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Construction Methods and Management, 8th ed. S. W. Nunnally

Chapter 4

LOADING AND HAULING

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

In calculating the time required for a haul unit to make one complete cycle, it is customary to break the cycle down into fixed and variable components.
Cycle time = Fixed time + Variable time
Fixed time represents those components of cycle time other than travel time.
Variable time represents the travel time required for a unit to haul material to the unloading site and return.

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

Rolling Resistance
To determine the maximum speed of a vehicle in a specific situation, it is necessary to determine the total resistance to movement of the vehicle.
The resistance that a vehicle encounters in traveling over a surface is made up of two components, rolling resistance and grade resistance.
Total resistance = Grade resistance + Rolling resistance

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

Table 4-1. Typical values of rolling resistance factor

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

Grade Resistance
Grade resistance represents that component of vehicle weight which acts parallel to an inclined surface.
When the vehicle is traveling up a grade, grade resistance is positive.
When traveling downhill, grade resistance is negative.

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

Effective Grade
The total resistance to movement of a vehicle (the sum of its rolling resistance and grade resistance) may be expressed in pounds or kilograms.
However, a somewhat simpler method for expressing total resistance is to state it as a grade (%), which would have a grade resistance equivalent to the total resistance actually encountered.
This method of expressing total resistance is referred to as effective grade, equivalent grade, or percent total resistance and is often used in manufacturers’ performance charts.

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

Effect of Altitude
All internal combustion engines lose power as their elevation above sea level increases because of the decreased density of air at higher elevations.
Effect of Traction
The power available to move a vehicle and its load is expressed as rimpull for wheel vehicles and drawbar pull for crawler tractors.

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

Table 4-2. Typical values of coefficient of traction

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

Use of Performance and Retarder Curves

FIGURE 4-1. Typical crawler tractor performance curve.

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

FIGURE 4-2. Wheel scraper performance curve. (Reprinted Courtesy of Caterpillar Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

FIGURE 4-3. Wheel scraper retarder curve. (Reprinted Courtesy of Caterpillar Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

Estimating Travel Time

Table 4-3. Average speed factors

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

FIGURE 4-4. Scraper travel time—loaded. (Reprinted Courtesy of Caterpillar Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

ESTIMATING EQUIPMENT TRAVEL TIME

FIGURE 4-5. Scraper travel time—empty. (Reprinted Courtesy of Caterpillar Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

DOZERS

Tractors and Dozers
A tractor equipped with a front-mounted earthmoving blade is known as a dozer or bulldozer.
A dozer moves earth by lowering the blade and cutting until a full blade load of material is obtained.
It then pushes the material across the ground surface to the required location.

Construction Methods and Management, 8th ed. S. W. Nunnally

DOZERS

FIGURE 4-6. Crawler tractor dozer. (Courtesy of New Holland Construction)

Construction Methods and Management, 8th ed. S. W. Nunnally

DOZERS

FIGURE 4-7. High-speed crawler dozer. (Courtesy of John Deere Construction & Forestry Company)

Construction Methods and Management, 8th ed. S. W. Nunnally

DOZERS

Dozer Blades

FIGURE 4-8. Common types of dozer blades.

Construction Methods and Management, 8th ed. S. W. Nunnally

DOZERS

FIGURE 4-9. Dozer blade adjustment.

Construction Methods and Management, 8th ed. S. W. Nunnally

DOZERS

Estimating Dozer Production

Table 4-4. Typical dozer fixed cycle times

Construction Methods and Management, 8th ed. S. W. Nunnally

DOZERS

Table 4-5. Typical dozer operating speeds

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

A tractor equipped with a front-end bucket is called a loader, front-end loader, or bucket loader.

FIGURE 4-10. Articulated wheel loader with articulated hauler. (Courtesy of Volvo Construction Equipment North America, Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

FIGURE 4-11. Track loader. (Courtesy of John Deere Construction & Forestry Company)

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

FIGURE 4-12. Backhoe loader. (Courtesy of JCB Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

Tool Carriers
Skid-Steer Loaders
Material Handlers
Estimating Loader Production
Job Management

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

FIGURE 4-13. Skid-steer loader with backhoe attachment. (Courtesy of the Bobcat Company)

FIGURE 4-14. Compact track loader. (Courtesy of the Bobcat Company)

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

FIGURE 4-15. Material handler. (Courtesy of JLG Industries, Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

Table 4-6. Basic loader cycle time

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

FIGURE 4-16. Travel time, wheel loader (haul + return).

Construction Methods and Management, 8th ed. S. W. Nunnally

LOADERS

FIGURE 4-17. Multisegment loader bucket.

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

Operation and Employment
Scrapers are capable of excavating, hauling, and dumping material over medium- to long-haul distances.
The scraper excavates (or cuts) by lowering the front edge of its bowl into the soil.
The bowl front edge is equipped with replaceable cutting blades, which may be straight, curved, or extended at the center (stinger arrangement).

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

FIGURE 4-18. Twin-engine all-wheel drive scraper. (Reprinted Courtesy of Caterpillar Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

FIGURE 4-19. Elevating scraper. (Reprinted Courtesy of Caterpillar Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

FIGURE 4-20. Twin-hitch scraper loading. (Courtesy of CMI Terex Corporation)

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

FIGURE 4-21. Pull scraper. (Courtesy of John Deere & Company)

FIGURE 4-22. Tandem pull-scrapers. (Courtesy of John Deere & Company)

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

Estimating Scraper Production

Table 4-7. Scraper fixed time (min)

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

Push-Loading

FIGURE 4-23. Methods of push-loading scrapers.

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

Optimum Load Time

FIGURE 4-24. A load growth curve.

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

FIGURE 4-25. Finding the optimum load time.

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

Calculating the Number of Pushers Required

Table 4-8. Typical pusher cycle time (min)

Construction Methods and Management, 8th ed. S. W. Nunnally

SCRAPERS

Push-Pull Loading
Job Management

FIGURE 4-26. Scraper application zones.

Construction Methods and Management, 8th ed. S. W. Nunnally

TRUCKS AND WAGONS

Operation and Employment
Trucks and wagons are still the most common forms of construction hauling equipment.
The heavy-duty rear-dump truck is most widely used because of its flexibility of use and the ability of highway models to move rapidly between job sites.

FIGURE 4-27. Forty-one-ton rear-dump truck. (Courtesy of Volvo Construction Equipment North America, Inc.)

Construction Methods and Management, 8th ed. S. W. Nunnally

TRUCKS AND WAGONS

FIGURE 4-28. All-wheel-drive articulated dump truck. (Courtesy of CMI Terex Corporation)

Construction Methods and Management, 8th ed. S. W. Nunnally

TRUCKS AND WAGONS

FIGURE 4-29. Bottom-dump wagon. (Courtesy of CMI Terex Corporation)

Construction Methods and Management, 8th ed. S. W. Nunnally

TRUCKS AND WAGONS

Determining the Number of Haul Units Needed
Job Management

Table 4-9. Spot, maneuver, and dump time for trucks and wagons (min)