Wheel tractor-scraper

History:
– R.G LeTourneau conceived the self-propelled motor scraper idea after a near-fatal auto accident.
– He approached Caterpillar in the 1930s with the idea but founded his own company when it was turned down.
– The first Tournapull, Model A, was introduced in 1937.
– The concept was further developed by LeTourneau Westinghouse Company.
– Most current scrapers have two axles, although tri-axle configurations were common historically.

Design:
– The scraper is used in mining, construction, agriculture, and earthmoving.
– It has a vertically moveable hopper with a sharp horizontal front edge.
– The hopper can be hydraulically lowered and raised.
– The scraper transports its load to the fill area and dumps it using the back panel or ejector.
– Elevating scrapers do not need push-tractors and can be very efficient on short hauls.

Configurations:
– Open bowl scrapers require a push-cat for loading.
– Elevating scrapers are self-loading and use an elevator to load material.
– Tandem scrapers have separate tractor and scraper engines for greater power and traction.
– Tandem Push-Pull concentrates the horsepower of two machines onto one cutting edge.
– Auger scrapers use vertically mounted augers to pull material upwards.

See also:
– Fresno scraper, a predecessor of modern scrapers pulled by horses.
– Grader, a rear-engined machine for scraping or spreading excess material.
– Laser Machine Control.

References:
– Wikimedia Commons has media related to Tractor-scrapers.
– Contractor Magazine articles on LeTourneau Model B and Model A Tournapull.