Various questions about mouse trap cars

[harrypotter99]

Hi,

For a mouse trap car that is traveling about 10ft in the least amount of time, is it advisable to use wheels with a large diameter?

Basically, I am asking that given two wheels with THE SAME MASS, will the larger wheel always be faster in the same system? I've been thinking and I cannot figure out whether or not a larger wheel will be slower... The larger wheel should give more distance per cycle of the axle... is that all there is to it?

Thanks a lot.

[Mech_Engineer]

Keep in mind a larger wheel will have a larger moment of inertia, making it "heavier" when accelerating. But, at the same time, a larger wheel will also have a lower rolling resistance.

I would keep the size of the wheels on the large side, but not huge (best way to go would be a large spoked wheel, for light weight and large diameter).

[skeptic2]

While a large wheel will give you higher speeds you will also need decent acceleration to get up to speed quickly. As you increase the diameter of your wheels your torque decreases and you may not have enough acceleration to reach max speed fast enough.

There always are trade offs and dealing with those trade offs to obtain the optimum results is what makes these contests interesting. Can you model wheel diameter versus acceleration and max speed to determine which wheel diameter will cover the distance in the least time?

[Danger]

Having both read and participated in several threads of this nature, I believe that I've finally come up with the perfect solution.
I would strike a plea-bargain with the mouse, under which it would tow the vehicle to the required distance in return for its life.

[jack action]

The wheel is your transmission. You must have the diameter as small as needed to take advantage of the maximum friction force from your wheel. Going smaller would result in wheel spin, hence losses. Since time is your objective, your entire car design should be to maximize the use of the maximum friction force. Within reasonable limit, the friction coefficient of your wheel is far more important than its mass.

Everything you need to know to maximize your design can be found on HPWizard.com (http://hpwizard.com/car-performance.html).