Brennan Gyro-Monorail - photos

Brennan Gyro-Monorail. Early 1900s.

https://s3-us-west-1.amazonaws.com/h..._monorail1.jpg

https://s3-us-west-1.amazonaws.com/h..._monorail2.jpg

https://s3-us-west-1.amazonaws.com/h..._monorail3.jpg


More:

https://en.wikipedia.org/wiki/Gyro_monorail
http://www.douglas-self.com/MUSEUM/L...an/brennan.htm

Previously:

https://www.homemadetools.net/forum/...184#post141648

My question is, if they could make this back then, why don't we see more gyro-monorails?