CONTROL LEVERSMost scrapers have three basic control leverslocated on the right side of the operator’s seat. The firstlever is the bowl lever (fig. 10-38, view A). The bowllever raises and lowers the bowl. The middle lever isthe apron control lever (fig. 10-38, view B). The aproncontrol lever opens and closes the apron, allowing therequired amount of material to enter or be ejected fromFigure 10-38.-Scraper control levers.the bowl. The third lever is the ejector lever (fig. 10-39,view C). The ejector lever forces the dirt out of the bowl.For maximum hydraulic cylinder operating efficiency,the engine should be operated at maximum rated speedand the control levers moved to their extreme operatingposition.SCRAPER OPERATIONSThe greatest engine power is available when theengine is running at top governed speed. The propertransmission gear ratios must also be engaged to obtainmaximum engine power output. When the transmissionis placed in a too high a gear ratio for full engine power,the result is a stall condition in the transmissionconverter. Stalling the converter prevents the enginefrom operating at maximum efficiency and results inrapid overheating and premature wear of the converteror transmission.The transmission must be downshifted correctlywhile the scraper is in motion to prevent damage to thepower train. Improper downshifting overspeeds thetransmission and engine and usually results inpremature wear and unnecessary transmissionbreakdowns.When moving the scraper from a full stop, alwaysstart with the transmission in low gear, depressing thethrottle for the degree of acceleration required. A wide,open throttle provides the fastest acceleration underfull-load conditions.When running downgrade, avoid overspeeding theengine by keeping the scraper speed at, or below, themaximum speed for the transmission range engaged. Asa general rule, downhill scraper speed should not exceed5 mph more than that attained on level ground in thetransmission ratio engaged.When the selected transmission ratio is too high,slow the scraper with the service brakes until thetransmission can be properly downshifted to therequired range for the grade.Downhill speed can be slowed, if necessary, bylowering the scraper bowl until the cutting edge dragsenough to slow the scraper to the required speed topermit proper downshifting or stopping.Do not fan the brakes by repeated depressing andreleasing. This practice can reduce air pressure belowthe point required for proper breaking. The air pressuresystem should indicate 105 to 125 psi on the air pressuregauge for effective braking. When the gauge indicatesa pressure drop below 105 psi for a long time, shutdownthe scraper until the trouble is corrected.10-20
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