Louis Brennangyro monorail
Interesting history of the gyro monorail to be found on Wikipedia
The small Louis Brennan Wiki page here.
His invention was a mechanically controlled set of gyro's that could keep up a 20 ton railwaycar running on a single track.
The mechanically interconnected counter rotating gyro's were forced to rotate so that the combined precessing force would righten the monorail. The Patent can be found on the gyros.biz website
A first glimpse of how it works is the below drawing.
Peter Healy made a Brennan style stabilization which is very stable Youtube
Note that therotational axes of the gyro's are horizontal (as with Brennan) contrary to almost all other examples on the internet including Lit.
That the Brennan inventions works quite well can be seen from the pictures of children in the model car. The one with the boy showing the transition from the rail to the steel cable and the girl seems suspended in mid air.
The last reference (for now) is Dave Woolard who had some very interesting gyrobike simulations on the internet. I cannot find him anymore .... But I copied one of his prictures, lets hope his simulations come online again some time.