So, I've been building a 50z high magma lift... and am now on the 3rd revision trying to get the thing to work, and this thing has already claimed the lives of several dwarves including both legendary mechanics. Here is the problem that keeps happening regardless of how I get the carts up the track/ramps: carts will go up about 20 to 40 or so z levels (have tried impulse ramps, and rollers), and then just stall out, not making it up the next ramp. Occasionally a cart will make it all the way up (or at least almost to the dump track stop/return route).
The bottom of the lift, the pump/fill basin is one more z level down.
Stuck test cart, 41 z levels above.
The rollers are set in the correct directions, at highest.
Problems encountered when trying impulse ramps included carts "bouncing" between the impulse ramp and normal "up" ramp, leading to multiple injuries when trying to clear the carts. The roller attempt results in similar, though less harmful jams, as once power is cut to the rollers the carts either just stop or start rolling back down.
Any ideas/suggestions would be welcome.
edit: Okay, came up with a possibility that might work. I'm going to put a small speed-loop about 30z up from the bottom, where the cart kicks out of the spiral into a small loop with impulse ramps and/or rollers to ensure highest possible speed before re-entering the spiral climb. Even though as far as I know, the rollers in use already should ensure it has enough speed to get all the way up without stalling.