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 The domestication of animals increased the efficiency of travel for our ancestors, as they could now travel faster, and carry heavier loads. Sidepacks gave way to slings and travois, allowing for more weight to be transported by the animals. In ancient times, heavy items were moved by placing the load on horizontally placed logs. The load could then be ‘rolled’ to the desired location. This method of moving heavy items probably led to the invention of the wheel. This important innovation is clouded in the mists of time. The first wheeled vehicles were probably travois which had wheels and axle added to them. From this simple vehicle carts and wagons evolved. The first archeological evidence we have in the history of the wheel comes from about 4000 BC. A clay model of a wheeled vehicle, a four wheeled cart, was found near Szigetszentmárton, Hungary. The earliest known civilization were the Sumerians, who lived in the area between the Tigris and Euphrates in present day Iraq. Sumerian pictographs dating from about 3500 BC show a sledge equipped with wheels. The earliest wheels in history were constructed from wooden planks held together with transverse struts. These wheels were very heavy, and required oxen to pull the carts equipped with them. The spoked wheel was developed around 2000 BC. These wheels were lighter, allowing smaller mules to be employed pulling wagons. Further improvement in wheel design lightened it more. The carts equipped with these improved wheels allowed the smaller, faster horse to be employed to pull them. This development, in turn, led to the development of the war chariot. The war chariot made the early empires of the Assyrians, Babylonians, and others possible by allowing the fast movement of troops over larger distances. The Persians made the wheel into a weapon of terror by attaching blades which were designed to mow down opposing infantry. The first major improvement to the wheel was the addition of the tire. A tire is defined by the Encyclopedia Britannica as a continuous band that encircles the rim of a wheel and forms a tread that rolls on either a road, a prepared track, or the ground. The first tires consisted of an iron band which was heated, causing it to expand. It was then pounded over the wooden wheel framework. The iron would then contract as it cooled, holding the wheel assembly together. With some modifications, this was pretty much the latest word in tires until the early 1800’s. European discoveries in the late 1400’s, had major historical implications for the wheel. Columbus, on his voyages, observed natives playing with a ball made from the gum of a tree. The Spaniard’s later observed American Indians obtaining a milk type of substance from gashes on certain types of trees. The natives would brush this ‘milk’ onto their cloaks to dry. It would then be pressed into a mold to obtain footwear, or to make bottles. A British scientist named Joseph Priestley called this substance ‘rubber’ after discovering its usefulness for rubbing out pencil marks. Rubber was first used to waterproof shoes and clothing. This early rubber had limited uses because of its tendendancy to soften under heat and harden under cold temperatures. It was also odorous, tacky, and perishable. A fellow by the name of Charles Goodyear developed the vulcanization process in 1839 which removed these undesirable properties. It was now useful for many other things, including bicycle, buggy, and later, automobile tires. Rubber absorbed bumps much better than steel tires, and was also more lightweight. These early rubber tires were solid rubber. Pneumatic, or air filled tires were invented first by an Englishman named Robert William Thomson in 1845. He also made a solid rubber tire which was more popular with the public. His pneumatic tire was forgotten until bicycles started becoming more popular in the late 1800’s. By 1888 John Boyd Dunlop began making pneumatic tires for bikes. Michelin & Cie, a French rubber manufacturer started making the first pneumatic tires for the newly popular automobile. Synthetic materials, developed in the twentieth century, have replaced rubber as a tire ingredient. It is impossible to calculate the importance of the wheel to the developement of our mobile civilization. Our history would surely be much different if the wheel had never been developed. |