Double Tracking a Plate Girder Bridge

The Kato double track girder bridge pieces, as noted before, have roadbed and ballast under the track, but the single track bridges are "see through"… and just a bit too wide to be used side by side even for alternate (33mm) spacing. Since I wanted the lacy appearance of the "see through" deck to the water below, I ended up cutting apart two single track bridges and using them to make a one double track bridge.

How to do it:

1) Use a razor saw to cut down the INSIDE side of one girder. Keep the blade of the saw flush against the girder, and don't worry if it scars it up a bit - the scrapes will be hidden when you glue the removed girders back to back later. Do the same for both bridges. No, it doesn't make any difference which side you cut off… you can always swap them end for end for assembly.

2) Attach a short piece of Kato Double track (I used two 20-042) at each end of the single units and snap them together. This sets the spacing and alignment of your bridge pieces and guarantees they will be perfect when you finish. Leave them assembled until you're finished with the project!


3) Turn the bridge upside down, and glue styrene "splice plates" to both pieces along the centerline of the bridge. I cut the styrene splice plates into short lengths to go between the cross members. (The black styrene is from old record store LP separators I happened to have around.) When you've done that, you can flex the bridge outside edges slightly "upward" (towards the top of the bridge…. which is upside down at the moment…) to open the gap between the "inside" ends of the pier faces and slip a drop of glue between them to glue them together as well.

4) I used Miliput epoxy putty to fill the gap between the bridge halves, though this might not actually be necessary. Use a small flat tool (the butt end of an Xacto blade reversed in the handle will work if nothing else is handy…) to smooth the putty into the crack and down to the splice plates. Try not to get it all over the diamond tread embossing on the walkways of the bridge… It's a pain to clean out, though you can do it if you're very patient and have a magnifier and steady hands…

5) Before the Miliput hardens, use some to fill in the middle of the piers under the bridge. Is this necessary? No… but it does look a bit more prototypical, and it adds some strength to the assembly. If you don't want to go to that effort, you can achieve much the same effect by just gluing a piece of sheet styrene across the inside pier faces and shaping it to match the slope near the centerlines of the track.


6) Sand the backs of the girders you removed from the bridges smooth and flat. Align them carefully and use masking tape to hold one end of the pair together. Spread the OTHER end, and apply glue to the inside faces. If you use a CA, be VERY aware of any leaks or seepage! I've not managed to glue my fingers together yet, but I DID get glue all over one finger… Just wait till it dries, then remove with fancy CA remover… or fingernail polish remover.

While your fingers are drying off, the glue between the pieces will set too, so after you get cleaned up, go back and take the tape off the bridge girders and spread the other end slightly, applying glue between them again. Odds are you'll pay more attention to any leaks this time.

7) While that's setting, sand the Miliput between the bridge sections flat and smooth, being careful not to obliterate the diamond tread detail you've so laboriously cleaned of putty. Fold a small piece of sandpaper around a bit of 0.080 plastic or something similar - It's much easier to control that way. Clean the dust away, then test fit the new center girder assembly. If all is well, glue it in place down the centerline of the bridge… right over the Miliput.


All finished!

This gives you a center girder that is both thicker and taller than the outside girders, which I believe is appropriate from an engineering standpoint. If you don't want that look, you could use just one of the girders, but I would suggest then placing the "detail" side toward the most commonly viewed side of the bridge.

If you sand the center girders down to be the same height as the others, you'll sacrifice detail from one edge, so I suggest making that the "bottom" side.

This bridge is to be one component of a wide river crossing on a triple length module… I'll post more photos when it's finished.


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