Algodoo

Zero Length Spring Swing

This swing acts like a zero length spring. This is accomplished by making the distance from the spring top anchor point to the swing bar pivot point equal to the spring free length. Doing this makes the spring/mass oscillation period equal to the pendulum period. The result is that the mass will travel in an elliptical path at any angle or aspect ratio depending only on the starting velocity. Grab the wooden seat with the hand tool and just release it or give it a push. When released at zero velocity, the path will approximate a straight line between the release point and equilibrium position (near the center of the cross bar). When the seat is near one end of travel and pushed in a direction perpendicular to the line, then an elliptical path will result. Changing the spring rate or mass of the rider does not change the basic operation, but does change the equilibrium point. Changing the location of of the swing bar pivot point will change the path to a Lissajous pattern.