Pumps with a purpose

This lesson asks you to describe the purpose, inputs and outputs of systems, and to identify the parts and processes that let a system do its job. The museum offers two designs for lifting water that are known from books; whether they were built is stated in each record. Safety, efficiency and food-processing systems are for the class to bring. ¹

The expectations ask you to name a system's purpose, its input and its output, and then its parts. For each pump, write one sentence for the purpose, one for the input and one for the output, and list its parts in the order the power passes through them.

In TDV's account of al-Jazari's double-piston pump, the drive can be followed step by step. Flowing water turns the wheel, and the wheel drives a gear in a vertical plane. This engages another gear in a horizontal plane. A vertical pin near the rim passes through a slot in a rod, and as the gear rotates the rod swings and the piston rods travel back and forth, operating the pumps ². Al-Hassani describes a synchronized pair of suction pumps ^{2 3}. The physical witness is a half-size model in the Science Museum, not an original from al-Jazari's lifetime ⁴.

The records preserve no sentence in which al-Jazari says why he described this pump; they show that his book was commissioned by Nasir al-Din Mahmud ². For Taqi al-Din's pump the record reads an intention in the design: six tubes joined to a shared outlet, so that delivery is successive rather than only one piston's pulse ⁵. The author allows one tube, prefers at least three for smoother delivery, and says two can achieve the purpose ^{6 7}.

It is easy to picture a six-cylinder pump working on an Ottoman farm. The record says instead that this is a documented design, not measured output on a farm, and that the modern engineering study lacks evidence of historical manufacture and assumes many of its model's dimensions ^{8 9 10}.

Al-Jazari's pump moves two pistons with a slotted rod, while Taqi al-Din's moves six with projections on a shaft. If you wanted water to arrive as smoothly as possible, which design do the records favour, and what in them makes you say so?

• The double-piston pump: the wheel, gears and rod, and the model in the Science Museum.
• The six-cylinder pump: six pistons, a shared outlet and a modern model.
• Al-Jazari: the engineer and his book of devices.
• Taqi al-Din: the Ottoman scholar who wrote the treatise.

Read about the double-piston pump and the six-cylinder pump. Draw each as a chain of boxes from the source of power to the water, and label what each box does.