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Technical Paper

Practical Approach for Vehicle HVAC Noise Reduction and Comfort Improvement

Comfortable cabin environment from temperature, noise and vibration point of view is one of the most desirable aspects of any vehicle operating in hot or cold environment. Noise generated from HVAC system is one of the most irritating phenomena resulting in customer dissatisfaction and complaints. It becomes absolutely necessary to have low HVAC noise levels when the target market has hot weather all round the year. Balance between control of temperature in desired way with least possible noise and vibration is the key for HVAC performance optimization within constrains posed by design and cost. This paper describes the approach for NVH refinement of front HVAC system proposed for a vehicle with limited off-road capability for which packaging constraints and late changes related to airflow and HVAC unit design for meeting comfort and crash requirements resulted in deterioration of noise and vibrations while operation.
Technical Paper

Optimization of Off-Road Mobility and Handling by Anti-Roll Bar Deletion and Shock-Up Tuning on Military Vehicle: A Case Study

A 4t off-road military application vehicle was offered to the customers for assessment. During the evaluation adverse feedback of 1) harsh ride in off-road terrain, particularly during hump-crossing and 2) issues during high mobility were reported. Vehicle configuration was front and rear rigid axle suspension with leaf spring anti-roll bar, 4×4 and all terrain tyres. Vehicle application was “on-road” [GS (General-services)], as well as “off-road” (Reconnaissance purpose). The feedback was critically analyzed on the vehicle with the simulation of field conditions. Since the vehicle was still under customer evaluation, solution for the feedback required was quick and within boundary condition (maximum possible allowable limits of modification) of no major change in the suspension design as it was affects homologation cycle. Present paper describes the detailed analysis of the influence of each parameter on system.
Technical Paper

Identification of Gear Shift Quality as a Key Attribute in Commercial Vehicle Development

Indian automotive market has grown extremely competitive in the recent past. In order to meet the ever growing expectations of the customers, automobile manufacturers are compelled to offer their products under superior quality with supreme comfort. Customers wish of high levels of tactile comfort in the cabin compartment and effortless operation of peripherals will result in negligible fatigue and a pleasant drive, needs to be duly fulfilled. One has to focus more on Gear shift lever and Steering wheel, which are being the most sensitive tactile points in an automobile. The gear shift lever knob is frequently used and significantly influences the perception of the shift comfort for a driver during actual vehicle application.
Technical Paper

Hydropneumatic Suspension Design for Light Military Tracked Vehicle

In this paper hydropneumatic suspension system design methodology for light military tracked vehicle is discussed in detail. A guide to locate the major impact factor & its effect on the system level design is demonstrated. Spring & damping characteristics of hydropneumatic suspension have significant bearing on the tracked vehicle mobility characteristics. A methodology has been derived to optimize the kinematics of the suspension system by optimizing the load transferring leverage ratio resulting in enhanced system life. The paper also discusses the analytical method used for prediction of spring & damping characteristics and the factors affecting them.
Technical Paper

Evaluation of Potential Benefit of 6 × 2 Over 6 × 4 Drive Mode to Improve the Fuel Economy on Heavy Commercial Vehicle

Reduction in the drivetrain losses of a vehicle is one of the important contributing factors to amplify the fuel economy of vehicle, particularly in heavy commercial vehicle. The conversion of 6 × 4 drive vehicle into 6 × 2 drive has a benefit of improving the fuel economy of a vehicle by reducing the drivetrain losses occurring in the second rear axle. It was cultured by calculation that in 6 × 2 drive the tractive force available at the wheels, of heavy commercial vehicle with GVW of 44 tons and above, will be much higher than the frictional force transmission capacity of tires, when the engine is producing peak torque on the driving duty cycle like going on steep gradient road. In such situations the tires will start to slip and may result in deteriorating the fuel economy and excessive tire wear. On the other side the flat road driving duty cycle in 6 × 2 drive will give better fuel economy than 6 × 4 drive.
Technical Paper

Design Methodology of New Generation Noiseless Antiroll Bar Bushes for Car Suspension

In this paper, design methodology of antiroll bar bush is discussed. Typical antiroll bar bushes have slide or slip mechanism, to facilitate the relative motion between ARB and bush. Inherently, this relative motion causes wear and noise of bush. To eliminate stated failure modes, the next generation bushes have been developed, which are using torsion properties instead of slip function. These bushes are already being used in various vehicles. This paper focuses on developing the simple mathematical model, design approach and optimization of ARB bushes. Also, comparison study is presented exploring, the differences and design criteria's between conventional and new generation anti-roll bar bushes.
Technical Paper

A New Approach to Evaluate Wear on Automotive Leaf Spring Suspension Bushes

Traditionally the bushes used for automotive suspension are tested by methods which either don't address the environmental conditions including dust or mud, which convert a 2-body wear condition to 3-body wear condition prevailing in the field or not representative of the complete load bearing area of the bushes coming in contact with the pin. To address the above issues, a novel method of testing has been designed to take care of the loading type, environmental conditions and load bearing area of the bushes to simulate the field conditions.