I have a couple of questions about railway bridge design. 1. What is the center to center distance of a double track on a bridge? 2. What is the size of a railway tie used on a bridge. This is important as I want to set the distance from the top of stringer to the top of floor beam to a reasonably accurate height. Your help is appreciated; Rick
I'm guessing it depends on what type of bridge you are considering, the age of the bridge, and the region you are modeling. There are many factors to consider. If you are modeling a particular railroad, you might be able to find old construction drawings on the internet to refer to. One great website with a trove of old archives is George Elwood's Fallen Flags Fallen Flag Railroad Photos (rr-fallenflags.org). If you find something of value consider tossing a few bucks his way to help support this terrific resource.
if you are an NMRA member you can get pages of excellent bridge design data and drawings including thicknesses of material under legacy data tab worth the price of membership itself I am building 4 different bridges this year and will use these sheets extensively
bridgehunter.com is another good bridge resource with reference photos and other geographic information. You can buy bridge ties in various scales, Walthers and Central Valley make HO versions, and Micro Engineering may have one in N scale. Any kind of dimensional data is going to be dependent on span and capacity, so it's hard to give one catchall number. For the track spacing, Google Earth is actually a pretty good tool. I have been able to measure things with their measurement tool, and strangely, I find the app to be more accurate than the website. I have tested it, and gotten very accurate results for things with known dimensions like shipping containers. You could do the same thing for the bridge you want to model, as I suspect track spacing can change for different types and designs of bridges.
I think there are plenty of resources online for railroad bridges. For example, starting on page 478 of this 'google book' there is a bunch of info about the PRR bridge #458 in Chicago: https://www.google.com/books/editio...y_of_Engine/vlPOAAAAMAAJ?hl=en&gbpv=1&bsq=458 . Unfortunately the fold-out drawings were not scanned, but there are some sketches with dimensions in the article.
