1. Gravity Vehicle

2. 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.

3. 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

4. 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

5. 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)

6. 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

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

8. Vehicle Construction Major components Chassis Wheels Braking mechanism
Axles
Bearings

9. 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

10. 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

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

12. 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

13. 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

14. 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

15. 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

16. Sources for more obscure materials
Wheels
R/C plane wheels, MPI CD’s
Bearings
, online, hobby shops, etc
Carbon fiber
Arrows, hobby shops, etc
Titanium
Amazon, smallparts.com, etc
Balsa
hobby shops, etc