You might ask this question on a narrow guage discussion group. I am guessing that plans have been published - you could also search the Narrow gauge and Shortline Gazette for possible plans/articles/information.
Guy
see stuff at: the Willoughby Line Site
Thank you both!
DJ&A completed a laser scan of the historic bridge and generated a computer model of the structure to support the Park Service’s efforts to make repair recommendations.
Cimarron Train Trestle Repair - DJ&A, P.C. (djanda.com)
Also, Wiki says that instead of being 120 feet "Crossing the turbulent Cimarron River just upstream from its confluence with the Gunnison River, the trestle replaced a wooden trestle built during the route's construction in 1882. Originally 288 feet (88 m) long, only the central span of it remains today. "
Is that the trestle at Cimarron, Colorado? I would suggest contacting the Colorado Railroad Museum in Golden. They have extensive archives.
https://coloradorailroadmuseum.org/library/
https://www.nps.gov/cure/learn/historyculture/cimcanyonexhibit.htm
So, this is probably going to be a weird one, so let me preface this with an explanation. I am a 3D artist, and currently the lead modeler on a game project that centers around recreating historically accurate narrow gauge operations in the US. Everything we're building is built as it actually existed in the world, using various sourced diagrams and plans. Recently, we found ourselves needing a good metal deck truss bridge... but we ran into a problem.
While we have plans that give us the general layout of the bridge itself, and photographs that can be used for detail references... we don't have anything that gives specific dimensions. Such as the length of certain parts, or the dimensions of the bridge itself, beyond stating that as built it was 120 feet long. That honestly doesn't give enough info, and well, it's making creation of this particular bridge rather difficult.
Would anyone here be able to point me in the direction of a diagram of this bridge, that actually has all the info I need?