Refusing to learn from the wiki sure makes for interesting challenges in minecarting. I picked up a few things while browsing other topics, but of, say, impulse ramps i only know the name and much of minecart pathing (including behaviour of derailed carts) is largely mysterious to me.
Still, i managed to build my first ~40 z purely gravity-powered minecart track that can actually get items delivered to the second stop! Hooray! The certainly ridiculously inefficient base design is as follows:
#######╔u##
#╔===d=╝=╗#
#|#######|#
#╚=======╝#
The cart comes down the 'u'p ramp (thanks to the thread which revealed how to make a tracked ramp actually accelerate a cart), makes two simple turns and leaves via the 'd'own ramp. If the cart is too fast, it will jump over the down ramp, and if there's a wall behind the hole it's supposed to go down, it'll crash into the wall and lose its payload, so here the jumping cart is caught by more track, run through a 'regulator loop' and, provided it's slow enough, eventually descends down the ramp.
The experiment which showed me the need for the regulator setup used a wooden cart, and i found that the cart crashed into walls on every third level or so. In this construction, i decided to err on the side of caution and built the regulator loop into every level past the third. This proved to be a good decision, because i was using a lead minecart loaded with dacite boulders, and it got so much speed that it jumped the ramp on every level. In fact, on almost half of all levels, it took two cycles to slow the cart down enough to get down the ramp. Very fun to watch.
Next up is seeing if track stops can be used to regulate a minecart's speed.