Curran Steam Commercial Vehicle, 1928

The Curran Steam Commercial Vehicle was a latecomer to the steam powered vehicles. The experimental steam bus chassis was built in 1928 utilizing the latest developments in metallurgy and steam power. The boiler was a combination of fire tubes and water tubes running at 600lbs pressure, The three cylinder engine was adjustable for steam entry into cylinders from full stroke length down to five percent of stroke length. The engine also acted as a brake as soon as steam entry was closed off, saving the mechanical brakes.  The fuel could be pretty much anything from gasoline down to low grade fuel oil. 

The bus chassis, loaded to 11 tons was tested on various roads and grades and was found to have high torque at start-up, a good power to weight ratio and ease of operation. However, the public was skeptical, all the steam car companies were long gone. The company failed to attract investors and the vehicle never entered production.