So, I’m going to scratch-build a bridge, oh boy!
Here is a ground-level shot of the girder bridge north of Akihabara Station. As you can see, there’s lots of fiddly details around the edges of it. I’ll come back to those fiddly details later. The shot also shows the girders extending below the bridge deck, and even provides a measured distance (the bridge clearance is 2.8 meters—why so low?), giving us a good idea of the absolute scale of things! What’s underneath?
This is the only photo I can find anywhere taken from underneath this bridge. Lucky there’s even one! This shot is taken underneath the shinkansen lines just east of the tracks in my model. The bridge in question is waaaay to the right, in the background. You can just make out the truss structure between the girders. I use this as the basis for today’s plans. You can also now see why the bridge clearance is set so low in the first picture: the bridges get lower and lower to the ground, the further east under them you go.
From the diagram of my diorama to the left, you can see that we need two kinds of girders: a pair that sit straight on underneath the two central tracks, and a pair that sit at angles underneath the edgeward tracks. After their respective angles, I will refer to the two kinds of girder needed as 0º girders and 7.7º girders.
The inspiration for the girder/truss design comes from the only photo I can find of the underside of this bridge. Comparing to the photos above, you can also see that I’ve simplified the construction somewhat.
The 0º girders are 140mm long, and are easier to construct, so I’ll do those first. Then I’ll tackle the 7.7º girders (148.3mm long each). After that, I’ll work on the interesting detail on the side of the bridge, including the railing, power cabling, and various support structures. Then, I’ll look at details on top of the bridge deck, including girders that extend above the deck. Finally, I’ll work on ground-level details such as the height-restriction sign.
So, as you can see, I’ve begun assembling the bridge! Very exciting. As per the plan above, I’ve begun with the 0º girders, or at least the portion that hang below the bridge deck. This truss will fit within one of the two 0º girders, just nestled between two Tomix pylons.
The plans for today are for this pair of girders. The plans give a side, top and edge-on view of the complete product, some guides for gluing some of the pieces, and a complete list of parts and how to cut them. Some parts aren’t so obvious where they fit, and they have been labeled for clarity. 0º Girder Plan (PDF)