|
 |  Photo collection by Th.Schiöler Spiral scoops, screws and the chain pump Spiral scoops Photo 146 |
| Spiral scoops |
 |
 | |
| The right angle gear for the scoop-wheel-sâqiya The gear ratio, the size of the wheel and the natural speed for the donkey are three elements, which affect the output. The problem of finding the maximum output can be solved mathematically or by using trial and error to find the correct gear ratio. [146] |