User:MentalMouse42/Sandbox/FM 4-way Flyers

Notes:
 * 20 slime blocks including cargo bays.
 * The spaces marked C? are optional cargo bays. If present, each consists of a slime block in that square, with fences attached on the two sides not already blocked by the layer-1 fences and blocks.  Each then has a minecart with chest on top.

Usage: The machine is started by updating an observer (one of the two with open faces) twice, using a flint-and-steel or a water bucket.
 * To go east:
 * Set fire (or water) behind the west-most observer.
 * Sit in the eastern minecart.
 * Before the fire extinguishes, click the note block nearest you to release the brake.
 * Wait for the fire to burn out (or remove the water) to trigger that observer again and start the engine.
 * To stop the engine, spam-click the same note block. Check that the carrier for your minecart is retracted, if not, click the note block again to retract it.
 * To go west, do the same in mirror image.
 * To switch to north-south movement:
 * mine the starred pistons (note the helpful logs below them) and rotate them a quarter-turn clockwise -- still facing outward, but the other outward
 * likewise, mine the starred observers, and put them in the positions and directions of the arrows.
 * To move north and south, similarly twice trigger the "rear" observer, and use the nearer note block to release the brake and stop the engine.