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…...................--- 100' N Scale 3D Printed Warren Truss Bridge ---

Working around the coal mine complex.

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I find the paper towels to work really well for at least an initial paper pattern. You can push it down and feel things like the roadbed next to the track and other features like the edge of the layout. I pretty much cut these out and mark the foam using them. If I really want to check things out before cutting the foam I'll use these to make a pattern on a piece of cardboard from a cereal box. Then place it in position and if I like it use it to mark the cut line on the foam.

After cutting the foam with a hot wire knife at about a 90 degree angle I come back in with a sculpting hot wire knife and make an angle cut to angle the face of the section before moving on to the next layer of foam that is marked using the new cut line at the top of the foam I just cut. More pictures of that ( HERE ).

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Time to build the needed bridge. It will cross over the two track mainline just before it enters a tunnel. I didn't want the bridge to overwhelm the scene so wanted a narrow bridge like you might find on a back road in the early 70's. The roadway through the bridge would be too narrow for larger roads vs. the little used road to the coal mine.

I spent about 12 hours over 2 days with Fusion 360 (free version) designing the bridge and then printed it (haven't finished it as I write this). The bottom, top and end bracing all prints separately. Each of the sides will have to be cut into 2 pieces to fit the resin printer's build plate. The sides could be printed as single units with the Ender filament printer but I want to see if I can get the rivet detail to print with the resin printer. It is too small for the filament printer.

Hope to report back if it prints OK and I can get it glued together and I don't have to end up redesigning parts or all of it. The bridge is a Warren Truss (equilateral triangles) and loosely designed on pictures of some I found on the internet. I'll probably print the deck for it on the filament printer.

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It took a total of 4 prints with the size of my build plate to print all of the parts of the bridge. The print above didn't come out so good the first time around. Some breakage of parts during the printing. I redesigned it a little and the second go around (shown above) is printing as I type this. Hopefully it will be better.

Some of the bracing is very thin and easy to break. I had printed extra bracing and ended up needing some of it. I think after doing this one I could get a second one glued up a little more square. Might print another one at some point but not now.

The deck the truck is on above is part of the model and the bottoms of the trusses are glued to it.

I designed a second deck with side railing that can sit on the primary deck shown in the image before the one above. I wanted the option for the railing and also this deck can be painted (railing and road surface) and then slid into the bridge. That should make painting it and and bridge somewhat easier.

The primary traffic over this bridge would be to and from the coal mine with no real through traffic on the road/bridge.

After taking the pictures above I found out that I can heat areas with a heat gun and get some of the warping out. I'll work on that a little but this is by no means suppose to be a commercial product and I don't want to spend much more time on it other than painting. Need to move on and I'm satisfied with the look.

Paint-booth is working great. For info on building it click ( HERE ).

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The rock face behind the bridge and tunnel portal will continue upward to the upper level where there will be another set of track s and a long bridge that will cross the canyon paralleling the tracks shown above. I'll also brush on some more highlights on the bridge when it is ready to be put in place and glue the roadway down flat on the bridge decking.

I'll probably put the print files up after painting it. It wasn't easy for me to assemble but I don't have much experience with kits and kitbashing.

to be continued.....

You can find the files to print the bridge, abutments and shoes on my thingiverse account later.

You can find all the files to 3D print this object and others on my thingiverse.com account ( HERE ).

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