Truss bridge for the OS-Railway system. It's not modeled after any particular full scale bridge, only a composition inspired by many pictures on google. The OS-Railway system is a project with the aim of creating a fully 3D-printable and functional toy/model railway system in O-scale (1:45) which means 32mm track width.
If you drop by this page and haven't seen any of this before, check out the other related designs here: https://www.thingiverse.com/Depronized/designs

IMPORTANT! You can use the slope found on the arc bridge page, these bridges have the same height: https://www.thingiverse.com/thing:2172709

Building is pretty straight forward even though it's time consuming, it's a big print!
NOTE! All STL's starting with Buildplate are the ones you should use, the other ones are only included to let you print spare parts. Prototype is 100% PLA.

1. Print the "Build plate accessories" first, in that way you can start assembling when you get the sides ready. This plate need support! The orientation of the parts is important, it's done in a way so that the layer strength is in the right direction! I know it's tempting to rotate the "lower end connectors" to allow them to be printed without support, but if you do so you will put the layer weakness right where the part needs its strength the most.

2. Print 2pcs of each STL called "Buildplate_Side_XXX". I suggest 0,2mm layer height.

3. Print the STL called "Buildplate_track_2pcs", (or the one inly called track if you need to arrange it different, it's the same part printed 2 times and turned 180deg). I printed the prototype with the Prusa profile "FAST" with 0,35mm layer height and it actually works, but I would recommend 0,2mm if you have time.

4. Print the STL called "Buildplate_tower_2pcs". NOTE! the towers are hollow, and you can stop the print at any desired height if you want a lower bridge. Standard height of the towers are 130mm (translates to 140mm to track base, same as my Arc Bridge). You an use 0,35mm layer height to speed this one up, it gives OK result, at least on the Prusa i3 MK2.

5. Insert the parts called "Connectors" in the outer sides and glue the inner sides in place. This will lock the connectors in place. (CA, Superglue, Cyanoacrylate works very well).
   The connectors has been designed with a large play/tolerance, this is because the printing process will leave lots of material inside the holes where the connectors are supposed to slide in, and in my prototype which had much tighter fit, this ended up damaging many of the parts. Better have lots of play and use melt glue or epoxy, than having such a tight fit that the parts crack when assembling. It is especially important to check the bond in the middle, where the two mirrored sections join, although the track is held together you should make sure you have a nice glue bond here especially if you run heavy trains on the bridge.

Although there are screw holes for most parts, it's not really needed, you can glue most parts instead.

There are 2 ways of mounting the bridge to the towers, either use the two M3 screw holes in the middle, and place it edge-to-edge. Or you can put it only half way in over the tower, in that way you can build a two-section bridge using only 3 towers. A small connecting piece of track will be added. If you against all odds manage to build two sections before I publish the track joiner, let me know in the comments! :)