Connecting Rod: Details about Connecting Rod & Gudgeon Pin of Engine

(Last Updated On: 18/04/2018)

As the name denotes connecting rod connects the crankshaft and piston assembly to each other.

To convert the reciprocating motion of the piston into rotary motion of crankshaft, you have to connect, piston to a crankshaft with the help of connecting rod and gudgeon pin.

Basically, every utility machine or an engineering product is an assembly of various parts.

Hence I am going to share some information of parts of an internal combustion engine.

Below you will find details about connecting rod and gudgeon pin used in an internal combustion engine.

connecting rod and gudgeon pin assembly

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So, Here are the details of Connecting Rod

The load on the piston due to combustion of fuel in the combustion chamber is transmitted to the crankshaft through the connecting rod.

One end of connecting rod known as the small end and is connected to the piston through gudgeon pin.

While the other end is known as a big end and is connected to the crankshaft through a crank pin.

For the large size, internal combustion engine, the connecting rods of the rectangular section have been employed.

In such cases, the larger dimensions are kept in the plane of rotation.

In a petrol engine, the connecting rod’s big end is generally split to enable its clamping around the crankshaft.

Suitable diameter holes are provided to accommodate connecting rod bolts for clamping.

The big end of connecting rod is clamped with a crankshaft with the help of connecting rod bolt, nut and split pin or cotter pin.

  • The material of Connecting Rod

Connecting rods are usually made up of drop forged I section.

Generally, plain carbon steel is used as material to manufacture connecting rod but where low weight is a most important factor, aluminium alloys are most suitable.

Nickel alloy steel is also used for heavy-duty engine’s connecting rod.

Connecting rod

  • So, Here are the details of Gudgeon Pin

Gudgeon Pin

This pin connects the piston with the small end of the connecting rod, and also known as piston pin.

It is made up of case hardened steel and accurately ground to the required diameters.

Gudgeon pins are made hollow to reduce its weight, resulting in low inertia effect of reciprocating parts.

This pin is also known as “Fully Floating” as this is free to turn or oscillate both in the piston bosses as well as the small end of the connecting rod.

There are very fewer chances of seizure in this case but the end movement of the pin must be restricted to score the cylinder walls.

This can be achieved by using any one of the following three methods,

A) One spring circlip at each end is fitted into the groove in the piston bosses.

B) On spring circlip is provided in the middle.

C) Bronze or Aluminum pads are fitted at both ends of the pin, which prevents the cylinder walls from being damaged.

The gudgeon pin may also be the semi-floating type, in which either the pin is free to turn or oscillate in the small end bearing but secured in the piston bosses or it may secure the small end bearing and allowed a free oscillating movement in the piston bosses.

This method provides more bearing area at the bosses and hence no need for providing bushes there in, is preferred.

Besides this information, you are suggested to read something more from below engineering books

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