I have had this thought for many years... so i desided to share the idea with you guys here is what i think. Making roller coasters is fun in all but every great coaster needs some loopdy loops! to accomplish making a loop there must be 2 things vertical rails and upside down rails! which will be then be able to make a loop! Now you could try making a big downhill slope to get the energy to do the loop or even add redstone power rails which will need some redstone work... But i came up with a solution for those people that don't like using redstone. It is a mine cart with a engine inside! Now i know this is getting a little to moderan for minecraft but these are just ideas. The only problem with the powered minecart is you cant sit in it so you have to put a cart in front of the powered cart. But then another problem happens the front cart might get too far ahead of the powered one and wont get speed for the loop so I think the powered mine cart and the normal one should be able to be connected to each other like a train! This way you can be pushed by the powered cart and connect other minecarts to pool your friends in! Tnaks for reading :P ~RioRiley