Barrel compression springs are very similar to conical compression springs since the diameters of the coils become tighter as the spring ascends. In the case of barrel compression and extension springs though, the body of the spring forms a convex or concave shape. A convex spring will have a larger outer diameter in the center coil and the coils in the ends will have the smaller outer diameter while a concave spring will have a smaller outer diameter in the center coil and larger diameters on the end coils. Barrel extension springs will usually be convex. These springs are primarily used to provide stability but may also be designed to perform a telescope effect when the barrel compression spring is being compressed.
Barrel springs are also non-linear due to the changing diameters of the coils. Like conical springs, the smaller coils will have more force than those that are larger. These non-linear springs will be most convenient if you have a barrel compression spring that runs the risk of buckling when compressed and it isnít going to be installed over a shaft or inside a hole.