String trimmer

A string trimmer, also called a "whipper-snipper", "weed-whacker", a "weed eater" or (in the UK) a "strimmer", is a tool which uses a flexible monofilament line instead of a blade for cutting grass and other plants near objects, or on steep or irregular terrain. It consists of a cutting head at the end of a long shaft with a handle or handles and sometimes a shoulder strap.

String trimmers may also be known as whipper snippers, weed whips, edge trimmers, and line trimmers.

History

The string trimmer was invented in the early 1970s by George Ballas of Houston, Texas, who conceived the idea while watching the revolving action of the cleaning brushes in an automatic car wash. His first trimmer was made by attaching pieces of heavy-duty fishing line to a popcorn can bolted to an edger. Ballas developed this into what he called the "Weed Eater", since it chewed up the grass and weeds around trees.

Design

A string trimmer works on the principle that a line that is turned fast enough is held out from its housing (the rotating reel) very stiffly by centrifugal force. The faster it turns the stiffer the line. Even round-section nylon line is able to cut grass and slight, woody plants quite well. Some monofilament lines designed for more powerful cutters have an extruded shape, like a star, that helps the line slash the material being cut; the line is thus able to cut quite large woody plants (small shrubs) or at least ring-bark them very effectively. These lines make disks less necessary for tough jobs.