Editing Water wheel (section)

=== Summary of types ===
{| class="wikitable"
|'''Vertical axis''' also known as tub or Norse mills.
* Horizontal wheel with a vertical axis
* A jet of water strikes blades mounted on the axle
* Driving surfaces – blades
* Water – low volume, high [[Hydrostatic head|head]]
* Efficiency – poor
|| [[File:Vertical waterwheel simple.svg|150px|Diagram of vertical axis water mill]]
|-
|'''Stream''' (also known as [[free surface]]). Ship wheels are a type of stream wheel.
* Vertical wheel with horizontal axle
* The bottom of the wheel is placed into flowing water
* Driving surfaces – blades – flat prior to 18th century, curved thereafter
* Water – very large volume, no head
* Efficiency – about 20% prior to 18th century and later 50 to 60%
|[[File:Stream waterwheel simple.svg|150px|Diagram of stream shot waterwheel]]
|-
|'''Undershot'''
* Vertical wheel with horizontal axle
* The water hits the wheel low down, typically in the bottom quarter
* Driving surfaces – blades – flat prior to 18th century, curved thereafter
* Water – large volume, low head
* Efficiency – about 20% prior to 18th century and later 50 to 60%
| [[File:Undershot waterwheel simple.svg|150px|Diagram of undershot waterwheel showing headrace, tailrace, and water]]
|-
|'''Breastshot'''
* Vertical wheel with horizontal axle
* The water hits the wheel roughly central, typically between one quarter and three quarters of the height.
* Driving surfaces – buckets – carefully shaped to ensure that the water enters smoothly
* Water – large volume, moderate head
* Efficiency – 50 to 60%
| [[File:Breastshot waterwheel simple.svg|150px|Diagram of breastshot waterwheel showing headrace, tailrace, and water]]
|-
|'''Overshot'''
* Vertical wheel with horizontal axle
* The water hits near the top of the wheel and in front of the axle so that it turns away from the head race
* Driving surfaces – buckets
* Water – low volume, large head
* Efficiency – 80 to 90%
|[[File:Overshot waterwheel simple.svg|150px|Diagram of overshot waterwheel showing headrace, tailrace, water, and spillage]]
|-
|'''Backshot''' (also known as pitchback)
* Vertical wheel with horizontal axle
* The water hits near the top of the wheel and before the axle so that it turns back towards the head race
* Driving surfaces – buckets
* Water – low volume, large head
* Efficiency – 80 to 90%
| [[File:Backshot waterwheel simple.svg|150px|Diagram of backshot waterwheel showing headrace, tailrace, water, and spillage]]
|}