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Tests of class 2,3,and 5 straight trucks were made to determine the affect of aftermarket aerodynamic aids on fuel economy and handling. It was determined that the potential exists for significant improvement in the fuel efficiency of these classes of trucks.

Allison Transmission has developed a family of two new automatic transmission products, the 1000 Series and the 2000 Series, for the light and medium duty commercial markets. This technical paper will introduce these products by reviewing the early development efforts which helped define the transmission attributes that they should bring to market. This included the analysis of Allison's product portfolio and industry rating requirement trends, and the extensive market research which identified the key product attributes and led to the concept selection. There is also a review of the 1000 Series and 2000 Series product features as well as a discussion on the development of their respective vocational ratings. Future papers will provide greater detail on the various technical aspects of this new product family's design.

This paper is a discussion of the thermodynamic properties of typical heavy duty mechanical truck transmissions, including maximum operating oil temperature requirements and rationale, effect of synthetic oil, sources of heat generation, prediction of total heat generation, and cooling systems.

Based on analysis problems of vehicle with present automatic transmission, an Intelligent Shift Strategy(ITSS) is proposed for the first time. Three kinds of information, which are the driver intention, the vehicle dynamic characteristics and the outside environment, are included in it, and the humachine technology is applied to decide shift strategy.

The active safety of tractor / trailer-combinations plays an important role in regard to traffic safety in general. For improving the active safety of tractor / trailer-combinations, it is necessary to investigate the interactions between the towing vehicle and the trailer during braking maneuvers. This paper describes the ECE-regulations for the braking force distributions of tractor/full trailer- and tractor / semitrailer-combinations. The influence of different layouts of the braking systems within these regulations on the coupling forces between tractor and trailer and the driving performance of the units during braking is investigated. The dynamical behaviour of a tractor/full-trailer-combination and a tractor / semitrailer-combination are both discussed with the aid of simulations of the ISO-standard testing procedures “Braking in a turn” and “Braking straight ahead”.

Difficulty of the Automatic Transmission(AT) is to properly control its clutch while the vehicle starts. An intelligent hierarchical controller is proposed in this paper. The upper of it is an intelligent PID controller based on a driver's experience and an expert's knowledge. It gives real time signals to the lower controller and coordinates the control between engine and clutch. The lower Variable Structure Fuzzy Controller (VSFC) executes the upper controller's direction signal.

The cruise control as one of promising vehicle active control has been receiving a considerable attention in recent years, so the related problems are discussed in this paper. Mathematical model of the engine under the steady state and general dynamics equation of the Continuously Variable Transmission(CVT) are given, the regulating principle of the operating state of the engine is analyzed, and the conjugate gradient method employed to solve the optimal control problem of the vehicle in the cruise control is described, so the operating state of the engine could be controlled. At end of paper, some results are provided to verify the approach based on the vehicular powertrain with a hydromechanical CVT.

A major co-operative international research program known as DIVINE (Dynamic Interaction between Vehicles and Infrastructure Experiment) has been completed by the Organisation for Economic Cooperation and Development OECD). DIVINE involved seventeen OECD member countries, and included specialists in vehicles, pavements, bridges, road management and transport policy. Inter-linked research projects were carried out in nine countries and the project took almost four years to complete. DIVINE set out to investigate the benefits of “road-friendly” suspensions for reducing pavement wear and to develop better means of assessing vehicle suspensions for road-friendliness. This paper summarises the most important results of DIVINE and presents means of assessing and simulating the road-friendliness of truck suspensions. Dynamic loading depends on the vehicle suspension, and the use of air suspension generally reduces dynamic loading.

A new oval test track will be designed, constructed and operated in a manner that will successfully pull-together representatives from virtually all of the key interests in dealing with the challenging issues of highway pavement and truck durability. With construction scheduled to begin in the Summer of 1998 and completion scheduled for late 1998 or early 1999, the mission and commitment for this venture is to pull-together the people from several state DOTs, respective universities, and, of vital importance, the truck manufacturing industry. Results from these tests, over a period of a few years, will provide answers that not only greatly improve performance of hot mix asphalt pavements in all state DOTs, but also efficiently and productively address issues of durability and wear performance of medium / heavy duty trucks and key components.

This study revisits pavement roughness and examines the suitability of the International Roughness Index (IRI) to describe passenger car ride quality, as well as heavy vehicle excitation and dynamic loads. It describes the development of a new pavement roughness index, called RIDE (Roughness Index for Driving Expenditure). RIDE is based on sprung mass acceleration, rather than relative axle displacement like the IRI. RlDE is calculated in the frequency domain on the basis of the transfer function of a reference vehicle. It results in the root-mean-square (RMS) acceleration of the sprung mass per unit length of pavement traveled. This index is compatible to the current ISO and it is also related to heavy vehicle dynamic excitation.

The development of larger more productive innovative heavy vehicle combinations for public road operations relies heavily on proving new vehicle concepts to both government and local authorities. In a number of cases simulation modelling has proved to be a useful tool in showing that proposed innovative heavy vehicle concepts are safer and more efficient alternative to conventional equipment. This paper provides examples of the use of AUTOSIM™ in developing custom yaw/roll and yaw/roll/pitch models for investigating the dynamic performance of combination vehicles. Models are described for large innovative road trains which incorporate B-doubles units. Consideration is given to the modeling of the trailing fidelity of these vehicles on non-planar surfaces and examples of model outputs for combination vehicles operating on various three-dimensional features are presented.

There are many ways to analytically represent a hydraulic powertrain mount. The application of the model significantly affects the type of model that should be used. An effective mass model can accurately represent hydraulic powertrain mount component level characteristics but a balanced force model is needed when the hydraulic powertrain mount is a component in a larger systems model. There are two types of hydraulic powertrain mounts that are widely used, inertia dominant and viscous dominant. Hydraulic powertrain mounts can be configured with a decoupler which can function as a small amplitude disconnect for idle isolation, affect the high frequency dynamic stiffness, and also affect the large amplitude ride frequency response.

The variation in the decoupling effect of exhaust flexible couplings under a vertical preload caused by changes in the direction of the exhaust pipe routing was investigated. Both self-supporting and underbody flexible couplings were tested. The results indicate that, in general, a preload decreases the decoupling efficiency of both types of flexible couplings. In addition, the results indicate that the efficiency of the flexible coupling is effected by the following three conditions: the direction of preload with respect to gravity, the location of the preload relative to the coupling, and the stiffness of the various components of the flexible coupling.

Many design philosophies have been used to design engine mount systems. One is to place the stiffness roll axis coincidental to the torque axis (crankshaft), to produce pure roll under static torque. Another is to focus the mount system to align with the inertial roll axis and uncouple dynamic roll. Recent trends have been to abandon mount system focusing as a criterion, in favor of controlling the six natural frequencies of the powertrain on the mount system. This paper discusses a technique to focus the mounts to uncouple the dynamic matrix, as much as possible within design constraints, while also maintaining control of the powertrain rigid body natural frequencies. Using engine mount system focusing to uncouple the dynamic matrix reduced lateral shake in an experimental vehicle. This reduction in vehicle shake was substantiated by total vehicle system models, experimental measurement, and subjective evaluation.

The laboratory tests used to define API GL5 have been the cornerstone of gear oil development for well over thirty years. In that time they have served the market very well. Lubricants developed with these test methods have provided adequate protection of axle components from severe wear, scuffing, corrosion, and oxidation. Recently, however, there has been an increasing trend toward extended drain intervals which changes the picture. Coupled with longer oil drain intervals there is a continuing increase of power throughput in the equipment. The combination of increased power and extended service life places significant stress on the oil such that the load carrying ability and thermal and oxidative stability could be greatly diminished under these conditions. During the past ten years the industry has been actively working toward a new gear oil specification that will address the performance needs of today's vehicles.

Navistar International has developed and launched a new model for local and regional vocations, meeting customer expectations while reducing complexity. This was accomplished by listening to customers and delivering a product in a short period of time. This vocationally focused vehicle proves that features associated with a line haul premium conventional can be incorporated in a value driven local / regional day cab tractor. The swift time to market was brought about by a developing climate for performance that includes living values which support success.

Austempered ductile iron (ADI) is a material having excellent mechanical properties and damping capacity. However practical mass production of ADI gears has not been possible due to ADI's poor machinability and distortion during the austempering heat treatment. With a new process method of carrying out hobbing before austempering when the material is in its soft condition, then austempering it and lastly, conducting the shave finishing process, we have diminished the above defects and developed practical ADI gears. These new gears generate less noise than ordinary nitrocarburized steel gears and are superior in pitting resistance.

Technologies and incremental costs for meeting the proposed 2004 US emissions standards for heavy-duty diesel engines are discussed in this paper. Manufacturers will most likely use a combination of technologies including reoptimized combustion chambers, fuel systems, air handling systems, electronic controls and aftertreatment. First year production incremental costs are estimated to range from between $257 and $467 to meet the new standards.

Road unevenness induces longitudinal as well as vertical forces in the suspension. The variation of vertical and longitudinal wheel forces can be of the same magnitude. Much work on vertical loads has been accomplished in heavy vehicle development, but less on longitudinal forces. Wheel forces have been measured on a semi-trailer tractor driven over a test track obstacle. The consistency of test results inspires confidence in the measured loads. Measured forces are compared with results from a simple simulation model. The influence of road-induced longitudinal forces on ride and chassis loads is demonstrated through simulations. The importance of longitudinal suspension compliance is discussed.

Meritor Heavy Vehicle Systems in conjunction with Detroit Diesel Corporation has developed an advanced patented shift system. The system monitors input and output speeds of the transmission, the neutral position of the shift lever, and the position of a ‘shift intent’ switch on the shift knob. The electronic controller processes this information and adjusts engine torque and speed to effect a shift of the manual transmission. This feature significantly reduces the driver workload while shifting.