An image of a 'single truck'. They have four wheels, a single motor on each axle, hold a trolley car. The motors are supported by bars b, which are supported by spring s. To prevent oscillation, extra springs S1 and S2 are added. The wheels are generally 30 to 33 inches in diameter.
example of a single railway truck, railway truck, single railway truck, what does a railway truck look like, what holds a trolley, what is a railway truck, what is a railway truck used for, what mechanism is used to move a trolley
International Correspondence Schools A Textbook on Electric Lighting and Railways (Scranton, PA: International Textbook Company, 1901)