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Mechanical Engineering in Minecraft I
http://www.rarityguide.com/articles/articles/2033/1/Mechanical-Engineering-in-Minecraft-I/Page1.html
By Nick M. Facer
Published on 04/10/2012
 
A basic summation of what you can use to make a machine in Minecraft.

Uses of Redstone
Time for another extended series Minecraft article set!  This protracted series will be all about working with machines in Minecraft.  Of course, you have to start any discussion of Minecraft machines and devices with the most basic element that makes such things even possible to begin with: redstone.

Redstone is a resource found deep in the ground- though not as absolutely at the bottom of the mineable world as diamonds are.  Easily recognizable, redstone blocks will generate four or five batches of redstone dust when mined, making redstone a surprisingly abundant resource- many veins of redstone will include six to eight blocks, making each of them a batch of more than twenty redstone- and occasionally a single vein will yield almost forty redstone on its own.

The primary form redstone takes is that of redstone dust, and virtually every mechanism that you can create using redstone will involve a fistful of redstone dust being placed.  Redstone is also needed for most powered objects, being a vital component of pistons, powered lights, detector rails, powered rails, note blocks, the compass, and the clock.

The compass and the clock are not involved in any machines, so I won’t go on about them here.  Powered rails, pistons, and note blocks will often be at the end of a redstone device, so those will be mentioned a lot later on.  Dispensers will be brought up then as well, but they also will appear a bit earlier on, as they can be used as part of the mechanism itself, in conjunction with pressure plates.

Pressure plates go in with levers, buttons, detector rails, and redstone torches as trigger items, but redstone torches can also be used in the midst of a mechanism, especially alongside redstone repeaters.

Something to keep in mind as you work with redstone is that it is relatively fragile- while each piece of redstone wiring laid down from a pile of redstone dust effectively occupies a block, dropping water, sand, gravel, or lava on it will outright rip it up.  Lava and water especially go further, outright destroying the redstone you have laid down as wire.  It is possible to construct some interesting and amazing lavaworks with redstone, but you need to craft them before putting the lava in- otherwise you will often find yourself losing ten or more minutes of work to a single disconnected piston and the resulting lava flow.