Page Ten

...[with a spoke] thickness of 1.2 inches, the tenon should be two-thirds of an inch. The total thickness of thirty spokes combined is 1 foot, 9 inches, 9 fen, 9 li, and 9 hao In the decimal system of ancient Chinese measurement, this total—effectively 1.9999 feet—is calculated to perfectly match the inner circumference of the hub. The "Way of the Zhou" original: 周道 (Zhou dao), referring to the engineering standards of the Zhou Dynasty requires that within the circumference of the hub, the space between any two spokes must be neither too wide nor too cramped.

If the zi the part of the spoke that enters the hub is made naturally thinner, and the tip of the zi is shaved to a point, it is because thirty spokes all converge toward the center of the hub. If the zi were thick or had a blunt tip, the center of the hub would not remain solid, and the mortise holes the slots carved into the hub would cut into each other.

Therefore, the Huainanzi a 2nd-century BCE philosophical text says in the "Lessons from Mountains" chapter: "A strong hub must be paired with 'weak' original: 弱 (ruo), here meaning the thinned tenons spokes; two 'strong' things cannot yield to one another." Furthermore, the "Lessons from Forests" chapter states: "When the spokes enter the hub, each must fit its own mortise and must not intersect with the others." Xunzi a foundational Confucian philosopher quotes the Book of Odes: "Once the hub is shattered, only then do they enlarge the spokes." These are all examples of having excess strength but insufficient stability.

The part of the spoke near the hub is called the gu literally "thigh"; the part near the rim is called the ge literally "shin-bone".

The Shuowen the first major Chinese character dictionary, compiled c. 100 CE says: "Gu means the upper leg; ge means the lower leg." The Record of Trades Kao Gong Ji: an ancient technical manual says: "Divide the circumference of the gu into three parts, then remove [one part to determine the taper]..."