SUPERSTRUCTURE

The strength and elegance of the wire-spoke wheel

- KEVIN CAMERON

The safety bicycle, which exploded into a popular craze around 1895, can be regarded as a confluence of technologies that matured at that time—the ball bearing, pneumatic tire, seamless-drawn steel tubing, roller chain and sprocket drive, and super-strong hard-drawn steel wire. A final ingredient might be the production and shaping of thin metal sheet by rolling.

The last two together made possible one of the most efficient structures known to mechanical engineering: the tension-spoked wire wheel. A roll-formed rim is made by slitting sheet steel into strips, then roll-forming those strips into a wheel-rim section that was finally roll-bent into a circle. The butt ends were joined by brazing or welding.

The wheel hub consisted of a pair of spoke flanges joined by a tube, spinning on the new screw adjustable cone ball bearings, supported on a nonrotating axle.

Rim and flanges were drilled or punched for a suitable number of spokes. The spokes themselves were threaded on their outer ends, and cold-headed and bent on their flange ends. Each spoke is provided with an internally threaded nipple (usually of brass, to prevent rusting to the spoke), which are pushed through dimpled holes in the rim from the OD side, to finally screw onto the spoke ends. The rim material around each spoke hole is dimpled inward to fit the head of the nipple, and each hole is angled to align with the axis of the spoke it will tension.