Until watching this video, I had no idea that rollercoasters don't have circular loops. Instead, they have oval shaped loops to prevent people from facing dangerously high g-forces.
There was a short lived time when coasters did, in fact, have circular loops. One of these coasters, the Flip Flap, was built in the early 20th century on Coney Island, but lasted only 7 years when people were passing out due to the wild g-forces on these rides.
It took engineers a while to learn how to make coaster loops that weren't so hard on people's bodies. The video explains what this process was like, and how after many trials and errors, the right kind of build for a coaster loop was discovered.
