What is the difference between a camshaft and a crankshaft?
3 Answers
Here are the differences between a camshaft and a crankshaft: 1. Different in nature: (1) Crankshaft: It is the most important component in an engine. (2) Camshaft: It is a component in a piston engine. 2. Different in principle: (1) Crankshaft: The crankshaft is subjected to the combined effects of centrifugal force from rotating masses, periodically varying gas inertial forces, and reciprocating inertial forces, causing the crankshaft to bear bending and torsional loads. (2) Camshaft: The camshaft is usually forged from high-quality carbon steel or alloy steel, or cast from alloy cast iron or ductile iron. The journal and cam working surfaces are polished after heat treatment. 3. Different in function: (1) Crankshaft: It receives the force transmitted from the connecting rod and converts it into torque, which is output through the crankshaft to drive other engine accessories. (2) Camshaft: It controls the opening and closing actions of the valves. Although in a four-stroke engine, the speed of the camshaft is half that of the crankshaft (in a two-stroke engine, the speed of the camshaft is the same as that of the crankshaft), its speed is usually still very high, and it needs to withstand significant torque.
I've been driving for over a decade and always hear mechanics talking about these two components during maintenance. The crankshaft is located at the bottom of the engine, connected to the pistons' up-and-down motion, responsible for converting linear motion into rotational power transmission. The camshaft sits at the top of the engine, specifically controlling valve openings and closings, determining when to intake and exhaust air. They also look completely different—the crankshaft has curved journals and counterweights, while the camshaft resembles a metal rod strung with uneven hills. In terms of working principles, the crankshaft withstands tremendous explosive forces, whereas the camshaft requires precise timing control; even a fraction of a second's deviation can affect power output. I've personally seen engines disassembled in repair shops—the crankshaft is as thick and sturdy as an iron rod, while the camshaft is much more refined, with its cams neatly aligned in a row.
Back when I was an apprentice at the auto repair shop, my master had me sort these two types of shafts. The crankshaft mainly operates in the lower crankcase of the engine, with its surface covered in bearing journals and counterweights. The camshaft, on the other hand, is located on the cylinder head, with each cam corresponding to a set of valves. In actual operation, the crankshaft serves the primary transmission function, driving piston movement via connecting rods. The camshaft acts like an orchestra conductor, controlling valve opening and closing frequency by rotating and pushing the tappets. During maintenance, the crankshaft requires regular wear inspection, while the camshaft demands extra attention to the synchronization of the timing system. Their materials also differ; crankshafts are typically made of high-strength alloy steel to withstand greater torque loads.
