I love bicycles and I have ridden a long way. Cycle commuting between home and Oxford from 1979 to 2006, I reckon I covered about 135,000 kilometres - three times the circumference of the earth or a third of the distance to the moon. But I was disappointed to find that, assuming 7 litres for 100 kms (the consumption of a deux-chevaux crawling along in heavy traffic) I kept only about 18 tons of CO2 out of the atmosphere.
My one original idea about bicycle design is that chain-wheels with 27, 36 and 48 teeth would give identical gear ratios beween small and middle and middle and large. Combine this with rear cogs with 12, 14, 16, 18, 21, 24 and 28, you would get as near as possible to equal jumps between gears, varying between 7/6 and 9/8. The problem of gearing using cogwheels is like the problem of tuning keyboards, except that for keyboards it is possible to depart from whole-number ratios, but that is a story for my music pages. I attach an article to explain. 
P J Stewart,
14 Feb 2010, 10:04