Water Wheels

The first reference to a waterwheel is in a Greek poem written about 2400 years ago, although historians believe that it was probably invented by the Chinese centuries earlier.

From the description, the Greek wheel was a horizontal wheel connected directly to grindstones by a pole.

It was used to grind grain and the local boys were very grateful for it, as they no longer had to turn the grindstones by hand. It was not very efficient, but did the job.

The waterwheel has been continually developed over the centuries and became vertical, this being far more efficient. Some 1000 years ago, there were over 6000 waterwheels in Britain, many of them used to grind grain. Other uses were to provide power for irrigation, sawmills, forging and fulling.

Waterwheels used in grain mills ran shafts which in turn drove the grind stones. The shaft coming from the wheel was horizontal and had to be changed to vertical in order to drive the stones. This was done through a series of gears, which also slowed down the speed of the final shaft. Sometimes, the wheel also drove a hoist for lifting the sacks of grain to the grinding floor.

They were increasingly used as the source of power in industry, mainly mines and factories. Their main use in mines was for pumping out water and crushing ore.

The siting of factories was often determined by the availability of a good water supply to drive the wheel. In these factories, which were mainly in the textile industry, the wheel powered horizontal line shafts, which ran through the buildings, usually at high level. From these shafts, machinery was driven by flat leather belts running on pulleys. This was very dangerous and resulted in a high number of injuries and deaths.

The waterwheel led to the development of

Paddle wheels for driving ships

Modern turbines used for generating electricity, aeroplane engines and compressors

In most cases, wheels were eventually superseded by steam engines, followed by internal combustion engines and electric motors. However, in recent times, there has been an increase in the use of water wheels for producing electricity on a small scale, such as for a house or a hamlet.

There are four main types of water wheel:

Overshot - the water enters the wheel past top dead centre:

Pitchback - the water enters short of top dead centre, rotating this wheel in the opposite direction to the overshot wheel:

Breastshot – the water enters the wheel at the middle rear:

Undershot or Stream - where water flows at the bottom of the wheel:

Overshot and pitchback wheels are more efficient than the other types because they are driven both by the force of water directed into the buckets and by the weight of the water.

The Nant-y-Coy wheel is an overshot wheel.

The undershot or stream wheel is the least efficient as it is driven only by the flow of water. The breastshot wheel comes between the two extremes.

Most wheels require a good "head of water", which is the difference in the heights of the water supply and the wheel. In order to maintain a supply of water throughout the year, many waterwheels are fed from a mill pond which is supplied by a river or stream. The pond can be kept at a near constant level. From the pond, the water is fed down a ditch or a pipe to the wheel. This ditch or pipe may be called a “head race”, “millrace”, “race”, “leat”, “leet”, “head goit”, “flume”, “lade”, “penstock” or “pentrough”, depending upon the local tradition.

The power which a wheel can generate is determined by its design and the water flow. This water flow is normally controlled by a sluice gate in the head race, which is raised or lowered as required. Any water not required by the wheel is diverted over a weir, or sometimes through a sluice, into an overflow ditch or pipe which usually returns the water to its source. When the water leaves the wheel, it flows down a ditch or pipe, called a “tail race”, again usually returning to its source.