The mill & the stone in fire & flood
As part of working on a fantasy novel set in the Bronze Age, some of the research I do is to confirm when certain pieces of technology originated. In my most recent chapter, I thought it might be fun if my protagonist used a waterwheel to help put out a fire. But first, I had to figure out whether that was plausible...
- Waterwheels serving only to lift water for agriculture date back as far as the 400s BCE, but the earliest evidence of actual watermills comes a century or so later.
- Millstones are patterned with furrows so that when they are laid face to face the patterns create a “scissoring” motion that guts or grinds the grain or dye or whatever and pushes the resulting flour out from the center of the stone and keep the grain from overheating.
- Over 200,000 watermills are still used in India to grind grain.
- A wooden gear, such as those used for watermills in Medieval Germany, will last for about 7 years before it must be flipped over, and then later discarded.
- Before hand mills were invented, grinding grain was done with a mortar and pestle. Later, water and windmills made it possible to use huge stones for grinding large enough quantities to supply whole villages.
Big Trees, Little Holes
The most difficult part of the invention process for the wheel (and by extension the waterwheel) was getting the axle size right. Although it's possible to build a waterwheel entirely out of wood, you need thick trees and metal tools to cut perfectly-measured holes for the axle so the friction is just right. [Read More]
Two Streams, One Wheel
Scholars aren't sure whether it's possible for a huge, horizontal waterwheel mill to be powered by two jets of water instead of the more traditional one. Much of the debate hinges on the cultural prohibition against having a wheel spin anticlockwise and whether this would damage the wheel. [Read More]
Flames of Friction
Fire is a big danger with mills because millstones can grind against each other at a rate of almost twice a second. The friction can cause the grain to burst into flame and burn down the typically-wooden buildings around them. Alternatively, because watermills are dependent on water sources, floods sometimes washed away entire millworks. [Read More]
Not For The Plains
Watermills are most common in mountainous regions, because the water must be “falling” to a lower elevation so that the water comes in at the top of the mill wheel and goes out at the bottom. One foot of "fall" is needed for every foot of wheel diameter. Water power can also be used to let smiths forge using huge hammers. [Read More]
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