 Welcome back MechanicalEI, did you know that couplings find many uses in daily life from connecting two train coaches to running the water pump through a diesel engine? This makes us wonder, what are couplings? Before we jump in, check out the previous part of this series to learn about what a knuckle joint is. Now, a coupling is a mechanical elemental part that connects two shafts together to accurately transfer the power from the drive side to the driven side while absorbing the mounting errors of the two shafts. Power can be transmitted even between axes of different diameters, inclined angles and axial displacements. They also help absorb the shock and arrest heat transfer from one shaft to another. Protective flange coupling is a type of shaft coupling having two separate flanges which are mounted on the shaft and both flanges are bolted together by means of nuts and bolts. It differs from unprotected and marine type flange couplings since its coupling bolts and nuts are protected by flanges on the two halves of the coupling. Universal coupling is a coupling connecting rigid rods whose axes are inclined to each other and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together oriented at 90 degrees to each other and connected by a cross shaft. An old ham coupling on the other hand has three discs, one coupled to the input, one coupled to the output and a middle disc that is joined to the first two by tongue and groove. The tongue and groove on one side is perpendicular to the tongue and groove on the other. The middle disc rotates around the center at the same speed as the input and output shafts. The center traces a circular orbit twice per rotation around the midpoint between input and output shafts. An advantage to this type of coupling as compared to two universal joints is its compact size. Hence we first saw what couplings are, then saw what protected flange couplings are and then went on to see what old hams and universal couplings are. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also thanks a lot for those constructive comments. You helped the channel grow. So here are the top mechanical EIs of our last videos.