It is a well-known fact that a vehicle is a large sum of tiny moving parts. These parts move in various ways but still in coordination to help you move from point A to Point B. The initiation of the movement begins in the engine. The engine contains parts like the body, valves, pistons, and the subject in question, crankshafts and camshafts. The difference between a camshaft and a crankshaft is significant as the two components vary in shape and function.
The Camshaft and Crankshaft are the mechanical components of internal combustion engines. Another common feature between the two components is that the various components or adds on the shafts are known as journals. Let’s begin with decoding – Camshaft vs Crankshaft.
Camshaft Vs Crankshaft
- Location: The camshaft is present in the higher region of the engine. It is found at the top of a combustion chamber. The crankshaft, however, is present at the bottom of the engine. The pistons of the cylinder will rest on top of a crankshaft.
- Proximity: The crankshaft is connected to a series of pistons through a connecting rod. The camshaft is present in a region close to the valves and is in direct contact with them.
- Movement: The camshaft is capable of converting a rotatory motion into a reciprocal motion. However, the Crankshaft can convert reciprocal motion into rotational motion. Therefore, the movement of both components is opposite to each other.
- Shape: The shape of the camshaft is an oval or an egg shape. Crankshafts are larger and do not have a definite shape like a camshaft.
- Function: The camshaft functions in the mechanism that opens and closes a valve of a compression chamber. The movement of the crankshaft is required for the movement of the flywheel.
Camshaft: Build and Details
The build and structure of the camshaft mostly involve a long rod with a number of camshafts fitted along the length of the rod. It is important to note that the camshaft is the rod. The rod, which can also be known as a shaft, houses several “cams”. The shaft contains several components known as journals. The front end of the camshaft is the cam position sensor. This sensor’s primary job is to detect any change in the cam angle; it senses the rotation in the cam angle and initiates movement in the cylinder. The movement in the cylinder comes from the combustion cycle.
Each cam contains a head that is in the tip of the egg-shaped apparatus. At the same time, the lower and more rounded portion is the heel. In this case, the lobe is the portion of the cam in contact with the valve.
In addition to this, the region next to the camshaft position sensor is known as the thrust. The thrust will hold the shaft in place while the engine is functioning.
Functions of the Camshaft
The connection between the camshaft and the valve takes place at the upper portion of the cylinder. This is where the cam is present and will be in connection with the valve. The valve which possesses a head and stem also contains a spring at the stem region. The head protrudes out into the open combustion chamber and will move into the chamber at periodic intervals. The cam constantly rotates as the vehicle is in motion. With this rotation, the lobe of the camshaft pushes against the spring. The compression of the spring opens the valve, and thus, the fuel can go in and come out as well.
The aforementioned reciprocal motion is the motion of the valve that goes up and down as the cam’s rotational motion takes place.
Since the camshaft is connected to a valve, it also influences the movement of the compression chamber. Each combustion chamber possesses two valves; each chamber will contain two camshafts.
The camshaft is a component of an internal combustion heat engine. This ICE works on the principle of converting chemical energy into heat energy. Chemical energy is the fuel stored in the tank; heat from the combustion chamber helps push the pistons and the cylinder in motion. The purpose of the motion will further be elaborated upon when talking about the function of the crankshaft.
The camshaft is an integral component of the engine, and it plays an active role in the combustion cycle. The combustion cycle is the process that contributes largely to the motion of a vehicle, the process that converts fuel into energy through a series of steps. The camshaft is involved in the first as well as the last step.
The first step, known as the intake stroke, requires the valves to be open. Therefore, the camshaft can is in motion in this stroke. The valves open to let the fuel into the combustion chamber. The fuel in is the gaseous form; the mixture released into the combustion chamber contains both air and fuel. The piston present towards the lower end of the chamber will move upwards. Thus the pressure inside the chamber will decrease.
With the decrease in the volume of the chamber and increase in pressure, the fuel is ready to be ignited through the spark plug present in the chamber as well. This process creates a large amount of heat; the temperature of the chamber can get to approximately 138 to 250 degrees celsius. The average peak temperature is 248 degrees celsius.
After ignition occurs, the air and fuel mixture undergoes combustion; the remaining gas will consist of nitrogen oxide. This nitrogen oxide originates from the oxygen and the nitrogen present in the air-fuel mixture. The gases will thus be removed from the chamber through the outlet valve. This is the final stroke or the step in the cycle; it is known as the exhaust stroke.
The position and movement of the camshaft can greatly influence the movement of the car. The placement of the cams will ensure that the timing of the opening and closing of the valves is also proper. Due to this, the car will be able to perform smoothly at higher RPMs as well.
Types of Camshafts
Camshafts are different based on the number of valves they come in contact with. The two types are:
- Single overhead camshaft: This type of camshaft is known to open and close the valves using one cam only. This camshaft is ideal for vehicles that can run on fewer numbers of valves. It will deliver lesser torque and horsepower as well.
- Double overhead camshaft: Double Overhead camshafts require one cam to open the valves and the other to close them. This type of camshaft is better for vehicles that require higher horsepower and a peak torque rating. The engine can house more valves as well with this camshaft.
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Crankshaft: Build and Design
A crankshaft is a larger apparatus upon which the cylinders of an engine rest. It is made of molten iron that undergoes rigorous polishing in order to ensure that it experiences lesser friction. The crankshaft contains irregularly shaped or, in some cases, ‘sinusoidal’. As mentioned before, the shaft possesses journals. In essence, journals are the portions of the shaft that rotates inside the bearing. They are of two types.
The first being the connecting rod journals. This is the portion that will see a connection with connecting rods and subsequently the pistons. The other type is the main bearing journals. They are present closer to the axis of rotation or, in other words, the shaft. A common phrase that is usually thrown around is the word crankpins. This refers to the connecting rod journals. With these definitions out of the way, the next item would be to mention the components present at the anterior (front) and posterior (back) of the crankshaft.
The anterior portion is known as a nose. It contains a toothed gear connected with several other components like a pulley, a valve train and others.
The main component in question is the flywheel. This is present towards the posterior portion, also known as the flange. The function of this flywheel is crucial to the movement of a car.
Crankshafts are subject to continuous motion when the vehicle is in use. Therefore, it is essential to ensure that there is no friction between the journals. For this reason, the crankshaft possesses a specialised pathway for oil to travel through; the entire rod undergoes lubrication. The pathway involves a series of holes to reach each journal.
The Functioning of a Crankshaft
The primary function of the crankshaft is to help the flywheel to start turning. However, the flywheel requires rotational motion to begin its motion, coming from the pistons are reciprocal or linear. Therefore, the crankshafts will move as the combustion cycle takes place. The crankshaft works towards creating the required rotational motion for the flywheel.
The flywheel’s rotational motion leads to a smoother delivery of power from the motor to the machine. The flywheel works on the basis of the conservation of angular momentum. This principle allows the engine to store energy and utilise it as it functions. The flywheel also helps prevent the wear and tear of the engine, especially the crankshaft, due to the inertia created.
In a nutshell, the flywheel aims to decrease the potential fluctuations in the speed of the engine as it powers through the combustion cycle.
For a crankshaft to deliver better performance, a manufacturer will employ an alternate method. This method involves shaping a solid block of iron into the traditional crankshaft shape. This type of crankshaft is seen in racing cars or custom made cars.
Among all the components of an engine, the crankshaft is the most unstable. This is because this region experiences the most energy loss due to the dissipation of heat, friction and even that familiar grinding noise. The reason for this instability is due to the awkward movements of the pistons. Therefore, the crankshaft has undergone several changes over the years.
Alterations and Modifications to a Crankshaft
- V8 Engines: At present V8 engines are all the rage. V refers to the cylinders’ orientation; a pair of cylinders are present at a 45-degree angle to each other. This type of configuration helps balance out the crankshaft. The crankshaft, in this case, will be small and easy to control.
- Stroker Crankshaft: The next alteration was seen in the duration of the stroke of the combustion cycle. This type of crankshaft is known as a stroker crankshaft. The radius of the crank controls the stroke, which creates the driving force of an engine. The radius refers to the distance between the main journals from the connecting rod journals. The increase in this radius will allow one to receive two benefits. The first benefit is the larger cylinder capacity. Therefore, each stroke will produce more energy. The second is that due to a larger cylinder capacity, each stroke’s duration will be longer.
- Therefore, the installation of a stroker crankshaft has seen an increase in newer car models. However, it must be kept in mind that this type of crankshaft will experience higher displacement in the pistons. For this reason, the connecting rods also saw a decrease in length.
- Offset Crankshaft: However, there is a more cost-effective method to carry out the same principle as seen in the stroker crankshaft. This is possible through the installation of offset crankshafts. The journals present in these crankshafts undergo grinding at a particular angle. As result, the centre of the journal moves away from the centre of the crankshaft. This causes an increase in the crank radius, which will automatically and safely increase the stroke duration.
With all this being said, it is essential to find the connection between the camshaft and crankshaft in the engine. This connection is seen through a chain known as the timing chain or belt. This chain is similar to the bicycle chain holding the gears of the cycle together. A revolution in the taking place in the camshaft will thus induce motion in the crankshaft.
In general terms, the crankshaft undergoes more motion in comparison to the camshaft. The ratio of the number of motions between the crankshaft and the camshaft is 2:1. That is, for every revolution of the camshaft, the crankshaft takes two turns.
In this way, two very different components of an engine coordinate successfully to create motion.