Design and Fabrication of a Universal Coupling (Hooke’s Joint ) Report Download
A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both.
A Universal coupling is a special type of coupling in which misalignment of shafts is allowed. Shafts are free to move any direction in order to transmit torque or power from one shaft to another. In this project work a Universal coupling was designed, in which safe torque on shafts and pin size of cross determined. Finally the Universal coupling made by Mild Steel, which is low cost and available in every workshop.
Couplings are mechanical elements that ‘couples’ two drive elements which enables motion to be transferred from one element to another. The drive elements are normally shafts. We tend to see lot of applications of the couplings mainly in the automobiles, for example the drive shaft which connects the engine and the rear axle in a bus or any automobile is connected by means of a universal joint.
The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. By careful selection, installation and maintenance of couplings, substantial savings can be made in reduced maintenance costs and downtime.
There are various types of coupling based on area of application and misalignment or degree of freedom to move in any direction. Such as the universal coupling allows the shafts to move in any directions.
Universal Coupling or Hooke’s coupling:
A universal joint, (universal coupling, U-joint, Cardan joint, Hardy-Spicer joint, or Hooke’s joint) is a joint or coupling that allows the shafts to ‘bend’ in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90° to each other, connected by a cross shaft. The universal joint is not a constant velocity joint.
A universal joint is like a ball and socket joint that constrains an extra degree of rotational freedom. Given axis 1 on body 1, and axis 2 on body 2 that is perpendicular to axis 1, it keeps them perpendicular. In other words, rotation of the two bodies about the direction perpendicular to the two axes will be equal.
In the picture, the two bodies are joined together by a cross. Axis 1 is attached to body 1, and axis 2 is attached to body 2. The cross keeps these axes at 90 degrees, so if you grab body 1 and twist it, body 2 will twist as well.
A Universal joint is equivalent to a hinge-2 joint where the hinge-2’s axes are perpendicular to each other, and with a perfectly rigid connection in place of the suspension.
Universal joints show up in cars, where the engine causes a shaft, the drive shaft, to rotate along its own axis. At some point you’d like to change the direction of the shaft. The problem is, if you just bend the shaft, then the part after the bend won’t rotate about its own axis. So if you cut it at the bend location and insert a universal joint, you can use the constraint to force the second shaft to rotate about the same angle as the first shaft.
Types of Universal coupling:
The universal couplings are categorized as-
i. Single joints
ii. Double joints
iii.Telescopic or assembled joints
Field of Applications of Universal Coupling:
Typical applications of universal joints include-
Medical & optical devices
Textile machineries etc
Mechanical design is a complex undertaking, requiring many skills. Design and fabrication of a Universal coupling was done in this project work. In designing problem safe torque on shaft was determined. The cross pin size (diameter) was determined considering bearing stress, shearing stress and bending stress taken into account. The application of a universal coupling also studied in this project work.