TABLE OF CONTENTS The bottom-dump scrapers discussed in this chapter are also known as carrying scrapers or pans, and by various trade names. They are highly mobile excavators with a centrally located bowl that digs, carries, and spreads loads. There are a wide range of types and sizes. Struck capacity is usually between 6 and 56 yards, but there are larger and smaller units also.
The typical modern scraper is a self-powered, rubber-tire unit. Controls are usually hydraulic or a combination cable-hydraulic.
Standard or conventional self-powered models have power and traction sufficient for most hauling needs, but require the help of pusher tractors or other machines in order to dig efficiently.
Self-loading scrapers, which ordinarily do not need pusher help, may have two engines with separate drive axles for extra power, or an elevator that reduces loading resistance.
There are also full trailer scrapers, which are towed by a drawbar attached to a separate tractor. These were once the dominant type, and are still useful for farming and in special situations. They are self-loading if the tractor is large in proportion to scraper capacity.
Scrapers are of primary importance in earthmoving. They are the standard tool for alternating cuts and fills, under the wide range of conditions where the cut is firm enough to support them, and the soil (including rock that is soft, ripped, or blasted) is digable.
The scraper digs, hauls, and spreads in a single cycle. It works in thin layers in the cut and on the...
