bodies.f

#### semion

Hello all.
I'm trying to find impact forces acting upon a stare climbing robot.
I'm using the impulse = change of momentum principle. In order to figure out the change in momentum in a pneumatic wheel bouncing off a stare when it hits it, I need the Coefficient of Restitution of a pneumatic (or just rubber) wheel with a 280 mm diameter. Does anybody know of a data table or any source where Coefficient of Restitution for various wheels are estimated?
Also, if there are other ways to calculate the impact force between a wheel and a stare, given the mass of the robot and the speed with which it approaches the stare, I would be thankful.

Semion

semion: Assuming the tire air pressure is ~240 kPa, I would currently estimate COR = 0.70.

You could drop the wheel from a known height onto a hard, level surface and then measure how high it bounces. The ratio of the two heights should give you a good approximation.

If you know the momentum of the robot (mass times velocity), you can divide that by the time it takes to the robot to stop to give you the average impact force.

What sort of measuring instruments do you have available?