The Self Balancing Monorail

This is the Brennan Monorail, a train from the early 20th century that seemed to defy the laws of physics. Not only did it stay perfectly balanced on a single rail, it mysteriously leaned in corners without driver intervention. This was a true invention and was presented to the public in 1910 by its inventor Louis Brennan.  The idea was that using a single rail instead of two would make trains faster and railroads cheaper to build. His train could take curves at higher speeds without leaving the tracks and his railway only needed half the material. Unlike the

monorail

s we know today, which have thick tracks built high in the air, Brennan's

monorail

could run on existing tracks.

Although it looks a bit incomplete, by design it was very stable. At the heart of the train was a gyroscope that could correct the tilt of the train before the passengers realized it.   This was a mind-blowing piece of engineering, especially for 1910. But how did it actually work? We modeled everything and studied the original patents to show you how incredibly clever this design was. But to understand exactly what's going on here, we need to know a little about gyroscopes. The basic principle is that if you spin a disk very fast, its angular momentum tries to keep it perfectly stable.  If you try to tilt it in this direction, it starts rotating about the vertical axis, this is called precession.

But if instead of tilting it, we have it render, it actually tilts the disk in the opposite direction. This is why a gyroscope will always try to find its way back to equilibrium. Brennan saw this as the key to keeping his train balanced and so experimented with placing a small steering wheel on a model train and connecting it to an electric motor. At first this worked and every time the train began to fall, the disc preceded it and kept the train upright.   The problem was that when the train turned, the gyroscope did not turn with it as it tried to maintain its position in space.

  From the train's point of view, the gyro was leading, causing the train to tilt and go off the track.    To solve this problem, Brennan put a second gyroscope on the train and spun it in the opposite direction. both were connected by a gear so that when one gyro preceded, the other preceded in exactly the opposite direction.   When the train turned a corner, both gyros wanted to continue facing the same direction, but this was impossible.   And so both gyros were forced to turn with the train, and this unwanted precession was cancelled. With another problem solved, he began working on the full-size prototype that he could test with real passengers.

It was a 12 meter long, 22 ton vehicle with two huge gyroscopes that rotated at 3.5 thousand RPM. But expanding his design uncovered a huge problem. Now that it was a significant weight, the gyros were not only fighting against their own rotation but also against the force of gravity that was trying to pull the train down.  This was much easier to overcome in the smaller Brennan model, but with 22 tons trying to stop the train, the gyros had to be much stronger. The next day, while he was having lunch, a letter arrived that would hold the key to this solution.

It was a letter from the king of Nigeria saying that he had a large amount of money for Brennan. Just kidding, this never happened.  But if it were, Brennan could have asked Incogni, today's sponsor, to stop it. Every day we are constantly bombarded with spam emails and phone calls from companies we never signed up for.  Why did this happened? Well, Data Brokers sell our information to marketing agencies who then send you everything you don't want.  The worst thing is that all the information they have in their databases can be easily leaked or stolen by criminals.  The good thing is that you have the right to protect your

self

.  That's why Incogni contacts all of these companies on your behalf and asks them to delete any information they have about you.   All you need to do is sign up, sit back and watch Incogni do its job.   These are all the companies that no longer have my data.

   To protect your personal information and get rid of spam in your life, visit incogni.com/primalspace and use the code Primal space for 60% off.   In order for Brennan's monorail to remain perfectly balanced, it needed to overcome its own weight, which was constantly trying to tip the vehicle over.   As it tilted, the center of gravity shifted and the vehicle went lower and lower. The natural precession was not strong or fast enough to keep the train stable, so Brennan came up with a new solution.  He realized that the key to all this was to take control of the gyroscope's precession.  By intentionally preceding them faster than they normally would, a stronger force would be applied to straighten the vehicle.

   He connected the gyros to a gasoline engine and enclosed them in vacuum-sealed housings to reduce friction. Even if the power ran out, the gyroscopes would continue spinning for up to 30 minutes before the train could fall.  He placed the gyroscopes on a single gimbal that allowed the entire system to rotate about the train's roll axis.   The axles of each gyro protruded from the housing and were placed between two guide plates that were attached to the train chassis. When the train overturned, the axles made contact with one of the plates and the friction caused them to roll like a wheel on the ground.

   This would cause the gyros to precede much faster than the previous design, bringing the entire train back into balance. The problem was that the vibrations caused the gyros to bounce off the guide plates and never produced a smooth, proportional force on the train. And then Brennan got rid of the guide plates and came up with an even better solution.   He attached the gyros to the train chassis so that they rotated with the train.   When the train overturned, the gyroscopes did their usual thing and began to precede naturally. In the right gyroscope, its shaft was directly connected to a mechanism that controlled an actuator rod.

This rod was attached to a lever and two valves that controlled the flow of compressed air.   This compressed air followed two tubes that entered each end of a large tube that passed through the center of the gyroscope.   Inside this tube was a rack that sat between the two gyroscopes and could move back and forth to rotate them. When the train tilted, the gyroscopes would precede and the clever actuator arm would activate the valves.  By closing one of the valves, compressed air would flow through one of the pipes to one end of the tube.    This would increase the pressure, pushing on the rack and forcing the gyros to precede in the opposite direction until the train returned to equilibrium.   All of this happened instantly and the gyroscopes would react before the train became too unbalanced.  The key here is that the compressed air acted as a pneumatic system allowing the smallest force to produce a much larger force.

The force of the compressed air is also sent through the air in the tube. Once it reaches the larger piston, the same force is multiplied over a larger area and therefore this piston moves with much greater force than the gyros applied to it.  This genius system took the force of the overturning train and multiplied it against it

self

to create a train that always wanted to stay level. His train was so strong that even if all the passengers stood on one side, the train would remain perfectly balanced. His prototype was a great success and at the time it really looked like the future, but unfortunately investors did not trust the design.

   Two-track trains were already well established by this time, and the fact that each car needed its own gyroscope put an end to the project. Either way, it is amazing to discover these incredible inventions and appreciate the geniuses behind their creation. And now it's time for the Primal Space giveaway. The winner of the previous giveaway is Cameron. Congratulations! In the next video we will give away another Primal Space Voyager poster available in our store to one lucky winner.   All you need to do is sign up at the link below, like the video and leave a comment saying what you think about Brennan's design.

Thank you very much for watching and see you in the next video.