Today, I visited a windmill which was just recently repaired. The odd thing about this windmill is that it has five sails, the usual number is four.
When I went inside, it occurred to me that so much engineering, maths, and physics went into the design of this windmill. I'll describe what the windmill was like from top to bottom as it's more logical that way.
The top floor was where we could see the gears of the windmill working but we weren't allowed to go right up to them in case they suddenly started moving. Windmills are extremely clever as they change the direction of motion using a series of gears. They convert the motion of the sails to motion which can turn the grindstones to grind the wheat. They do this using a crownwheel and a pinion. The pinion is turned by the sails and the crownwheel meets the pinion at angle to turn the grindstones.
The next floor was the bin floor where gravity is taken advantage of. Grain is stored on this floor and when the grindstones run out of grain, this where they refill it, by letting the grain fall down the bins and into the grindstones.
The last working floor is the stone floor where the grindstones are located. This where the grinding of the grain happens. The two grindstones that rotate to cut the grain have to be the thickness of a tissue paper to be able to cut the grain properly because if they were any further apart, it wouldn't grind the grain and if they were too close, you would end up with bits of ground down rock with the flour as well.
As a souvenir of the fascinating trip to the windmill, I bought flour from the mill itself as well as yeast! Can you guess what I made? (If you would like to visit this windmill, here is their website http://www.holgatewindmill.org/index.htm)