Chain
Decorative small chains fashioned from gold and silver were made back in the time before Christ. By 200 B.C. Greeks used chains for water-raising machines; later, Romans used bronze chains in their galleys. Other uses of chains were explored during the Renaissance. Leonardo da Vinci sketched both hinged link chains and continuous chain drives with sprocket wheels in his manuscripts, but its not known whether the chains he drew were ever made. Iron chains and buckets were used in the 1500s as part of pumping machinery to replace ropes and earthenware pots. In a 1588 drawing of a water-raising machine, there is a chain with square links that fit over projecting teeth on wooden wheels; each square link is connected to the next one by three oval links.
Due to the high cost and scarcity of suitable metals, as well as the absence of good tools to create chains, there was a very limited use of chains before the Industrial Revolution before Thomas Bunton invented chain links with a central stud, which added strength to the links, neutralizing their tendency to stretch under strain. About the same time, in 1808, Samuel Brown patented a design for an improved iron chain. This was followed in 1820 by the first ship's cable, created by Noah Hingley, an English blacksmith who used only a forge, hammer, and anvil.
Because England had a rich source of iron ore, it became the center for chain making; its iron was superior to steel, which tended to corrode too badly to be useful over a long period of time. The chain drive was perfected about this same time. In 1864 Englishman James Slater patented a driving chain precise enough to be useful for driving bicycles and various machines. His factory was later acquired by a Swiss, Hans Renold, who devised a better chain in 1880--the bush roller chain which allowed more weight to be added to the chain. In France Andre Guilmet invented a bicyclette that had the chain drive attached to the rear wheel. This early bicycle was then manufactured by Meyer et Cie in 1868. The chain drive in use then was still comparatively weak until another Frenchman, G. Juzan, developed what he called bicyclette moderne in 1885: it had same-size wheels with a better chain drive to the back wheel. Finally, John Kemp Starley created a commercially successful "safety" bicycle in 1885 with the same features as the French model. From the bicycle came the use of chain drives in motorcycles.
Today's large chains are made by forge welding. With this process, metal studs can be inserted into the links while they are still hot if added strength is necessary. Special hydraulic machines can then test the finished product.
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