I'm a rather experienced DFer but I just started studying complexer mechanics. So I got a few questions.
1. A simple question. Can I have 2 layers of windmills or does every windmill need all open space above it?
2. Quite a bit harder. I am a tad confused about transferring power. I can manage it just fine but I'm getting the feeling that I could waste less power on it. I'm using the axles and gears so that axles have to end at a gear. So axles through z levels must approach the gear from only the top or bottom and axles from N to S and E to W have to also go straight to a gear. But I saw a picture on the wiki that had them like this:
o
x=====
o=axle through z levels
x=gear
==axle on the same z level
If I can use them like that then I would save a lot of power on the turns.
This is a side view...
# + + + + ~ +
# + + + + ~ +
# O + + + W +
# * ═ ═ ═ W +
# + + + + W +
# + + + + ~ +
# + + + + ~ +
Is the picture I saw. I don't think rivers flow that way.
And what about the windmill question?
It won't work like this, if the o is supposed to be a vertical axle. Perhaps it's a millstone? Vertical axles connect only above or below. Try to imagine your machine components as things with a few red sides. Screw pumps and gear assemblies are totally red, for example. You have to make red-red connections.
Axles have to end either at gears, other axles in the same direction, or pumps/windmills/waterwheels.
Also, you can't build two windmills directly over each other, because windmills don't support constructions or machine components, and
only connect vertically under the center tile.