Water that does the work

This lesson asks you to describe, with the aid of diagrams, how selected energy-transformation technologies operate. The museum offers two water-driven machines from one medieval book, in which flowing water turns a wheel and a shaft; the wind turbines, photoelectric cells and heat engines, and the calculation of energy and efficiency, are for your class. ¹

Draw the machine as a chain that starts at the water and ends at what it achieves. At each link ask: what moves, what pushes it, and what must be supplied for the chain to keep going?

Follow the energy through the double-piston pump link by link. TDV's description of the drive can be followed step by step ²:

1. Flowing water turns the wheel.
2. The wheel drives a gear in a vertical plane.
3. This engages another gear in a horizontal plane.
4. A vertical pin near the horizontal gear's rim passes through a slot in a rod.
5. The rod's other end is fixed by another pin; the piston rods are connected to it.
6. As the gear rotates, the slotted rod makes an angular movement and the piston rods travel back and forth, operating the pumps.

The record sets beside it the hidden-drive lifter: discharged water passes over a wheel in a chamber beneath the floor, transmitting motion upward ³.

The records give no reason in al-Jazari's own words. They show the practical problem: this is a pump powered by flowing water, not a bucket lifted by hand ². TDV places the book's fifty devices in six divisions, one of them for water raising ².

"Synchronized" does not mean "at the same moment". Al-Jazari explains alternating action: movement to one side discharges one cylinder while water enters the other through its intake, and the return movement reverses those states ⁴. Both delivery pipes join one vertical riser, so synchronization means coordinated filling and discharge, not both cylinders necessarily discharging at every instant ⁵.

The text gives a design height of about twenty cubits, related to the riser's length, but no measured volume per time or documented efficiency test in this passage ⁴. The museum model of the pump is half-size: its catalogue measurements and weight belong to that model, not to an independently inspected original ⁶.

Hill's text gives a design height of about twenty cubits for the pump but no measured volume of water per time. If you wanted to say how much water the pump lifts each minute, what would you need to measure, and why can the drawing not tell you?

• The double-piston pump: the drive, the cylinders, the valves and the model.
• The hidden-drive water lifter: water turns a wheel below the floor.
• Al-Jazari: the book the two machines come from.

Read about the hidden-drive water lifter and the double-piston pump. Draw a diagram of each from the supply of water to the water it lifts, and label what must be supplied to keep it working.