I would think you would want to put a plate girder bridge there (not a deck plate like Colonel's), due to the clearance under the bridge. When there is limited clearance under, railroads usually use a plate girder or truss bridge. I also agree w/ Derek - a wooden trestle wouldn't fit there as nicely as a metal bridge would. I like the idea of a combination plate girder and truss bridge. You could use an Atlas truss bridge and then kitbash/cut up a couple of plate girders and have a cool bridge. Each of those bridges are only about $3 each so you could do it relatively cheaply also!
Something like this? Or actually the right side 1/3 portion could be underneath (since I have the clearance) like a warren deck truss or deck plate girder (hope I said that right)? I might end up like that kooky bridge after all! [ 09. October 2004, 01:41: Message edited by: nscale_lover ]
Looks good to me! I definitely like the variety. Except I would make it assymetrical. Like shove the through-truss to one end or the other. Depends on what kind of history you want for it though. Maybe it was originally three through-trusses but as they deteriorated they got replaced with girders. Often, big through trusses are built with smaller girder approach spans, similar to the picture shown in the link, so maybe I would put the through truss on your longest span. (It's from a google image search...I can't cite it from anything) http://www.trainweb.org/pa/hughesville01/pages/0014-cab-forward.htm
While we're on the topic...Where do you get those cool bridge abutment feet? The pin/roller under the end of truss and girder bridges linking the bridges to the abutment? I assume it came with whatever kit that is...
LOL I guess that was my first scratchbuilding project, the pin roller under the truss is actually a cut down section from a tootpaste container Here is a closer shot [ 09. October 2004, 07:13: Message edited by: Colonel ]
Within a bridge you need to keep a reasonable consistency of span length to span type, or it will look wrong. Generally a truss is only used when the span gets too long for a plate girder - usually over about 150 feet span (down to 100 ft for older bridges). Or looking at it another way, you effectively start cutting holes in the huge plate girder to keep the weight down (see also centrebeam flatcars). So in Mike's picture at the top of this page the truss should be the left span and the plate the middle. The one shown for the right hand span would be OK for variety if you really have enough clearance below (is that track much lower than the others?), else it could probably be a through truss or plate girder. If a through truss then if the span is shorter than the other truss, it would likely have a lower height as well.
The outermost lower track is 1/2" below the other two... so I do have some extra room there From left to right, span measurements are 9" - 4" - 7 3/4" (hoping my N scale conversion math is correct, that would be 120' - 53' - 103') And with the suggestion above, I'm guessing something like this: Colonel, why only 1? And where would you put it? [ 09. October 2004, 18:13: Message edited by: nscale_lover ]
Mike, I depends on the length of the truss bridges you decide to use but personnally you want to be able to see the trains and have access under the bridge in case of derailments and believe me thats where they will happen. I do like your latest option with the two truss bridges and the single girder bridge
Mike, that looks good. Don't forget they will all be skew spans, as was mentioned in an earlier post I think (can't find it ). Ie: each side has its ends on the supports, so the two sides are staggered. It is possible to have sides different lengths, but it gets messy. I'd suggest you bring that right hand abutment round so it is parallel to the track.
Actually the abutment you see is perpindicular to the bridge, and the one to it's right (that you wouldn't see if it was there) will be parallel to the tracks. With the way the flyover is set up, that's basically the only way it can happen, unless I build up and extend the groud back to where it was (you can see the patch of lighter area not yet painted) in that last pic. But I kinda like it open like it is.
Why not something like this? Having the lower track go "through" the middle pier (actually between two separate piers) avoids the need for extreme skewing on the bridges. The piers could be extended out to the sides to resist lateral stresses; I've tried to indicate that the "feet" of the piers extend out past the tops, but it's a bit hard to show in 2-D.
Very nice... I like the idea... I see the feet with no problem. Would the trusses be of same height? Or the one on the left a bit taller due to longer span?
Actually, as drawn the right truss is a bit longer than the left, but they're not very different. I imagine the design could go either way, depending on how difficult it is/was to make different-sized truss members. On one hand, if the left truss could be built with (for example) six panels (is that the right term?) and the right truss could be built with seven identical panels, it might be cheaper and easier to "overbuild" the left truss a bit to share design elements. This would be especially true if the railroad had standard designs for particular ranges of lengths (i.e. "all E-70 truss bridges between 100 and 125 feet shall use these dimensions"). On the other hand, if each bridge is an independent design, the right truss would probably be built a bit taller than the left. So as I said, it's something of a judgement call. (Caveat: I am not a civil engineer, nor do I play one on the Internet...
I meant right....not left Can you tell I'm lysdexic? Pretty soon I'll need a pair of them "L" and "R" shoes... (NOTE -- ALL PICS MOVED TO NEW ALBUM IN RAILIMAGES - WILL SHOW UP AS RED "X"s UNTIL I RELINK) [ 12. October 2004, 01:24: Message edited by: nscale_lover ]
I'm not sure how to fix it but I would definatly fire / sue the survey team that got you into the mess.
You could go with something similar to this: http://www.walthers.com/prodimage/79958988/47968263013136.gif Using your exsisting ideas for the actual bridges, but use these types of piers. You are going to be more realistic if your piers are as close to 90 degrees to the bridge as possible. With this style of pier, the pier fondations don't have to be under the bridge. This system is widely used on elevated transit sytems in big cities.
