working with foam below your track

[railBuilderDhd]

Jeff,

First, let me say I'm not bothered at all with the post. In fact, I'm happy to see this. Your bride is much like one I'm designing now in my head and figuring out how to support the bride as well. I would love to see how you did the support with the music wire. Why did you use the music wire and not just the support of the I-beams that could be the support.

Feel free to start a different post or carry on here.

Dave

I think thin metal alone would be less sturdy than the combination of foam on plywood. Unless the metal was fairly thick, it seems to me it would flex a lot, whereas the foam/plywood construction is solid and stiff. I suppose something like 1/8-inch aluminum sheet could work if properly supported, but the hassles of shaping it and drilling it would discourage me from trying it.

It just so happens that I have a long bridge over some tracks on a different part of my layout:

Here is later, more finished view:

Although it's not real obvious from the photos, this bridge is gently curved. I kitbashed it from Walthers through plate girder kits. The I-beam supports that appear to be holding up the bridge are for cosmetic purposes only. I built 1/8-inch steel music wire into the structure of the bridge which makes it totally self-supporting. The I-beams are just for realism, although I'm not sure how prototypical they are! Somewhere there is a prototype for everything, right?

- Jeff

P.S. - I apologize to Dave (railBuilderDhd), the original poster for this thread, if I have contributed to taking his thread off-topic.

 

[jdetray]

Hi Dave -

The bridge is kitbashed from four Walthers through plate girder kits. Because the bridge is curved, it was not straightforward to attach one bridge section to the next. When I finished the bridge, it was somewhat fragile. I knew it would be a while before I got around to scenicking the area beneath the bridge and adding the I-beam supports, but in the meantime, I wanted to run some trains! I decided to add some type of reinforcement so that the whole span would be strong enough to stand on its own without any supports.

I knew that many bridges serve double duty by also carrying pipelines of various types. That's when I got the idea of using the 1/8-inch music wire (also known as piano wire). It would give the bridge structural integrity while also simulating pipelines. In the photo below, looking down on a portion of the bridge from above, you can see the two "pipelines" beneath the deck on either side of the bridge:

This made the bridge quite sturdy without the I-beams, and I was able to run trains without fear of a catastrophic bridge collapse!

- Jeff