How to start a water mill

There is no start button at a water mill. The wheel turns when water flows onto it, and when the water stops flowing, the wheel stops turning. So how do you control the flow of water?

In chapter 17 of Ulysses, Bloom's approach was -

to tap the current by turning the faucet to let it flow

In other words, he turned the tap on. The principle is the same at the mill, but it's a bit more complicated than that.

Although the mill sits next to the river, it's not driven directly by the river. The amount of water coming down the river varies enormously, from a gentle trickle in dry weather to a raging torrent at times of flood. Imagine the damage that could be caused to the mill if the river flowed straight through it.

Tap the current

Instead, water from the top of the river is diverted towards the mill through a kind of wooden aqueduct called a launder. This allows the miller to take a reasonably constant amount of water from the river, whether it is flowing gently or violently.

There is a gate at the top of the launder, to control water flowing in towards the mill. And there is a gate at the bottom to control water flowing out of the launder onto the water wheel. There is also a gate at the side of the launder to allow water that has flowed into the launder to escape again before it reaches the water wheel. This is the miller's safety valve.

Here is a breastshot mill (like the Heron Corn Mill) with the side gate of the launder open. The water is escaping through the side gate before it gets as far as the wheel. The wheel is designed to turn clockwise as you look at it.

At the Heron Corn Mill, the gate at the top of the launder is shut overnight so that no water goes anywhere near the water wheel when there's nobody around. At the start of the working day, Stuart the miller has to do a few things before he's ready to let the water onto the water wheel.

First of all, for safety's sake, he opens the side gate of the launder so that any water flowing along the launder will escape at the side before it reaches the wheel. Then as a belt and braces, he closes the gate at the bottom of the launder, next to the water wheel. Now he is sure nothing can actually start the machinery turning until he's ready.

At this point it's safe to take a leisurely walk up to the top of the launder and open the gate there to let the river water in. This is the first opportunity to tune the flow of water to the water wheel. If the river is running slowly, Stuart can open the gate wide; if the river is running fast, he can just open the gate part way. He can adjust the amount of water going into the launder, without anything turning the water wheel, until the flow looks about right.

I can imagine millers of old taking five minutes at the top of the launder to enjoy their last bit of peace and quiet before the long, hard, noisy day's work began.

Turn the faucet

Once he has set the water running into the launder, Stuart makes his way back down to the mill where there is a strategically placed window looking upstream along the launder. There he can see how much water is being taken from the river, and he can also see it escaping again through the side gate of the launder. Right by the window is a wheel with a handle attached which opens or closes the side gate of the launder. It works on the same principle as this worm drive - you have to turn the handle many times to turn the wheel once.

The point is that however much water is flowing along the launder, opening or closing the side gate in an emergency is never hard to do.

The side gate is the second opportunity to tune the flow of water to the water wheel. If the flow of water from the river unexpectedly picks up, which can happen if it has been raining out in the hills, opening the side gate a little will quickly calm the flow of water onto the wheel. But generally, the side gate is closed when the mill is running.

Let it flow

With the side gate closed, river water reaches the gate at the bottom of the launder. Ratcheting up the bottom gate finally lets the water flow right inside the mill and onto the waterwheel. The water fills the buckets, and the wheel groans into action.

The bottom gate is the third opportunity to tune the flow of water to the water wheel. Stuart usually raises the gate by two notches, and then locks it at the right height. If the mill starts to run too fast, he can let the gate down a notch, and if he wants a bit more speed, he can raise it a notch to let more water in.

This picture shows an overshot wheel, being turned by the weight and flow of the water falling onto it from above. This wheel turns anticlockwise as you look at it. The breastshot wheel at the Heron Corn Mill, where the water hits the wheel part way down the side, turns in the opposite direction .

The Heron Corn Mill's waterwheel has buckets to hold the river water and exploit its weight. Undershot waterwheels have simple paddles instead of buckets. Here it is just the flow of water in the river that drives the wheel, not the weight.

Sometimes, if the wheel just won't start, desperate measures are called for.

Tuning the flow of water onto the waterwheel is only one way the miller can control the milling process. The machinery inside the mill has lots of other features built in, but that's another story.