We model the motion of two identical pendulums swinging in parallel planes, attached by a spring. We describe the motion by the pendulums' angles of deflection over time. We assume that the pendulums swing in the x-z plane, their hinges are d units apart on the y-axis, they have unit length and unit mass, and their mass is concentrated at the ends. Pendulum 1 swings about the origin, and pendulum 2 swings about the point (0, d , 0). We assume the spring has natural length d .