What is a Rocker Arm in Engines and its Working?

A vehicle is nothing but effective coordination and amalgamation of various complicated components. Knowing about its parts can help you understand and take care of your vehicle. One such component is a rocker arm located in the central valve train of an engine. It opens up the valves by converting the motion of the rods. 

Keep reading this article for a complete overview on rocker arm in engines. 

The engine of a vehicle is largely responsible for its proper movement. Among others, the rocker arm in an engine plays an important part. It transfers the energy that a camshaft produces into a force for pushing against the valves during combustion. 

This function within an engine ensures greater fuel efficiency and overall performance quality. 

A rocker's arm comes in various shapes and sizes. These depend on the application of this component. However, all types of rocker's arms make an engine more efficient with the help of a camshaft.

The purpose of a rocker's arm is to enhance the efficiency of an engine, fuel and overall performance in a vehicle. It is responsible for transmitting the movement of a camshaft, taking it towards the intake and exhaust valves within an engine. 

This process occurs according to the shaft's movement and following the direct contact of these parts with the tappets. 

It is important to understand the working of a rocker's arm to get a clearer notion of its existence in vehicles. In simple terms, this component acts as a lever inside the engine and is capable of moving parts within an engine, such as the pushrods, valves, and lifters. When this arm rotates, the lobe-shaped bumps within a camshaft interact with it. 

While rotating, these bumps cause up-and-down movements in a rocker's arm. This process, in turn, transfers the mechanical energy into a force that pushes against the valves within an engine. Either pressure from springs or hydraulic pressure is used in this process. 

Then, the valves open and close at regular intervals to allow in air and fuel while exhausting the rest of each cylinder during the combustion.

Now that you know what a rocker's arm is, it will be helpful to learn about the various types of this component available in the market. Here are the types of rocker arms you will currently find in the automotive sector:

1. Stamped Steel Rocker Arm

It is the most commonly found rocker arm, mainly for being cheap and easy to manufacture. Manufacturers stamp them from one piece of metal. A trunnion pivot holds the arm in place with a nut having a rounded bottom while it pivots up and down.

2. Roller-Tipped Rocker Arms

These are similar in terms of structure to the previous one, with an additional roller on the tip of the valve towards the end of an arm. With this, there is less friction and more power, which helps to reduce the wear of the valve tip. This type of rocket arm also uses trunnion pivot nuts and studs.

3. Full Roller Rocker Arms

Such arms are made of either machined steel or aluminium, with bearings replacing the trunnion pivot. They do not use the nuts but may use studs from the trunnion pivot. These come with a short shaft with bearings on each end. The bearings help the arm pivot, and the shaft is safely bolted.

4. Shaft Rocker Arms

With a similar build as the previous one, these arms come with a shaft that goes through the rocker's arms. The purpose of this shaft is to maintain rigidity, which is much more effective than merely using studs. With a strong and rigid valve train, deflection or uncontrolled valve train motion is impossible, even at a high RPM.

Are you still confused about whether or not to use a rocket arm for your vehicle’s engine? Here are the primary reasons that show the importance of this component:

Engine Efficiency

The main reason for using a rocket arm is to ensure complete engine efficiency within a vehicle. These arms are effective for transferring sufficient mechanical energy into force. Most traditional methods, like hydraulic lifters or pushrods, are not as capable of doing this as rocket arms. 

Simple Design

Rockets arms are designed simply, making it easier for most mechanics and car owners to fit and use these for their vehicle's engine. They are easily available due to this kind of design.

Cost Effective

Such arms are usually inexpensive, mainly because they are composed of either steel or aluminium. This makes it easier for most vehicle owners to afford these for their engines. They get better efficiency at a low range.

Durability

Another reason for getting rocker arms is because of their exceptional durability. They can last for a long time, and you do not need to change them before at least 100,000 miles of drive.

This ratio refers to the length of the valve side, which is divided by the length of the Cam or Pushrod. A rocker arm usually multiples the motion by its Rocker Ratio, as the valve side is generally longer than a cam side or pushrod. 

The rocker arm ratio usually ranges between 1.45 and 1.7. This indicates that for each .100" of cam motion or pushrod, one gets .145" to .170" of valve motion. Increasing this ratio helps provide a higher lift cam in a vehicle without installing a new cam. It can improve breathing in an engine by increasing the number of open valves. 

People often try to modify the rocker arm ratio in their vehicles for multiple reasons. While this can turn out to be beneficial, here are a few factors to keep in mind before doing this to stay on the safe side:

• One needs to be careful, as manufacturers put much time and effort into customising a vehicle's rocker arms. Changing this ratio means modifying its originality, which can damage its engine. 

• An engine will have limited power improvement if you simply increase the duration for valves to stay open in this ratio. 

• Increasing the rocker ratio causes more valve lift, which can lead to the binding of the valve spring coil. Moreover, the valve retainer might hit the valve guides. 

• Major changes to this ratio can lead to piston-to-valve clearance, which causes valves to hit the pistons. It also occurs due to camshaft changes. 

• There is also a possibility of increased stress on an engine's valve train when you increase a rocker ratio. It requires the cam lobe to push harder on the lifter, which increases the stress. 

• Engines with larger rocker ratios ensure more flexible rocker arms. However, these can lead to a possibility of valve toss and can be unsuitable for high RPM valve train dynamics. 

Hopefully, that gives you a better understanding of a rocker arm and its importance in the functioning of a vehicle's engine. As this article pointed out, it is a mandatory component to ensure the complete efficiency of an engine. These come with simple designs and are cost-effective, which makes it easier for most people to afford them.