Wire wheels
The rims of wire wheels (or "wire spoked wheels") are connected to their hubs by wire spokes. Although these wires are generally stiffer than a typical wire rope, they function mechanically the same as tensioned flexible wires, keeping the rim true while supporting applied loads.
Wire wheels are used on most bicycles and motorcycles. They were invented by aeronautical engineer George Cayley and first used in bicycles by James Starley. A process of assembling wire wheels is described as wheelbuilding.
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On automobiles
Before 1960, sports/racing cars often had wire wheels equipped with "knockoff" (central wing nut) hubs that could be unscrewed by striking a wing of the nut with a mallet or "knockoff hammer", but in the 1960s cast light-alloy or "Mag(nesium)" wheels became common and now predominate.
On motorcycles
On bicycles
Bicycle manufacturers build millions of wheels annually, using the common crossed-spoke patterns whose crossings of adjacent spokes are governed by the number of spokes in the wheel. Wheelbuilders of racing teams and in good bicycle shops build wheels to other patterns such as two-cross, one-cross, or no-cross (also called radial). Many of these patterns have been used for more than 100 years but it is claimed that crossed patterns have more strength and stability while irregular patterns are art forms and have little structural merit (Brandt, 1993).
In the 1980's, cast wheels with 5 or 6 rigid spokes began to appear in the Olympic Games and professional racing: these have advantages in specialized applications, such as time trials, but wire-spoked wheels are used for most purposes.
Reaction to load
When a radial load is applied at the hub to a well tensioned wheel, such as by a rider sitting on a bicycle, it causes the wheel to flatten slightly near the ground contact area. The rest of the wheel remains approximately circular.[1][2] The tension of all the spokes do not increase significantly. Instead, only the spokes directly under the hub decreasing their tension.[3][4][5]
Some authors conclude that the hub "stands" on those spokes immediately below it that experience a reduction in tension.[3] Other authors conclude that the hub "hangs" from those spokes above it that have higher tension than the ones below it.[5]
References
- ^ Whitt, Frank R.; David G. Wilson (1982). Bicycling Science (Second edition ed.). Massachusetts Institute of Technology. pp. 106–138. ISBN 0-262-23111-5.
- ^ "Bicycle Wheel Analysis". http://www.astounding.org.uk/ian/wheel/index.html. Retrieved 2008-12-31.
- ^ a b Brandt, Jobst (1981). The Bicycle Wheel. Avocet. pp. 12–20. ISBN 0-9607236-2-5.
- ^ Wilson, David Gordon (2004). Bicycling Science (Third edition ed.). Massachusetts Institute of Technology. pp. 389–390. ISBN 0-262-73154-1.
- ^ a b "Hubs hang from the rim!". http://hea-www.harvard.edu/~fine/opinions/bikewheel.html. Retrieved 2008-01-22.