Off-highway Trucks Research Articles

Effect of Truck Payload Weight on Production

Most constructors intuitively understand that there is a relationship between payload weight and haul unit performance. At the same time, project managers constantly push the limits of rated truck payload as they seek increased productivity. This is because it is believed that increased productivity translates into reduced project cost. These ideas are quantitatively examined using payload data from seven Caterpillar 785B off-highway haul trucks working on an earth/rockfill dam in California. Caterpillar's Vital Information Management System was used to collect load data from 54,300 truck cycles representing approximately 14,419 operating hours and haulage of more than 7.25 million metric tons (8 million tons) of material. There was a diminished productivity increase when the load weight exceeded the truck's rated gravimetric capacity. Adding sideboards actually caused the average monthly production of the fleet to decrease. The plot of load times versus load weight appears to indicate a human factors rel...

An introduction to the integrated design of surface mine haul roads

The world-wide expansion of surface mining has led to the development of very large off-highway trucks currently capable of hauling payloads in excess of 160t. Typical axle loads ranging from 110 to 170t are applied to haul roads that have been, at best, empirically designed on the premise of “satisfactory” or “failed”, both in terms of structure and function of the road. The use of these empirical pavement design techniques will prove inadequate when high axle loads are encountered. Not only will the maintenance costs of existing haul roads of inadequate thickness increase, but vehicle operating and maintenance costs will also increase prohibitively. Under these conditions there is thus a clearly defined need for improved construction and management techniques for flexible mine haul roads, appropriate for the wheel loads of vehicles now in use. The aim of this paper is to introduce developments in haul road structural, functional and maintenance design and management which overcome the limitations associated with the previously empirical design techniques and to show how these developments are combined into an integrated design strategy combining construction techniques, available material and road maintenance equipment with hauler choice to realise a reduction in haulage and road maintenance costs. Future contributions will enumerate on the fundamental haul road structural, functional and maintenance design and management research from which these developments originated

Evaluating the Performance of Construction Equipment Operators in Egypt

Problems in operating construction equipment in Egypt were perceived as resulting in low productivity. Productivity was considered in this study as a measurement dimension that sufficiently describes operator's performance. The objectives of this study are to provide an analytical approach for identifying causes of productivity loss and evaluating their effects, and to evaluate the performance of equipment operators. The performance ability ratio (PAR) compares the actual productivity against the estimated productivity to demonstrate the amount of loss of productivity and, thus, judge the level of operator productivity. The study was conducted at 11 jobs concerning 11 pieces of earthmoving equipment: three bulldozers, three elevating scrapers, three off-highway trucks, and two hydraulic backhoe excavators. The analysis led to basic conclusions concerning the amount of downtime and its variation according to equipment type, and the average PAR values for operators of the four types of equipment.

The effect of pneumatic tire characteristics on the performance of off-highway trucks

Abstract A mathematical model for pneumatic tire-soil interaction is used to evaluate the effect of pneumatic tire properties on the performance characteristics of a typical off-highway truck operating in sandy and clayey soil conditions. An example is given to demonstrate the good agreement between the results obtained from the mathematical model and information contained in the Caterpillar Performance Handbook.

Continuity Strengthens South Fork Hoh River Bridge Replacement

T South Fork Hoh River Bridge (see Fig. 1) is a 142 ft 3-Y4 in. (43.4 m) long, three-span continuous prestressed concrete structure made up of pretensioned decked bulb tee girders. The bridge replaces an old deteriorated timber structure using the existing middle piers. To increase the load capacity of the bridge, the girders were post-tensioned for continuity. The bridge is designed for off-highway logging trucks and overload crossings of large tower and yarder units. This article describes the preliminary studies, design and economic considerations, advantages of continuity, post-tensioning layout and joint details, construction aspects and post-tensioning operations used to construct this unique bridge. The South Fork of the Hoh River is Iocated on the Olympic Peninsula, southeast of Forks, Washington (see Fig. 2). This region has the highest average annual rainfall in the continental United States, averaging 140 in. (3556 mm) per year. Storms have been known to bring up to 6 in. (152 mm) of rain in a 24-hour period and this, when combined with melting snow, can cause the river to rise quickly, sending logs and debris rushing downstream. In this constantly moist environment, decay is rapid and omnipresent, thus presenting formidable obstacles to bridge construction and longevity. The South Fork Hoh River Bridge, also known as the Marsh Bridge, was originally built in 1960 for HS20 loading using log stringers and timber decking over two interior reinforced concrete support piers on footings embedded in rock. Twenty-two years later, the log stringers were decaying, threatening structural integrity. After the original bridge was built, the

Optimizing off-highway truck characteristics for minimum haulage cost

Critical equipment characteristics are isolated and analysed by traditional operations research techniques, using off-highway trucks as an archetype. A computer search technique has been developed, employing various production and cost analyses. With this model, the optimum combination of horsepower, capacity, velocity, and total cost can be found, minimizing haulage cost per ton. Horsepower is treated as the most important characteristic. An example of the program's use and interpretation of its results conclude the paper. The optimization is useful as an aid to off-highway truck selection, evaluation, and design. Model limitations are offered and advantages to its use are given.

26. A unique concept in off-highway trucks : Moreno, E.F. and Domes, E.A. S.A.E. Paper, Earthmoving Industr. Conf., April 6–7 1965, p. 13

26. A unique concept in off-highway trucks : Moreno, E.F. and Domes, E.A. S.A.E. Paper, Earthmoving Industr. Conf., April 6–7 1965, p. 13

Automatic Transmissions in America

Since the internal-combustion engine was first adopted for automotive use, American industry has conducted a constant search for a transmission with infinitely variable ratio, fully automatic operation, and high efficiency. The fully automatic transmission has now evolved into a unit providing greater safety and ease of operation for the driver. It is no longer considered novelty or luxury equipment in the passenger car and its value is rapidly becoming recognized in commercial applications. Engineering research and development in the United States of America has been active in this search for two decades. The first approach was the development of friction, electrical, and hydraulic displacement drives, all of which resulted in bulky and heavy mechanisms inefficient and impractical in use. Then came the development of hydrodynamic drives, the fluid coupling, and the torque converter. Here, continual commercial successes have been made. The first use of the torque converter was in city service 'buses in 1934, replacing the manual shift transmission which was subjected to a gear shift every eleven seconds of its operation. In 1939, the first successful automatic passenger-car transmission, the Hydra-Matic, was produced. From that date onwards all competitive American passenger-car manufacturers followed in suit with their own designs. In many cases, the different transmissions have been mere re-arrangements of already proven designs, the features chosen representing the respective engineer-management judgement of the desirability of the various characteristics of known automatic transmissions. The extent of the field is evidence by the production of automatic transmissions in the United States of America, which in 1951 was 2,422,131 units. While development work was progressing in the passenger car field, the field which offers the greatest promise of commercial rewards, extensive activity was also prevailing in the commercial and military fields. Here engineering research and development has led to the design and current production of automatic drives, using either the fluid coupling or torque converter, for use in highway and off-highway trucks, earth-moving equipment, cranes and hoists, railroad equipment, oil-well servicing and drilling equipment, and, in the logging industry, yarders and hauling equipment. Military applications are currently being made in all weights of tanks, trucks, and track-laying vehicles. So it can be seen that the scope of the American field of automatic transmissions is large and the development has been extensive. It has an interesting history and the field shows promise of still further gains.