1, $$\theta=arctan\left(\frac{2\pihe^{2\mu}}}{p\tauf}\right)$$.
2. Where $\theta$ is the winding angle, $$h$$ is the diameter of the steel wire, $$\mu$$ is the coefficient of friction between the steel wire and the pipe, $$e$$ is the ratio of the inner diameter of the pipe to the outer diameter at the time of winding, $$p$$ is the number of layers of winding, $$\tauf$$ is the distance between two neighboring steel wires, and $$f$$ is the bending stiffness of the pipe.