Posted: 08/18/2023
Aside from sounding like a metal band from the early 90s (which it was), when you hear the word “crankshaft” you’re probably thinking about automobiles. There’s a good reason for that: the crankshaft of a car is an essential component that ensures the engine's energy is effectively transformed into the motion propelling the vehicle forward. In other words, without a crankshaft, your car doesn’t move.
The crankshaft is designed to convert the linear motion of pistons into rotational motion. Typically made of steel or iron, the crankshaft features a series of arms and crankpins extending from its central shaft. In layman’s terms, the pistons move up and down due to combustion, and then the crankshaft's function is translating this motion into the rotation that ultimately drives the vehicle's wheels, moving you forward to your destination. If you ever want a lesson on cause and effect, automobiles are a great place to look.
Beyond simply making your car move, the crankshaft's design and balance are pivotal in the engine's overall performance. A well-balanced crankshaft ensures minimal vibrations, leading to smoother engine operation and better fuel efficiency. Its position within the engine is strategic, allowing it to interact seamlessly with other engine parts, such as the pistons and connecting rods.
The crankshaft itself is intricately designed with several essential parts. Main journals support the crankshaft's rotation, mounted directly on the engine block. Offset from these are the crankpins or rod journals, which connect to the pistons' connecting rods, which are pivotal in converting the pistons' linear movements into rotational motion. Counterweights are strategically placed along its length to ensure the crankshaft operates smoothly and reduces vibrations. At the rear, the crankshaft flange comes into play, attaching the crankshaft to the flywheel or flexplate, which connects to the transmission. Each part of the crankshaft works together, ensuring your car’s engine operates efficiently. The crankshaft's functionality only comes into play when all 4 parts are working in unison, keeping your crankshaft balanced and spinning at the optimal rotational speed.
Crankshafts for cars and trucks are not one-size-fits-all. They come in various designs and materials to suit different engine configurations and vehicle types. Here's a look at some of them:
Flat-plane: Commonly found in V8 engines, especially in high-performance cars, the flat-plane crankshaft is named for its flat, or 180-degree, orientation of crankpins. This design allows for lighter weight and higher revving capability but can produce more vibration.
Cross-plane: Another design for V8 engines, the cross-plane crankshaft has its crankpins oriented at 90-degree angles to each other. This design provides smoother operation and better balance but often comes with added weight.
V-type: Used in V-shaped engines, this crankshaft design caters to engines with an odd number of cylinders on each side. The v-type crankshaft can handle such machines' unique firing order and balance requirements.
Straight: Commonly used in inline engines, straight crankshafts are more straightforward in design and commonly found in four or six-cylinder engines. They offer a good balance between performance and smoothness.
Each type of crankshaft is designed to the specific needs and characteristics of the engine it serves. By understanding each variation, you can better appreciate the engineering nuances that go into ensuring your car’s engine runs at peak performance. While the essential question of how the crankshaft works can be complicated by the different styles of crankshaft available, all of them maintain the same function in translating rotational power into forward momentum. The key is simply finding the correct one for your vehicle.
A healthy crankshaft leads to optimal performance. However, like all mechanical components, it can wear out or get damaged over time. Recognizing the bad crankshaft symptoms early on can prevent more extensive damage and costly repairs. Here are some common indicators:
Unusual Vibrations: One of the most noticeable signs is excessive vibrations coming from the engine. While some vibration is expected, a sudden increase or change in the pattern can indicate an issue with the crankshaft. One of the key factors here is a sound that’s not repetitive, like scraping or an ongoing noise that feels off-rhythm.
Engine Misfires: A damaged crankshaft can disrupt the engine's firing sequence, leading to misfires. This can manifest as a stuttering engine or reduced power during acceleration.
Oil Leaks: If you notice oil leaking near the front of your vehicle, it could be due to a faulty crankshaft seal. While this doesn't necessarily mean the crankshaft is damaged, it's a sign that the surrounding parts might be failing. Be sure to read our related article on determining whether your vehicle has a main seal leak.
Metallic Sounds: A clunking or knocking sound from the engine can indicate a damaged crankshaft or bearing. Addressing this quickly is essential, as continued operation can lead to further damage.
Difficulty Starting the Vehicle: If the crankshaft is severely damaged, it can prevent the engine from turning over, making it challenging or impossible to start the vehicle.
If you observe any of these signs, it's best to consult a professional technician. What complicates the situation is that there are similar issues experienced with a bad crankshaft as you would get with a bad crankshaft sensor, so it may not even necessarily be the crankshaft itself causing the issue.
Arnold Motor Supply has been a leading supplier of auto parts since 1927. Founded and based in Iowa, we have auto parts stores all over the midwest. Order your parts today and you'll be notified via email once your purchase is ready for pickup at your local Arnold Motor Supply parts store.
