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There are several analogies of mechanical design between the bicycle and nature. The coasting ability of a bicycle is analogous with the coasting ability of birds; the chain transmission has an analogy with the four-bar linkage in bird wings; the spoke-rim wheel layout has analogies with natural structures; and the tyre is analogous with some of the shock absorbing structures in animals. Comparing optimal design in the bicycle and nature demonstrates that the bicycle is very efficient as a transport machine and as a structure. However, one key difference with nature is that coasting animals like birds avoid steep gradients by flying on a level course or by using thermals to gain altitude. Analysis of the energy demands of cycling show that uphill cycling has a major negative impact on journey times and energy efficiency. Investing in dedicated cycle paths in order to avoid steep gradients could significantly increase the take-up of cycling and this would have significant long-term environmental advantages.
Bicycle, coasting, gradients, structural efficiency
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