A constant force spring is a roll of the pre-stressed strip that exerts a nearly constant restraining force to resist uncoiling. The force is constant because the change in the radius of curvature is constant. Long extension capabilities, constant torque, and a virtual absence of inter coil friction have led many designers to specify constant force springs in various applications such as brush springs for motors. Constant force springs are typically made from stainless steel and coiled tightly into a flat spiral. During operation, the spring exerts a nearly uniform force throughout its extension due to the consistent curvature of the material. The constant force is a result of the spring’s design, which allows it to store and release energy evenly over its range of motion.