If you’ve ever been on a modern looping roller coaster, you may be surprised to learn that when such “railways” were invented in the 1840s, they were painful, precarious, and not popular. Their biggest problem? The early loops were perfect circles.

Watch and see how roller coaster engineers changed the loop’s design over time, trying different materials, adjusting the g-forces to exhilarating instead of nauseating, and introducing the clothoid loop.

For all things roller coaster, check out the American Coaster Enthusiasts.