As soon as I can think of some new compliment, I´ll comment on this one. Until then - 
Personally, I am not bored at all with your "Voysey" stuff. Keep them coming.
And just out of curiosity - did you by any chance find that "Heidelberg" link useful?
Lancaster maybe? 
Anyway, this is worth checking out IMO: http://richard.ferriere.free.fr/index.html
As for the tutorial, Anders Lejczak´s site is a valuable resource too: http://www.colacola.se/
Although he is a C4D/Modo user, the principles are similar and will give you a hint about how to model an airplane.
I believe that you´ll find Fredo´s Curviloft particularly useful in joining contours (i.e. cross sections - and you´ll find a lot of them in the "3-views drawings" section of the former link) along the given rail.
Happy sketching! Keep us posted!
Probably the file that was attached in the first post. Because I don´t see it anymore, either 
No plugins needed. Except maybe for that tapered curved part: http://www.drawmetal.com/
Just in case you guys haven´t find anything useful here: http://forums.sketchucation.com/viewtopic.php?f=40&t=486, you could try Wood Workshop: http://www.spiralgraphics.biz/ww_overview.htm
The fact that I don´t comment on your posts too often does´t change a thing about how much I enjoy them.
Beautiful work. I really like the atmosphere.
I don´t know. If it helps, here are some more pics: http://www.wildcatmines.com/photos.html
If you are really determined to reconstruct it to the last detail, you´ll have to visit the nearest museum
Sorry, I don´t have a better drawing. But there are lots of images in those links Gaieus and others have posted - it doesn´t look that complicated to me.
Some more images here:
http://www.railroadmichigan.com/miningequipment.html
Keep up the good work!
I have this converter: http://web.axelero.hu/karpo/, it supports .stl and a whole bunch of other formats, so...
What file format are you actually trying to convert?
@agamemnus said:
Bonus: Also, perhaps a large sliding door on either the front-bottom or back-bottom of the minecart (where the "plate" is?), enabling the balls to roll out?
Unfortunately, I can´t help you with Sketchy Physics. But I think that the (standard) minecart features a hinged design that allows its base to rock back and forth, so it can be dumped to either side.
Something like this:
So much for the sliding door
Without looking at it - did you by any chance apply texture on reversed face?
And which rendering engine is that?
I am not sure, but I believe that this was the idea behind LightUp: http://www.light-up.co.uk/
You could try draw - sandbox - from contours. But it would be much easier if you could post an image of what you´re trying to do.
It could be a good start. Check out what hellnbak has done with another 3DWH model: http://forums.sketchucation.com/viewtopic.php?f=333&t=39789&hilit=roadster
