Browsing Youtube tonight, I came across Trailers From Hell, hosted by Joe Dante. This film, The Black Scorpion, is a typical 1950's sic-fi movie, featuring the tried and true scenes played out in so many films of that era.
Of course, a train gets attacked by the giant scorpion. However, the film makers didn't try to hide the fact that a model train was used in the scene. Take a look at the film and in particular the scene starting at 1:21.