Crankshafts are generally made from steel and sit below the cylinders and pistons in the engine block.
Their job is to convert the vertical movement of the pistons into a rotation.
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Crankshafts are one of the most crucial components of internal combustion engines and are subjected to very high dynamic loads during engine use. The selection of materials and manufacturing methods depend on the type of engine and the geometry and design of the crankshaft.
It is necessary to use high strength materials to ensure a long operational life. Steel crankshafts are usually manufactured by forging or die forging or by casting if the material is cast iron.
There are basically three different types of crankshafts you can use in an engine.
These types of cranks are around for a long time and are found in a lot of diesel and petrol engine. As the name suggests, these are made from Malleable Iron through a casting process. These are pretty cheap to make and works fine too hence they are a common choice for manufacturers.
A flat plane crank is one where the journals are 180 degrees apart common in all in-line four engines. Whereas a cross-plane crank, on the other hand, needs a mould of multiple parts because the journals and counterweights are not symmetrical. Cast cranks can be flame hardened to improve wear resistance in particular areas.
Forged Steel Crankshafts
These are a more robust crankshaft than a cast crank. They are more commonly found in higher stressed engines and come standard with some 16v engine. A forged crank is made in a totally different way. A set of dies are machined to the approximate shape of the crank. These dies to sit in a very large hydraulic press having a clamping force of many tons.
A hot bar of high-grade steel alloy is placed onto the bottom die and the dies are closed. Once the dies are closed the metal is squeezed in very tightly. The material is then both compacted and aligned better than the casting process. These type cranks are also hardened like the cast types but it uses Induction Hardening.
Billet steel Crankshafts
Billet cranks are the best type of crank you can have in your engine if you want to get the most from it. 4340 steel is normally used to manufacture this kind of crank. This contains nickel, chromium, aluminium, and molybdenum amongst other elements.
These cranks are popular because of lowest crankshaft machining time. They also require minimal balancing due to the uniform makeup of the material.
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