Murdock

In 1786 William Murdock built a prototype steam powered 3-wheeler whilst he was working as an assistant for James Watt.  The vehicle however was not succesful though as James Watt discouraged further development, dismissing high pressure steam as impractical and dangerous. The principals were later used by Richard Trevithick for his steam coaches.

1786 Murdock. (My thanks to Kerry Croxton for sending me this picture)