MTH has sold this model bridge for years. Has anyone seen an actual railroad bridge like this one in the U.S.A? (Overseas you may see something very similar.) This would be considered a bow string truss.
Photo from MTH website.
As a student of bridge types, I haven’t seen one like this on a mainline or regional railroad. If it needs a pier in the middle it would be considered a poor design for a truss.
Strong bridges. Two being installed in place of these two on the Roseyville Division of the NS.
[;)]
Couldn’t find any examples of RR bridges.
Did find similar examples in Pittsburgh, PA and London, Ontario, as well as the double span connecting Cumberland, MD with Ridgely, WV.
And yes, the middle span is a little redundant.
I was able to locate one in Cerritos, Ca. (Note does not use the center truss).
The middle pier is not just redundant, it’s harmful. A truss like that is designed with the assumption that it will be supported only at the ends. When you fix the location of a third point, the truss becomes “statically indeterminate”; and truss members can easily be overloaded with no actual load on the bridge.
I had a problem like that when we built our house. I designed 20-foot-long trusses for the second story floor. The trusses (as is usual) had a camber to keep them just clear of the intersecting first-story walls. The framers believed that they were helping by nailing the trusses to the walls below. They would nail during the day, and I would pull or cut the nails in the evening. They tried to put the nails where I wouldn’t see them; but I think I got them all. (My technique was to touch either the truss or the wall and then bang on the other with a hammer. If I felt the hammer blow, I knew there was a nail in there somewhere.)
We have a couple of bowstring-truss bridges in Austin, but for roads, not railroads. I found a web site with a searchable bridge catalog. It returned no bowstring railroad bridges for the entire US.
Old pic of the Brewick to Nescopeck Pa. Bridge over the Susquehanna.Cica 1910.
laz57
I always thought that was a more European design. Seem to remember Polla or one of the other overseas manufacturers making them in HO years ago. Atlas had them for a while too.
http://www.toysperiod.com/atlas-887-ho-curved-chord-truss-bridge-nickel-silver-pi-79.html?invis=0
Interesting responses.
Laz, that is not a bow string truss.[:(]
Don, fire your structural engineer tomorrow.
Bob, you are absolute correct and I have never found a bowstring truss used for a railroad bridge.
Fife, are you referring to the Smithfield Street Bridge? It used to have a trolley track, but it is not a bowstring truss. It is called a lenticular truss bridge. I have been over it a dozen times. The tracks are gone now.
The bridge that Atlas sells is a model of the old NYC bridge across the Wabash River in Lafayette, Indiana. The Lionel bridge that the Chief has is a generic truss bridge. So what did MTH model their bridge from??
Buckeye,
It looks to me that MTH simply took a box truss, curved the top, adjusted the supports, and then removed 80% of the top.
I’m no engineer, but that is what it looks like to me. [:)]
88… When you are at York, would you ask MTH what they were thinking and where a prototype is located? [swg]
Anybody found one yet?
Nope.
Here is the closest I’ve found. I’m familar with the bridge in this link.
Scroll down to fourth picture.
http://www.johnweeks.com/river_mississippi/pagesA/umissAR09.html
John, That’s pretty close, but the ends of the MTH bridge are vertical. Your Mississippi does have X bracing on the side.
Here is the closest thing I have found and it is not in the USA, but in Austria across the Danube. It is slated for demolition. It is over 100 years old and carries rail and road traffic.
http://thebridgehunter.areavoices.com/files/2012/05/Linz-3-1024x680.jpg
Another in Germany.
After studing this photo, it is really close. Plus Wolf is a German name.
http://www.flickr.com/photos/80355464@N05/10330623276/in/photostream/