What Is the Function of Connecting Rods in Aircraft

In a reciprocating aircraft engine, connecting rods are built to transmit thrust to the crank to turn the crankshaft. These devices must be strong enough to maintain rigidity under a heavy load, yet light enough to lower the inertia forces produced when the rod and piston stop, change direction, and start again at the end of each stroke. There are three different types of connecting-rod assemblies, including plain, fork and blade, and master and articulated types, each of which will be discussed in the following blog.

To start, the master and articulated rod assembly is commonly used in radial engines that feature a piston in one cylinder of each row that is connected to the crankshaft by a master rod. Articulated rods help the other pistons in the row connect to the master rod by articulated rods, those of which feature two cylinder rows, two master rods, and 16 articulated rods in an 18-cylinder engine, as an example. They are often made of forged steel alloy shaped like an “I” or “H” in order to create a cross-sectional shaped assembly. Bushings are often placed in the bores of each articulated rod to establish lock knuckle pins and piston pin bearings. The master rod helps link the piston and crankpin together, and articulated rods are then attached through flanges which are present on the end of the crankpin. Lock knuckle pins have articulated rods attached to the master rod, and if a split-spline or split-clamp crankshaft is used, a one-piece master rod is relied on. These lock knuckle pins are solidly constructed for proper functioning. On the other hand, if the crankshaft is a one-piece type, the larger side of the master rod and master rod bearing split, while the rod is fitted on the crankpin.

Another type of connecting rod is the fork and blade rod which is often used in V-type engine aircraft, and they are infrequently found in modern engines. The fork and blade connecting rods are different in that the crankpin features a split which allows for a blade rod to be positioned between the prongs. Adversely, inline and opposed engines tend to use the plain type of connecting rods, where the end of one side is connected to a crankpin and fitted using a two-piece bearing and cap. The bearing cap is fastened to the rod using bolts and studs; it is important to always return the rods to their original position within the same cylinder as they were before.

Overall, all reciprocating engine types need different connecting rods, though each assembly type offers the same benefit of power transfer from the piston to the crankshaft for operation. When you are in the market for high-quality connecting rods and other aircraft parts, be sure to get in contact with us at Aerospace Sphere where we have more than 2 billion new, used, obsolete, and hard-to-find components ready for your immediate purchase. We operate with AS9120B, ISO 9001:2015, and FAA AC 00-56B accreditation to ensure the reliability of our products and services, and many products we offer are subjected to rigorous quality control measures to ensure the caliber of our offerings. Our supply chain network spans the United States, Canada, and the United Kingdom, ensuring that we are able to expedite shipping for both domestic and international customers, alike. Fill out our online RFQ form today to get your quotes to commence your parts procurement process with a partner you can trust.


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