The strange ramp effect provides reliable power and a pretty regular overall speed to the cart. I've no idea how to regulate the repeat times apart from adding low-to-medium friction track stops on the flat tracks.
The setup can also be easily used for a latch with no moving parts: a simple 2x2 round circuit, two of them on flat ground, two on ramps below. Can be primed and stopped by a lever-operated hatch over one of the ramps. Basically the repeater in pictures one and two above without the western half on the upper loop.
And while i was at it, a compact powerless repeater without moving parts:
upper half:
The minecart is moving across a NW track corner.
lower half:
Just like in the self-lifter, a NW and SW track ramp on the bottom. Ordinary carved NS ramp to the north, beyond the pressure plate. The tricky bit is that because of the different design of the upstairs loop, forcing carts to come in from the south, the southern one of the two track ramps apparently works as an impulse ramp. The cart will go several rounds on the circuit until it reaches derail speed, then shoots off north, bounces into the wall/ramp and rolls back into the accelerator loop. It takes about 80 ticks to get to derail after entering the loop, so this was the shortest design that actually releases the plate before the cart passes over it again. You'll need a longer bounce track if you want to operate spikes this way, but the return time seems to be very reliable.
And what happens if you leash several of these self-derailers after each other, to hopefully get nice intervals for delay-response actions like spikes and bridges? Madness:
Not only do _i_ have a hard time understanding the design, it's very erratic - there are three self-derailers here, two heading south and one heading north. After the cart derails on the northwestern loop, it goes directly up a ramp and into the second loop. Once it leaves that, it takes a 180° turn and enters the southeastern loop before exiting that and going through the return track (Overall movement counterclockwise). I first tried it with only two derailers and an upper-level return track (there are remnants of that attempt still visible), but the cart comes out of the loops so quick that it often jumps off ramps, bouncing into walls or ceilings and stopping dead. In fact, that always happens when it moves from the northwest to the southwest derailer - it slams into the wall, but fortunately falls on top of a ramp and regains speed there. The overall time for a full circle is _around_ 400 ticks, but it seems to vary. A bridge linked to two pressure plates which were just over 200 ticks apart in a sample is waving very very erratically.