Of the several components that make up reciprocating aircraft engines, the crankshaft is the backbone as it is the part that converts linear motion into rotational motion. Crankshafts and piston engines are found on the majority of all business class and general aviation aircraft, and understanding their function is a crucial part of owning and operating such aircraft. This blog will discuss the different components of a crankshaft, its function, and common types.
Typically made of cast iron or steel, crankshafts are incredibly durable moving parts that are constantly under tension. While individual designs may vary slightly, nearly all crankshafts are made up of eight essential components. There are two different “journals” that make up a crankshaft. The main bearing journals
are connected directly to the engine block, and they create the axis that the rest of the crankshaft will rotate on. As their name suggests, connecting rod journals are attached to connecting rods that are secured to pistons. Connecting the two types of journals is a flat piece of metal called a crank web. As the pistons go through thousands of strokes per minute, the connecting rod journals create a tremendous amount of rotational force. This force is counteracted by a piece called a counterweight which is attached to the crank web and allows for the system to be stabilized at high RPMs.
Lubrication is crucial for the several moving components in a crankshaft, and, as such, the system needs a constant and appropriate amount of oil. Oil passages are holes drilled into the main journal where pressurized oil is released with every repetition. Thrust bearings
are attached to grooves on the engine block and are designed to keep the main bearing journals from moving back and forth laterally. A
flange connects the crankshaft to the flywheel, which is a device that can store mechanical energy for later use. Finally, the
are synthetic rubber lip seals that prevent oil from escaping at the openings in both ends of the crankshaft.
The crankshaft regulates several functions, but the end goal is to convert the linear energy of the pistons into rotational energy. As the explosions caused in the combustion phase of the 4-stroke cycle push the pistons up in the cylinder, energy is created. This energy is transferred through the camshaft
, flywheel, and eventually the airplane’s propellers. As the cylinders are designed to fire at slightly different times, there is always at least one adding power to the propeller.
There are multiple types of crankshafts, and they are typically classified by the method in which they are manufactured. Different kinds of engines may require a certain variation of the crankshaft. In a built-up crankshaft, all the different components are manufactured separately before being heated and cooled down, which merges them together. Commonly found in diesel engines, semi-built crankshafts contain groups of parts, like the web and journal, that are manufactured together while the other components are machined separately and added during assembly. Welded crankshafts are made up of separately manufactured parts, and they are welded together in the finished product. These are expensive to manufacture, but are typically stronger as compared to other types. Finally, billet crankshafts are made from a special steel alloy containing nickel, chromium, aluminum, and molybdenum. Billet crankshafts take the least amount of time to produce and require minimal balancing.
Aerospace Exchange is a leading supplier of crankshafts and many other aviation components. We provide the largest selection of new and obsolete parts from top manufacturers on a single platform. When procuring parts from Aerospace Exchange, customers can have confidence in knowing that their order has gone through our rigorous quality assurance program, which includes visual inspection and document verification to ensure that you are getting the correct parts with no defects. Due to our consistent efforts to uphold such practices, we are AS9120B, ISO 9001:2015, and FAA AC 00-56B
certified and accredited enterprise. Our supply chain that stretches across the United States, Canada, and the United Kingdom guarantees expedited shipping, and with rapid lead times, we will help you find what you need regardless of your time constraints. When you are ready to initiate the procurement process, please give our team a call or email, and we will be happy to assist you.