Years ago I visited a site in Canada called Bankcamp a coal mining camp. There was a small locomotive engine there on display which ran off of air. It traveled miles to and from the mine and came back with tons of coal on one charge of air. Has anyone else looked into this old technology or noted this locomotive? I understand the reason was because coal dust in the mine would of been ignited with a conventional steam fired locomotive. Just food for thought. Beachbum