40d:Windmill

A windmill is a machine component that provides power via wind on the surface of a fortress map. The power produced by a windmill depends on the map; on some maps windmills produce 40 units of power, on some others 20, and some maps have no wind at all. Building a windmill uses 4 pieces of wood.

Construction

To get some useful power out of a windmill:

1. Build the windmill. Outside.
2. Build a millstone or pump one z-level below the center of the windmill. You are done. No digging or rigging required.

Since this basic setup is usually not sensible, here are more complicated options:

1. "Excavate" a "path" one z level under the windmill, at it's center. (There are no paths - he talks about digging a channel?)
2. Add a vertical axle or gear assembly there. It will have power. A gear assembly is required to change direction of power. A floor between the windmill and this is fine.
3. Connect further gear assemblies or axles to transport power to its final destination. Avoid assemblies, they eat more power than axles.
   

You can build windmills underground if the central square in the windmill is "outside" (channel the roof away above it).
In rare cases, building a gear assembly before the windmill will not connect the gear assembly to the windmill. Simply reconstruct the gear assembly to connect it.
Several windmills can be linked together via gear assemblies and axles. Their total power output is additive (minus power lost to gear assemblies and axles.)
Gear assemblies can be used to transport the power back to the surface, if desired.

Windmill tower

The "windmill tower" option is useful if you can't dig below your windmill (if, for example, there is a room or underground river there). This option is also often more power-efficient, as it often eliminates the need to transfer power between z-levels.

1. Build a 3×3 platform out of floors one level above the ground floor (technically not needed, as long as the gear assembly is planned/built a windmill can support itself on that alone, the dwarf just needs a place to stand to built it).
2. Build the windmill on top of the platform.
3. Directly beneath the windmill, on the ground floor, build a gear assembly.
4. Connect this assembly to horizontal axles, and power your machines. No digging required!

A windmill can also be built directly on top of a gear assembly, obviating the need for a platform. However, if switched off via lever, a windmill constructed in this fashion has a tendency to collapse.

How to transfer power between z-levels

After you have a gear assembly in place on a level, you need to switch to the level above it and remove the floor between its tile and the tile above it. Then, build a vertical axle or a gear assembly above the first gear assembly.

Construction Example

1. A Pond To Drain
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2. Add Some walls to control output, and an access ramp (leaving access is a good idea)
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3. add 3 floor tiles above the gap, then build your windmill
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4. build a lever and gear assembly, then link your lever to the gear
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5. Finally, throw the lever, add your screw pump and the final wall section
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Alternatives

• Skip the lever and gear and power the pump directly, "always on".
• The "Blowback" wall method:

This allows water to flow past the pump when the pump is off, allowing for two pumps to use a single set of walls to contain the flowing water, with the direction based on which pump is on. It also allows for maintenance access from the pipe, at the cost of 3 extra wall sections and one extra floor.

A simple pump b/w lever

Side view:

     =O=    <- windmill supported by unlinked gear assembly
     **     <- two gear assemblies: left gear is linked to lever
     @@     <- screw pump
~=~=~#####  <- water
##########

The right gear does not need to lie on the screw pump, as long as it's orthogonal to the gear that -is- placed over the pump.