Curves on a Bridge revisited
- Thread starter Rico
- Start date
Alcomotive
Grandson of an ALCO Builder
Interesting! Very cool....look forward to seeing the other pics you! When you develop them do you get them on a CD?
Maxitrains
Member
I think I might have asked such questioh, cause I have many bridges on curves. I would like to add this too, are bridges like the above found curved, or they are only widened to accomodate a curve?
I bought two sets of bridge plates to make such bridge, and I curved them to take the shape of the track. Did I do wrong ? I never saw how such bridges are made and even if I checked on internet, there might be no photos to fully explain how they are!!!
This is how I made it, even though I still have to break it apart again cause it came narrow
I bought two sets of bridge plates to make such bridge, and I curved them to take the shape of the track. Did I do wrong ? I never saw how such bridges are made and even if I checked on internet, there might be no photos to fully explain how they are!!!
This is how I made it, even though I still have to break it apart again cause it came narrow
Selector
Well-Known Member
There are no really curved decks or girders. Instead, such bridges comprise segments of straight decks with planking or decking of varying dimensions to allow for a generally curved function.
In the case pictured above, the deck is undoubtedly wider than usual, perhaps by as much as 6' to keep passing engine parts well away from pedestrians and the girder flanges. Of course, it depends on the degree of curvature. The view above is foreshortened due to the low angle. If the actual deviation from tangent at the centreline is only 1', they may have gotten away with a standard bridge size.
In the case pictured above, the deck is undoubtedly wider than usual, perhaps by as much as 6' to keep passing engine parts well away from pedestrians and the girder flanges. Of course, it depends on the degree of curvature. The view above is foreshortened due to the low angle. If the actual deviation from tangent at the centreline is only 1', they may have gotten away with a standard bridge size.
Maxitrains
Member
So you mean that I have to rip that bridge apart again and make a straight one, but wide enough to hold that curve and my long SD40-2 ? that will be a really wide bridge to make :S
The lower curve in the picture can give you a slight idea of teh curve I have to tackle for that bridge.
The lower curve in the picture can give you a slight idea of teh curve I have to tackle for that bridge.
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Curved viaduct bridges like the one the rear of your first photo are common and they usually followed the curve of the track. Curved plate girder bridges, like the second bridge in your photo, would almost enver have been used. It's basically impossible to maintain the girde strength when it's curved and making a piece of steel that size in the right degree of curvature is very difficult and expensive. The way the track curves off the end of your wood bridge but the birdge it self is straight is the most common way to handle curves on bridges. What you have to do is make the bridge deck itself wider but straight so the straight girders will support the deck structure, as seen in Rico's picture.
Rico
BN Modeller
Having problems with the 2nd pic for some reason...
Alcomotive, I sometimes get them put on CD but this many would break me!
Maxitrains, could you get away with a trestle built on a curve?
I have pictures of a mile long steel viaduct coming out of the Shaughnesy (?) Tunnel that has "curves" in it, I'll try to post them later.
Alcomotive, I sometimes get them put on CD but this many would break me!
Maxitrains, could you get away with a trestle built on a curve?
I have pictures of a mile long steel viaduct coming out of the Shaughnesy (?) Tunnel that has "curves" in it, I'll try to post them later.
Maxitrains
Member
The Viaduct and the Trestle are not my problem, the Problem is mostly for the grider. The right end of the Girder will be pointing into a hill / mountain tunnel, which right now is not indicated, but were the crew cabin of the SD40-2 in the 2nd picture is, will be a tunnel. So now I ask you, is that girder adequate for sucha place, or should I do something else instead? One thing I should make you notice, I was working on such bridge, cause I do not have any space to spare below, since the space is very tight for another train to pass under it ( as shown in the following picture )
Maxi, the picture that Rico just posted is a through truss type of bridge and you can once again see that deck of the bridge is made wider to accomodate the curve. It would be the same concept whether you used plate girders or a through truss type of bridge. You just nned to widen the deck so the train doesn't foul any of the bridge parts on the curve. Then you make a series of straight bridge section to hook things together. OTOH, since it's not very likely that you're going to get a lot of railroad bridge experts looking at your layout in Malta, you can just leave it alone and use the curved girders.
Doc Holliday
Gentleman Gambler
While it might technically be "wrong" I did the same thing. I needed a bridge that would support a switch on a curve and didn't want to use another trestle. I found a prototype pic on the net and came up with this. I don't think it looks too bad although rivet-counters have labeled it and my other two bridges "distracting".
Doc
Doc, I think that girder bridge looks pretty impressive, even if it's not quite "right" from an engineering point of view. It's not impossible to make curved girder bridges, just really expensive. Tell them your railroad had money to burn so it built the kind of bridges it wanted.
Selector
Well-Known Member
Trestles appear to be curved overall, but in fact they comprise no curved timbers or milled lumber. All elements are straight, although they may be placed in such a way that the function of the resultant structure is 'curved'.
Take a look at this site to see that a deck on a "curved" trestle is not really curved, but is instead straight timber in straight segments between bents that have their transverse axes slightly off parallel to each other as they would be on a tangent track trestle. Scroll about halfway down to where they mention a curved trestle deck and see the insert at left that has a diagram of the way the stringers are placed.
http://members.cox.net/sn3nut/trestles part 1.htm
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Rico
BN Modeller
Doc that is an impressive series of bridges!
Here's a viaduct from the CPR Cranbrook Sub, East approach to the Shaunessy tunnel. It must be at least a mile long, 20 to 50 feet high on the North side, and 50 to 150 feet high on the South!
It's steel beams on concrete pillars.
Might be just what Maxi needs?
Here's a viaduct from the CPR Cranbrook Sub, East approach to the Shaunessy tunnel. It must be at least a mile long, 20 to 50 feet high on the North side, and 50 to 150 feet high on the South!
It's steel beams on concrete pillars.
Might be just what Maxi needs?
Maxitrains
Member
The bridge that I need has to be clear from below, since another train has to pass and there is very little clearance as you can see from the photos I posted.
MilesWestern
Member
Maxi, why are you torturing yourself with all these tight clearances and trying to run modern (tall) equipment~? It seems like an exercise in frustration, frankly. Why not model an earlier era with smaller equipement, or plan a better layout in the same space without the insanely unrealistic trackwork? I don't mean this offensively at all, I'm stating a fact here. Would a (modern)railroad use industrial trackage sharp curves and steep grades to loop over itself?
Maxitrains
Member
hehe, nice try Miles I've been working on and off on this layout for the last 6 years, with only this result, if I start allover again, my grand children will probably see it ready. Actually i started this scenery to make a mountainous area, in the era of the 50's - 70's.
I've been working on and off on this layout for the last 6 years, with only this result, if I start allover again, my grand children will probably see it ready. Actually i started this scenery to make a mountainous area, in the era of the 50's - 70's.
Maxitrains
Member
Jos, yours is a good idea, but I forgot to tell you that from under the wooden bridge turning down heading under the girder, there is a river, so I cannot block its path. I will try to post a picture on how it should look like.
Sorry I'm not a painter
Sorry I'm not a painter
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