In archeology, scrapers are unifacial tools that were used either for hideworking or woodworking purposes. Whereas this term is often used for any unifacially flaked stone tool that defies classification, most lithic analysts maintain that the only true scrapers are defined on the base of use-wear, and usually are those which were worked from the distal ends of blades-- i.e., "end scrapers " or grattoirs . Other scrapers include the so-called "side scrapers " or racloirs, which are stuck from the longest side of a flake, and notched scrapers , which have a cleft on either side which may have been used to attach them to something else.
Most scrapers are either oval or blade-like in shape. The working edges of scrapers tend to be convex, and many have trimmed and dulled lateral edges to facilitate hafting. One important variety of scraper is the thumbnail scraper , a scraper shaped much like its namesake. This scraper type is common at Paleo-Indian sites in North America.
In civil engineering a Wheel Tractor-Scraper is a piece of heavy equipment used for earthmoving. The rear part has a vertically moveable hopper with a sharp horizontal front edge. The hopper can be hydraulically lowered and raised. When the hopper is lowered, the front edge cuts into the soil like a cheese cutter and fills the hopper. When the hopper is full (8 - 34 m3 heaped, depending on type) it is raised, and closed with a vertical blade. The scraper can transport its load to the fill area where the blade is raised, the back panel of the hopper is hydraulically pushed forward and the soil load tumbles out. Then the empty scraper returns to the cut site and repeats the cycle.
Scrapers can be very efficient on short hauls where the cut and fill areas are close together and have sufficient length to fill the hopper. The heavier scraper types have two engines ('tandem powered'), one driving the front wheels, one driving the rear wheels, with engines up to 400 kW (550 hp).
Two scrapers can work together in a push-pull fashion but this requires a long cut area.
See also
Last updated: 05-13-2005 07:56:04
