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Connecting Rods

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Connecting rods are used in numerous situations, most commonly in the engines of automobiles. Connecting rods connect the crankshaft to the pistons and are necessary for the proper functioning of an internal combustion engine.

The purpose of a connection rod is to provide fluid movement between pistons and a crankshaft. Connection rods are widely used in vehicles that are powered by internal combustion engines. All cars and trucks that use this type of engine employ the use of connecting rods. Farm equipment like tractors and combines also use connecting rods. Even construction equipment like bulldozers use internal combustion engines, thus requiring connecting rods.


Connecting Rods History

The earliest evidence for a connecting rod appears in the late 3rd century AD Roman Hierapolis sawmill. It also appears in two 6th century Eastern Roman saw mills excavated at Ephesus respectively Gerasa.


The crank and connecting rod mechanism of these Roman watermills converted the rotary motion of the waterwheel into the linear movement of the saw blades. Sometime between 1174 and 1206, the Arab inventor and engineer Al-Jazari described a machine which incorporated the connecting rod with a crankshaft to pump water as part of a water-raising machine, but the device was unnecessarily complex indicating that he still did not fully understand the concept of power conversion. In Renaissance Italy, the earliest evidence of a ? albeit mechanically misunderstood ? compound crank and connecting-rod is found in the sketch books of Taccola. A sound understanding of the motion involved displays the painter Pisanello (d. 1455) who showed a piston-pump driven by a water-wheel and operated by two simple cranks and two connecting-rods. By the 16th century, evidence of cranks and connecting rods in the technological treatises and artwork of Renaissance Europe becomes abundant; Agostino Ramelli's The Diverse and Artifactitious Machines of 1588 alone depicts eighteen examples, a number which rises in the Theatrum Machinarum Novum by Georg Andreas Bockler to 45 different machines.

Connecting Rods Types and Materials

All connecting rods for automotive use need to be lightweight but strong enough to withstand and transmit the thrust from the pistons to an engine's crankshaft. Holes on both ends of a connecting rod are machined to perfectly connect to pistons and the crankshaft. Connecting rods are available in a variety of sizes and materials ideal for certain situations.

Connecting Rods Types

Currently, there are several manufacturers of various types of connecting rods. Windsor is a company that specializes in the manufacturing and distribution of all types of connecting rods. Omkar Motors is another company that manufactures engine parts including connecting rods. They mostly deal aftermarket spares for newer models include Chevy Accessories, Hyundai Accessories, Ford Accessories, Toyota Accessories and Mitsubishi Accessories among the others. GRP Connecting Rods produce connecting rods that are used in many race engines throughout the world.

There are a few materials that are commonly used in the creation of those auto accessories.

Connecting rods are usually drop forged out of a steel alloy. Rods manufactured under this method are capable of bearing very heavy loads without twisting, snapping or bending. Aluminum and titanium are both materials that are also used in the manufacturing of connecting rods for performance vehicles. Since an internal combustion engine depends on the proper function of its connecting rods, it is of utmost importance that the connecting rod is manufactured properly with a quality material. All connecting rods should include torque specifications.

Connecting-Rods with cenrl oil feed

A connecting rod with improper torque specifications is liable to fail and cause extensive damage to an internal combustion engine.

Connecting Rods Solutions

Many-cylinder multi-bank engines such as a V12 layout have little space available for many connecting rod journals on a limited length of crankshaft. This is a difficult compromise to solve and its consequence has often led to engines being regarded as failures (Sunbeam Arab, Rolls-Royce Vulture). The simplest solution, almost universal in V6 and V8 road car engines, is to use simple rods where cylinders from both banks share a journal. This requires the rod bearings to be narrower, increasing bearing load and the risk of failure in a high-performance engine. This also means the opposing cylinders are not exactly in line with each other.

Connecting-Rods row

In certain engine types, master/slave rods are used rather than the simple type shown in the picture above. The master rod carries one or more ring pins to which are bolted the much smaller big ends of slave rods on other cylinders. Radial engines typically have a master rod for one cylinder and slave rods for all the other cylinders in the same bank. Certain designs of V engines use a master/slave rod for each pair of opposite cylinders. A drawback of this is that the stroke of the subsidiary rod is slightly shorter than the master, which increases vibration in a vee engine, catastrophically so for the Sunbeam Arab.

The usual solution for high-performance aero-engines is a "forked" connecting rod. One rod is split in two at the big end and the other is thinned to fit into this fork. The journal is still shared between cylinders. The Rolls-Royce Merlin used this "fork-and-blade" style.