Torsional stiffness

by | Mar 1, 2012

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There are many words and expressions commonly used in vehicle dynamics, many of these are very abstract and hard to visualize. One of these words is torsional stiffness.

The torsional stiffness of chassis is relevant to help understand how roll stiffness torques from the front and rear axles interact through the chassis. Changing the roll stiffness distribution between axles is a very common way to modify the balance of a vehicle. If the chassis is too weak, the torsional stiffness is too low; any difference in roll stiffness between front and rear will be absorbed as twisting of the chassis. On a race car, this can sometimes be noticed as a car that doesn’t respond to changes in roll stiffness distribution. Something we need to keep in mind, but that we can’t see with our eyes.

If we talk about pick-up trucks, the story is quite different. In a recent PR campaign by Chevrolet, the torsional stiffness was made a marketing tool. Take a look at this video to see some serious chassis twisting:

Lots of twisting, no doubt, will it have an effect on the road handling of these trucks? If we review the test in more detail we quickly realize that the roll stiffness torques will have opposite directions. The resulting twisting torque will thus be much bigger than what we would see in a corner, where both roll stiffness torques will have the same direction. Only the difference in magnitude of torque will then cause the chassis to twist. However, seeing big pieces of metal twist is always fascinating!

Want to know more about roll stiffness distribution and how to measure the torsional stiffness of your vehicle, check out our 3-day seminars!

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