Illustrated Explanation of the Chariot System in the Artificers' Record

Illustrated Explanation of Carriage Systems: Volume I, Page 5 (cont.)

The large circumference of the hub gu: the central part of a wheel that rotates on the axle is 2 feet, 9 inches, 3 fen, 3 li, and 3 hao approx. 33.3 inches; therefore, this dimension is said to be "appropriate."

As for the hollow space within the hub through which the axle original: zhou. is passed, this is also termed the hub (gu). The Explaining Graphs and Analyzing Characters original: Shuowen Jiezi. The first dictionary to analyze Chinese characters, compiled by Xu Shen (c. 58–147 AD). writes this term as gao original: 橰. and defines it as "the hollow interior of a chariot hub." The Primer for Quick Learning original: Ji Jiu Pian. A Han-dynasty literacy manual. also writes it as gao, which is simply a phonetic variation of the same sound.

Because the hub is a hollow object, certain units of measurement are also named after it. The Record of the Ritual of Missions in the Etiquette and Ceremonial original: Yi Li. One of the three ancient ritual texts of Confucianism. states that sixteen dou A unit of dry volume; sixteen dou would be a significant capacity. is called a sou original: 藪. Literally a "marsh" or "thicket," used here as a term for a hollow container..

Looking at the Record Referring to the Kao Gong Ji (Record of Trades)., it says: "Measure its hollow center (sou) with millet." While the sou of a hub is not necessarily as large as sixteen dou, it is clear from this that the term refers to the name for the hollow space of an object that receives material.

The earlier and later Zheng scholars Referring to the famous Han dynasty commentators Zheng Zhong (d. 83 AD) and Zheng Xuan (127–200 AD). both agreed that the sou refers to the hollow center of the hub. However, the Minister of Agriculture Zheng Zhong. read sou as in the word for "beehive" (feng sou). Zheng Kangcheng Zheng Xuan. explained it as "the place where all the spokes original: fu. converge." Both of these interpretations refer to the mortises or holes carved into the exterior of the hub to hold the spokes, rather than the hollow center of the hub itself.

The Record further states: "Use one-third (le) of its circumference to pare down its hollow interior (gao)." Zheng Xuan’s commentary defines le original: 阞. as one-third. In this context, one-third of the total circumference is used to determine the dimension of the sou the hollow axle-hole.