The first phase of activation consists of the transfer of energy between the loaded springs and the sliding mass referred to as mass 1, m1. Fig. 2: Conservation of Energy in the First Phase The conservation of energy can be viewed in between two states. State 1 has all of the potential energy because the springs are fully compressed and mass 1 is at rest. State 2 consists of all of the energy being converted into kinetic energy, as mass 1 is now traveling at a velocity U, and the springs are now at their equilibrium points. The second phase is the collision of mass 1 and the skateboard contraption, referred to as mass 2, m2. Fig. 3: Conservation of Momentum in Second Phase The final velocity of the system is dependent on mass 1, mass 2, and velocity, U, from phase 1. The third and final phase of jump is the point at which the wheels of the skateboard are no longer touching the ground and the whole contraption, that is mass 1 and mass 2, are moving together with a final velocity, V. The system can now be modeled as a single particle following a projectile motion. Fig. 4: Single Point Model Projectile Motion in phase 3 The initial velocity given in the x-direction will be provided by the skateboard starting its run at the top of the ramp. The final equation of the height achieved in the jump is dependent on four parameters: mass 1, mass 2, spring constant k, and the compression of the springs x. How It Works: The jump will occur due to the collision of a sliding mass and a contraption rigidly constrained to the skateboard. The sliding mass will gain its velocity from the release of the potential energy of the compressed springs. The collision will transfer momentum from the sliding mass to the skateboard, which is at rest, and will propel the skateboard upward, causing the entire system to jump. The jump can be broken down into the physics behind three phases. Prototype The prototype consists of a center shaft made from a copper pipe which holds an aluminum slider with two brass weights attached. When pushed down, two 34 lbs/in springs in series resist the slider, causing the mass to crash back up into an aluminum stopper. When the stopper is hit, the rigidly attached base underneath jumps off of the ground. Robotic Skateboard Rachel Dittemore, Joshua Harling, Jonathan Ladner, Ryan Meeks, David Quintanilla Department of Mechanical and Aerospace Engineering at the University of California, San Diego Sponsored by the UCSD MAE Department, Spawar, and BAE Systems Project Managed by Dr. Raymond de Callafon Overview Physics is often viewed as a boring and difficult subject, and because of this, many high school students show little interest in it. However, physics is fundamental to all engineering, and engineering is incredibly important for developing technology in today’s world. Teachers have looked for countless ways to make physics more appealing to students with little success, but this can be changed by incorporating the popular sport of skateboarding. The UCSD Robotic Skateboard project was created to infuse fundamental principles in physics with skateboarding by designing and fabricating a self- jumping robotic skateboard. Project Requirements and Deliverables A full scale robotic skateboard that is able to jump a minimum of 12 inches A mini robotic skateboard that is safe for student operation and is simple enough to be reproduced A ramp that will be used to give the robotic skateboard an initial velocity Incorporate physics principles into designs Demonstration of robotic skateboards at the San Diego Science Festival on March 18, 2013 Fig. 1: Deliverables: Bunny Hop Skateboard, Mini Hop Skateboard, and Ramp. Team (starting at left): Josh, Rachel, David, Ryan, Jonny Final Bunny Hop Design Four threaded rods for strength and adjustability Two Steel poles as guide rails One 42 lb/in spring on each pole, 84 lb/in total Total compression of 6 inches in springs PVC piping used as linear sliders Hairpin latching mechanism Steel plates used for weight within mass 1 Fig. 6: Bunny Hop Skateboard Impact on Society The main goal of this project is to encourage young students to become interested in science and engineering. This project ties the popular activity of skateboarding and science together by experimenting with springs and their ability to create large amounts of energy. Through demonstration and interaction at the San Diego Science Festival, students are able see how exciting science can be. Acknowledgements We would like to thank the following people, without whom this project would not have been possible or successful: Dr. Raymond de Callafon Dr. Nathan Delson Paul Schmitt Pedro Navarro Tom Chalfant, Isaiah Freerksen, and Mark Steinborne Alejandro Valencia Latching Mechanism This mechanism takes advantage of an over-dead- center crank which, when loaded requires only six pounds of force to release a 500 pound load. When the latch is locked, as shown in the figure below on the left, the load travels up the center and a solenoid prevents it from unloading. When the solenoid is actuated the latch can freely and safely unload the mass-spring carriage. Fig. 7: Latch Mechanism Mini Bunny Hop Skateboard 12 x 4 inch 2 Delrin deck with maximum height of 9 inches All components and body made out of Delrin Single tower shaft as guide rail Two 20 lb/in compression springs in series for a 10 lb/in equivalent and 40 pounds maximum load Small load and safe use for students Mechanical latch and release, string pulled The mini bunny hop skateboard is a safe, easy to use model of the full scale bunny hop. The latch hooks are moved to the side, allowing room for the mass to be compressed down, and then the hooks are moved back to latch onto the mass. The latch is released by the pull of the string that pulls both hooks off. Fig. 8: Mini Bunny Hop The prototype was a successful design and matched the model equations very well. With a projected 5.1 inch jump and an actual jump of 4.9 inches, this 4% error is understandable due to the unaccounted friction within the system. Figure 5: Bunny Hop Prototype BEFORE RELEASE AFTER RELEASE