Editing v0.31:Water wheel

{{AV}}
{{Quality|Exceptional}}
{{Machine_component|name=Water wheel|key=w
|construction=
* 3 {{L|Wood|Wood}}
|construction_job=
# {{L|Architecture|Architecture}}
# {{L|Carpenter|Carpenter}}
|power=Needs 10 power. <br>Generates 100 power. <br>Net gain of 90 power.
}}

A '''water wheel''' is a {{L|machine component}} that provides {{L|power}} via {{L|water flow}}. To build a water wheel, select {{key|b}}uild menu and choose {{key|M}}achine components. It requires 3 {{L|wood|wood}} and generates 90 net power, which can be used for operating a {{L|Screw pump|pump}} or {{L|mill}}. You can use {{L|axle|axles}} and {{L|Gear assembly|gears}} to access the power produced by a water wheel, or connect machinery like a {{L|Screw pump|pump}} or {{L|millstone|millstone}} directly.

Waterwheels do ''not'' work with waterfalls, nor in magma - it takes water that is flowing according to the DF use of the term.

''For a basic overview of how the different machine parts work and work together, see {{L|machinery}}.''

== Construction ==
The {{L|Building_designer|architecture}} and {{L|Carpenter|carpentry}} labors are needed for the construction.

A water wheel occupies 3 adjacent tiles (N-S or E-W axis, no diagonals).  It is the color of the first wood selected for it, so you could build a red wheel with one piece of goblin-cap and two of fungiwood.

Although you can build a stable water wheel on solid ground, this isn't going to do you any good. For this reason, water wheels are almost exclusively built in a hanging state with gaps in the floor below. To do this the water wheel must be attached to a nearby machine component on either side of its center tile.  Do not hang it from a gear assembly you wish to control with a switch, a disconnected gear assembly can't support anything and will cause the waterwheel to deconstruct.

{{L|Power}} is generated from a water wheel as long as it has {{L|water_flow|flowing}} water at a depth of 4/7 or greater under at least one of its tiles. The easiest way to achieve this is by placing the water wheel over a {{L|river|river}} or {{L|brook|brook}}. With a {{L|brook}} you must first channel through the surface since brooks have a floor of sorts over them. 

You can transport the power wherever it is needed via horizontal and vertical axles and gear assemblies. It is possible to support a waterwheel by building its center next to a preexisting water wheel's center.

==Designs==


{|style="border: 1px solid #0b0; background: #dfd"
|+'''Basic watermill design'''
|- style="font-family: monospace; font-weight: bold; font-size: 135%"
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|- style="font-family: monospace; font-weight: bold; font-size: 135%"
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{|style="border: 1px solid #0b0; background: #dfd"
|+'''Dual watermill design'''
|- style="font-family: monospace; font-weight: bold; font-size: 135%"
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|- style="font-family: monospace; font-weight: bold; font-size: 135%"
|style="color: #777; padding: 0"|#
|style="color: #333; padding: 0"|O
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|- style="font-family: monospace; font-weight: bold; font-size: 135%"
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|style="color: #970; padding: 0"|═
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This is by no means the limit of water power from one location, depending on the width of your river/brook/channel you can stack many waterwheels side-by-side (really big assembles will need to be artificial as there's a limit to how wide the game created water flows get). Just remember to make sure there's a support structure in place before you place the next wheel.

== Perpetual motion ==

Due to the relatively low power draw of a {{L|screw pump}}, a ''self-powering'' assembly can be made with a water wheel that still leaves plenty of excess power for other uses. This is an {{L|exploit}} (violating basics principles of physics), and possibly a bug, but this is also Dwarf Fortress, so... 

To get it working, you must start the pump manually.*

:''(* Exceptions are {{L|aquifer}}s, which can sometimes have naturally occurring {{L|flow}}.  This is sometimes a good thing, because then a wheel simply works by itself - or a bad thing, if, for example, you want the wheel to '''not''' provide any power while you build a pump adjacent to it. It's not clear what causes an aquifer to have flow and then keep it - it's difficult to replicate reliably, and can be lost with additional {{L|channel}}ing, so designs will have to be adapted if such are found.)''

It is good to have a ready source of water to refill the machine, as water tends to escape and evaporate, and once the water falls below a certain level, the machine stops. Below an earlier level, the power supply becomes intermittent. 
 '''Key:'''
   
   '''║ ═ ╝ ╚ ╔ ╗ ╣ ╠ ╩ ╦''' = '''Wall'''
   <font color="#777">+</font>    = '''Floor'''
   <font color="#970">W</font>    = '''Water Wheel'''
   <font color="#777">*</font>    = '''Gear Assembly'''  
   <font color="#808000">═</font>    = '''Axle E/W'''
   <font color="#808000">║</font>    = '''Axle N/S'''
   <font color="#00FF00">X</font><font face="Arial" color="#008000">X</font>   = '''Pump from west'''

'''*REMEMBER TO BUILD AN ORTHOGONAL PUMP, VERTICAL AXLE OR GEAR ASSEMBLY BEFORE THE WATER WHEEL*'''

===Dwarven Water Reactor===

This compact design, once started, produces 170 surplus power (less additional power train).

<div style="float:right; margin:2ex 20ex;">    <!-- I wanted to float this on the left, but the wiki version of bulletpoints behave oddly with the margin. -->
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</div>

Dig the V-shaped channel and fill it with water (either from an outside source or by designating it as a {{L|pond}}).  Meanwhile, construct the pump, pumping from the South.  Construct the two water wheels.  Start the pump manually ( {{k|q}}, {{k|Enter}} ) - if there is enough water*, the "reactor" will start immediately and the pump operator will leave.  The water from the north end of the pump will spill over the top-most floor tile, filling that to 7/7 and the two tiles east and west of it to ~5/7, but will not overflow back past the water wheel to the walkway area.    Note that for the upper level, no southern walls are shown as none are needed.

*''(* Estimated minimum depth to prime the reactor is 3/7 to 4/7, though this is not guaranteed.)''
* The ideal amount of water in this design is apparently 63 units of water. In other words six tiles below in the V are full up to 7/7 and three more above are also full up to 7/7 which will generate reliable flow permanently without ever losing any of that water to evaporation. An easy way to do this is to simply leave your pond fill command on after the reactor activates. They will eventually fill it up to the optimal level and stop. 

The reactor can be safely halted either by blocking the tile the pump draws water from or "overloading" the reactor (since drawing more power than the reactor supplies will stop the pump that keeps the cycle going until the load is reduced and the pump is manually restarted by dorf-power),  More drastically, the reactor will obviously be halted by deconstructing the pump.  Deconstructing one wheel will cause a flood (and almost immediately cancel any job order to deconstruct the other components), and deconstructing the pump will cause both wheels to collapse (unless they are attached to {{L|machinery}} outside them, not shown).

{{L|Power}} can routed up from the pump or off to the side from a wheel; the bottom of the pump is difficult to access without danger of water escaping.  Power can also be routed out of the reactor via a gear or horizontal axle ''over'' the tile the pump draws water from with neither interference in the pump's operation, danger of flooding, nor increased difficulty in designating and using pond zones to initialize the reactor.  In either case, it's typically wise to place a {{L|gear assembly}} linked to a {{L|lever}} early in the power train in order to allow disconnecting the power at that point, as opposed to needing to halting the reactor to stop the power supply.

Expanded versions can produce more power, and can be added later with minimal advance planning; such extensibility is easily attainable by placing disengageable gears on either side of the two water wheels, then attaching minireactors at your leisure, or halting the original reactor by other means. Alternatively, it may be easier to simply produce a second reactor, then connect to the power train at another location.

''Note: If created in an aquifer, there is a chance that the channeled tiles will have a natural {{L|water flow}} - this will cause the pump to start the moment the first wheel is finished, flooding the work area for the second.''

===Mini Water Reactor===

This even more compact design is quite similar to the original Dwarven Water Reactor, but can be used in tight spots that do not need more than 80 surplus power.  This plan can also be considered an extension unit to the DWR, in that it can be added to one or the other side to provide an additional 80 power to the resulting power train.  Safely constructing a mini reactor to add to a previously built reactor without potential flooding and/or loss of power is possible only if you first turn off the original reactor with floor hatches.  Planning ahead is a much better option, so if you're going to need more than 170 power, build a larger reactor to start with.

As stated previously, the design below produces 80 surplus power (less additional power train).

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'''<span style="color:#080">X</span><br /><span style="color:#0F0">X</span>''' = '''Pumps from south'''

Construction of the mini reactor follows the same order as for the DWR, though the channel is slightly different and only one water wheel is needed.  If this is an addition to a full size reactor or set of reactors, all channels will need to be fairly full with water to start the reactor.

{{buildings}}