Greg asked if there was a video of Danny’s Rat Trap Racer in action. There is not. Danny accomplished his mission in AP Physics, but when showing the racer off in another class, the front end was snapped off by the repeated blows. With a 96 grade on file, Danny tossed the racer in the trash. (He’s not a pack rat like his Dad.)
With no video available, I can only describe what I saw in our hallway and our driveway during test runs the night before. I also want to offer this clickable front view of the racer:
Sleek, huh?
In early tests in the kitchen the racer had some design problems. Danny tied a single string to the trap arm with the other end to the rear axle. Danny would wind the string and set the trap. By dropping a pebble on the bait lever, the trap would violently spring, spinning the wheels. The car would move a foot or two, and more often than not the string would be broken.
After many experiments, three modifications turned the Rat Trap Racer into an amazing machine.
First, Danny stopped tying the string to the axle. I told him how my Grandfather, Papa, used to wind a string around a top and throw it. This solved one problem, because the string was being rewound on the axle, acting as a brake.
Second, he added duct tape along the edges of the rear CD wheels. This gave the wheels much better grab, especially on slick surfaces.
Third, Danny put two strings on either side of the arm and either side of the rear axle. Instead of the arm violently snapping, it would close in a more controlled way, allowing the car to accelerate to top speed.
By this time, the hallway was far too short to contain the speedy Rat Trap Racer. Final tests were conducted in the driveway where the racer zipped along some 30 to 40 feet on an upward slope!
The teacher has video of Danny presenting the physics of the Rat Trap Racer. I hope to get my hands on that and provide a transcript.
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