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When a scooter is put on main stand, it keeps the vehicle from falling as it rests against the engine crankcase. As the main stand is operated it transmits a large amount of load to the crankcase, thus creating a necessity to check the durability of the later. Practical tests showed that continuous application of the main stand resulted in the failure of its pivot area on the crankcase. This raised questions not just on the feasibility of the crankcase design in terms of durability, but also on the main stand design in terms of a load transmitting member. However, as the project was at its later stage, crankcase design could not be altered; thus it asked for a main stand design optimization. The base main stand model was thus taken for MBD simulation and loads were generated for further FEA analysis. The meshed crankcase model was taken in a commercially available FEA code for checking its durability.

A single cylinder gasoline engine of a sports bike generates sufficient hot gases to pose great challenge to the designers of exhaust system. The high temperature exhaust gases in muffler creates thermal elongation on the solid parts of exhaust system, which is mounted on the chassis. This arrangement induces thermal stress in exhaust assembly. It is necessary to analyze this thermal stress to ensure the durability of muffler components. The exhaust design has a diversion at the header pipe to distribute the flow in two branches. This junction and the branches heated up excessively and showed repeated failure. To analyze the thermal stress, the temperature distribution in the muffler components is obtained from Computational Fluid Dynamics (CFD) analysis. The complete motorcycle with detailed exhaust system is modelled in the standard wind tunnel using a commercial CFD software.

With ride comfort in a motorcycle gaining significance, it is important to minimize vibration levels at the customer touch points. The reciprocating piston imparts rotary motion to the crankshaft which in turn induces unbalance forces and produces vibration in the vehicle, thus influencing the ride quality. Generally, the primary inertial forces are balanced by a combination of balancer body and crank web. However, being a commuter bike, a balancer body could not be accommodated due to cost and space constraints. In such scenario, the first order unbalance force cannot be completely eliminated but can only be redistributed by adding counterweight to the crankshaft. Proper distribution of these forces is required for optimum vibration levels at motorcycle touch sensitive points (TSP) such as handle bar, footrest etc.

This paper depict the difference in the endurance factor of safety with usage of static and quasi static FE analysis and corrective measures take to solve the problem. The importance of the dynamic loading and subsequent effect of it on the multi axial fatigue analysis. Considering the modern trend prevailing among the vehicle manufacturers and specifically talking about two wheeler industry, it is clear that while the engine remains the same but the frame is changed to cater the market with new models to cut down on the development time. Initially the crankcase was designed for a double cradle frame where the crankcase was mounted on the frame. Later, the frame design was changed to single cradle where engine acts as a stress member link. This kind of arrangement makes the crankcase mountings participate in the chassis loads. Therefore, the crankcase mounting experiences road loads when the vehicle encounter the road irregularities.

India is considered to have one of the maximum two wheeler density in the world. Hence, all the scooter and motorcycle manufacturers are striving to keep their market share by quickly bringing quality products with high mileage at a cheap price tag. As emission norms are becoming stringent day by day, these OEMs have to take care of every detail in the engine that is driving their vehicles. So today's engineers are obliged to refine and improve the technologies they use, faster and with greater accuracy than ever before. This paper focuses on reducing Cylinder Bore deformation for a two wheeler engine through CAE simulation. In standard testing conditions this deformation was observed to cause engine seizure. Bore deformation is of great significance to the overall performance of an engine. It can increase oil consumption, blowby and emissions and may influence piston dynamics to a great extent.

Piston is a critical component of the engine as it exposed to high inertial and thermal loads. With the advent of high performance engines, the requirement of the piston to perform in extreme conditions have become quintessential. Piston scuffing is a common engine problem where there is a significant material loss at the piston and the liner, which could drastically affect the performance and the longevity of the components. This detrimental phenomenon would occur if the piston is not properly designed taking into consideration the thermal and structural intricacies of the engine. A water-cooled gasoline engine which had significant wear pattern on its piston skirt and liner was considered for this study. The engine block was made of aluminum alloy with a cast iron sleeve acting as liner. The piston-liner system was simulated through a commercially available numerical code which could capture the piston's primary and secondary motion.

An inadequate sealing of the combustion chamber gasket interface may have severe consequences on both the performance & emission of an engine. In this investigation, both the distribution of the contact pressure on the gasket and the stresses of the cylinder head at different loading conditions are explored and improved by modifying the design. A single cylinder gasoline engine cylinder head assembly has been analyzed by means of an uncoupled FEM simulation to find the sealing pressure of the multi-layer steel (MLS) gasket, strength & deformation of the components involved. The thermal loads are computed separately from CFD simulations of cylinder head assembly. The cylinder head assembly consisting of head, blocks, liner, cam shaft holder, bolts, gaskets, valve guides & valve seats, is one of the most complicated sub-assembly of an IC engine.

High fuel efficiency, low ownership/ maintenance cost and favorable driving climate are the major reasons for the increasing demand for low-power commuter motorcycles and scooters, particularly in developing countries like India, Brazil and China. Noise Vibration and Harshness (NVH) has now become a new subject for the battle between competing manufacturers in attracting customers. Valvetrain noise is quite significant in the engines of these cost gasoline vehicles as they don't incorporate a Hydraulic Lash Adjuster (HLA) to keep the manufacturing costs less. The aim of this study was to understand how the cam ramp velocity and height affects the noise generated by the engine and what effect they have on its performance.For this study, a small scooter gasoline engine with an Over Head Camshaft (OHC) and a rocker arrangement with a roller-follower was considered. A commercially available numerical code was used to simulate the kinematic and dynamic behaviour of the valvetrain system.

The Valve Train system is an integral part of any engine and the impact of its design is very crucial, particularly in high speed engines. Maintaining the required valve timing throught the engine operating speed and longer component life are the two important parameters which drive current valvetrain designs. An engine ValveTrain system designed for a valve lift of 7mm is to be modified for an increased valve lift of 8mm. A study was conducted to understand which design parameters are to be changed /modified to make this possible. For this study, the valvetrain of an air-cooled motorcycle engine is taken up. The valvetrain arrangement was an Over Head Camshaft (OHC) design with a Roller-Follower. A 1D commercially available numerical code was used to simulate the kinematics and dynamics of the system.

Piston is a very important part of the engine as the contribution to its efficiency and performance is huge. This study is to understand in detail, the effect of piston skirt design on the functioning of an engine. A small gasoline engine was taken up for study. A commercially available numerical code PISDYN was used to analyze the piston liner interface. The Finite Element (FE) models of piston and the liner were used to simulate Elasto-Hydrodynamic Lubrication (EHL) between skirt / liner and piston pin / pin hole. Friction of the numerical model was validated through a tear-down motoring of the engine. The secondary motion of the piston is studied. Understanding of how the profile and the ovality of the piston skirt affects the friction, wear and impact force at the piston liner interface is gathered. Asymmetrical skirt profile is proposed and its utility to reduce the thrust force on the liner and hence its friction and vibration of the engine is explained.

Engine designers today are faced with two paramount obstacles viz. rising demand for fuel efficient vehicles and stricter emission control norms. In this regard, the piston liner interface is a very important part of the engine, as it is the source of almost half of the frictional loss of an engine and defines the blowby, lubrication oil consumption and to some extent influences the hydrocarbon emission. A single cylinder 4-stroke 110cc gasoline engine is taken up for study. A commercially available numerical code is used to simulate the piston and ring dynamics of the engine. The analytical FMEP results are correlated with the experimental FMEP found out by conducting a tear down motoring test on the engine. The blowby of the simulation model is validated with experimentally measured value of the fired engine. The effect of bore clearance and design of the piston rings on friction, oil consumption and blowby is studied.