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OK, so all this gets me thinkingf: What makes a winning mousetrap car?

Well, if F=ma, and F is fixed, to maximize a we need a small m. Right? So I conclude the way to get the most is to have the smallest mass possible, all else being equal.

Yes, one must ensure the drive system is suitable - the string pulling the axle, the friction between the wheels and the ground, all that needs to be good, but there's a wide range of 'just fine' there. Also, you need to bring friction down to a negligible factor - those bearings are sick, but quite right.

If the CDs used as wheels could be swiss-cheesed, you should be able to get a lot better. Can you cheese the trap, too? (no pun intended).

Don

Re: pic: mousetrap car
 

this mousetrap car was optimized for the grading scale(total distance/5m time)
by having the string pull on a cone that i actually managed to thread. this enabled the car to have the best acceleration in the class and the furthest distance due to its very low rolling resistance.

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Don, while all of this is true...some contests dont just feature how fast the car is, but how far it goes too...which means you want o maximize distance (x or s).

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That is sweet..... Your probably the only person that I know of that has ever used a water jetted frame on their MOUSETRAP CAR!

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the "don't go against a robotics kid" came about in my physics class when we built trebuchets. they could weigh no more than 10 pounds - minus the counterweight - and had to throw a golf ball. Mine threw the golf ball 290 feet. Next closest was 150 feet (by a fellow robotics kid)

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A lot of that depends on the rules of the particular contest. The original poster's contest was distance/<time for first 5 meters>. This means that you want high accelleration. Other contests are just farthest distance. Others are fastest time for a set distance.

Way back when I was in HS, I built a mousetrap car where the score was the product of the mass and the distance traveled. Most of the entries were a few hundred grams and traveled a few meters. Mine was over 2 kilograms and traveled tens of meters. Only one other vehicle came close - it actually traveled slightly farther than mine, but was less than half the mass.

The main winning factor in my design was having a very high gear ratio. The wheels were 3-4 inches in diameter, and the axle was 1/4 inch. The mousetrap pulled a "ripcord" string which was wrapped around the axle. I made sure there was high friction between the string and axle, and low friction between the axle and the berring. Accelleration was very low, but the top speed was quite high.

The other design which did well was a hovercraft. It consisted of a container of dry ice which had a small hole in the bottom, and no other opening. The bottom of the vehicle was very smooth, and the floor was tile. This allowed the whole car to float on a cusion of CO2. The mousetrap was then attached and used to "push off" of a wall-like object at the starting line.

Mousetrap cars, balsa wood towers, popsicle stick bridges - these are all fun easy projects to work on that provide a great intro to engineering. Several years ago my FIRST team did one of these types of projects each week throughout the fall as a way to get the team to get to know each other and to learn various engineering priciples.

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This car ended up having a score of 11.
22meters/2second 5m time.
most other scores were around 1 or less

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Excuse me sir but I managed to get an 8 or so in that competition!

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I remember doing this in grade 8 as well, My car used records as wheels! So my actually took the same amount of time for one rotation of a CD with almost three times the distance to travel. We didn't have any fancy do-dad's on it back then and ours went all the way down the hall and hit the gym door!!!

That was a highlight of my life pretty much and it was two years before the robot team started at my highschool (that I wasn't a part of at the time)

Congrats on the win!! I love the waterjet, we don't even have that for our bot lol!:p

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Last year I attended my first Latin Convention (this is my sixth year taking Latin), and helped build a float-arm trebuchet that won the catapult contest by about twice as far as everyone else's catapults. It was this insane wooden and steel contraption about six feet tall with a three by three foot base. Since our leader graduated, I'm leading it this year! :) "Never go against robotics kids" for sure. I'm a happy nerd through and through. :D