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Splines are widely used in mechanical drive systems to transfer rotational motion from a shaft to the gear or from a gear to the shaft. The failure investigation was performed on the differential housing of three different four-wheel-drive car models with gasoline engines. Compilation of failure reports was performed by a first author as a professional car expert from the famous car repair shop in Mashhad city for 6 years. Failure zones appeared on the housing splines after an average operation of 60,000 km. Experiments were performed on two matched members, including the failed ductile cast iron housing and undamaged transfer case shaft of tempered martensite steel. For this purpose, a series of experiments including fractography using scanning electron microscopy (SEM) only for housing and chemical composition, mechanical properties, microstructure, and hardness were performed for both matched members, and finally, stress analysis was performed for two matched members numerically. The results showed that the strength and hardness of the housing material were lower than that of the shaft. Also, striations associated with the teeth flank and face surfaces of the housing using SEM imaging showed that failure was of fatigue type on housing spline teeth.

When aiming to improve the performance of industrial sports cars at the limits of driving dynamics, the passive vehicle setup should be tuned under consideration of the actuator configuration and t...

The research was carried out within the framework of the grant financing project of the Republic of Kazakhstan for the years of 2018-2020 “Transport facilities, farm machinery, oil and gas equipment, and mining and metallurgical equipment. Applied research” in the field of АР 05131236 “Modernization of mining and metallurgical equipment with the use of innovative materials and drive arrangement”.

Optimizing the configuration of a complex production line is an NP-hard problem in various machine settings. Solving real-life-size instances of this problem becomes a more common challenge because the current trend of reshoring induces multi-national firms to transfer manufacturing facilities from workforce-intensive to capital-intensive production environments which usually require re-configuration of the transferred manufacturing systems according to the availability of better machinery in a capital-intensive environment. This paper focuses on the problem of optimizing production line configuration and proposes several simulation-based optimization approaches based on myopic search, ant-colony, simulated annealing, and response-surface methodologies. We investigate the relative performances of these proposed algorithms on a real-life manufacturing system transfer case in automotive industry according to solution quality and computation-time metrics under different parameter scenarios. Thus, our numerical results may guide the decision makers in choosing a suitable solution approach for this problem depending on the problem size and time availability. Our results also illustrate that ant-colony optimization, a methodology not widely applied in simulation-based optimization, provides high-solution quality for this problem when matched-up with a myopic search to find a good initial solution.

A high-speed reduction transfer case is usually employed by an excavator, wheel loader, or bulldozer. When powerful torque is required in the case of climbing steep roads or towing heavy equipment, the high-speed reduction mode of the gearbox is used. Generally, a transfer case using a spur gear type with a speed reduction system has a speed reduction ratio of 1 to 1 or 2 to 1. However, the structure of a transfer case achieved at a high speed of 1 to 1 and a low speed of 4.5 or under 5.5 to 1 with the speed reduction by use of a planetary gear type with a speed reduction system was proposed in this study. By employing a planetary gear type with a speed reduction system, the compact structure of the transfer case was achieved, and the impact or the partial defect of gear teeth was eliminated.

This paper presents the vehicle handling performance improvement by means of transfer case and torque vectoring system. The focus is on the agility and stability during handling situation. Transfer case can control the torque distribution ratio between the front and rear axles. The left and right torque vectoring system of the rear axle is a device that can control both the torque flow amount and its direction between the right and left wheels. The controller for lateral dynamics was applied by using a sliding mode control method and a commercial dynamic analysis tool was used for the vehicle performance simulation.

Before developing a central reducer of the drive intermediate axle, it is necessary to choose its kinematic scheme to define the most important truck properties. Examples prove that a type of gearing, kinematic scheme and mutual position of gear or worm wheels of the central reducer has impact on the mass of the intermediate axle, placement of the engine and brake mechanisms, and truck configuration as a whole. They also influence on a possibility to use a long-stroke suspension, provide a differential connection between axles, and a torque transfer to the next axle.The work analyzes various schemes of the intermediate central reducers using one or two pairs of gear or worm wheels. It defines the ways to provide normal operating conditions for the engine drive line of the non-intermediate axle. The paper shows that, in most cases, the two-shaft transfer cases with a coaxial or non-coaxial arrangement of the output shafts, connected in front of or behind a conical or hupoid reducer, allows implementation of intermediate reducers.According to a set of properties, for the trucks equipped with a dependent or independent long-stroke suspension, the most rational is the hub-reduction final drive with helical-bevel and conic central reducers, respectively, in intermediate and non-intermediate axles. To apply double helical-bevel central reducers in intermediate and non-intermediate axles is expedient if it is necessary to ensure unification of crankcase parts of axle, improve protection, and raise a driveshaft durability of the non-intermediate axle drive.The paper presents the most rational schemes for three drive axles to be group-driven. Creating a three-axis group-driven cart is possible to implement by setting one more axle in front of the two-axis cart, with central reducer of this axle having the same scheme, as a reducer in the intermediate axle of the two-axis cart. Thus, in case of differential connection between axles and identical vertical loads towards the axles in the central reducer of the first axle of the tridem drive axles it is necessary to use the asymmetrical inter-axial differential, unlike the central reducer of the second intermediate axle of the same cart where the symmetric inter-axial differential is set.

Drive train noise is more annoying for passenger. For a V-hull base mine protected 4WD defence-vehicle, metallic noise was observed from drive train. To resolve this kind of NVH problem of complicated vehicle like defence required commending knowledge base and experience or say know-how. The critical constraint of subject vehicle was fixed position of engine or engine mounts and transfer case. This causes higher slope equivalent angle of first drive shaft with respect to the installation standard. Noise issue observed as consequence of aforesaid issue which has impact installation parameters of torsional, inertia and secondary coupling excitation frequencies. In this context, a structured methodology has been followed in present work for finding root causes and optimizing the design to come out with optimum solution. Engine mounts have major influence to finalize first drive line slope angle. Hence, re-designing and verification have been done for engine mounts considering its major design parameters and criteria (e.g. shape factors, shore hardness, static deflection and isolation efficiency). At the same time, effects of those changes have been verified theoretically and practically on vehicle. Pass by noise, cabin inside noise, isolation efficiency of front and rear mounts and vehicle floor vibration level were measured. The objective of the exercise is to find out a solution for minimization of drive-train noise.

Coupled vibration between transmission shaft and drive axle gears is one of the main factors influencing NVH in the FR transmission system. Based on the transmission shaft and drive axle gears, using UG to establish three-dimensional model, establishing flexible-body dynamics model and solving coupling vibration laws of transmission shaft and drive axle gears by ADAMS, and analyzing influencing factors on coupled vibration between transmission shaft and drive axle gears.It is of theoretic significance, for design parameters and installation matching between transmission shaft and drive axle gears.

In the case of 4 wheel drive (4-WD) type car, power switching occurs to 4-WD by operating lever or switch that operates power switching device attached in transfer case which can operate motor by electric signal. So if the RPM of motor is high, power switching will not exactly occur and can cause damage to gear in transfer case according to circumstances. So in this study, we applied 2 level of planet gear type motor spindle of motor drive part of a power train. And conducted decelerating to increase torque to switch power safe and accurately. Also, we researched efficiency of gear by designing reduction gear ratio and gear type and by calculating contact stress and bending strength. Based on researched content, we made drive head of power switching device and a reduction module which uses type that uses motor spindle as sun gear and ring gear as cover.

Through a Transmission bench test of a certain automobile Drive axle Assembly ,the abnormal vibration in Rear axle can be found. This paper establishes three demensions modle and Finite element model of the Rear Drive axle Assembly and calculates the modal of the Assembly and Axle housing respectively. It can be found that the frequency of the abnormal vibration in the Rear axle Bench test Coincides with the frequence of the Assembly First-order bending.It presents that it is the Assembly Resonance that leads to the abnormal vibration of Rear axle,not just Axle housing Resonance

By carrying on the stress and transform analysis of the box of a kind of main reducer which was self— designed and manufactured for vehicles, by ROMAX modeling get accurate bearing load and conducting ANSYS finite element analysis. it is shown that structure design of the main reducer box is very important for the intension capability of the box, and for the transmission functions of the main reducer. The hidden trouble of the main reducer transmission due to the designers was solved, which couldn’t estimate the transform of main reducer box by traditional design method, and provided the necessary basis for further optimizing and ameliorating the whole transfer case system. By using the UG software we constructed a complicated model of the box, and carried on a series of accurate intension and fatigued analyses for the model by using ANSYS software.

By carrying on the stress and transform analysis of the box of a kind of transfer case which was self-designed and manufactured for vehicles,by ROMAX modeling get accurate bearing load and conducting ANSYS finite element analysis. it is shown that structure design of the transfer case box is very important for the intension capability of the box,and for the transmission functions of the transfer case.The hidden trouble of the transfer case transmission due to the designers was solved,which couldn’t estimate the transform of transfer case box by traditional design method,and provided the necessary basis for further optimizing and ameliorating the whole transfer case system.We constructed a complicated model of the box by using the UG software,and carried on a series of accurate intension and fatigued analyses for the model by using AN SYS software.

The performance of transfer case as an essential component of intelligent four-wheel drive is studied mostly from the perspective of mechanical transmission. However, friction heat during the transmission of power is rarely discussed. In this paper, a multi-plate clutch model is constructed based on heat load characteristics. And a performance simulation model in Matlab/Simulink is built to analyse the influence of friction disc on the dynamic transfer characteristics from aspects of structural dimension, material property and working condition. Then, the thermal load characteristics of the multi-plate clutch are analysed. Results show that the heat load has a great influence on the friction coefficient and the viscosity of the lubricating oil. In summary, this paper verifies the important role of heat load in the working process of transfer case, and the operating characteristic change rules during connecting process are discussed, which can be provided as a theoretical basis for the designing of transfer case.

New driveline architectures equipped with torque-biasing devices such as active differentials and active transfer cases have yielded a new generation of on-demand four-wheel-drive vehicles, where the torque distribution between left and right and between front and rear axles can actively be modulated online. This allows one to design active vehicle-control systems that are capable of altering, via electronic control, the behavior of a car dictated from its mechanical layout, e.g., understeering and oversteering characteristics. This paper proposes a control strategy that optimizes vehicle performance while guaranteeing vehicle stability and drivability by actively controlling the transfer case. The performance of the overall control strategy is assessed on both a multibody simulator and an instrumented test vehicle.

A hydraulic power-assist system is a hydraulic regeneration system that can significantly improve fuel economy when installed on a conventional bus operating in urban traffic. This paper presents a methodology for matching a new hydraulic power-assist system (HPA) to a conventional bus. The HPA and the conventional bus were modeled using the AMESim environment. The HPA was optimized using a simulation-based orthogonal design method with two indexes, the fuel economy and the acceleration performance. According to the simulation results, the volume of the accumulator was the primary factor affecting fuel economy, and the gear ratio of the transfer case was the primary factor influencing the acceleration performance. As a result, tradeoffs between the two indexes are required for a practical operational scenario. Experimental results demonstrated that the optimal HPA installed on a conventional bus was able to satisfy the acceleration performance requirement of the vehicle and also reduced fuel consumption by 25 percent.

With the elimination rate of mechanical products is getting higher and higher, it has become a huge problem for manufacturing enterprises to resourcefully dispose the used mechanical products. In order to optimize the resource utilization of the used components, a decision-making model for determining the appropriate remanufacturing plan was established from the perspective of the component reliability based on historical life data. In this study, the three-parameter Weibull distribution function was used to evaluate the component reliability, and the degree of reliability was computed quantitatively. The appropriate remanufacturing plan for the used component was then determined by combining the degree of reliability with the remanufacturing reliability threshold values provided by the manufacturer. The feasibility of the presented model was verified by applying the model to the failure of the bearing on the transfer case. This study can provide technical support for the research and application on remanufacturing scheme decision-making models and active remanufacturing technology of the used components.

AWD (All-Wheel Drive) system transfers drive force to all wheels so that it can help vehicle escape low mu surface or climb hill more conveniently. Recently, AWD system for on road vehicle has become popular to improve vehicle driving performance. However, there has not been enough research of applying AWD system for vehicle stability especially for lateral movement. Compared with ESC (Electronic Stability Control), AWD system does not cause any inconveniences to the driver because it controls vehicle only by distributing front and rear drive torque, without using brake. By allowing slipping/locking of wet clutch inside the transfer case, AWD system can distribute different amount of torque between front and rear axle. This paper introduces modelling of AWD system and suggests the control of AWD system based on peak slip ratio and slip angle at which tyre saturates. Carsim based vehicle simulation results of AWD controller is presented.

Goal-directed utilization of active torque distribution to the four drive wheels has become increasingly important in the last few years, especially with a view to improving both driving dynamics and traction. With the Vector Drive rear axle transmission, ZF generates such a torque vectoring system at the rear axle. This paper describes how such a rear axle torque vectoring system can be implemented while fulfilling the requirements of precise torque control and robust functional availability with adherence to safety requirements as well as suitability for volume production. Based on the technical description of the system and its setup, the interaction of the individual components within the overall functionality is demonstrated.

The transfer case based all-wheel drive electric vehicle (TCAWDEV) and dual-axle AWDEV have been investigated to balance concerns about energy consumption, drivability and stability of vehicles. An ideal AWDEV (IAWDEV) powertrain architecture is proposed by this research; the architecture has an independent driving motor at each wheel; in essence, the IAWDEV is a distributed powertrain that provides various combinations of torque vector control. This research also investigated the simplified methods to estimate the battery capacity and the operation envelope of motors, and employed model-based evaluation approaches to recursively identify the proper powertrain components. The model-based evaluation was conducted in LMS AMESim. The results show that the IAWDEV could reduce the complexity of drivetrain, and also can harvest more braking energy under poor road contact.Copyright © 2015 by ASME

In hybrid electric vehicles, there is a set of electricity generating system. This system was modified to meet requirements of vehicle-mounted power plant. The new system is mainly composed of engine, generator, planetary gears, motor, battery, transfer case, control system and etc. and the planetary gears mechanism has two sets of planetary, control system includes vehicle controller, engine controller, motor controller, and inventor. This system can perform the functions which include vehicle driving, generating with vehicle ruining and generating with vehicle stopping. It can meet requirements of special purse vehicles.

In this paper, a technical concept is described for a power transmitting unit to control the split of power between the drive axles of a 4×4 hybrid-electric vehicle. This new power transmitting unit uses a planetary gear set and eddy current brake to provide a continuously variable gear ratio that can be integrated into the vehicle driveline between the transfer case and front axle. The paper details the electrical and mechanical characteristics of the device, including its operation mode, its mathematical model built from the equations of the planetary gear set and eddy current brake, the optimization equation by which the device will be controlled to improve vehicle slip efficiency, as well as its torque and electrical current usage. Computer simulations are performed on a mathematical model of a 4×4 military truck using the power transmitting unit in conjunction with a series hybrid-electric configuration transmission.Copyright © 2014 by ASME

In this paper, a technical concept is described for a hybrid-electric power transmitting unit (HE-PTU) to control the split of power between the drive axles of a 4×4 hybrid-electric vehicle. This new power transmitting unit is a mechatronic systems by its design and uses a planetary gear set and eddy current brake to provide a continuously variable (dynamic) gear ratio that can be integrated into the vehicle driveline between the transfer case and front axle. The paper details the electrical and mechanical characteristics of the device, including its various operation modes, its mathematical model built from the equations of the planetary gear set and eddy current brake, an optimization condition by which the device will be controlled to improve vehicle energy efficiency, as well as its torque and electrical current usage. Computer simulations are performed on a mathematical model of a 4×4 military truck using the power transmitting unit in conjunction with a series hybrid-electric configuration transmission.Copyright © 2014 by ASME

In this paper, an investigation is performed into the optimization of wheel power distribution between the drive axles of an AWD hybrid-electric SUV. The paper presents a criterion to maximize the vehicle’s slip efficiency through control of the kinematic discrepancy factor. The optimization criterion is combined with a mathematical model of a driveline for an AWD hybrid-electric vehicle using a new hybrid-electric power transmitting unit to control power distribution between the front and rear drive wheels. A technical concept is described for the hybrid-electric power transmitting unit that is functionally fused with a series hybrid-electric transmission. The mode of operation of the power transmitting device is described and simulations are performed for a 4×4 hybrid-electric vehicle of different driveline characteristics to compare the influence of driveline type on vehicle energy efficiency, including battery depletion, and vehicle mobility when traveling on a road or off-road under severe terrain conditions.Copyright © 2014 by ASME

This chapter is about torque transfer in different types of all-wheel drive (AWD) systems including rear-wheel drive (RWD), front-wheel drive (FWD), and rear engine-based driveline systems as well as part-time, full-time, and on-demand systems. Part-time modes such as two-high (2H), four-high (4H), and four-low (4L) are explained, and so are terms such as shift on the fly (SOF), transfer case, and power transfer unit (PTU). In addition, couplings and coupling activation systems are discussed. Section 1 gives an overview of AWD fundamentals and shows the distinction between FWD- and RWD-based layouts. Section 2 is about how specific torque transfer cases work with RWD-based AWD systems in the different working modes: part-time, full-time, and on-demand. Section 3 states what distinguishes PTUs for front-wheel-based systems from transfer cases and how a PTU works, and also covers how PTUs enable rear-engine-based AWD systems. Eventually, Section 4 shows different types of coupling systems for on-demand systems and common active and passive coupling actuation strategies. Keywords: all-wheel drive (AWD); torque transfer case; power transfer unit (PTU); part-time; full-time; on-demand; shift-on-the-fly (SOF); torque coupling; coupling control system; rear-wheel drive (RWD) based; front-wheel drive (FWD) based; torque management

Car manufacturers have become increasingly interested in the efficiency of driveline components and other fuel-saving potentials, due to European customers’ growing demand for vehicles with lower fuel consumption as well as the corporate average fuel economy (CAFE) regulations of the United States. In order to support these needs, Steyr-Daimler-Puch-AG began to measure and simulate spin losses in 1995. This systematic investigation was initiated by the author’s thesis in cooperation with the Institute of Mechanical Engineering at the TU Graz.

This paper presents a novel approach to improve both energy efficiency and lateral dynamics of an all-wheel drive (AWD) vehicle by means of active functional/operational fusion of a driveline system, which distributes power between the front and rear driving axles, and a steering system that steers the front driving wheels. The paper starts by presenting the kinematic discrepancy factor, which is a normalized difference of the front and rear theoretical velocities that influences the wheel power distribution, as a mathematical function of the tire rolling radii in the driven mode, the gear ratios of the driveline system, and the steering angle of the front wheels. Using this function, the gear ratios from the transfer case to the front and rear wheels are determined to optimize vehicle energy efficiency by minimizing the kinematic discrepancy at the vehicle’s straight line motion and on a curve. It is also analytically shown that the wheel power distribution leads to the variation of the circumferential force of the front wheels that significantly influences the magnitude and direction of the front wheel lateral force. Thus, the paper introduced the wheel power distribution between the driving axles as an instrument for controlling oversteer-understeer transition of a vehicle, i.e., controlling vehicle lateral dynamics. Finally, the steering angle of the front wheels is considered and analyzed as an input of an active steering system to control the vehicle oversteer-understeer process in combination with the effect of the steering angle on the kinematic discrepancy factor. Longitudinal velocity control is added to constrain the lateral acceleration. Thus, the functional fusion of the active steering and driveline systems for enhancing both AWD vehicle energy efficiency and dynamics is introduced for the first time.

The National Transonic Facility (NTF) utilizes Inlet Guide Vanes (IGV) to provide precise, quick response Mach number control for the tunnel. During cryogenic operations, the massive IGV structure can experience large thermal gradients, measured as “Delta T or ∆T”, between the IGV ring and its support structure called the transfer case. If these temperature gradients are too large, the IGV structure can be stressed beyond its safety limit and cease operation. In recent years, ∆T readings exceeding the prescribed safety limits were observed frequently during cryogenic operations, particularly during model access. The tactical operation methods of the tunnel to minimize ∆T did not always succeed. One obvious option to remedy this condition is to warm up the IGV structure by disabling the main drive operation, but this “natural” warm up method can takes days in some cases, resulting in productivity loss. This paper documents the thermal gradient problem associated with the IGV structure during cryogenic operation and how the facility has recently achieved an acceptable mitigation which has resulted in improved efficiency of operations.

The BMW X5 4.6is is the new top version of the successful X5 Series. It combines the off-road capabilities of the X5 4.4i with the characteristics of a very sporty on-road vehicle. In this article, the most important features of the new 4.6 litre engine are described. This engine was developed on the basis of the tried-and-tested V8 engine fitted in the X5 4.4i.

New driveline architectures endowed with torque biasing devices, such as active differentials and active transfer cases, have made available a new generation of on-demand four-wheel-drive vehicles which allow designing control systems capable of altering the car behaviour dictated from its mechanical layout, e.g., under- and over-steering characteristic. This work proposes an active transfer case controller aimed at optmising vehicle performance in terms of amount of traction torque transmitted to the ground while guaranteeing vehicle stability and driveability by keeping the vehicle side-slip angle within safety bounds.

This paper presents a new technique for contingency screening. Contingency ranking has been done by estimating the post-contingency voltage collapse point (CP), given a power system operating point, a load demand forecast and a generation dispatch. The new algorithm presented in the paper, provides more accurate post-contingency "distance to collapse" estimate. The distinguished features are ability to directly estimate the post-contingency CP, consideration of breaking point and to rank contingencies quickly and accurately. Proposed method has been tested for all 6689 single branch outage of 3493 bus system for two possible particular transfer case. Results obtained from new algorithm were compared with results obtained from full continuation power flow and it shows that proposed algorithm is very robust, efficient, accurate and fast.

Evaluations of candidate driveshafts for the FMTV program from Dana, Arvin Meritor (2 designs), and GKN were conducted. The evaluations included instrumented road testing. A 1000 mile durability test that included high speed driving and submersion, laboratory measurements, and DADS modeling. The driveshafts were (un)balanced to their manufacturers production limits prior to evaluation and then tested on the vehicle using a special transfer case transducer capable of measuring driveshaft dynamic forces. A principle focus of the program included several methods of measuring installed critical speed.

Three transfer case models to improve the fuel economy of four-wheel-drive vehicles have been designed and developed for production. Improved economy is obtained by (1) minimizing churning and friction losses for highway made two-wheel-drive operation, (2) minimizing the weight of the transfer case assembly, and (3) providing low-range transfer case ratios compatible with the lower numerical axle ratios demanded for highway fuel economy.

Transfer case drive assemblies for four wheel drive vehicles have changed drastically to improve fuel economy. New designs have also improved driver ease of operation. This paper describes three new internal transfer case control systems which enhance driver operation and control of four wheel drive vehicles.

A review of the last 20 years of rear suspension design has not shown a dominant position for one type of axle. This indicates a good balance of advantages and disadvantages among rear axles built today. The evaluation scheme described here based on the criteria economy, handling and comfort is therefore helpful when choosing the appropriate axle type for a given purpose. The characteristic features of: rigid axle, trailing arm axle, semi-trailing arm axle, sping strut axle, and trailing arm torsion beam axle are discussed and their suitability for front wheel drive is examined.

A four-by-four is a vehicle with four wheels on the ground and four wheels capable of driving. It is used for work, recreation, and/or personal transportation. The drive system of a four-by-four usually consists of the addition of a front drive/steer axle and transfer case to the power transmission system of a two-wheel rear-drive vehicle. The transfer case is an auxiliary gearbox which is mounted either directly to the main transmission or remotely to the vehicle chassis. It is connected to the rear drive axle via another propeller shaft. A front driveshaft disconnect is included in the transfer case of a conventional four-wheel-drive system. It converts the system to two-wheel drive by directing power only to the rear axle. The paper covers: 1) Changes in the four-by-four market; 2) the effect of federal regulation on four-wheel-drive vehicle manufacturers; 3) an overview of E.P.A. fuel economy testing; 4) suggestions for reducing vehicle fuel consumption; and 5) a prototype of a fuel-efficient four-wheel-drive vehicle.

An analysis was carried out on the collision behavior of front engine/front drive cars in comparison with the other types such as: front engine/rear drive and rear engine/rear drive. An evaluation was made of the results of standardized collision tests, integrated with nonstandardized tests with particular devices.

This chapter focuses on the universal joints of motor vehicle. A universal joint is a mechanical connection between two shafts with interconnecting axes. It provides a positive drive while allowing angular movement of one or both of the shafts. The Hooke's type of joint or cross arrangement is widely used, and consists of a four-legged spider or cross fitting into Y-shaped yokes on each shaft. One principle for constant velocity depends upon the engagement between the two shafts taking place in the plane bisecting the angle between them. The propeller shaft connects the gearbox to a live rear axle or a sprung rear drive unit. It revolves at engine speed in direct drive, and accurate dynamic balance is essential to prevent vibration. The drive shafts connect to independently sprung front or rear road wheels. Being on the output side of the final-drive unit, they operate with that ratio of torque increase and speed reduction compared with a propeller shaft. For vibration less running, propeller shafts and drive shafts must be dynamically balanced and run true.

Methods for evaluating vehicle power train components and their effect on optimum vehicle performance and efficiency are considered. The assessment of overall vehicle costs includes the evaluation of each component, and optimizing power train components and performance to provide the most cost-effective vehicle for a given job. Medium and heavy duty trucks and buses involve a great variety of vocations and performance requirements. Any effort to evaluate power train specifications must include an understanding of key parameters defining performance requirements: gross vehicle weight; on-grade startability; and capability to negotiate a given grade at a selected speed. In general, power train components include the engine, transmission, drive shafts, auxiliary transmission or transfer case, and drive axle (s). Engine characteristics critical to vehicle performance and efficiency are power and governed speed, peak torque and corresponding speed, and brake-specific fuel consumption. The transmission must match engine characteristics to the duty cycle. Changes in vehicle operations and components are occurring rapidly; they encompass the desire for bigger and heavier loads, more axles and double-triple trailers, more diesel engines, larger engines, low-speed engines, and new buses, transmissions, and axles. The computer simulation method is replacing obsolete and costly methods such as trial-and-error and actual testing for analyzing vehicle vocation variables and different types of power trains and components. Using computers should bring closer an optimum match of vehicle, engine, transmission, axle, and tire parameters for a given vocation.

The program consisted of the design and installation of an Experimental Waterjet Propulsion Kit on a Government-owned M-113 Vehicle, Serial No. F13127, USA12CK01. Two Aerojet-General Type A Waterjet pumps were equipped with special inlets, discharge nozzles, and maneuvering gates designed to provide optimum propulsion of the vehicle. The waterjets were driven from the vehicle transfer case by use of a special power transmission system. The complete water propulsion system which is suitable for field retrofit on existing vehicles, was installed and tested prior to delivery.