Like the earlier centrifugal railways in Europe, Flip Flap Railway was notorious for the extreme g-forces that it produced in its riders. The circular nature of the coaster's loop, as well as its relatively small diameter of 25 feet, meant that it could produce forces of approximately 12 g.

The Flip Flap Railway, a historic wooden roller coaster that operated at Sea Lion Park in Coney Island during the late 1890s, was notorious for producing extreme G-forces—reportedly as high as 12G. The primary reason for this dangerously high centrifugal force was the design of its vertical loop, which was a perfectly circular shape. In physics, a circular loop requires a very high entry speed to ensure the car stays on the track at the apex, which results in a massive spike in vertical acceleration at the bottom. Modern roller coasters avoid this by using a clothoid or "teardrop" shaped loop, which has a varying radius that allows for a much smoother transition and lower, safer G-forces. The 12G forces experienced on the Flip Flap Railway were essentially at the limit of human endurance, often causing passengers to suffer from neck injuries or "gray-outs" (temporary loss of vision). This extreme physical toll is exactly why the ride was short-lived and why engineers moved toward the teardrop designs we see in 2026, which typically cap G-forces at around 4G to 5G to ensure a thrilling yet safe experience for the general public.