Disconnected gears
Gears can be "disconnected" by being connected to a lever, and then activating that lever. However, be warned that devices connected vertically to a linked gear may collapse when disconnected. The same is true of a horizontally connected hanging device. An example is a windmill built directly on top of a gear: in this case, disconnecting the gear via the lever will cause the windmill construction to collapse.
In order to avoid this, create a second gear adjacent to the linked gear but not otherwise connected to the system; This gear will support the windmill if the linked gear is disconnected, but will not transfer power, since it only draws it from the now-disconnected gear.
Note that the above is only necessary if the windmill is entirely unsupported outside of the gear on which it rests. Windmills (and other components) which have "Stable foundation" in their q view should not collapse if a gear beneath them is disconnected.
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