"The legacy of rotary machine design can be seen, in part, as an inhibition of linear motor experimentation, even as far as the 1970s. In rotary machines, the tangential direction was the thrust direction and the axial direction was simply a means of increasing power output. Three-dimensional thinking was, in some ways, more advanced in the Victorian era... the Second Age of Topology can be seen as having had its beginnings in the demand for high-speed propulsion, the problem of the long pole pitch and the resulting development of the TFM concept."