The birthplace of the modern wheelbarrow was China, possibly as early as 100 B.C. One early version consisted of a large single wheel at or near the front of a platform. The load would be placed behind the wheel, and the operator would lift the heavy end and push the load. The modern wheelbarrow can have one, two, or four wheels. These wheels can be either in front or beneath the load. Other conveniences include storage space compartments or side clips to carry tools. Wheelbarrows are considered a necessity for the backyard gardener as well as industry, for they are considered simple, unmotorized, yet effective ways for one person to carry a heavy load.A wheelbarrow consists of a tray or bed composed of steel, wood, or plastic. A steel brace attaches this bed to steel support legs and to a steel or plastic wheel, with a rubber tire around it. In two- or four-wheeled models, the wheels may be similar to bicycle tires, complete with inner tubes. Some handles are metal with foam or hard plastic grips, while some wheelbarrows intended for the home gardener have solid wooden handles with no grips. Because wheelbarrows exist in a variety of forms, made from many different materials, manufacturing procedures vary widely depending on the exact kind of wheelbarrow being made. Some wooden wheelbarrows are simple enough to be made with hand tools used by weekend hobbyists with modest carpentry skills. Some heavy-duty wheelbarrows, intended for industrial use, are manufactured with heavy machinery which shapes thick steel sheets.The most important factor in the quality control of wheelbarrows is ensuring that all the components fit together correctly. During the shaping of steel components, each part is compared to a standard part of the same type that is known to be correct. A sample wheelbarrow can be tested by assembling it, filling it with a load, and moving it around. Factors to be considered in order to produce a wheelbarrow that will satisfy consumers include ease of assembly, ease of motion, stability, ability to be steered accurately, and ability to carry a heavy load with minimal effort on the part of the user.
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