Knuckle Joint – Introduction, Parts and Applications

Many people have asked me to explain knuckle joint with its parts, advantages, disadvantages and applications. I decided to write this article. Read every section of this article carefully and refer the images for a clear understanding. This article has the following sections:

1. Introduction
2. Parts
   1. Exploded View
   2. Assembled View
3. Advantages
4. Disadvantages
5. Applications

Introduction to Knuckle Joint:

Knuckle joint is a type of mechanical joint used in structures, to connect two intersecting cylindrical rods, whose axes lie on the same plane. It permits some angular movement between the cylindrical rods (in their plane). It is specially designed to withstand tensile loads.

Knuckle joint is named so because it is free to rotate about the axis of a knuckle pin.

Parts of a Knuckle Joint:

A typical knuckle joint has the following parts:

1. Fork end
2. Eye end
3. Knuckle pin
4. Collar
5. Taper pin

All the above parts can be visualized if you take a look at the exploded view shown below.

Exploded View of a Knuckle Joint

Coaxial holes are provided in the fork end, eye end and collar. The fork end and the eye end are held together in position by means of a knuckle pin. The knuckle pin is held in its position with the help of a collar and a taper pin.

The assembled view of a knuckle joint is shown in the image below. Both the fork end and the eye end are capable of rotating in their planes about the axis of the knuckle pin.

Assembled View of a Knuckle Joint

Whenever a tensile load is applied on the cylindrical rods, the fork end and eye end adjust their positions about the axis of the knuckle pin.

The knuckle pin remains stationary. It does not rotate about its axis.

Advantages of Knuckle Joint:

1. Knuckle joint can withstand large tensile loads.
2. It has good mechanical rigidity.
3. It is easy to manufacture and set up.
4. It can be easily dismantled and assembled.
5. Design is simple and easy.

Disadvantages of Knuckle Joint:

1. The joint cannot withstand large compressive loads.
2. It permits angular movement in only one plane.
3. It is not as flexible as universal joint.

Applications of Knuckle Joint:

Knuckle joints find a wide variety of applications. They are used in:

1. Bicycle chains
2. Tractors
3. Trusses
4. Automobile wipers
5. Cranes
6. Chain straps of watches
7. Earth movers
8. Robotic joints
9. Structural members

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