Here is a lovely early Victorian drawing of a steam loco from 1846. The drawing is by the engineer, David Joy.
This kind of technical drawing is distinguished by its precision. The drawing has to be big enough to carry the detail and, at the same time, remain clear enough to be useful…
The Institute of Mechanical Engineers has a wonderful archive of this material.
More recently, the artist William Fenton made coloured versions of this kind of image. These images were published in a series of large-format picture books during the 1970s. These books are now quite rare, as they were often broken up for framing.
William Fenton has worked for London Transport. You can see his work in the archive of the LT Museum.