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Technical Paper

Optimisation of Steering System Geometry of Longer FOH Commercial Vehicles

Commercial vehicle industry is presently striving towards development of buses with enhanced passenger safety and comfort. This calls for additional components and aggregates that eventually lead to increase in the overall length and gross vehicle weight (GVW) of the bus for the same passenger capacity. Usually, steering system of longer front overhang (FOH) vehicles have multiple linkages such as bevel box arrangement or intermediate pivot arm arrangement instead of single direct draglink because of packaging and design constraints. In this work, an attempt has been made to design the steering system for one of the longer FOH bus with single direct draglink arrangement. Here, single draglink was packaged and designed with commercially available higher strength tube material. Design optimisation of steering geometry was carried such that the steering performance was atleast on par with existing performance.
Technical Paper

Light Weight, Cost Effective and Eco Friendly Material Development for Passenger Seat Applications

The automotive industry needs sustainable seating products which offer good climate performance and superior seating comfort. The safety requirement is always a concern for current seating systems. The life of the present seating system is low and absorbs moisture over a period of time which affects seat performance (cushioning effect). Recycling is one of the major concerns as far as polyurethane (PU) is concerned. This paper presents the development of an alternative material which is eco-friendly and light in weight. Thermoplastic Polyolefin (PO) materials were tried in place PU for many good reasons. It is closed cell foam which has better tear and abrasion resistance. It doesn't absorb water and has excellent weathering resistance. Also it has a better cushioning effect and available in various colours. Because of superior tear resistance, it is possible to eliminate upholstery and would reduce system level cost.
Technical Paper

Field Failure Simulation of a Non-reactive Suspension Tie Rod for Heavy Commercial Vehicle Using a Road Simulator

The suspension system in a vehicle isolates the frame and body from road shocks and vibrations which would otherwise be transferred to the passengers and goods. Heavier goods vehicles use tandem axles at the rear for load carrying. Both the axles should be inter-connected to eliminate overloading of any one axle when this goes over a bump or a ditch. One of the inter-connecting mechanism used is leaf spring with tie rod, bell crank & linkages, when the first rear axle moves over a bump, the linkages equalize the loading on the second rear axle. This paper details about the failure analysis methodology to simulate the tie rod field failure using a six poster road simulator and to identify the root cause of the failure and further corrective actions.
Technical Paper

Failure Analysis and Design Optimisation of Steering Linkage Pivot Shaft of Commercial Vehicle

Commercial vehicles have steering systems with one or more steering links connecting the steering gear box pitman arm and front axle steering arm. In case of twin steer vehicles, intermediate pivot arm is used to transfer the motion proportionately between the two front axles. Intermediate pivot arm is also used in some longer front over-hang vehicles to overcome their packaging constraints and to optimize the mechanical leverage. The pivot shaft is a mechanical part of the intermediate pivot arm assembly upon which pivot arm can swivel in one axis. Steering forces transferred through the drag links generates resultant forces and bending moments on the pivot shaft. In this work, study has been carried out on premature failure of the pivot shaft in city bus application model (Entry + 1 step). Metallurgical analysis of failed part indicated the failure to be due to fatigue. Pivot shaft was tested in rig with similar load conditions in order to replicate the failure.
Technical Paper

Evolution of Bus Design in India

Buses have been main means of mass transport in organized as well as unorganized sectors in India. Though the art and science of Chassis Designing had been practiced and matured by all Indian OEMs, Body design had long not been accorded high priority by them. Till 1989, there was no comprehensive set of rules enforced. Bus designs were developed with scant regard for safety and emission. OEMs sold their products in the form of drive away chassis and the Body Design & Body Building was largely left to Body Builders, many of whom employed poor design, build and quality control practices. Spurious materials, parts, non-uniform construction resulted in number of accidents and many of them were fatal. Central Motor Vehicle Rules (CMVR) kicked-in 1st July 1989. With roll out of CMVR, various safety related features like entry/exit door, emergency exits, window frames, their locations, dimensions and designs were defined.
Technical Paper

Durability Improvement of Track Rod in Commercial Vehicle Operating in Off-Road Application

With advancement of technology, better safety and higher vehicle reliability is primary requirement of end customer especially in public transportation. Hence there exist challenges in design and development of steering system for long haulage and tipper application. In the steering system, track rod is used to steer both the front tyre under different operating condition assisted by power steering system. This paper deals with the failures observed on track rod in long haulage and tipper application with loading conditions. Also the methodology adapted to resolve the field failures.
Technical Paper

Durability Enhancement of Powertrain Mounts for an Off-Road Commercial Vehicle

The durability of the components in a vehicle plays one of the major roles in its life cycle cost. The powertrain mount is one such component since its rubber characteristics have significant impact on the vehicle's NVH and fatigue life. This paper presents the enhanced durability benefits obtained by changing the polymer composition, manufacturing methods and design optimization of a powertrain mount for an off-road commercial vehicle. The methodology involved characterization[2] of the existing mount, arriving a new compound formulation, making of prototypes, experimental validation for durability[3] and repeatability in the laboratory combined with rigorous on field vehicle trials. NVH measurements were also carried out on the improved mounts. The above exhaustive exercise resulted in the development of a comprehensively far better mount than an existing mount with improved durability without compromise on NVH properties.
Technical Paper

A Systematic Approach of Cooling System Design, Development and Application for Commercial Vehicles

A methodology for design and development of commercial vehicle cooling system is derived with an objective to minimize part cost, engineering resources and time to market. This approach is very useful in companies with more variant of engines and vehicles. For this it is identified to have a common cooling system for a set of engines. A systematic approach to develop cooling system based on heat rejection is conceptualised. Engines are classified based on heat loads in to various groups. The cooling package selected for a particular group is independent of type of vehicle (bus or truck), cab (day, sleeper, FES or FBS), Type of drive (LHD or RHD), Emission norm (BSIII or BSIV) and fuel (Diesel or CNG). These packages will cover up the entire range of vehicles and engines. The packaging space available for each group is derived and the cooling package size is finalised. Fan and fan pulley options are listed based on air flow and fuel efficiency requirements.