Hi, I'm supposed to constuct a small rollercoaster using any material i want... I will be using tubing/hosing. A marble is what will be running through it. Now, what i am looking for is a few things that will help me build it to spec for the class. It needs to be at least a 90 second ride. In needs a few loops and turns and stuff. For the most part, I can see how to fix adjust the ride if it doesn't keep the marble on track, but if there are any tricks (simple equations? tips? anything?) that I can apply when building the track so that I can have the ball rolling at a moderate speed, yet not SPEEDING through, that would be great. On top, a slightly more specific and theoretical question: If I were to make loops (like the type where it goes around and around and around.. on a slight angle to the ground, kind of like a funnel, what would be the size of the circles, and the angle downward of the loops that would keep the ball moving at a decent speed without causing those.. 3 or 4 loops to go by in a flash of 3 -5 seconds. Am I looking at a LARGE circle with a small angle in the loop? a small circle with small angle? Large circle with large angle? etc. Does anyone know what I mean by this ? lol Thanks in advance for any help!