I had never realized that this particular photographic technique was in such widespread use until I did a Google search after my post of the diesel
loco engine innards.
My post of the loco engine calling it x-ray photography turns out not to be the best choice of words. It is more aptly called "light painting photography".
In addition to my Google search words suggestions in the loco post, uTube has numerous tutorials. It appears that a lengthy time exposure technique is one of the major tools for doing this type of photography.
The embedded image shows one end result from a uTube vid; the photographer used a specially designed lighting tool to create the wings on the model (while the camera was 'on').
So the insides of that train were actually "painted" on? Clever and effective!
This is one of those "hobbies" that is only limited by one's imagination (not that the gear is apt to be cheap either; no idea what the going rate
is for a "starter kit", but one practitioner uses both film and what I think is a high end digital camera; those tend to be quite expensive). I
presume that the camera has to have certain "features" built into it to do this kind of work.
This embedded image from a gallery caught my eye.