Design and Optimisation of Chain Sprocket of a Formula Student Car Vishnuvel

Research Article Volume 10 Issue No.6

Design and Optimisation of Chain Sprocket of a Formula Student Car Vishnuvel. K1, Kajendran. M2, Akil Saran. D3 Department of Automobile Engineering Kumaraguru College of Technology, Coimbatore, Tamil Nadu, India

Abstract: Chain sprocket is one of the most important parts used in transmitting power from the engine to the drive shafts. This study mainly deals with the design and analysis of rear sprocket of a Formula Student car. This sprocket is designed such that it is light in weight and functions efficiently with the KTM Duke 390 engine. The type of chain used is roller type chain. The main challenge faced is determining the proper material and number of teeth for chain sprocket. Many iterations were carried mathematically to determine the total number of teeth and final drive ratio. The CAD model was created in SolidWorks and Finite Element Analysis was carried out in ANSYS Static Structural module. Initially a solid sprocket was created without any slots for different materials and Static structural analysis was performed. For doing static analysis, the forces and torques acting on the teeth of sprocket were calculated. Boundary conditions were applied such that the bolt ends were made to be fixed and parameters like tensile force, torque were applied at the sprocket teeth that were engaged during the operation. By observing the stress distribution in the solid sprocket, slots were created, in order to reduce the overall mass of the sprocket. Various CAD models were created in SolidWorks and were analyzed in ANSYS by applying static loads and assigning different materials. The best material and optimal design was selected based on the mass property and results obtained from ANSYS.

Keywords: ANSYS, Chain sprocket, engine, FEA, FS car, SolidWorks, Static structural.

I. INTRODUCTION design. Using these results optimization of sprocket for weight reduction have been done. As sprocket undergo vibration, Chain sprockets play an important role in transmitting power modal analysis was also performed. The design of sprocket from the engine to the drive shafts with the help of chain. FS has been successfully optimized with weight reduction of vehicle generally uses two types of drive systems-chain drive 15.67%. Also von-mises stress of modified design was lesser and belt drive system. Chain drive is mostly preferred as the than preliminary design with little increase in deformation, transmission loss is less compared to belt drive and requires which ultimately results in the safety and reliability of design. less maintenance. Chain system generally consists of a driver sprocket, driven sprocket and chain. The driver sprocket is [2] RonakSuthar,“Analysis of sprocket strength Finite Element directly mounted to the output shaft of the gearbox and the Method”, clearly explains the forces and torque acting at rear driven sprocket is connected to the drive half shafts via a sprocket. Moreover the existing mild steel sprocket was differential, in this case a spool differential is considered. The replaced by carbon fiber sprocket and finite element analysis contact between the driver and driven sprocket is established was performed in ANSYS. by a chain, in this system a roller type chain is considered. [3] Eldiwany and Marshek (1984) studied the load Torque from engine is transferred to the gearbox where a gear distributions on sprocket tooth and chain strands were studied reduction takes place and it reaches the driver sprocket. Next, with the help of a model and experimental analysis. The a final gear reduction takes place in the rear sprocket. Due to authors reported that the load distribution was not same on this reduction , high tensile loads and a boosted torque act on each tooth and varied with pressure angle and number of teeth. the teeth of rear sprocket. As, the loads acting on the rear The authors also made a study on the effect of lubrication, sprocket are high, it must be properly analyzed such that there misalignment, sprocket rotation at low speeds on load is no failure. Hence static structural analysis is carried out and dynamics. the safety factor for the optimized sprocket is determined. [4] Nikhil P. Ambole and Prof. P. R. Kale, “Finite Element II. OBJECTIVE Analysis Carbon Fiber Sprocket using ANSYS”, In this paper, the stress of chain drive was studied and the existing sprocket The main objective of this study is to reduce the overall of Bajaj Pulsar 180 motorcycle was compared with the weight of the rear sprocket by choosing appropriate material sprocket of carbon fiber material. They have achieved this by and ensuring that it does not fail at higher loads. using ANSYS 13, by applying torque in to the model of sprocket. Sprocket of mild steel (MS) was considered as an III. LITERATURE SURVEY object and input variables have been taken from standard conventional rear wheel sprocket model of Bajaj Pulsar 180. [1] Parag Nikam and Rahul Tanpure, “Design Optimization of Sprocket have been designed as per standard design procedure Chain Sprocket Using Finite Element Analysis”, In this with input data of Bajaj Pulsar 180. From results of finite research, the chain sprocket was designed and analyzed using element analysis, they observed that stresses are maximum at Finite Element Analysis for safety and reliability. ANSYS joint locations and both the materials have stress values less software was used for static and fatigue analysis of sprocket than their respective permissible yield stress values.

IJESC, June 2020 26133 http:// ijesc.org/ [5] Sagar N. Vasoya, P. L. Koradiya and B. J. Patel, with thickness of 8.4mm. Mesh was created with the help of “Development of Sprocket to Improvement the Torque for Off ANSYS mesher. Triangular elements were chosen as mesh Road Bike”, In this paper, the process of development in type with a minimum element size of 1mm.The whole sprocket was studied and gear ratio between them was component was made up of around 1928400 elements. investigated. They discussed four types of materials which will be best suited for sprocket namely Mild Steel, Chromoly Steel, Carbon Fiber and Aviation Grade Aluminium Alloy. They developed the Sprocket using 15/41 Teeth into the 13/39 Teeth and found that torque has increased by 9.91% by using the developed sprocket ratio.

IV. CALCULATIONS

Mf = Te * Primary reduction * First gear ratio Mf = 35 * 2.66 * 2.66 = 247.646 Nm Figure.2. CAD model Figure.3. Meshed CAD model T = Mf / Pitch radius of front sprocket T = (247.646 / 0.03813) = 6494.78 N A.BOUNDARY CONDITIONS: The forces and torques that were calculated previously were applied as boundary conditions. The bolt holes were made to be fixed and a force of 6385.19 N was applied in the x- direction and a force of 1188.03 N was applied in the y- direction at the engaged teeth of sprocket. A moment of 658.73 Nm was also applied at the engaged teeth of rear sprocket. Figure.1. Free Body Diagram

o Tx = T * cos Ф = 6494.78 * cos (10.54 ) = 6385.19 N o Ty = T * sin Ф = 6494.78 * sin (10.54 ) = 1188.03 N Final drive ratio = nf / nr = 15/40 = 2.66 Mr = Mf * Final drive ratio Mr = 247.646 Nm * 2.66 = 658.73 Nm where, Mf = Torque at front sprocket (Nm) Te = Engine Torque (Nm) T = Chain tension (N) Tx = Tension acting in x- direction (N) Figure.4. Boundary Conditions Ty = Tension acting in the y- direction (N) Ф = Sprocket pressure angle (degree) B.DEFORMATION PLOT: nf = Number of teeth in front sprocket nr = Number of teeth in rear sprocket Mr = Torque at rear sprocket (Nm) The engine torque, primary ratio, first gear ratio and no.of teeth in front sprocket were taken from KTM Duke 390 user’s manual.

V. MATERIAL SELECTION

Generally passenger vehicles likes bike use sprockets made of medium carbon steel. Hence, medium carbon steel(AISI 1045) Figure.5.Deformation plot of sprocket A (AISI 1045) is considered for analysis. But AISI 1045 is not a lighter metal. So, lighter material namely, aluminium 7 series (Al 7075 T6 ) is also considered for analysis.

Table.1. Material Properties

Figure.6.Deformation plot of sprocket B (Al 7075 T6)

From the above figures, sprocket B which is made up of Al

7075 T6 experienced a maximum displacement of 0.0302 mm VI. PRELIMINARY DESIGN at the teeth in the tightened side of the sprocket. Whereas, the Initially a solid sprocket without any slots was created in sprocket A made up of AISI 1045 experienced a maximum SolidWorks. The pitch circle radius was kept as 100.75 mm displacement of 0.0165 mm at the teeth and no displacement near the bolt holes.

IJESC, June 2020 26134 http:// ijesc.org/ C.VON-MISES STRESS PLOT: forces and torque were applied at the engaged teeth of the modified sprocket.

Figure.7.Stress plot of sprocket A (AISI 1045) Figure.11.Boundary Conditions

B.DEFORMATION PLOT:

Figure.8.Stress plot of sprocket B (Al 7075 T6)

Figure .12.Deformation plot of sprocket C (AISI 1045) From the obtained Von-mises stress plot it is seen that sprocket A experienced a maximum stress of 48.96 Mpa at the bolt holes , which is less when compared to the its yield strength. The sprocket B experienced a maximum stress of 49.254 Mpa which is also less than its yield strength.So, both the designs are safe. But the weights of both sprockets are high, so design optimization should be done such that the final sprocket weighs less without any failure.

VII. OPTIMISED DESIGN

Figure.13.Deformation plot of sprocket D (Al 7075 T6) With the help of the stress and deformation plots obtained from the solid sprocket, material is removed in the regions The sprocket C showed a maximum deformation of 0.033mm where the stress distribution is minimum, inorder to reduce the which occurred at the teeth in the tightened side and the mass of the existing sprocket. The material is also removed in sprocket D made of Al 7075 T6 showed a maximum such a manner, that the sprocket looks good aesthetically. deformation of 0.092 mm at the teeth as the force acting on Slots in the shape of triangles and irregular hexagons are cut in teeth is high. the solid sprocket. Triangles are chosen as slots, as they have greater strength and stability. C.VON-MISES STRESS PLOT:

Figure.14.Stress plot of sprocket C (AISI 1045)

Figure.9.Modified CAD model, Figure.10. Modified mesh model

Triangular elements are chosen as mesh type for this model too with minimum mesh size of 1mm.

A.BOUNDARY CONDITIONS: The same boundary conditions were applied as the previous solid sprocket. The bolt holes were made to be fixed and Figure.15. Stress plot of sprocket D (Al 7075 T6)

IJESC, June 2020 26135 http:// ijesc.org/ From the obtained Von-mises stress plot it is seen that X. REFERENCES sprocket C experienced a maximum stress of 97.614 Mpa at the bolt holes , which is less when compared to the its yield [1]. The Complete Guide to Chain (U.S. Tsubaki, Inc., strength. The sprocket D experienced a maximum stress of Wheeling, Illinois 1997) 96.317 Mpa which is also less than its yield strength. Though the stress values are high when compared to the solid sprocket, [2]. V.B. Bhandhari, Design Of Machine Element (McGraw it does not affect the safety factor as the stress values are very Hills Education pvt. Ltd. 1994) much less than the yield strength of the material. [3]. R.S. Khurmi, J.K. Gupta, A textbook of Machine design D.SAFETY FACTOR: (Eurasia Publishing House Pvt. Ltd. 2005) Factor of safety was calculated for sprocket D (Al 7075 T6) based on the Strain-life parameters. [4]. Kavit M. Shah and Prof. Dhruv U. Panchal, “Experimental Investigation on Effect of Plasma Nitriding on Wear of Chain- Sprocket Assembly Used in Motorcycle, IJSRD - International Journal for Scientific Research & Development, Vol. 2, Issue 03, June 2014, ISSN (online): 2321-0613

[5]. Ebhota Williams S, Ademola Emmanuel and Oghenekaro Peter,“Fundamentals of Sprocket Design and Reverse Engineering of Rear Sprocket of a Yamaha CY80 Motorcycle”, (IJET) – Volume 4 No. 4, April, 2014, ISSN: 2049-3444.

Figure.16.FOS of sprocket D (Al 7075 T6)

The sprocket D showed a maximum Factor of safety of 15 and a minimum Factor of Safety of 1.821.Thus the optimized design showed a permissible safety factor with a successful weight reduction.

VIII. RESULTS & CONCLUSION

Table.2. Mass Of Sprockets

Figure.17.Sprocket D assembly

As, the main objective of this study is to reduce the weight of the sprocket without compensating the safety factor, sprocket D made of Al 7075 T6 is chosen as the right sprocket for the FS car. Moreover sprocket D weighs only 423.3 g which reduces the overall mass of the drivetrain system. A overall weight reduction of 32.36% is achieved.

IX. FUTURE SCOPE

In future, dynamic loads that are acting on the sprocket is to be studied and dynamic analysis is to be performed. Alternative material like carbon fiber is to be applied and analysis is to be performed.

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