# Paddle wheel

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A **paddle wheel** is a form of [waterwheel](/source/Waterwheel) or [impeller](/source/Impeller) in which a number of paddles are set around the periphery of the wheel. It has several uses, of which some are:

- Very low-lift [water pumping](/source/Water_pump), such as flooding [paddy fields](/source/Rice_paddy) at no more than about 0.5 m (20 in) height above the water source.[1]
- To move and mix algae culture in the raceway ponds used for [algaculture](/source/Algaculture).
- [Propulsion of watercraft](/source/Paddle_steamer) (as a paddlewheel)
- [Low head hydro power](/source/Low_head_hydro_power) (as a waterwheel)
- Flow sensors
- Aerators

The paddle wheel is an ancient invention but is still used today in a wide range of industrial and agriculture applications.

## Ship propulsion

Main article: [Paddle steamer](/source/Paddle_steamer)

Paddle wheels would enable ships to travel without needing wind or oars. They were made obsolete by [propellers](/source/Propellers), which had greater propulsion with lower weight and fuel usage. This was demonstrated by an 1845 [tug-of-war](/source/Tug-of-war) competition between [HMS *Rattler*](/source/HMS_Rattler_(1843)) and [HMS *Alecto*](/source/HMS_Alecto_(1839)) with the screw-driven *Rattler* pulling the paddle steamer *Alecto* backward at 2.5 knots (4.6 km/h).[2]

## Physics

The paddle wheel is a device for converting between [rotary motion](/source/Rotary_motion) of a shaft and [linear motion](/source/Linear_motion) of a fluid. In the linear-to-rotary direction, it is placed in a fluid stream to convert the linear motion of the fluid into rotation of the wheel. Such a rotation can be used as a source of power, or as an indication of the speed of flow. In the rotary-to-linear direction, it is driven by a [prime mover](/source/Engine) such as an [electric motor](/source/Electric_motor) or [steam engine](/source/Steam_engine) and used to pump a fluid or propel a vehicle such as a [paddle-wheel steamer](/source/Paddle_steamer) or a [steamship](/source/Steamship).

## References

1. [Paddle wheels used for pumping](http://www.fao.org/docrep/010/ah810e/AH810E06.htm)

1. [Propeller versus Paddle: The Tug of War between HMS Rattler and the Alecto](https://bowcreektoanatahan.wordpress.com/propeller-versus-paddle-the-tug-of-war-between-hms-rattler-and-the-alecto/), Bow Creek to Anatahan.

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Adapted from the Wikipedia article [Paddle wheel](https://en.wikipedia.org/wiki/Paddle_wheel) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Paddle_wheel?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.