Gravity Vehicle

Disclaimer This PowerPoint is based on the DRAFT rules for Gravity Vehicle 2013. The rules may have changed. The rules and parameters in the 2013 Rules Manual is the final say.

Goal: Construct a gravity powered vehicle and ramp to move the vehicle down a track as quickly, as accurately and as close to their predicted time as possible. Two components Vehicle Ramp

Competition Track 5 – 10 m 50 cm interval regionals 10 cm at state 1 cm at nationals 50 cm wide x 75 cm deep x 200.0 cm high rectangular start box Start Dot at center of box Finish Dot perpendicular

Scoring Four components – Low Score Wins Distance Score Time Score Distance from the fixed point to the Target Point in millimeters. This is a point-to-point measurement. Time Score 25 * (Run Time). Predicted Time Score 50* (Predicted Time-Travel Time) Height Score – NEW THIS YEAR 400* Vehicle Height in cm/ (300 cm – Vehicle Height in cm)

Construction rules Vehicle Ramp Total mass must not exceed 1.500 kg. Bent paperclip as a fixed point (measurement point) on either the leftmost or the rightmost edge/face of vehicle between front and rear axles extending down to within 1.0 cm of track surface Only wheels contact floor Automated braking mechanism Ramp With vehicle loaded fit within 50 cm wide x 75 cm deep x 200 cm high box Release mechanism activated by unsharpened #2 pencil

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

Vehicle Construction Major components Chassis Wheels Braking mechanism Axles Bearings

Chassis Stiffness critical Good place to add weight 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

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

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

Axles Critical Qualities Carbon Fiber Rods (From Arrows) 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

Bearings Simple or complicated Tubes Ball bearings 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

Ramp Straight Curved 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

Ramp materials Frame Surface Lots of Skateboard ramp references online 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

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