Engineering Fair project

[Turtle]

Originally Posted by hongher2005

ah, but i just want it to slow down but have as just as much strength.. but the thing is.. i was wanting to know if it could happen without making it lose power

The power of the rubber band wound on the spool does not change, only how fast it is delivered I believe. Here is my thinking with the big wheels.

Remember, or if you don't know, that you can measure the diameter of a circle (distance across the round end of the spool) and multiply that by 3.14 (pi), to find the circumference (the distance around the spool).

So I have a spool 1" diameter and 1" * 3.14 = 3.14" around. Now let's use my test of 4 wraps of the rubber band around the spool. If the wheels were also 1" around, the car would move 3.14" * 4 turns = 12.56" before the rubber band was all unwound, and anymore forward movement would have to be coasting.

Now imagine you make the wheels 8" across. This means they are 8" * 3.14 =25.12" around the circumference. So now after the four turns of rubber band on the spool run out, you have traveled 25.12"*4 turns = 100.4". Because the rubber band power doesn't change, the large wheels make the car slow down, but go farther before the power runs out.

Hope this helps, and by all means if I have misstated the case, don't anyone hesitate to correct me.

[hongher2005]

alright, well, im going to the store today to buy the stuff for my project..

hmm.. so let me get this straight. if I have 5'' radius wheels, and say i wrap it.. 5 times.. the equation for circumference is Pie, R, Squared. So, i get 25*3.14 and it would be 78.5'' of distance? and Im thinking logically here.. If i had TOO big wheels, the rubber band wouldnt be able to pull the wheels resulting in the car stalling.. correct?

[Turtle]

Originally Posted by hongher2005

alright, well, im going to the store today to buy the stuff for my project..

hmm.. so let me get this straight. if I have 5'' radius wheels, and say i wrap it.. 5 times.. the equation for circumference is Pie, R, Squared. So, i get 25*3.14 and it would be 78.5'' of distance? and Im thinking logically here.. If i had TOO big wheels, the rubber band wouldnt be able to pull the wheels resulting in the car stalling.. correct?

No; circumference is 2 * r * Pi, not r squared. The diameter is twice the radius, so you can substitute diameter for the 2 * r. For your 5" radius wheels, they would be 10" in diameter and 10" * 3.14 = 31.4" in circumference.

Yes; if the wheels are too big, the car will stall. Good luck, and keep us posted.

[hongher2005]

Lol its going ok. I was going to post wut i looked like, but ill do it later.. i have thing to do xP