An angle joint is a generic term for a wide classification of connection methods where one piece enters the joint in a specific direction and another piece leaves in a different direction. There are two classifications of angle joints, fixed and adjustable. A fixed joint doesn’t move from its initial position, while an adjustable angle joint has some degree of movement. Fixed joints are common in non-moving places like the inside of a wall or a picture frame, while adjustable joints are often in machinery like engines or industrial tools.
Angle joints are pretty much everywhere there are people. Whether it is two sticks lashed together to make a tent or the inside of a remote control car, people use angle joints in many things. In a fixed structure, the joint is generally used to change the direction of pressure applied to the object. When used in a machine, the joint typically allows energy to move in a non-linear path.
Fixed joints allow two items to connect to one another without sacrificing strength. This allows the joint location to alter forces placed upon it by changing its direction or creating lateral stability. For example, the corners of a house are made with fixed joints. These joints absorb the force placed on the walls from the floors above and direct it downward into the ground. If the walls were simply made of freestanding and non-jointed walls, the building would collapse under its own weight.
Adjustable joints are generally much more complicated than fixed joints. Since a fixed angle joint simply needs to not break, they are usually quite simple. On the other hand, an adjustable angle joint needs to flex, spin and transfer energy without sacrificing strength. As a result, most adjustable joints are made entirely of metal. The two most common forms of adjustable angle joint are universal joints (U joints) and constant-velocity (CV) joints.
A U joint is made with two hinges that allow the joint to move freely at any angle greater than 90 degrees. Each shaft connected to the joint has a Y-shaped fork on the end. One fork is turned 90 degrees to the other so they form a plus-shape with the fork ends. Between these forks is a simple connector that attaches freely to the tip of each end, creating two swing hinges. The two-hinge design allows both shafts to turn simultaneously, but at an angle independent of the other.
A CV angle joint is a modified ball-and-socket and is typically used when the joint needs to transfer energy at an angle that never changes. The ball-end on one shaft fits into the socket on the end of the other. Grooves on the ball and the inside of the socket hold a set of ball bearings that allow the ball to turn and transfer energy. These joints have a very high energy transfer potential, but require more maintenance than other adjustable joints.