Donner Domination

Vishesh, Scott, Alan

Section A, Group 10

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(We have since removed the arch and attached the rubber bands to the underside of the chassis)

Operating Principle: Step By Step Details

Four of our rubber bands are on the underside of the chassis attached to eye hooks, and they start off pulled back, wrapping around the rear axel. There is a string attaching the front axel to the mousetraps, and it is initially slack. Upon release, the rubber bands unwind to propel the car down the first 20’ of the track. This whole distance the string is winding around the front axel, and it becomes taut at 20’, tripping the traps. The mousetraps, aided by the remaining two rubber bands, rotate the dowel through an arc, unwinding the string from the front axel and propelling the vehicle back to the finish line.

Interesting and Original Features:

• Our wooden wheels have more surface area than CD’s, giving us better traction.
• The chassis is made out of a clipboard for strength and durability.
• Our spliced string attaches the front axel to both the dowel and the cheese, cutting down on the string in the system, as opposed to having two separate strings, minimizing the chance of tangling.
• We cut an eye hook in half (imagine Captain Hook’s hook) and screwed it into the rear axel to catch the rubber bands to expedite the setup process. It prevents the rubber bands from slipping as they unwind, but releases them after they become slack so they don’t impede the motion on the way back.

Repeatability and Performance:

Trial Times:

• 12.05
• 11.59 (Best Time)
• 11.78
• 11.81
• 13.55
• 12.45
• 12.43

Our car is not as consistent as we would like. There are times when the traps trigger early, but it is never more than a foot, so we can compensate by overshooting a small amount. There is also a small chance of skidding as the mouse traps release, causing it to go out of bounds, but we rotated the wheels and the problem has mostly disappeared.

Biggest Roadblock:

The problem we encountered that was most difficult to overcome was steering. The axels are not perfectly parallel, so the vehicle had a tendency to swerve to the left. We added an additional layer of rubber bands to the wheels on the left to increase their radius, but that didn’t completely solve the problem. We determined part of the problem was the left wheels didn’t have enough traction and were slipping, so we tried redistributing the weight of the car to increase the normal force on the left wheels. Now, the car drives fairly straight.