Gravity Vehicle

Disclaimer This PowerPoint is based on the DRAFT rules for Gravity Vehicle 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 cm high rectangular start box Start Dot at center of box Finish Dot perpendicular

Scoring Four components – Low Score Wins Distance 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 – Total mass must not exceed 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 – 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 Aluminum hubbed MPI wheelsPark-flyer style 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 – 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 – 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 – 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 –

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

Sources for more obscure materials Wheels – R/C plane wheels, MPI 29.html, CD’swww.maxxprod.com/mpi/mpi- 29.html Bearings – online, hobby shops, etc Carbon fiber – Arrows, hobby shops, etc Titanium – Amazon, smallparts.com, etc Balsa – hobby shops, etc