Search Results

SIX BASIC suggestions are offered on how to design for practical, producible, economical structures of brazed honeycomb sandwich. The author illustrates the application of some of these design suggestions and explores the step-by-step theoretical reasoning a designer might use to arrive at a satisfactory design for a hypothetical large missile wing. The final design of a honeycomb sandwich component must take into account the process as well as structural and configuration requirements.

Career development planning is critical to getting the most out of one's working years. It should start when one starts a career, but even if you start in mid-career, it's not too late. For those who haven't done it, career planning may seem difficult and confusing. Increasingly, your community library and state employment service agency provides valuable help in the form of computerized and manual aids to career planning and job-getting. This article follows Dave Brown, a mid-career engineer, through the career-planning process, introduces library and government resources to you and provides a list of computer programs relating to career planning and job getting.

Data obtained when harvesting with a combine equipped with a yield monitor were used to develop yield maps. A prototype yield monitor was developed that uses a combination of light emitters and receivers mounted in a rectangular frame. The monitor was mounted in the combine in the top of the clean grain elevator. As grain flows through the monitor, a voltage change proportional to light reduction was recorded. This voltage was then correlated to grain flow rate. At the same time, site-specific location was recorded using the global positioning satellites (GPS) system. The location data, yield monitor output, cutting width, and combine forward speed were stored in a spreadsheet format. The data were then used to prepare the yield maps.

In this paper, a gain-scheduling optimal control approach is proposed to enhance yaw stability of articulated commercial vehicles through active braking of the proper wheel(s). For this purpose, an optimal feedback control is used to design a family of yaw moment controllers considering a broad range of vehicle velocities. The yaw moment controller is designed such that the instantaneous tractor yaw rate and articulation angle responses are forced to track the target values at each specific vehicle velocity. A gain scheduling mechanism is subsequently constructed via interpolations among the controllers. Furthermore, yaw moments derived from the proposed controller are realized by braking torque distribution among the appropriate wheels. The effectiveness of the proposed yaw stability control scheme is evaluated through software-in-the-loop (SIL) co-simulations involving Matlab/Simulink and TruckSim under lane change maneuvers.

This paper investigates the yaw dynamic behaviour of a seven axle tractor semitrailer combination vehicle developed by VRDE (Vehicle Research & Development). The semitrailer has four steerable axles which follow command steering law i.e. all axles of semitrailer are steered in a particular relation with articulation of tractor. A 4 dof (degree of freedom) linear yaw plane model was developed for this combination vehicle. Yaw response characteristics such as lateral acceleration, yaw rate and articulation angle for step and sine steer is obtained from this model. Effects of speed on the above parameters are also studied to the same steering inputs. Lateral tyre forces due to semitrailer steering at various speeds are estimated to understand its distribution on each axle. Steady state yaw rate and articulation angle gain are obtained to predict the understeer / oversteer behaviour of combination vehicle.

The idea of a world truck is a fascinating challenge - whereas cars are purchased more or less as seen; truck purchasers demand more individual configurations. In national and global terms, that means a highly complex truck market. Historically, a few European and North American manufacturers produced almost all the trucks for the world market. That changed through the 60's and 70's, with more local assembly plants around the world and increasing worldwide manufacturing capabilities. Concurrently, international component design standards have made some progress towards compatibility. Much greater co-operation is needed, however, before a genuinely international set of standards can be applied. As the task assigned to trucks is the same worldwide, namely to transport goods from A to B; it should be desirable and possible to work towards a greater commonality of vehicle - to ultimately achieve a world truck. The only unknown is the time scale.

In this study, we propose a method of measuring and analyzing the load on bolted joints used in a machine under off-road vehicle operation. Working load measurement under actual machine operation and the results of its analysis are shown as load frequency diagrams. An example of the measurement analysis of a load (three types of load: axial force, bending moment, and torsional torque) added to a bolted joint shank during actual machine operation is shown. In this paper, we describe how to apply the results of load analysis to the load condition at the design and experimental development stages.

Knitted wiremesh along with radial gas tight seals provide reliable mounting system for low temperature underbody converters. The compression characteristics of the wiremesh is modified by wire material, wire diameter, wire geometry, mesh crimp heights; wire density, wiremesh courses per inch, needle count, number of strands, wiremesh temper, wiremesh surface profile and surface characteristics. The radial mounting pressure provided by the wiremesh is matched with the mounting pressure requirement. Wiremesh systems can be tailored to any required radial mounting pressure from conventional to ultra thin-wall substrates. The wiremesh mounting system is proven durable, without any failure on more than 25 million underbody converters in light duty vehicles. Cp and Cpk show the capability of the manufacturing process. Thus the wiremesh mounting support is a viable alternate for low temperature gasoline and diesel applications.

SINCE 1954 the CIMTC Subcommittee has been engaged in a program to meet military requirements through industry's production of construction equipment which can give satisfactory cold weather performance down to temperatures of −65 F. Individual contracts for three crawler tractors and one motor grader were negotiated by ERDL for these projects, and their performance is discussed. Industry participation was subsequently expanded to include engineering tests in the cold weather conditions of the Mesabi Iron Range. This joint report of the Winterization Sub-committee of the CIMTC and ERDL Winterization Section consists of separate papers by various members and consultants of this Sub-committee and ERDL personnel.

The development of this vehicle is described from concept, through design and assembly. The design intent of this unique vehicle was high fuel efficiency, good ride and handling characteristics, and a high degree of passenger safety at a competitive cost. A combination of some of the latest in automotive and motor home construction technology was used to meet the desired goals.

To investigate the feasibility of various test procedures to determine aerodynamic performance for the Phase 2 Greenhouse Gas (GHG) Regulations for Heavy-Duty Vehicles in the United States, the US Environmental Protection Agency commissioned, through Southwest Research Institute, constant-speed torque tests of several heavy-duty tractors matched to a conventional 53-foot dry-van trailer. Torque was measured at the transmission output shaft and, for most tests, also on each of the drive wheels. Air speed was measured onboard the vehicle, and wind conditions were measured using a weather station placed along the road side. Tests were performed on a rural road in Texas. Measuring wind-averaged drag from on-road tests has historically been a challenge. By collecting data in various wind conditions at multiple speeds over multiple days, a regression-based method was developed to estimate wind-averaged drag with a low precision error for multiple tractor-trailer combinations.

A 1:10-scale wind tunnel development program was undertaken by the National Research Council of Canada and Airshield Inc. in 1994 to develop trailer side skirts that would reduce the aerodynamic drag of single and tandem trailers. Additionally, a second wind tunnel program was performed by the NRC to evaluate the fuel-saving performance of boat-tail panels when used in conjunction with the skirt-equipped single and tandem trailers. Side skirts on tandem, 8.2-m-long trailers (all model dimensions converted to full scale) were found to reduce the wind-averaged drag coefficient at 105 km/h (65 mi/h) by 0.0758. The front pair of skirts alone produced 75% of the total drag reduction from both sets of skirts and the rear pair alone produced 40% of that from both pairs. The sum of the drag reductions from front and rear skirts separately was 115% of that when both sets were fitted, suggesting an interaction between both.

A wind tunnel experiment has been conducted to determine the changes in drag and side force due to the presence and position of cab extenders on a model of a commercial tractor-trailer truck. The geometric variables investigated are the cab extenders angle of incidence, the tractor-trailer spacing and the yaw angle of the vehicle. Three cab extender angles were tested-0°, 15° (out) and -15° (in) with respect to the side of the tractor. The cab and trailer models have the same width and height. The minimum drag coefficient was found for the tractor and trailer combination when the cab extenders were set to 0° angle of incidence with respect to the headwind. This result holds for all yaw angles with moderate gap spacing between the tractor and trailer. This study suggests that commercial tractor-trailer trucks can benefit from adjustable cab extender settings; 0° when using a trailer and -15° when no trailer is used.

The use of devices to reduce aerodynamic drag on large trailers and save fuel in long-haul, over-the-road freight operations has spurred innovation and prompted some trucking fleets to use them in combinations to achieve even greater gains in fuel-efficiency. This paper examines aerodynamic performance and potential drag reduction benefits of using trailer aerodynamic components in combinations based upon wind tunnel test data. Representations of SmartWay-verified trailer aerodynamic components were tested on a one-eighth scale model of a class 8 sleeper tractor and a fifty three foot, van trailer model. The open-jet wind tunnel employed a rolling floor to reduce floor boundary layer interference. The drag impacts of aerodynamic packages are evaluated for both van and refrigerated trailers. Additionally, the interactions between individual aerodynamic devices is investigated.

The trucking industry is being encouraged by environmental and cost factors to improve fuel efficiency. One factor that affects fuel efficiency is the aerodynamic design of the vehicles; that is, the vehicles with lower aerodynamic drag will get better mileage, reducing carbon emissions and reducing costs through lower fuel usage. A significant tool towards developing vehicles with lower drag is the wind tunnel. The automobile industry has made great improvements in fuel efficiency by using wind tunnels to determine the best designs to achieve lower drag. Those wind tunnels are not optimum for testing the larger, longer heavy trucks since the wind tunnels are smaller than needed. The estimated costs for a heavy truck wind tunnel based on automotive wind tunnel technology are quite high. A potential nozzle concept to reduce wind tunnel cost and several other new possible approaches to lower wind tunnel costs are presented.

Since 1992, Caterpillar has invested millions of dollars to purchase CAD software, and spends nearly $2M per year keeping its engineers up-to-date, via instructor lead training (ILT), as new enhancements are introduced. Periodic upgrades to the software also require huge resource (people, costs) commitments for the planning and execution of the training requirements required for a large global workforce. This paper will examine gaps uncovered in the efficiency and effectiveness of the current training process, and the cultural change required as a result of switching from an instructor led environment to a completely web-based solution, which, once deployed, had promised to change the way Caterpillar approached training for the future. The proposed change promised to improve human resource capability by utilizing new technological capabilities, and resulted in improvements in organizational capabilities as well.

HIGH output per cubic inch of piston displacement is desirable not alone for the purpose of being able to transport more payload faster, but more particularly for the invariably associated byproduct of lower specific fuel consumption, and especially at road-load requirements. The only way of accomplishing this purpose is through the use of higher compression ratios, and the limiting factors for this objective are fuel distribution and the operating temperatures of the component parts. A manifold is proposed which not only definitely improves distribution at both full and road loads, but has the inherent additional advantage of reducing the formation of condensate, thus still further facilitating a reduction in road-load specific fuel consumption. Hydraulic valve lifters, obviation of mechanical and thermal distortion, and controlled water flow are the essentials in improved cooling.

In selecting springs for commercial vehicles, it is essential to consider the fundamental principles of the suspension system as a whole, as well as the specific spring characteristics. This paper discusses the applications of these principles; also, it compares the many types of springs available, including single leaf, multileaf, and two-stage leaf springs, and coil, rubber, and pneumatic springs. Among the considerations stressed are: the relationships of spring static deflections to vehicle pitch frequency and oscillation center location, the questionability of two-stage leaf springs, the disadvantages of single tapered leaf versus multi-leaf springs, the advantages of coil springs in low weight and variable rate, and why pneumatic springs are ideal for large load range, heavy commercial vehicles.

Continuing education is important; in fact, it is absolutely necessary for the person or corporation that expects to be successful. Yet a lot of continuing education programs seem to be of little or no use as measured by the changes they effect in both people and companies. This study shows why so little success occurs, and makes suggestions to correct that shortfall. Good programs must be supported with time and resources provided by the employer. However, a truly successful continuing education program must be managed and driven by the individual. Otherwise, it will not pay off. The smart employer provides time and financial support, but expects the individual to direct his own career program.

Financial planners are always anxious to assist engineers and scientists in making retirement decisions. Many engineers, especially Industrial Engineers (IE), have had courses that provide the knowledge to make these retirement financial plans themselves. This paper will provide a method of estimating retirement needs utilizing Excel software and IE college coursework.