Knuckle Joint | Definition | Construction | Design | Applications and More

Do you want to discover everything about the Knuckle Joint?

You’ve arrived at the correct location. From start to finish, you’ll learn all there is to know about this joint.

Before I begin, let’s review the fundamentals of these concepts. This will allow you in grasping this topic more clearly.

What is Knuckle Joint?

  • The knuckle joint connects two rods whose axes coincide or meet and lie in the same plane, and it is exclusively used to transmit tensile loads.
  • This joint allows for limited angular movement of the rods around the pin’s axis. It isn’t utilised to join rotating and torque-transmitting rods.
  • Steel or wrought iron may be employed as the joint’s material. The single eye is put between the double eyes, making all three holes concentric, and the components are secured with a pin.
  • In constructions such as bridges and cranes, knuckle joints are frequently employed to link rods that are subjected to tension. A chain’s links can alternatively be thought of as a series of knuckle joints.
  • Knuckle joints are simple to produce while remaining sturdy and stiff under tension loads. They’re also simple to put together and take apart.
  • A revolute joint, also known as a pin joint, is a kind of one-degree-of-freedom kinematic pair formed by a knuckle joint. This means that only relative rotation around a single axis is possible.
  • All rotations and flips around any other axis are prohibited. A pivot point is another term for this sort of joint.

Knuckle Joint

Part of Knuckle Joint-

The key components of the knuckle joint assembly are as follows:

  • Single eye end
  • Double-eye end or fork end
  • Knuckle pin
  • Collar
  • Taper pin

Here is the suggested article about Pin, you should go through-

Construction of Knuckle Joint-

  • The knuckle joint connects two rods with one having a single-eye end and the other having a double-eye end or fork end.
  • Because one end has one hole and the other has two, these ends are referred to as single and double-eye ends.
    Between the double eyes of the double-eye end or fork end, the single-eye end is positioned.
  • Following that, a knuckle pin is placed into the eye and fork end holes. The fork and eye ends are held together with a knuckle pin.
  • A portion of the knuckle pin outer from the fork end’s lower portion hole. A little hole is located towards the bottom of the knuckle pin. The knuckle pin is locked in the eye and the fork ends with a collar and a tapper pin.
  • The collar has two holes, and the collar is set so that the knuckle pin’s hole corresponds with the collar’s holes, and then a tapper pin is put into the collar’s holes through the knuckle pin’s hole.
  • And this way a knuckle joint is produced.

knuckle joint parts

Design of Knuckle Joint-

  • Selection of Materials-  Because the joint is subjected to reversible loads, the stresses created will be repeated, and the joint will eventually break due to fatigue. As a result, low carbon steel is chosen as the material of choice since it will handle the strains while remaining within budget.
  • Material properties: C-30 materials will be good enough for most of the knuckle joint components.
  •  Factor of Safety(FOS)–  The joint is subjected to reversible stress and can go to fatigue failure, Hence choosing High FOS material is needed.
  •  Permissible stresses– Maximum primary stress, shear stress, and the Imperial relation are all permissible stresses.
  • Miscellaneous Dimensions– Pinhead diameter and pinhead thickness are two further dimensions to consider.

Related Article- Difference between Knuckle joint and Cotter joint

Failure of Knuckle Joint-

Knuckle joint failures can result in serious accidents. To avoid this disaster, it is vital to the design and builds a system that can bear strain without failing.

The following are some of the failures:

  • Knuckle Pin Bends and Knuckle Joint Shear Failures
  • The pin is squeezing the rod.
  • Solid rod and flat end bar tensile failure.
  • All of the parts of this joint have tensile and shear failure.
  • The bending of a pin in a single-eye end’s knuckle pinhole.

Applications of Knuckle Joint-

Knuckle Joints are used in the following ways:

  • To link the tractor to the trolley.
  • In the structure of a bridge, there is a tension link.
  • Roller chain link
  • To link robotic arms together
  •  Join the train’s compartments
  • Used in reciprocating engine’s valve mechanism
  • Links the locomotive’s connecting rod to the wheels.
  • Used in roller chain links, bicycle chains, and watch chain straps
  • Mostly employed in the mechanical and car industries

Read Also- Universal Joint: All you need to Know

Advantages of Knuckle Joint-

The following are some of the benefits of knuckle joints:

  • Large tensile loads can be absorbed by the knuckle joint.
  • It possesses a high degree of mechanical stiffness.
  • It is very simple to construct and set up.
  • It’s simple to put together and take apart.
  • The design is basic and straightforward.
  • It is less expensive and more durable
  • It has the ability to allow angular movement between rods.
  • Even with changing material thickness and tensile strengths, high repeatability is achieved.
  • Prolonged Tool life

Disadvantages of Knuckle Joint-

The following are some of the drawbacks of knuckle joints:

  • Only one plane or axis can be used for angular movement.
  • It is unable to handle huge compressive loads
  • It has less flexibility than a universal joint

Read Also- Cotter Joint: Definition, Types, Applications, Advantages, Disadvantages


Wrapping Up-

When a little degree of flexion or angular movement is required, a knuckle joint is used to connect two rods under tensile stresses. I hope you now understand what a “knuckle joint” is.

For the time being, that’s all there is to it. I believe I have addressed a variety of subjects related to the Knuckle Joint in a simple and digestible manner.

I hope you enjoyed your time here and that it was beneficial to you.

If so, please consider sharing with your friends and coworkers, as well as others in need,  To help spread the word

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