The point of this thread was not about minecarts being useless. They're invaluable in every area but mining.
Magma hauling indeed works. Someone has even come up with an automated version:
1) Set up a stockpile for minecarts only.
2) Build a trackstop tacking from it and dumping into a magma moat.
3) Build three-tile long medium rollers in moat. The exit ramp should be covered by rollers.
4) Place second minecart stockpile so that cart exiting moat would stop on it.
5) Place third cartpile where you need carts to be hauled assign wheelbarrows and set it to take from the second.
(1-week necro only)
While this seems really promising, it seems to have one fatal flaw: you can't set track stops to take from anywhere, it's the route that the minecart is assigned to. And you can't set a route to automatically take new minecarts once it loses the old one, or have I missed something?Ah, the ambiguity of "dumping in magma moat" got me. The track stop is set to dump in the direction of the magma moat, and it has it's own minecart on it, which then gets loaded with empty minecarts from the stockpile, which then get automatically dumped in the moat.
This system is really quite nice, and has the great side of being able to stockpile magma-filled minecarts wherever you want, without any oversight needed. A bucket chain method for magma, really. And now I'm envisioning magma-cannon setups (with manual loading, not like the pressurized-water-requiring autocannon one).
P.S. if
this method can be used to fill the minecarts, you don't even need to power the rollers. Might be tricky to get to work with the fact that the scheme above requires that the minecarts end up in magma after being dumped out on on a cart stop (the ending up in a minecart stockpile full part is easy, just derail into one). One possibility might be them falling down a dump chute with track ramps at the bottom, which hopefully will "catch" the minecarts, if they're treated the same whether they're previously-on-a-track minecarts or minecarts as items which were being hauled. I'll have to test this, once I get around to digging deeper from all my moat-fiddling and siege cleanups.