User:Bjh21/Dwarven block signalling

This page is not yet finished. What's already here probably works, though.

Minecarts are great, but things go wrong when they collide. This page presents a signalling system for minecarts that should stop them colliding.

The block concept

The critical concept is a block, which is a length of track that should only at most one minecart at any time. The job of the signalling system is to ensure that this is always true.

Blocks are delimited by pressure plates that are set to detect minecarts. A block can in principle have multiple entrances and multiple exits, but a single pressure plate can't be both an entrance and an exit for the same block.

Signals are used to control minecarts. A signal that can prevent a minecart from entering a block is said to protect the block and is an entrance signal for that block. A signal that can prevent a minecart from leaving a block is called an exit signal for that block. Any given signal will usually be an exit signal for one block and an entrance signal for the next block.

Signals

A standard signal is constructed from a power source (shown as P), two rollers, a gear assembly, and a pressure plate arranged like this:

█	█	█	P	█	█	█	█	█	█
═	═	═	╢	☼	╟	^	═	═	═
█	█	█	█	█	█	█	█	█	█

The track runs continuously under the signal from left to right. The left roller drives to the right constantly. When the gear assembly is engaged, it will cause the right roller to drive the minecart back to the left. This means that the minecart stays at the signal but never stops moving, which ensures that dwarves don't decide that it's finished its journey. When the block ahead is clear, the gear assembly disengages and the minecart can continue.

Another kind of signal is a station signal, used when you want a minecart to stop in the block, for instance to load and unload goods. This is very similar, but uses a track stop in place of the forward roller:

█	█	█	P	☼	█	█	█	█
═	═	═	≡	╟	^	═	═	═
█	█	█	█	█	█	█	█	█

Here, if a dwarf pushes a minecart rightwards from the track stop while the roller is running, the minecart immediately returns to the track stop. Once the roller is stopped, the minecart can pass it and continue along the track.