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Gravity Vehicle

Gravity Vehicle. SOSI 2012 Matt Chalker, Bro. Nigel Pratt, Dennis Papesh chalker7@gmail.com. Goal: Construct a gravity powered vehicle and ramp to move the vehicle down a track as quickly and accurately as possible (in draft rules) Two components Vehicle Ramp. Competition. Track 5 – 10 m

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Gravity Vehicle

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  1. Gravity Vehicle SOSI 2012 Matt Chalker, Bro. Nigel Pratt, Dennis Papesh chalker7@gmail.com

  2. Goal: Construct a gravity powered vehicle and ramp to move the vehicle down a track as quickly and accurately as possible (in draft rules) • Two components • Vehicle • Ramp

  3. Competition • Track 5 – 10 m • 50 cm interval regionals • 10 cm at state • 1 cm at nationals • 50 cm x 50 cm square start box • Start Dot at center of box • Finish Dot perpendicular

  4. Scoring • Four components – Low Score Wins • Distance Score • Distance from the fixed point to the Target Point in millimeters • Time Score • 25 * (Run Time). • Predicted Time Score • 25*abs(Predicted Time-Travel Time) • Height Score – NEW THIS YEAR • 2*Highest point of vehicle in cm in ready to launch position

  5. Construction rules • Vehicle • Less than 2.5 kg • Bent paperclip as a fixed point • Only wheels contact floor • Automated braking mechanism • Ramp • With vehicle loaded fit within 50cm x 75cm box • Release mechanism activated by unsharpened #2 pencil • Padding on base?

  6. General tips • Potential energy (u) = mgh • Maximize mass and height – maximize energy • Get fewer points • Minimize friction for speed

  7. Vehicle Construction • Major components • Chassis • Wheels • Braking mechanism • Axles • Bearings

  8. Chassis • Stiffness critical • Pay attention to joints • Carbon Rods (from arrows) • Wood • Good place to add weight • Design with braking mechanism in mind • Adjustable axle/bearing mounts • Steering

  9. Wheels Park-flyer style Aluminum hubbed MPI wheels • Thinner better for speed • More difficult to mount • Difficult to align • CD’s useful • Require special adapters for mounting • Rubber bands/balloons for traction

  10. Braking Mechanism • Threaded rod and wing nut (or tapped block)

  11. Axles • Critical Qualities • Stiffness, weight, ability to hold wheels/braking mechanism • Carbon Fiber Rods (From Arrows) • Smooth, light, stiff • Steel Threaded Rod • Easy to find, cheap, braking mechanisms, heavy • Aluminum Threaded Rod • Difficult to find, light, weak • Titanium Threaded Rod • Expensive (order online), stiff!, light

  12. Bearings • Simple or complicated • Tubes • Easy, cheap, use graphite, functional • Ball bearings • Reduce friction drastically, can get expensive • Ceramic hybrid best if willing to spend • May require some breaking in

  13. Ramp • Straight • Much easier to construct • Easier to transport • Not as efficient, • floor/ramp interface issues • Curved • Delivers energy much better • Winning team at Nationals will have one • Interesting math problem • http://en.wikipedia.org/wiki/Brachistochrone_curve

  14. Ramp materials • Frame • PVC pipes • Easy disassembly • Difficult to make curved ramp • Plywood/other wood • Heavy, difficult transportation • Surface • Particleboard, Masonite, others? • Lots of Skateboard ramp references online

  15. Sources for more obscure materials • Wheels • R/C plane wheels, MPI www.maxxprod.com/mpi/mpi-29.html, CD’s • Bearings • www.bocabearings.com , online, hobby shops, etc • Carbon fiber • Arrows, hobby shops, etc • Titanium • Amazon, smallparts.com, etc • Balsa • www.lonestar-balsa.com, hobby shops, etc

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