The potter's wheel may have been invented before the first wheel was put on a cart, according to some scholars. Researchers know this from examining earthenware pots from ancient sites. Pots shaped on a wheel are distinctive. Regardless of which came first, the potter's wheel and the two-wheeled cart arrived on the scene at about the same time - in Sumeria (modern Iraq) around 3500 BC. Rollers made of logs had been used for 2,000 years. Land sledges (big sleds) had also been around for a long time. Combining rollers with sledges was new. The first carts, though crude, were revolutionary.
By 3000 BC, Assyrians were using carts. In 2500 BC, carts were being used in the Indus River Valley (modern-day India) and China. They spread to central and northern Europe sometime after 1000 BC. Britain had them by 500 BC. Early wheels were made of three pieces of wood held together with bronze strips and copper nails. They were heavy, and hard to move. Lighter, spoked wheels made possible the Sumerian military chariot in 1500 BC. But to be most effective, wheels needed good roads on which to roll. The Romans built excellent roads for their chariots, beginning with the Appian Way in 312 BC. Some survive to this day.
It is one of the most abundant metals on earth, but it was once far more precious than gold. In 1869, gold cost $20 an ounce, but an ounce of aluminum was $500. In 1761, Baron Louis-Bernard Guyton de Morveau had proposed the name "alumine," based on his belief that alum was an oxide of an undiscovered metal. In 1807, British chemist Sir Humphrey Davy dubbed it "alumium," although he never extracted any. German chemist Friedrich Wohler determined the basic properties of the metal in 1845, after producing pinhead-size blobs of it. Finally, in 1886, Charles Martin Hall of the United States and Paul Heroult of France independently discovered the same basic process for extracting aluminum profitably. The same process is used today to extract the lightweight metal used in half the bicycle frames produced each year. Interestingly, the metal is "aluminum" in the US, but it's "aluminium" in Britain. Legend says this was due to a typographical error. Not true. According to the American Chemical Society, Sir Davy agreed to call it "aluminum," which the British scientific community later changed to "aluminium." It was "aluminium" in the US, too, until 1925. That's when the ACS officially changed it.
For surfaces that slide or move, lubricants - oil, grease, etc. - reduce friction and wear. The earliest lubricants were probably mud and reeds. They were placed under the runners of land sledges used to move heavy loads. Next came animal fats, which were the principal form of lubrication until the rise of the petroleum industry in the 1800s.
In 1872, African-American Elijah McCoy patented an automatic oiling system for steam locomotives. Before McCoy's invention, trains had to stop periodically and be relubricated by hand. McCoy's device released oil into the machinery to lubricate it as it operated. His invention had so many poor imitators that people began to demand "the real McCoy," a phrase still used today to denote "the genuine article."
John Boyd Dunlop is called the "father of the tire," but he didn't invent it - he reinvented it. What Dunlop called the pneumatic (air-filled) tire was first invented in 1845 by a London engineer, Robert Thomson, who patented an "elastic best for carriage wheels and other rolling bodies." Before then, wheels were made of wood with iron rims. Thompson's invention didn't catch on. Rubber was expensive, and the tires weren't very durable. By 1870, when rubber became more affordable, solid-rubber tires became popular. But solid rubber was hard, and the ride was jarring, especially on rough roads. Scottish-born Dunlop solved the problem - again - in 1888. His son complained about the jolting ride his solid-rubber bike tires produced. After weeks of work, Dunlop made a soft, inflatable inner tube filled with air, which acted as a cushion. Not only that, it rolled much more easily than a solid-rubber tire. His tires not only made bicycling more popular, they brought about a demand for better roads and speeded the development of the automobile.
Ancient Romans used ball bearings. We know this from a table that dates back to the reign of Roman emperor Caligula (AD 37 to 41). The table, which rotated on ball bearings, was excavated from a ship found in Italy's Lake Nemi. Leonardo da Vinci drew sketches of ball bearings in the 16th century, but apparently never produced one.
The invention of the pedal cycle and the burgeoning bicycle industry actually spurred great advances in bearing technology, beginning in the late 1800s. Ball bearings cut down on friction by reducing the area of contact between two surfaces. They do this by means of small balls of hardened steel or some other material. (Think about it: Which is easier to spin - a sphere, or a flat-bottomed cylinder of about the same size and weight?) The balls, or bearings, are lubricated and spin in grooves called races. Ball bearings are now used in: the front and rear hubs of a bicycle's wheels; in the bottom bracket (where an axle connects the two pedal cranks), the front fork tube (for easier steering), and in the pedals.
(c) Copyright 2001. The Christian Science Publishing Society