What you need is a small, extremely simple mining car set-up, so look at how-to mining literature. Historical stuff should be loaded with calculations you might need to consider. Another good place to start would be to look at roller coaster lifts, and the like, along with diy backyard roller coasters that people have built. I would think you are mostly limited by your available skills and budget. If you can weld, and are fairly mechanically inclined, this should be a piece of cake. There are no-weld options as well. Steel is damn pricey these days, at least it is in my parts, so without some source of surplus materials, it might not be worth it. That is, not until you need it one day, and don't have it! Lol good luck!