What is the purpose of the arm?

Answer 1

In traditional engines (not overhead cam), the camshaft pushes lifters UP. Lifters push the pushrods UP, but the valves need to be pushed DOWN... so the rocker arm "rocks" on a shaft that pushes one side down when the other side goes up.

It's not a difficult job. Rocker arms aren't doing the most stressful job in the engine, but they do eventually wear out.

Part of the problem is, Engineers attempt to make the rocker arms s light as possible so they can move back when the camshaft/lifter/push rod relaxes. The weight of the valve train (all those components PLUS the weight of the valves) tend to contribute to valve "float", that's when the spring can't push that mass of material back fast enough when the engine is operating at high RPM.

Since the valve train has deliberately been kept "lightweight", they tend to wear. That's one of the reasons for an overhead cam in an engine. You do away with the push rod and rocker.

Answer 2

The purpose of the arm is multi-faceted and critical for performing a wide range of tasks that enable us to interact with the world around us. The arm provides support and mobility for the hand, which is essential for fine motor tasks such as grasping, writing, and manipulating objects.

Here's a breakdown of the arm's key functions:

Movement and Reach: The arm enables the hand to extend further than it could by itself. This added reach allows us to perform tasks like picking up objects from a distance, throwing, reaching high places, or even stretching to grab something behind us.

Strength and Stability: The arm provides the strength necessary for lifting, carrying, pushing, or pulling objects. Muscles in the shoulder, upper arm, and forearm work together to create force, enabling us to handle both light and heavy tasks.

Coordination with the Hand: The hand is an incredibly dexterous part of the body, capable of fine movements and precise tasks, but it requires the arm to position itself properly to be effective. The arm provides both mobility and stability to allow the hand to work in a wide variety of ways.

Balance and Support: The arm is also involved in maintaining overall body balance, especially when we are standing, walking, or engaging in physical activities. It can assist in maintaining posture, providing counterbalance when bending, or supporting weight in certain positions (e.g., when leaning on the arm during a rest).

Interaction with Environment: Beyond the physical tasks, the arm allows us to engage with the environment in a meaningful way—carrying out tasks like eating, dressing, brushing our teeth, driving, or engaging in sports. The arm serves as a bridge between us and the objects or tools we need to use in daily life.

In essence, the arm is designed to offer both flexibility and strength, working in coordination with the hand and other parts of the body to perform everyday tasks and maintain our overall function in life.