Wobbly suitcase on wheels? French scientists say run!

Have you ever been in a rush to get somewhere, trailing your luggage behind you, and found that your wheeled suitcase won’t stay on the ground? Or worse, a small bump or jolt causes it to flip over entirely?

French researchers from the University of Paris Diderot undertook a study looking into the mechanics of what exactly makes these kinds of suitcases so unstable. Dr Sylvain Courrech du Pont, one of the researchers involved in the study, told Agence France Presse, "The problem is the interaction" -- the clash, in other words -- "of rotational and translational motion. It may seem paradoxical, but it is precisely because the suitcase is designed to roll in a straight line that it moves sideways."

The researchers' study explains in more detail. “Lifting a wheel forces the rolling suitcase to shift sideways. This coupling follows that wheels roll without slipping and that the tilt rotation axis of the suitcase, going from the handling point to a rolling wheel, is not perpendicular to the rotation axis of the wheel,” the study says.

Dr Courrech du Pont added that the rule applies to all moving vehicles with similar mechanics, including caravans being trailed by a vehicle, and that this new found knowledge could help with future technology such as driverless cars.

"Earlier efforts to study this problem only looked at the motion of a solid block, so they missed the coupling," he added.