Doing my project on a gravity car powered by 1kg weight Gravitational Potential Energy, and we used rubber wheels. can you tell me the benefits of using that?
Advantages of rubber wheels: 1. High coefficient of friction with the ground. 2. They are slightly flexible, so the car or the track it runs on are not perfectly flat, all four wheels will still be in contact with the ground all the time. Disadvantage: As the flexible rubber squashes and springs back, it dissipates some energy (as heat) - but that would be small compared to the advantages. Sold wheels made from CDs don't waste any energy by squashing, but you would need a 3-wheel car to be sure all the wheels touch the ground all the time. Also the coeff. of friction is lower, so you might waste energy spinning the wheels instead of moving the car. On the other hand a CD is probably lighter than a rubber wheel, if you are trying to get the maximum performance from your car. There is rarely a simple answer to an engineering design problem, uusally you have to choose a balance between the good things and the bad ones.
I can't see any advantages to rubber wheels. Since you are powered by gravity you are not applying any torque to the wheels so you don't need to worry about friction and slippage. CD's are better because they don't use any energy to deflect themselves from out of round. Plus the rubber has a little stickiness that resists the tire from moving when it contacts the ground. Ever notice how much your gas mileage goes down when your tire is deflated a lot? That is an exaggeration of the out of round, but it shows that your car engine is putting more work to turning those tires deflated. Then look at trains. They carry huge loads and they do it on steel rails with steel wheels because the load they would carry on tires would make them need a engine with twice the horsepower and they would get half the fuel efficiency. On your car you want to use every bit of that potential energy and don't waste any in flexible wheels and eliminate any frictional losses at the axles also.
it means engine malfunction
This all depends on what type of skateboard and the style of riding you prefer. If it is a long board, you need the softest rubber wheels possible, for grip. Soft rubbery wheels will grip better, and hard plasticy wheels will slide better. If you are doing freestyle type riding, you may want something in between. You want a little slide when landing difficult trick variations that may require a slight pivot upon landing. But if you're just riding ramps, most people prefer a slightly softer wheel to grip the ramp a little better.] Just remember: SOFT GRIP HARD SLIDE
