Building a Safety Bicycle — Chain Drive, Equal Wheels, and Personal Freedom

The bicycle that everyone rides today was settled in the 1880s and is still called, in the trade, the safety bicycle — to distinguish it from the terrifying high penny-farthing it replaced. Two equal wheels, a diamond frame, a chain driving the rear wheel, and soon air-filled tyres made cycling safe, fast, and available to ordinary people.

Each feature solves a problem. Equal wheels and a low frame mean you can put a foot down and cannot be pitched over the handlebars. The chain and gearing let a small wheel travel fast without the giant front wheel of the penny-farthing. The diamond frame, built of brazed steel tubes, is astonishingly light and strong for its weight. And Dunlop's pneumatic rubber tyres turned a bone-shaking ride into a smooth one.

The safety bicycle was more than transport. Cheap, simple, and needing no horse or fuel, it gave working people and especially women a freedom of movement they had never had — which is why it is often credited with as much social change as mechanical.