Cheapest/Easiest ways to make a perpetual motion machine to do work?

[Mixster]

Built a high round tower. Place a ring gate at the top of the tower, and one at the bottom of the tower. The tower should be as high as possible, ideally it would be 100 miles high, but this might be a little outside of your building skills. Then poor in water untill you have reached the saturation of the ring gates and excess water will go out below.

Then, you'll place waterwheels inside this tower at 300 feet intervals, these will all drive different axles and will each receive 16.66 pounds of water falling at 50ft/second, every second. Having a tower as high as 1200 ft, would thus give you pretty much force.

Having Zombie bears power a Threadmill is cheaper and yields more force though.

[Gavinfoxx]

So what skills do you think a character would need to have to be able to make some of these contraptions? Knowledge: Architecture/Engineering, Craft ?, Spellcraft? What would the DC's for checks to make it be like?

Something like this would be nice for my Binder Jacob to have for the town he's rebuilding but I'll need to be able to justify the construction and how to apply the output to something useful. He has 150K GP available for additions to his stronghold. I've already made a purchase of a decanter of endless water and a spade of plant growth for the town. My cohort has a lyre of building and my binder can supply unlimited plant based materials, in 20 cubic foot increments.

I've been playing a strategy game with D&D 3.5e rules (run by a DM), and you can really do a WHOLE LOT with all of that.  IM me, so we can talk on IM, cause there is no wayyy I could conceivably say all this stuff in a well organized, cohesive post.