In a topsy-turvy report for Vox, producer Edward Vega explains the history of roller coasters, specifically explaining why the loops aren’t perfectly circular due to the danger it poses to the human body. Unfortunately, this information wasn’t as researched in the early days of rollercoasters as it is in modern times.
Between the 1840s and early 1900s, loops on roller coasters were perfectly circular — meaning riders would go from traveling in a fairly straight line to immediately moving into a curve. This rapid onset of curvature caused extreme G force spikes that rattled passengers to their core. The first looping roller coaster in North America — Coney Island’s Flip-Flap Railway — could exert up to 14 G’s on a person.
Once the danger of extreme G force was revealed, these circular loop coasters were shut down. The newly designed, much safer clothoid loops became the norm. Additionally, hollow steel replaced wood, and single-car became multi-car. Examples of these new materials and designs include “The Matterhorn” at Disneyland (hollow steel) (1959) and “The Great American Revolution” at Six Flags Magic Mountain (1976). Since that time, others have followed suit.
With clothoid loop-shaped coasters, designers could distribute the G’s more evenly and decide more precisely how many Gs to hit… about 4.9 in the case of the Great American Revolution. …This clothoid loop — crafted using strong and easy-to-bend tubular steel, and built 113 feet high meant that the Great American Revolution could support 20 riders at G forces that feel exhilarating instead of harmful. And since then loops have exploded in popularity.