I hope I’m posting in the right place. I want to make a Union Pacific 4-8-8-4 “Big Boy” locomotive but I don’t know where to fine a good set of very detailed blueprints for the wheels, suspension and all the pipes involved.
I tried the-blueprints.com but I can only fine a small side image that isn’t vary detailed. If anyone knows of a site that has some detailed blueprints for this train that would be great 
Try here:
Also do a Google search.
Google is probably your best resource when looking for blueprints. You can also request blueprints at smcars.net.
I checked smcars.net but didn’t find what I was looking for. I did find this one http://engineeringartwork.com/union-pacific-4884-big-boy-locomotive-p-31.html and even though I will need to pay a little money, it looks like that will be what I need. Thanks for your advice
Try this resource: http://www.livesteamlocomotives.com/drawings/bigboy.htm
You can have 'em all for less than $400 (USD).
Another: http://www.trainzresources.com
Another: http://steamcad.railfan.net/index.htm
CAD files are available in some cases. I’ve got some original drawings for some smaller Alco’s but they are, of course, draftsman’s sheets, and original… so I don’t let them go out.
Be aware, however, (and here I do know whereof I speak…) that unless you have both exceptional needs and exceptional computing firepower at your disposal, what you are going to want to build is a series of facades, each for every shot you intend to build. You will need to put into each rig only the exact geometry needed for that particular shot. If you have ideas about making an all-inclusive model and then just plopping it down and shooting it from various angles… heh.
Historians do expect great detail. Especially steam historians and industrial archaeologists. They know more about an engine that ran one hundred years ago than they care to know about the toaster in their kitchen. They are passionately knowledgeable. But there is so much geometry there, and so much of it is or could be in-motion, that you’ll have to be very ruthless (ruthless, but accurate) in selecting what you choose to include in each shot, if you plan to get any of them done.
For instance, the valve-gear of one of the larger steamers has immense complexity, because everyone was looking for fuel-and-water economy while also striving to put a few more tons of tractive force on the drawbar. There were hundreds of inventions that were tried and discarded. A particular close-up shot might therefore need all of that exquisite detail, whereas a longer shot might not … but if the geometry is there, even though it affects only a few pixels, the computer will dutifully … try … to … com … put … e … it … Zzzzz …
If you want a hand with this, contact me offline. (I’m rather a steam computer nerd, I guess…)