OLLIE PHYSICS: The dynamics of getting a weighty object to levitate


ONE REASON THE OLLIE HAS PLAYED SUCH A PROMINENT ROLE in skateboarding since its discovery is because it seems magical, perhaps more so than any other move. The board appears to levitate away from the surface in defiance of reason and the laws of nature. The skater jumps and the board follows . . . with nothing to pull it along.

When you study it closely, however, you find this magic carpet ride is an illusion, a sleight of foot that is only possible because of a few basic principles of physics.

If you walk up to a skateboard resting flat on its wheels and kick the tail down, the board will begin to rise. Even though you apply a downward force, this sets the board’s center of mass into an upward motion, and where the center goes the rest of the board follows. So kicking down on the tail is the Ollie launch engine. Apply enough downward force and the board will leave the ground.

If there were no gravity or air friction, the board would continue moving upwards away from the surface without slowing down. This is an example of Newton’s first law of motion which states that an object put in motion tends to stay in motion, with the same speed and in the same direction, unless it is acted on by an external force. It is another way of saying you can’t get something for nothing.

On Earth, gravity applies an external force that causes the board to stop rising and fall back to the surface. The weaker the gravity, the higher the board can go for a given launch kick. On the surface of Mars, where the pull of gravity is only about a third of that on Earth, you could ollie much higher than you could here. Ollieing over a standing person would be within reach of many skaters. On the Moon, where the surface gravity is just one-sixth of Earth’s, ollieing over a small building in a single bound would even be feasible. On Venus, which has about the same gravity as Earth, you’d be crushed and cooked by the super-dense, smoldering atmosphere, so that one’s right out.

Beyond the strength of gravity, there are two primary factors that determine how high you can ollie on flat ground. The first is how fast you can make your board leave the surface. The more forcefully you kick down the tail, the greater the initial upwards speed you impart to your board, and the faster that initial speed, the higher the board can rise before coming back down. Because light objects are easier to accelerate than heavy objects, using a lighter board also allows a higher initial upwards speed and higher maximum height.

The shape of the tail can influence the launch speed as well. Once your board’s tail strikes the surface no more force from your down kick can go into accelerating the board upwards. No matter how hard you push down, the launch engine shuts off the instant the tail pops. This means to get the highest Ollie you should use a board that allows the nose to rise considerably before the tail strikes the surface. This favors boards with inclined tails and shorter tails. On the other hand, if the tail is too short or too steep this will give you less leverage and impair your ability to perform a rapid down kick.

When I first learned the move, I was using a lighter board with a moderate kicktail. When Alan Gelfand worked out the move, he found a wider, heavier board with longer tail is what worked for him. His signature board even had the front truck and wheels mounted very close to the nose. This further slowed his board’s rise when the tail was kicked down. The reason for these differences was I learned the move on steep banks and flat ground while he learned it on vert. When riding on a vertical surface, gravity doesn’t keep you pinned to the wall. If you do a hard dynamic hop near the lip of a pool or half pipe—by kicking down the tail aggressively to get the board to move away from the surface as fast as possible—you risk floating too far out and landing down on the transition. Alan’s board design reduced this tendency by allowing him to do a slower and less dynamic hop. This allowed him to become the first person to consistently pull off big Ollies on vert. The tradeoff was he wasn’t able to do them well on flat ground or banks. In contrast, I could do them well in those terrains, but early on I tended to hop too far off from the wall when I did them on vertical, which made for some interesting landings. The takeaway is board design influences how well you can ollie because it governs how fast and how far you can make the board move away from the surface. Depending on your style and the kind of terrain you will be skating, faster is not necessarily better.

The other primary factor limiting your maximum attainable height on flat ground is how high you can jump. If you kick down on your tail forcefully and step out of the way, the board will rise higher than you can leap straight up. This means your Ollie height is not only limited by how high you can make the board rise, but also by how high you can jump up with your board as you launch it.

You can leap higher if you squat first, but this makes it more difficult to get the foot movements right. Rodney Mullen was apparently the first person to figure out those movements and consistently do high Ollies from flat ground. By late 1978, a few of us in South Florida were already ollieing up on curbs and over other small obstacles, but we hadn’t worked out the subtle refinement needed to get higher than about a foot. We were mostly skating walls then where more height wasn’t needed, and by 1981 most of us had quit skating after the original skateparks in the region closed. Rodney was a freestyle skater who saw opportunities to do new tricks by doing higher Ollies on flat ground. His technique expanded the envelope on what was possible and helped street skating flourish after the parks were demolished.

The really interesting physics at work in an Ollie is found in the board’s rotational tendencies. Whenever you step down on the tail you not only cause the board to begin moving upwards, you also cause it to begin rotating backwards. If you walk up to a skateboard, kick down the tail and step away, the board won’t go straight up and then come straight back down and land at the same place. Instead, the board will cartwheel backwards through the air.

There is a rotational variation on Newton’s first law of motion that comes into play here: an object put into a state of rotation will continue to rotate, in the same direction and at the same rate of spin, unless acted on by an external torque. Torque is the rotational analog of force. The more torque you apply to an object initially at rest, the faster you will make it rotate. To Ollie, you first kick down the tail. This provides a torque that rotates the front of the board upwards and rearwards, pivoting about the rear axle. The harder you kick, the faster the board rotates.

As you generate this initial torque by kicking down the tail, your front foot has to be raised at the same rate as the nose rotates upward. If you are too slow your front foot will block the nose’s rise, and if your front foot is lifted too quickly it will come off the deck and you will “lose” the board. This launch phase is fairly easy to figure out. Even so, if you did nothing other than kick the tail down and lift your front foot at just the right rate you would never pull off an Ollie. Something else is required to get the back of the board to rise up to join the nose. It turns out it is your front foot that helps bring the rear of the board up, and it does so in a way that is similar to how your rear foot brings the front of the board up during the launch.

After you kick down on the tail and lift your front foot with the rising nose, the board will be rotating upwards. Suppose you allow the nose to rise about a foot off the ground then suddenly stop lifting your front foot. Because the board still has momentum and a tendency to continue moving upwards, halting your front foot effectively starts to push down on the nose. This creates a new torque that opposes the board’s original nose-up rotation. The opposite of a nose-up rotation is a tail-up rotation. (Some skaters launch with their front foot placed a little behind the front truck and then slide it up towards the nose after launching; this also has the effect of pushing down on the nose to induce a tail-up rotation.)

If you now lift your rear foot precisely when your front foot begins pressing on the nose, the rear of the board will begin to rise and pivot about your front foot. Another way to look at it is if you stop your front foot while the board still has upward momentum, the only way the board can continue to rise is if you lift your rear foot. Here too the timing is critical: raise your rear foot too slowly and you block the rear of the board from rotating upwards; raise it too quickly and you lose the tail of the board.

As the rear of the board is rising, if you then stop your rear foot at the same height as your front foot, your feet will automatically level the board off. You may even feel the board press up against the bottoms of your feet as it tries to rise further (a nice feeling which lets you know you’ve done it right and could have gone even higher). This leveling-off phase allows you and your board to descend together for an even landing. When you get the level landing perfected, you can begin working on variations, such as landing on the front or rear wheels first to enter a manual.

What the nose-up and tail-up rotations mean in practice is when an Ollie is done correctly your board will do a seesaw motion as it rises: you press down on the tail to raise the nose, then press down on the nose to raise the tail. Learning the timing to shift from the nose-up rotation to tail-up rotation at precisely the right moment is the hardest part of mastering the Ollie. Kicking the tail down is easy. Jumping up is easy. But moving your legs with just the right timing to allow the board to rise up and stay in contact with your feet is not obvious and is difficult to get right.

When you finally do get it worked out, it will feel magical. It will seem like you are briefly cheating gravity. Fortunately, it isn’t necessary to know anything about forces, torques or the laws of physics to ollie well. But for those who have a curiosity about how things work, understanding what makes this levitation possible may help you reach new heights and perhaps create a few new illusions of your own. ◼︎

tom wolfe

Kicking down on the tail: The “Ollie launch engine.”

Photo: WikiHow

Philosophiæ Naturalis Principia Mathematica

Newton’s Laws of Phyiscs were first published in 1686 in Latin in Philosophiæ Naturalis Principia Mathematica, or Mathematical Principles of Natural Philosophy. The title page from the first edition is on the left, and the page containing the first and second laws is on the right.
Photo: Creative Commons

earth and moon gravity games

Earth and Moon: gravity games.
Photo: Hyperphyiscs, Georgia State University

Stacks Image 3045

The G&S Stacy Peralta Warptail 2 (1977) and the Powell-Peralta Alan Gelfand Model (1980) are two of the boards that Alan Gelfand rode during his influential period. The AGM was typical of late 1970s board design. It was nearly 11” wide and featured a short nose and a longer and wider than average angled tail.
Photo: Craig Snyder

Stacks Image 3078

Alan Gelfand performing his signature move at the Pinball ramp at Concrete Surf skatepark in Miami, circa 1979. Note how the board has almost no nose and Gelfand’s left foot extends nearly to the front of the board.
Photo: Rick Furness

Stacks Image 3051

During the pre-Ollie era of the mid-1970s Roger DiLorenzo of Hollywood, Florida, negotiates a step by applying weight on the nose to lift the rear wheels up and over the obstacle. Street curbs posed the same challenges to skaters until the flatground Ollie was introduced.
Photo: Courtesy of Roger DiLorenzo

Nicolas DelValle ollie skateboarding photo

The advent of the flatground Ollie, and subsequently the street Ollie, made hugs shifts in skateboarding once the physics of the move was understood. This female skater in contemporary Bogota, Colombia, negotiates something that would have been off limits to previous generations of skaters. This woman is also flipping the board, invoking the rotational variation of Newton’s Law that Jeff Duerr speaks about in the article.
Photo: Nicolas DelValle


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