Knuckle Joint: Definition, Assembly, and Application

What is Knuckle joint?

A knuckle joint is a mechanical joint used to connect two rods which are under a tensile load. When there is a requirement of a small amount of flexibility or angular movement is necessary. There is always an axial or linear line of action of load.

The knuckle joint assembly consists of the following major components:

  • Single eye
  • Double-eye or fork
  • Knuckle pin.

At one end of the rod, a single eye is formed and a double eye is formed at the other end of the rod. Both, single and double eyes are connected by a knuckle pin inserted through the eye. The knuckle pin has a head at one end and another end there is a taper pin or split pin.

For gripping purposes, all three holes are concentric and a pin is used to secure the joint. Now, when the two eyes are pulled apart, the pin holds them together. The solid rod portion of the joint in this case is much stronger than the portion through which the pin passes.

Materials use in Knuckle joint parts

Knuckle joints can be made from various materials like aluminum, stainless steel, structural steel, magnesium, and gray cast iron have been studied and it was found that knuckle joints made of aluminum have the highest factor of safety for 50 KN loading condition. Hence knuckle joints made of aluminum are best suited for 50 KN loading conditions.

The knuckle joint used in some industries is generally making by a combination of cast iron and stainless steel. The rapid growth of technology in recent decades led to a reduction in the cost and weight of the materials as a result accidents have reduced and safety has increased. Knuckle joint may cast or fabricated or forged.

Teflon can also replace with the cast iron. Recent researches have proved that if we use composite materials instead of cast iron, there will be many advantages such as the making of knuckle joints are easy, having maximum safety, and ecofriendly.

knuckle joint

What are the application of Knuckle Joint?

Following are the knuckle joint applications:

  • The joint between the tie rod joint of a roof truss.
  • The joint Tension link in bridge structure.
  • Tie rod joint of the jib crane.
  • Link of roller chain, bicycle chain, and Chain straps of watches.
  • Connecting rods between locomotive wheels.
  • The valve mechanism of a reciprocating engine.
  • The fulcrum for the lever.
  • The knuckle joint is also used in Tractor wheel alignment parts.
  • In an automobile, a knuckle is supporting the skeleton for wheel assembly.
  • It uses downhole string on some occasions like the flush eccentric work barrel steps, the lateral drilling, Re-entrance into the bottom of the well, fishing, and so on.
  • knuckle joints are mainly used to joint to coaches of the train.
  • It is used in the windshield wipers of the vehicle.
  • It also uses in Robotic arms or Earth Movers like Crain or tank etc.
Knuckle Joint Application

Advantages of knuckle joint

The advantages of knuckle joints are as follow:

  • Knuckle joint can withstand large tensile loads.
  • It has good mechanical rigidity.
  • Also, it is simple to manufacture and set up.
  • It can be easily assembled and dismantled.
  • Design is simple and easy.
  • Fewer parts are less costly and more reliable.
  • It can permit angular movement between rods.
  • High repeating accuracy even with varying material thickness and tensile strengths.
  • Reduced impact shock and high system rigidity.
  • Long tool life.

Disadvantage of knuckle joints

The disadvantages of knuckle joints are as follow:

  • This joint cannot withstand large compressive loads.
  • It permits angular movement in only one plane.
  • It is not as flexible as a universal joint.

Failure of Knuckle Joints

Failure of knuckle joints may cause accidents so it is necessary to design knuckle joints to withstand under tension without failure.

The modes of failure are:

  • Shear failure of Knuckle pin(single shear).
  • Crushing of pin against the rod.
  • Tensile failure of flat end bar.
  • Tensile failure of solid rod
  • Bending of knuckle pin,
  • Tensile failure across knuckle pin single eye or rod end hole
  • Shear failure of single eye end beyond knuckle pinhole (double Shear).
  • Bending of a pin in the knuckle pinhole of a single eye end.
  • Tensile failure of double eye end at knuckle pinhole.
  • Shear failure of double eye end beyond knuckle pinhole
  • Bearing failure of the pin in knuckle pinhole of double eye end,

Design of Knuckle joints

  • Selection of Material: As the joint is subjected to reversible stresses, then stresses induced will be repeated and the joint may fail due to fatigue. Hence the selection of material is carried out by considering low carbon steel which will withstand stresses developed in the above case and the cost of material will be within range.
  • Properties of material: Hence select C-30 as material for all parts [Hint: we can select in between C-15 to C-45]
  • Selection of FOS: As the joint is subjected to reversible load and to account for fatigue failure, let us select higher FOS.
  • Permissible stresses: Maximum principal stress, shear stress, Imperial relation
  • Design of rod: Consider the rod is subjected to a direct tensile stress ς = P / π d2
  • A design of knuckle pin
  • Design of single eye end
  • Design of double eye end
  • Miscellaneous Dimensions: Pinhead diameter and Thickness of pinhead

FAQs.

What is a knuckle joint?

A knuckle joint is a mechanical joint used to connect two rods which are under a tensile load. When there is a requirement of a small amount of flexibility or angular movement is necessary. There is always an axial or linear line of action of load.

What is the application of the Knuckle Joint?

Application of Knuckle joint:

  • The joint between the tie rod joint of a roof truss.
  • The joint Tension link in bridge structure.
  • Tie rod joint of the jib crane.
  • Link of roller chain, bicycle chain, and Chain straps of watches.

What is Knuckle joint assembly?

The knuckle joint assembly consists of the following major components:

  • Single eye
  • Double-eye or fork
  • Knuckle pin.

Which is an example of a knuckle joint?

A knuckle Joint is a mechanical component that is used to join the two components under tensile loads. It is also known as the Forked pin joint. For example, Tractor and trolley. The trolley is being attached to the tractor with the help of a knuckle joint.

Is a part of knuckle joint?

Knuckle Joint has mainly three components – eye, fork, and pin as shown in Figure. The eye is formed on one of the rods and the fork is formed on the other. The eye fits inside the fork and the pin is passed through both the fork and the eye.

What is the other name of knuckle joint?

Anatomically, it is said that the knuckles consist of the metacarpophalangeal (MCP) and interphalangeal (IP) joints of the finger. The knuckles at the base of the fingers may be referred to as the 1st or major knuckles while the knuckles at the mid-finger are known as the 2nd and 3rd, or minor, knuckles.

Which of the following are part of knuckle joint?

Following are the main parts of a knuckle joint: Two rods. Double-eye end or fork end. Single eye end.

What material is knuckle joint?

Knuckle joints are made up of cast iron and stainless steel. With the advancements in the field of polymers, Teflon can be used for knuckle joints also.

How many parts are there in knuckle joint?

A knuckle joint always has a fork end, an eye end, and a pin. Typically, these are all specially made parts although standard rod ends are sometimes used for the eye end.

What are joints name the different types of joints?

The six types of a freely movable joints include ball and socket, saddle, hinge, condyloid, pivot, and gliding.

How is knuckle joint manufactured?

Disassembly of Knuckle Joint.

Step 1: Firstly, we remove the Tapper pin. Step 2: We put out Collar which is enclosing our Pin. Step 3: We remove Pin from Fork end and Eye end. Step 4: We pull the Eye end from the Fork end and our Knuckle joint is dismantled.

What material is the fork end of a knuckle joint?

The material of the knuckle joint is considered as mild steel grade 30C8, in order to do the stress analysis; mesh was developed for the knuckle joint. The mesh consists of 64229 nodes and 4310 elements. ANSYS software was run and the stress contour, displacement contour, strain energy contour was obtained.

Which material is used to joint?

Ultra-high-molecular-weight polyethylene (UHMWPE) is the main polymer used for joints, and it is widely used as acetabular cup material due to its superior biocompatibility, high impact strength and non-toxicity.