New Revolution
Revolution was the first modern coaster to have a vertical loop.   A couple of unsuccessful coasters had loops from 1895 to 1910, but those rides had circular loops which subjected riders to extreme g-forces.  Revolution's 45-foot diameter loop has a larger curvature radius at the bottom of the loop than at the top, so it is more tear-drop shaped than the earlier unsuccessful circular loops.  Modern loops have a clothoid shape, also referred to as a Euler spiral.

©2016 Joel A. Rogers.