I had observed that minecarts with a "ride" command sometimes end up heavier after a ride, as though the rider was still inside. But curiously, this doesn't always happen. So i fiddled with it in .43.05 and it appears that
whether or not a cart retains its rider's weight after a ride depends on whether or not the cart's weight was observed during the ride.I knew minecarts are at least partially quantum-mechanical entities, but i hadn't expected them to go all Heisenberg on me.
If i let the rider just do their thing, the cart would revert to its normal empty weight once the rider dismounted (24 kg). But if i viewed the cart during the ride via "k" (view tile)
or if a weight measurement was taken by a cart-sensing pressure plate, the cart would display the altered weight (103-153 kg, depending on bulk of the rider) after the dwarf had dismounted, and would also trigger pressure plates responding to 100+ weight.
It looks like you can generate carts of unusual "empty" weights this way, which may prove useful in dwarven computing and in achieving transterminal speeds. These weights appear fairly persistent (survive carrying, guiding and pushing the cart) but are reliably re-set by saving/restoring the game, or of course by an "unobserved" ride.
And before you ask - i haven't found a way to add the weight of cargo to an empty cart, the bug seems to only work for riders.
Demo save:
http://dffd.bay12games.com/file.php?id=12802In the track rectangle, carts are alternately ridden over a pressure plate or over plain track before being pushed over a 100+ pressure plate. If you don't "view" the cart during the non-plate ride, the cart will re-set to standard empty weight (24kg) once the rider dismounts and doesn't trigger the southern plate. After the ride over the plate, the (dwarfless) cart will still weigh over 100kg and triggers the northern plate when pushed over it.