Martinez-Benicia UP/SP Bridge Construction Thread

[dcutting]

Yesterday I dug out my set of plans for the Martinez-Benicia railroad bridge and decided it's time to get busy building one. As a kid, I remember getting glances of this bridge driving back and forth from my grandparents' house. This bridge is MASSIVE. It is the longest railroad bridge west of the Mississippi. It spans 5603' 6" from end to end (Suisun Point to Army Point), so just over a mile. That span is broken up into no less than 23 spans. Seven of those are identical Warren trusses, measuring 531' long. Thirteen of them are deck girders. There are also two deck trusses and one lift span.

Historic bridges has some photos of it: https://historicbridges.org/bridges/browser/photosviewer.php?bridgebrowser=california/martinezrr/&gallerynum=1&gallerysize=1

Scaling everything to N, the bridge would be over 35 feet long. That's the length of my house Each of the warren trusses come out to over three feet long. For reference, that's 2.5 times the length of the longest truss I know to be commercially available in N scale, the BLMA 200' brass bridge.

Construction is going to be a trick with a bridge this large. 3D printing is probably not possible with a span of this length at the detail level that I'm looking for, and I don't think it would have the right feel. I'm going to etch the structure from brass, and it turns out that my usual etching house can actually do sheets large enough to build the bridge without splitting up components like the stringers lengthwise. I'm hoping that I can offer this bridge as a kit so other modelers can build similar behemoths.

Here's my first effort in CAD:

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[Skeebo]

So, you didn't answer the question of the hour........    Are you going to model the entire span? Inquiring minds want to know,

      Jim Semikoski

[dcutting]

Haha that's still TBD. I'm going to start by building one of the through trusses and see where the project takes me from there.

I've completed some more work this afternoon on the design. I started back over from scratch, this time I'm designing it to be etched from the get-go. Here's an end view showing the first floorbeam along with all four of the stringers. I haven't yet added any rivet detail, that will come last and take some guesswork from what photos I can scrounge up. Too bad I don't have a boat and don't live in the bay area anymore

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Each stringer is actually made up of six parts. I put two pieces of brass back-to-back so I can put rivet detail on both sides (without having to quarter-etch the material). To the stringer are added four stiffener angles, two per edge. These are also bent from 0.1 mm brass sheet material. Measuring in at just under 1mm x 1mm, but at more than 3 ft long, these are going to be a challenge to form correctly.

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[NtheBasement]

Not sure if handling 4 foot sections of etched brass is a good idea, and you have gussets anyway at the joints.  Do you have a resistance soldering tool?

[Spades]

David

Is this the drawbridge section?  In case anyone is interested Crossing the Bar: The Adventures of a San Francisco Bay Bar Pilot by Capt Paul Lobo is an easy read with a great of stories involving the  Benicia-Martinez Railroad Drawbridge.

[dcutting]

Not sure if handling 4 foot sections of etched brass is a good idea, and you have gussets anyway at the joints.  Do you have a resistance soldering tool?

Nope, but looks like I'll be buying one for this project. I guess I should break up the stringers...

Is this the drawbridge section?

Nope, I'll be starting on that one eventually. For now I want to get the longest and most complex spans out of the way.