# Connecting Rod

## Abstract

The connecting rod converts the reciprocating motion of piston into the rotating motion of the crankshaft. Generally, it can be seen in three parts, i.e., small end, shank and big end. The connecting rod motion is complex as the small end is reciprocating along cylinder axis and big end is rotating along with the crankpin. The Loads on a connecting rod are categorized as three types namely, Firing load, Inertia load and other loads. The analysis of loads on Connecting Rod by classical method must be carried out for sizing and shaping before going for detailed analysis using the finite element method for both static and dynamic loads. The examples for the classical method are available in the appendix. The analysis for the four load cases namely, Bolt Preload and Bearing and Bush Interference, Gas Pressure Loading, Inertia Loading and Combined Loading is presented. Enhancing the yield strength and fatigue strength is achieved by choice of Materials and heat treatment. Some practical aspects during design like Weight grouping of connecting rods, Push-out force test and Testing of the connecting rod are given. The fracture splitting method for connecting rods is becoming popular as an exercise in cost reduction. The manufacturing process of connecting rod is described in brief. At the end of the chapter various failure modes are described which are borne in mind while designing the connecting rod.

## Notes

### Acknowledgements

Authors acknowledge with thanks SAE, Society of Automotive Engineers for granting the permission to use Figs. 13.3 and 13.7 from reference (Wani et al. 2005) through Copyright Clearance Centre, www.copyright.com. They are thankful to “Sulzer Tech. Review and Sulzer Management Limited, Switzerland” for permitting to use the Figs. 13.13, 13.14, 13.15, 13.16 and 13.17 along with the equations in Annexure III from reference (Bremi 1971).

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