This operable Erector model was undoubtedly inspired by Mr. Ferris's original 1893 design. It is not to scale.
In this version - which is larger than the classic version available from 1935 to 1962 - the wheel itself is about 1/80 full size(about the scale of HO model trains!) and the cars are about 1/30 full size.
There was a special Set B available to build this model, but with no motor and only four cars. The motorized version shown here is built from a Set B plus a LOT of extra parts. The car roofs are reproductions.