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My layout plan is currently for a switching layout set in a city. I have a curved mainline heading into my Union Station that I would very much like to have a road go under so the scene looks more cramped and citylike. But, I have had trouble finding a bridge that fits my needs.
So what I need is a bridge that:
1. Can carry two curved tracks of around 23" radius (I'm probably going to be using shorter passenger equipment)
2. Fits the modern era (probably the newest locomotive I'll have is a Dash 8, anything from then to now works)
3. Fits in a city
4. Is priced within reason (I'd have to say I'll spend at most $70 or $80 on this bridge, including stuff to kitbash with if necessary)
5. Makes sense with a road going under it
6. Looks somewhat realistic
Micro Engineering makes a through girder bridge that would probably do, but you would want to cut them in half as described, and also you would need two of them since their decks are intended for single track. But it would look prototypical and cool. It is not atypical to have twin through girders instead of a wide decked single through girder.
I tend to go with the suggestion from Beachbum. How the track surface itself looks probably isn't important, just how the sides and abutments look to the viewer. Some Atlas girder plates and styrene to constuct the abutments would make up into a good looking bridge. You could either make one double track bridge or two single track bridges, side by side. As Crandell said, this isn't uncommon in large cities since a single double track bridge takes up more real estate than two singles. The two bridges also give you more structure to make it look like the road disappears beneath the bridges.
If I recall correctly, there are metal "pans" under the tracks on the decks and no ballast but ballast between the pans. I haven't been on BNSF / METRA for 2.5 months though so I might be wrong. Never bothered to take pix since I commuted weekdays for 7 years.
I tend to go with the suggestion from Beachbum. How the track surface itself looks probably isn't important, just how the sides and abutments look to the viewer. Some Atlas girder plates and styrene to constuct the abutments would make up into a good looking bridge. You could either make one double track bridge or two single track bridges, side by side. As Crandell said, this isn't uncommon in large cities since a single double track bridge takes up more real estate than two singles. The two bridges also give you more structure to make it look like the road disappears beneath the bridges.
I actually don't need the road to disappear, not at that point anyway. The track isn't up against the backdrop. And in fact, if the bridge is going to be kitbashed, I'll need something else to distract viewers from the model!
I also don't see how two single track bridges take up less real estate than on double, especially seeing as there'd have to be more space in between tracks for the girders that run in between. Two single-track bridges might cost less (though I doubt it), but I think they take up more space. In any case, that's what I want, as I want it to be a pronounced scenery feature.
As I'm thinking of using styrene for the roads, styrene for the deck would work perfectly.
Probably buying just the girders, gluing them to the styrene deck and making abutments out of styrene would help keep costs down.
I am thinking about something like a concrete art deco type like walthers makes. But then the walthers bridges arent curved. You could always make a city viaduct type too.
I probably should restate myself. It's not the bridges themselves that take up less real estate, it's the approaches. Think of how much space a double track curve takes compared to a single track curve. That problem is compounded when you have a double track curve approaching a bridge with a superstructure. You need more space for the curve easement so the train doesn't hit any of the bridge superstructure.
It is slightly more expensive to build a double track bridge than two single track bridges because the double track bridge has more weight to carry than a single track bridge. More weight means more steel for the bridge and supports, and more steel directly translates to cost. This was only true back when labor was cheap. With modern concrete bridges, one structure is cheaper. Railroads also preferred two bridges in congested areas because you could do maintenance work on one bridge and route traffic over the other bridge. With a double track bridge, the bridge would have to be shut down or track workers would have to be exposed to a lot more hazards if the other track could be kept open.
I probably should restate myself. It's not the bridges themselves that take up less real estate, it's the approaches. Think of how much space a double track curve takes compared to a single track curve. That problem is compounded when you have a double track curve approaching a bridge with a superstructure. You need more space for the curve easement so the train doesn't hit any of the bridge superstructure.
Well, if I have to use long easements, I'm definitely going with the two bridges. It's a small layout and while the bridge area has a lot of space, the rest of it doesn't. I need this curve to get my tracks into position for stations on both sides of it (as I have somewhat accelerated the pace of the scenery transition from downtown to the suburbs, I felt I needed a couple of stations other than the Union Station to make it feel right), so I can't really afford to take up much more space in really any area other than where the road will be.
@chevelleSSguy: A city viaduct won't really work in this case. It's not a long bridge, only long enough to cross over one road and that's it.
Also, in the setting I have, I just can't picture an art deco bridge fitting.
@chevelleSSguy: A city viaduct won't really work in this case. It's not a long bridge, only long enough to cross over one road and that's it.
Also, in the setting I have, I just can't picture an art deco bridge fitting.
Good point. For some reason I had thought it may have been a longer distance. Im back to thinking of an art deco style however. Around here, the most common bridges over a roadway would be a girder type with a balasted deck. Its probably the easiest to model too. You could just build the deck of the bridge any way you want and lay the track down w/ roadbed and then balast it. Then you could add steel girders on the sides. That would even work on a curved section too. Its much easier to see it in person or look at a picture of this sort of thing then type it.
Good point. For some reason I had thought it may have been a longer distance. Im back to thinking of an art deco style however. Around here, the most common bridges over a roadway would be a girder type with a balasted deck. Its probably the easiest to model too. You could just build the deck of the bridge any way you want and lay the track down w/ roadbed and then balast it. Then you could add steel girders on the sides. That would even work on a curved section too. Its much easier to see it in person or look at a picture of this sort of thing then type it.
Yeah, I know what you're saying, and that was exactly what I planned to do.
Do you think .60 inch sheet styrene will be enough or should it be thicker?
(.60 styrene is what I'm using for the roads as there are a couple of grade crossings and a paved intermodal terminal)
Maybe a couple photos would help.
This curved bridge is just down the road from my place. It was foggy the day took these shots but they're clear enough to express what has been said.
As I recall these 3 sections are filled with ballast, actually they're not all that deep.
Hmm... I'm noticing a slight dip in the bridge there, I might want to check out some more prototype photos and see if that's normal.
Though that bridge doesn't seem to be in that urban a setting, it would look right in such a setting.
Also, is that bridge still used often? I'm assuming you know better than I do about the safety of this but one of your photos appears to be taken from the tracks...
Hmm... I'm noticing a slight dip in the bridge there, I might want to check out some more prototype photos and see if that's normal.
Though that bridge doesn't seem to be in that urban a setting, it would look right in such a setting.
Also, is that bridge still used often? I'm assuming you know better than I do about the safety of this but one of your photos appears to be taken from the tracks...
The bridge is on a curving steep grade, so I doubt there's any dip, it is banked for the curve. I believe the issue here was to spend a lot of money, even the overpass for the #4 hwy is curved. It's as if the engineers didn't know that the shortest distance between two points was a straight line.
Although it's not urban yet give it a few years and it will be as it's at the present town limits. It's about 12 years old as is the highway, The old bridge is still in place and still used on the same route. After the old bridge there is a trestle this is rough country
The Spur line services a Michelin Tire plant and a Paper Mill so maybe a couple runs per day.
Are you thinking of the rail line being at grade with the road being an underpass, or is the road at grade with the trains running on an elevated structure? The former tend to be concrete structures (since they were built in recent years by the highway department) while the latter are usually steel (since they tend to be built by the railroad back when the line was put in).
Are you thinking of the rail line being at grade with the road being an underpass, or is the road at grade with the trains running on an elevated structure? The former tend to be concrete structures (since they were built in recent years by the highway department) while the latter are usually steel (since they tend to be built by the railroad back when the line was put in).
The idea is that the railroad ends up on sort of a fill at this point. But it's not a very high one and so it's kind of a combination of both railroad overpass and highway underpass.
It's intended to be an older city, so I think steel would fit better even if it was an underpass in this case.
Actually, even modern rail bridges that cross freeways are still mostly steel. They have concrete piers but the bridge structure itself is still steel. Concrete is too expensive compared to steel for the loads a railroad bridge has to support. Smiley, the next time you go under a railroad bridge in the Bay Area, look at the underside. You'll see the steel girders that actually support the tracks. The concrete is mostly decorative to blend in with the rest of the freeway bridges.
Actually, even modern rail bridges that cross freeways are still mostly steel. They have concrete piers but the bridge structure itself is still steel. Concrete is too expensive compared to steel for the loads a railroad bridge has to support. Smiley, the next time you go under a railroad bridge in the Bay Area, look at the underside. You'll see the steel girders that actually support the tracks. The concrete is mostly decorative to blend in with the rest of the freeway bridges.
In mild climate areas like California, concrete works well for bridges because it's not exposed to road salt and freezing and thawing, both of which work to destroy concrete. It's also more ductile and resistant to earth movement than riveted or welded steel. However, there have been major advances in the last 10 years in high performance concrete (HPC), which resists corrosion better than steel and requires less maintenance. It can be precast and pre-stressed for a particular location and assembled at the site, much like steel, but the HPC concrete is able to handle much higher live loads, like trains, than older styles of concrete. I expect that almost all replacement bridges in the future will be of HPC concrete. I'm just a bridge fan so, anyone who's an engineer, feel free to correct any errors I've made.
