Circus Rookies (1928)

Francis Byrd (Arthur), is in love with circus acrobat, and daughter of the show's owner, La Belle, and tries to join the show to be near her. However, his rival Oscar Thrust (Dane) is the keeper of a "Man-Eating Gorilla" named Bimbo, who's a featured act. He sabotages Byrd's efforts at impressing Belle, enough so she sees him as a coward. When the circus is travelling by train, Bimbo gets loose, rampaging through the cars, chasing Belle onto a roof , and the engineer off the engine. Byrd manages to stop the train, avoiding what would have been certain doom.