A connecting rod (also sometimes referred to as a con rod) is the part of a piston engine that connects the piston to the crankshaft, which is almost the backbone of the internal combustion system.
The crankshaft is responsible for ensuring the correct manoeuvres of the engine take place, converting a linear motion to a rotation. The predecessor to the con rod is a mechanic linkage, used by water mills to convert the rotation of the water wheel into reciprocating motion.
The most common usage of con rods (or integrated engineering H-beam rods) is in internal combustion or steam engines. They have been a key component in delivering the power needed for high-powered turbo and racing setups for years.
This component plays a crucial part when it comes to the transmission to the compressive and tensile forces from the piston, rotating at both ends. They work with the crank to convert the reciprocating motion of the piston into the rotation of the crankshaft.
How Do Connecting Rods Work?
As part of internal combustion, a connecting rod consists of the 'big end', 'rod' and 'small end.’ The small end attaches to the gudgeon pin (also called 'piston pin' or 'wrist pin'), which can swivel.
Typically, the big end connects to the crankpin using a plain bearing to reduce friction – although smaller engines may use a rolling-element bearing instead to avoid the need for a pumped lubrication system.
The Rod Carries the Force to the Crankshaft
For this reason, it is constantly subjected to stretching, squashing and bending forces as it acts as the intermediary in this push-pull relationship.
This component must be structurally strong. There’s no coincidence that it takes the form of a miniature steel I-beam – similar to its older brothers working to hold up towers, skyscrapers and bridges. The profile of the I-beam gives maximum structural strength, with the minimum weight cost. You want to keep the weight of the con rod as low as possible.
What Causes Connecting Rods to Fail?
The constant compression during the power stroke and stretching during the exhaust stroke, taking place thousands of times a minute, will eventually lead to fatigue. This describes the wearing down of the metal, causing it to become brittle and break. In addition, if the piston pin snaps, the rod will no longer be connected to the engine – so maintaining this is crucial to avoid damage.
Over revving is another main cause of failure in both new and high-performance systems. If the tachometer hits the red – even for a brief period of time – the rods are in danger of getting damaged then broken, which is not what we want.
If you’re working with high performance street and entry to mid-level motorsport applications, NITTO H-beam connecting rods are specifically designed for you.
Remember: The forces acting on a con rod increase dramatically at high revolutions, and can lead to damage over time.
Check out the Manley Pro Series I-Beam, which is the renowned standard for fully machined/ billet style high end connecting rods in the performance industry.
For all other questions, have a chat to the experts at Pro Speed Racing today. We stock all the parts you need to enhance your performance and give you a smoother ride.
