From two pistons to six

This lesson asks you to research the historical development of a hydraulic or pneumatic system, to ask why it was developed and how it was improved, and to describe the common components of such systems and what each does. The museum offers two pumps from two medieval books, one with two pistons and one with six, both with pistons and valves; modern systems, their social effects and the full history of pumps are for your class. ¹

Compare the two pumps. List the parts they share and what each adds. What does each record say the design was meant to do?

Find where the valves sit in the pump you read about. What would happen to the water without them?

Look inside one cylinder of al-Jazari's double-piston pump. Each copper cylinder has two clack valves allowing upward movement only, one at its intake and another at its delivery pipe ². An iron piston rod ends in two discs with hemp cord packed between them, sealing the fit inside the smooth cylinder ². Both delivery pipes join one vertical riser ³. Now ask what the water would do on the downstroke if the valve at the delivery pipe were missing.

The records say what each design was meant to do, not why its maker took it up. For al-Jazari, TDV describes an engineer improving earlier work ⁴. For Taqi al-Din's pump, the record reads the intention as successive delivery rather than only one piston's pulse ⁵. Al-Hasan compares al-Jazari's pump and identifies earlier cam arrangements in Heron and China ⁶.

More tubes are not a rule. Taqi al-Din's text allows one tube, prefers at least three for smoother delivery, and says two can achieve the purpose ⁷. A preference is not a physical limit prohibiting all pumping with fewer than three ^{7 8}.

The six-cylinder pump is read in Ahmad Yusuf al-Hasan's edited text, not in an original machine ⁵. The modern study of it explicitly lacks evidence of historical manufacture and assumes many model dimensions ⁹. The museum's model of the double-piston pump is a reconstruction ¹⁰.

Taqi al-Din's text allows one tube, prefers three and says two can do the job. Why might a designer prefer more tubes when fewer can work, and what would you measure to test that preference?

• The double-piston pump: the valves, the packing and the riser.
• The six-cylinder pump: six pistons moved by cams and returned by weights.
• Taqi al-Din ibn Maruf: the author of the book that describes it.

Read about the double-piston pump and the six-cylinder pump. Make a table with a row for each pump and columns for the source of power, the number of pistons and the way the water leaves.