Any of you guys ever try SketchUp? It looks real simple, works easy, and can draw up very complex objects. You actually build each part from scratch, from lines, curves, and solids. It shows shadows, so for a building ( my use for it) you can show a customer the shadow lines on (and in!) a building during a day, at different times of year.
You could model that dump mechanism, watch it dump in 3-D and stay in perspective too! 8 hours free use to hook you in, then $500. It's NOT mechanical engineering software, though, but you can model almost anything. Takes a bit of getting used to isolating one part of an object from another, as they naturally stick together and stretch together. Once past that, you're in good shape. Good help, tech support, and a very helpful forum that rivals this one in enthusiasm.
Jim