Trencher (machine)

A trencher is a piece of construction equipment used to dig trenches, especially for laying pipes or electrical cables, for installing drainage, or in preparation for trench warfare. Trenchers may range in size from walk-behind models, to attachments for a skid loader or tractor, to very heavy tracked heavy equipment.

Trenchers come in different sizes and may use different digging implements, depending on the required width and depth of the trench and the hardness of the surface to be cut.

A wheel trencher or rockwheel has a toothed metal wheel. It is cheaper to operate and maintain than chain-type trenchers. It can work in hard or soft soils, either homogeneous (compact rocks, silts, sands) or heterogeneous (split or broken rock, alluvia, moraines). This is particularly true because a cutting wheel works by clearing the soil as a bucket-wheel does, rather than like a rasp (chain trencher). Consequently, it will be less sensitive to the presence of blocks in the soil. They are also used to cut pavement for road maintenance and to gain access to utilities under roads.

Due to its design the wheel may reach variable cutting depths with the same tool, and can keep a constant soil working angle with a relatively small wheel diameter (which reduces the weight and therefore the pressure to the ground, and the height of the unit for transport).

The cutting elements (six to eight, depending on the diameter) are placed around the wheel, and bear the teeth which are more or less dense depending on the ground they will encounter. These tools can be easily changed manually, and adjusted to allow different cutting widths on the same wheel. The teeth are placed in a semi-spherical configuration to increase the removal of the materials from the trench. The teeth are made of high strength steel (HSLA steel, tool steel or high speed steel) or cemented carbide. When the machine is under heavy use, the teeth may need to be replaced frequently, even daily.

A system of spacers and ejectors allows the excavated materials to be moved away from the edges of the trench to avoid possible “recycling”.

Wheel trenchers may be mounted on tracks or rubber tires.

A chain trencher cuts with a digging chain or belt that is driven around a rounded metal frame, or boom which resembles a giant chainsaw. This type of trencher can cut ground that is too hard to cut with a bucket-type excavator, and can also cut narrow and deep trenches. The angle of the boom can be adjusted to control the depth of the cut. To cut a trench, the boom is held at a fixed angle while the machine creeps slowly.