How to Create

A high-speed slingshot loop-the-loop rollercoaster track uses steep initial drop ramps and flexible, curved cardboard tubes to propel marbles through an upside-down vertical 360-degree loop. This design requires calculating the relationship between potential energy and kinetic energy: the starting drop ramp must be positioned significantly higher than the loop itself to generate the velocity needed for centrifugal force to keep the marble pressed against the track at the apex of the loop. Achieving a successful inverted loop provides an exciting engineering milestone for young builders as they balance entry speed, track curvature, and friction loss.

To create this loop-the-loop track, join three paper towel rolls end-to-end to build a very tall, steep thirty-inch starting launch chute angled at sixty degrees against a tall wall or bookshelf. Cut two flexible paper towel tubes in half lengthwise, joining them end-to-end with duct tape along the smooth outer seam to create an extra-long, flexible half-pipe strip. Bend the flexible cardboard strip into a smooth five-inch circular loop, taping the overlapping lower crossing points securely to a rigid wooden or cardboard baseboard so the loop does not flex or deform under pressure. Connect the bottom of the steep launch ramp directly into the entrance of the loop, ensuring the transition curve is gradual and smooth without sharp kinks. Release a dense steel ball bearing or heavy glass marble from the top of the launch ramp, adjusting the starting height until the marble completes the full inverted loop without falling from the ceiling.