Whether intentional or accidental, everyone has likely encountered a phenomenon where the board flips when dropped upside down. Let's consider the principle behind this movement, known as Biebelheimer.
Summary
Elastic Rebound and Rotation in a Tilted Board
When a skateboard hits the ground at a slight tilt, its center of gravity shifts inward from the contact point. The curved tail and nose cause rolling motion, generating rotation. At the same time, elasticity pushes the board upward. These two forces combine, producing the characteristic flipping motion.
Gentle Impact Flips Better than Hard Slams
Slamming the board too hard flattens the nose and tail, amplifying vertical rebound but eliminating rotation—making the board pop straight up without flipping. A softer impact preserves curvature, allowing elasticity and geometry to work together, making flips far more consistent and effective.
How the Vertical Bounce Forms
Suppose you drop a skateboard upside down onto the ground. The board's weight presses it down, momentarily deforming the tail and nose. Because the deck has elasticity, the tail and nose try to spring back, propelling the board's center of gravity upward. It's the same phenomenon as when a ball bounces—any object behaves this way.
How the Rotational Force Forms
Now, what if the deck is slightly tilted? The tail and nose still begin to deform instantly upon hitting the ground, but the board's center of gravity is now positioned inward from the point of contact with the ground. As the center of gravity tries to get closer to the ground, the rounded shape of the tail and nose causes the board to roll, generating rotational force.
Meanwhile, the tail and nose try to return to their original shape, pushing the board upward. This upward force combines with the rotational force generated earlier, creating the flipping motion of the board.
Is it better to slam the board harder?
It's quite usual for the board to fail to spin. So, should you slam it harder into the ground? Not quite. When it hits too hard, the nose and tail flatten out under pressure. That amplifies the rebound from the ground, causing the board to pop straight up without flipping. In other words, a gentler impact preserves the natural curvature of the nose and tail, making it easier for the board to flip.
