Primal Space (which has some fantastic videos with 3D model recreations) shows us the innovative Brennan gyroscopic monorail designed in the early 1900s.

Louis Brennan wondered if he could help the spread of rail by making it half as expensive – needing only one rail instead of two rails. But how do you balance tons of train on one rail?

In the end, he designed a monorail that defied conventional limitations by balancing on a single rail, leaning into corners without external input, and remaining stable (no hunting oscillation) even when stationary by the use of 2 extremely clever interconnected gyroscopes.

What seems to have largely done in the idea is that each car in the train would need its own gyroscope motor and assembly. It makes me wonder if there would be a way to reduce that space requirement using an interconnected air system in modern train brake systems to power the gyroscopes. But it also would have the unfortunate problem of falling over if the gyroscopes stopped/malfunctioned/ran out of fuel or weren’t parked with supports. It also didn’t remove the problem of needing to design and acquire right-of-way to lay the tracks in the first place.

Still – it’s quite amazing to see this thing in action. All done before computers and mechanically.