high molecular weight hydrocarbons, or whichasphalts, tars, pitches, and asphaltites are typical.BLASTING MAT– A heavy, flexible fabric of wovenwire rope or chain, used to confine blasts.BLEEDING OR FLUSHING– Is the upwardmovement of asphalt in an asphalt pavement,resulting in the formation of a film of asphalt on thesurface. The most common cause is too muchasphalt in one or more of the pavement courses,resulting from too rich a plant mix, an improperlyconstructed seal coat, too heavy a prime or tack coat,or solvent-carrying asphalt to the surface. Bleedingor flushing usually occurs in hot weather.BLUE TOPS— Grade stakes with blue tops to indicatefinish grade level, usually a 2-inch by 2-inch by6-inch hub stake.BM— Bench mark.BODY— The load carrying part of a truck or scraper.BOGIE AXLE— Two or more axles, mounted to a frameso as to distribute the load between the axles andpermit vertical oscillation of the axles.BOOM CHORD— A main corner member of a latticetype of boom.BOOM, CRANE— A long, light boom, usually of latticeconstruction.BOOM HOIST— Mechanism to control the elevation ofthe boom and to support it.BOOM LACING– Structural truss members at anglesto and supporting the boom chords of a lattice typeof boom.BOOM, LATTICE— A long, light boom fabricated ofcrisscrossed steel or aluminum angles or tubing.BOOM LENGTH— Boom length is a straight linethrough the center line of the boom pivot pinto thecenter line of the boom point load hoist sheave pin,measured along the longitudinal axis of the boom.BOWL— (1) The bucket or body of a carrying scraper.(2) Sometimes the moldboard or blade of a dozer.BUCKET— A part of an excavator that digs, lifts, andcarries dirt.BULLDOZER— (1) A tractor equipped with a frontpusher blade. (2) In a machine shop, a horizontalpress.CAPILLARY ATTRACTION— The tendency of waterto move into fine spaces, as between soil particles,regardless of gravity.CASING— A pipe lining for a drilled hole.CAT— (1) A trademark designation for any machinemade by the Caterpillar Tractor Company. (2)Widely used to indicate a crawler tractor of anymake.CAT HEAD— A capstan winch.CATWALK— A pathway, usually of wood or metal, thatgives access to parts of large machines.CENTRIFUGAL FORCE— Outward force exerted bya body moving in a curved line. It is the force thattends to tip a car over in going around a curve.C-FRAME— An angling dozer lift and push frame.CHECK VALVE— Any device that will allow fluid orair to pass through it in only one direction.CHOKER— A chain or cable so fastened that it tightenson its load as it is pulled.CIRCLE REVERSE— The mechanism that changes theangle of a grader blade.CLAM— A clamshell bucket.CLAMSHELL— (1) A shovel bucket with two jaws thatclamp together by their own weight when it is liftedby the closing line. (2) A crane equipped with aclamshell bucket.CLAMSHELL BUCKET— Usually consists of two ormore similar scoops hinged together and a headassembly connected to the outer corners by struts.When the head and hinge are pulled toward eachother, the scoops are forced together to dig and holdmaterial. Control is by a holding line reeved over aboom point sheave and attached to the headassembly to support the bucket in open position andusually by a closing line also reeved over a boompoint sheave, ending in a force amplifying tackle orother means between the head assembly and scoophinge to close the bucket.CLAMSHELL BUCKET, HYDRAULIC— Usuallyconsists of two or more scoops hinged to a headassembly housing the hydraulic cylinder orcylinders and the force amplifying linkage to openand close the scoops and to supply the digging forcefor the scoops. The bucket assembly is suspendedfrom the boom by a rope. Because digging ability islargely dependent upon bucket weight, buckets aresupplied in various weight classes which range fromAI-2
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