Here's a paper model of a chemical container train car I've used as a prop in my Savage Cyberworld -campaign. Print it on two A4/Letter sheets, on cardstock, 120g paper or something else strudier than standard paper. I haven't added instructions as the model is quite simple, and I didn't see it necessary to add the parts that attach train cars to each other (whatever they are called in English), model worked quite well without them.
Did you assemble and paint WW2 military aircraft as a kid? I did, although I really didn't like much the glues and paints used in them, the ones I'm using currently in modelling and with miniatures are way easier to handle, an healthier too I guess. I also read Commando -comics and was generally fascinated about technology of The Great War. If you are also Plasticrack addict(tm), you'll be easily tempted to these.