Final Design

The skateboard Jumping down the ramp!

            Invented in the 1970's by Alan "Ollie" Gelfand, the ollie has become a fundamental trick in skateboarding which allows the rider to jump over gaps and obstacles. But what are the physics behind the ollie? Learning physics can prove to be difficult for high school students. Therefore, the objective of this project is to combat the declining interest in math and science among children by making the topics more fun and interactive. High school science can seem dull as students sit at their desks when they should be up and about, learning in a more hands-on manner. By designing a skateboard that demonstrates the basic scientific principles of energy and momentum conservation, we aim to help children see science in a more exciting light, ultimately increasing the number who will go on to become scientists and engineers. We have created a robotic skateboard that performs a basic jump, or otherwise named a "bunny hop," which beautifully demonstrates the fundamental principles of the conservation of energy and momentum.

Here is a photo of the final design which jumped a height of 27 inches

The first step to creating a basic bunny hopping skateboard is to model the system which it is imitating. The design begins with a mass that is pushed down on top of two springs in order to store a certain amount of potential energy. When this is released, this energy is converted into kinetic energy which causes the mass to strike a plate that is rigidly attached to the skateboard. This causes a transfer of momentum, seen in equation 2, from the mass into the skateboard and results in the skateboard jumping off of the ground. Here, we assume an inelastic collision in order to simplify the model equations.

From here, the height of the jump, h, can be found through a simple motion analysis, using equation 3, where the final velocity of the skateboard is zero at the peak of its jump.

In the first few weeks of the project, we created a prototype in order to confirm the equations listed above. Through the mathematical model, the jump height was projected to be 5.1 inches and the actual jump height was 4.9 inches. This 4% error is understandable due to friction that was not accounted for. Therefore, this error is an acceptable amount and verified the mathematical model of our mass-spring system.

Here is a photo of the prototype which jumped 4.9 inches

When the final model was built, there was a projected height of 27 inches and we recorded heights between 25 to 27 inches regularly. On March 18th, 2013, the design team joined Paul Schmitt at the San Diego Science Festival and presented our findings to encourage kids to get excited about the fun applications of science and engineering.

Here is the description of the event on the San Diego Science Festival website