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Outdoor Power Equipment

String Trimmers

String Trimmers Article

A line-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 and thus it is 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.

The line is hand-wound onto a reel before the job is started, leaving both ends extending from the reel housing. The motor turns the reel and the line extends horizontally while the operator swings the trimmer about where the plants are to be trimmed. The operator controls the height at which cutting takes place and can trim down to ground level quite easily. As the line is worn, or breaks off, the operator knocks the reel on the ground so that a release mechanism allows some of the line in the reel to extend and replace the spent portion. A small cutter on the line-guard ensures that the line length exposed for cutting does not exceed the length that can be swung efficiently by the motor. Newly extended line operates more efficiently because of its heavier weight and surface effects (the star-shaped edges).

Trimmers that have nylon or metal blades usually have straight driveshafts because of the higher torque required to turn the disk and because of the shock loads that are passed back from the blade to the driveshaft and its gearbox(es). Smaller line trimmers have curved driveshafts to make holding the cutting-head at ground level much easier and with less strain on the operator.

String Trimmers Items

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