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[Larix]

This sub-topic made me think - hatches over ramps can indeed switch a minecart's direction (by sending it down a level or not). Hatches are also activatable by pressure plates and have various benefits over other switching methods:
- other than bridges, hatches don't fling minecarts around (usually, if a minecart moves across a bridge's tiles while the bridge changes status, the cart will stop moving and may also get thrown off by a tile) and have an immediate response.
- other than rollers, hatches don't need power to switch the cart's course, just a signal.

There are also two downsides: hatches presumably have a much larger friction (not an issue if you're just using a single hatch) and the need to properly navigate ramps restricts the usable speeds - a cart moving at derail speed will just jump over a downward ramp, carts coming up a ramp at high speeds can also jump and have trouble re-joining a track on the upper level. This predestines hatch switches for use with rollers, preferably not at highest speed.

I messed around with it and came up with a very compact repeater, self-timered via hatch switch:

Code: [Select]

╔▼
╔^
RH
╚╝

^- Pressure plate on a SW track corner, linked to:
H- Hatch over downward ramp
R - Roller running N->S, medium speed (some other speeds might work, too)

and on the level below:

W▲
 ║
 ▲
 W

Walls to make the ramps work, obviously. The southern ramp has an engraved NS track, the northern ramp is a corner ramp going SW.

Total space consumed: 2x4 on the upper level (no walls required), 1x4+1 on the level below (the walls are necessary). Basically, 2x4 on two levels; it's not likely you'll have much use for the 1x3 bit that remains free.

Either power the roller via a switchable gear and put the route stop on top of the switched-off roller or hurl in the cart from the side via push order.

The hatch is opened when the cart passes over the pressure plate, switching it to the 'outer' loop, keeping the cart away from the plate until it resets and the hatch closes again. With a medium speed roller, i got an overall time of 114 ticks between plate activations. Timing can presumably be changed by adding track or installing low-friction track stops or somesuch, but the shortest return time will be about 105 ticks - the cart must arrive on a closed hatch and needs to pass it and move onto the plate for the next signal.

This signal can be used to wave a bridge, but i think the timing is a bit shaky and the bridge occasionally misses a beat. I got a 'bridge cycle' of ~260 ticks for a return to the original state, which doesn't fit with the pressure plate's actual cycle.

Edit: with a highest speed roller and three medium-friction track stops, i got signal repeat times of about 106 ticks. The need for providing its own timer means the perfect 100 can't be reached and tuning for longer repeat times still requires extra track, but i find it's a nice combination of fast repeats and small size.

EDITEDIT:
Ahaha, i ran into one of the weird ramp bugs while trying other designs and can now proudly present the extra-tiny powerless repeater:

Code: [Select]

^¢╗
╚▼╝

^ - Pressure plate on SE corner track, linked to
¢ - Hatch cover over downward ramp

No adjacent walls required, as far as i could determine.

And below:

###
#▲#
#▲#
###
Northern ramp engraved with SE corner track
Southern ramp engraved with NE corner track

Better have wall all around it, because the cart is likely to derail down here.


The only object that needs activating is the hatch cover, which causes a bit of lag, but shouldn't be worse than alternative designs with two bridges. And thanks to the hatch's instant response, it doesn't hold down the plate and allows a reasonably short repeat interval. Obviously, it also only needs a single pressure plate to work. It can be started simply by putting the cart on top of the hatch and opening the hatch via lever. You'll have to lever the hatch back to closed so the cart can cross the pit and trigger the pressure plate to get the cycle started.

Throw a cart inside, and better have a lever-activated track stop on the loop, because this shit ain't gonna stop. I've no idea what exactly happens, but with only track ramps to sit on in the pit, the cart seems to gain momentum constantly until it springs out of the pit and goes on another round. I had run into this on a powered circuit and wondered why cutting the power didn't help - i eventually threw in another cart and the collisions finally stopped the movement. A solitary cart sitting in the pit however levered itself back out and started causing havoc again. I got a return time of about 132 ticks.