Spoke

The radial members of a wagon wheel were made by carving a spoke (from a log) into their finished shape.

Eventually, the term spoke was more commonly applied to the finished product of the wheelwright's work than to the materials they used.

The earliest physical evidence for spoked wheels were found in the Sintashta culture, dating to c. 2000 BCE.

[1] Soon after this, horse cultures of the Caucasus region used horse-drawn spoked-wheel war chariots for the greater part of three centuries.

They moved deep into the Greek peninsula, where they joined with the existing Mediterranean peoples to give rise, eventually, to classical Greece after the breaking of Minoan dominance and consolidations led by pre-classical Sparta and Athens.

While a good quality spoke is capable of supporting about 225 kgf (c. 500 pounds-force or 2,200 newtons) of tension, they are used at a fraction of this load to avoid suffering fatigue failures.

Since bicycle and wheelchair wheel spokes are only in tension, flexible and strong materials such as synthetic fibers, are also occasionally used.

Instead of individual wire spokes, a continuous thread of Kevlar (aramid) was used to lace the hub to the rim under high tension.

The threads were encased in a translucent disk for protection and some aerodynamic benefit, but this was not a structural component.

Constructing a tension-spoked wheel from its constituent parts is called wheelbuilding and requires the correct building procedure for a strong and long-lasting end product.

For each spoke crossed, the hub is rotated with reference to the rim one "angle between adjacent flange holes".

Equivalently, the law of cosines may be used to first compute the length of the spoke as projected on the wheel's plane (as illustrated in the diagram), followed by an application of the Pythagorean theorem.