G'day David,
I am anew member who yesterday spent most of the day reading this thread, superb work on these models. Can I offer a suggestion for smoothing Shapeways models - ice cream sticks, tooth picks and balsa wood are good for burnishing the rough surface, a straight edge on the ice cream stick for flat surfaces and balsa wood where you have corrugations will often help polish off the excess powder without doing damage to detail.
You also mention in a recent post that you made the Plasser track machines from photographs, Plasser UK, US and AU have pdf side elevations of their machines along with outline dimensions on their websites that may help you.
Any chance of creating and selling some rescaled to 1/160 Plasser machines on Shapeways? Yours would be the only ones out there and would satisfy many elsewhere in the world.
Cheers,
Chris