Need Info on building a large bridge

[Chessie System]

I am working on plans for my next layout, I am going to model an over and under 4x9 like I had when I was a kid. This is just something for under the Christmas tree and maybe to take down during the year to play with a bit but I want it to be a very nice looking layout to take away from the fact that its just a twice around.

My layout as a kid had the Tyco bridge pier kit raising the track to make the bridge, I would like to do the same thing but I want to model a complete truss style bridge, the kicker is it has to be a curved bridge. I am very good at this kind of challenging stuff and really want to scratch building this piece, however I would like to read up on it and maybe check out pictures and articles on this type of bridge.

If anyone has any info to get my mind started, I would appreciate any help given.

[ndbprr]

No one makes a curved truss bridge and I don't even think a real one was ever built.  There would be no way to support the load that wasn't centered on the bridge piers.  The way the prototype would go about it would be to make a series of wider staright bridge sections and curve the track on them.  The Atlas truss bridge turned upside down is called a Warren truss ( I think).  You could space the sides wider and do the same thing.  Bachman years ago had a very short truss bridge that you might be able to modify also.  Central Valley makes a long one but it would ne a nightmare to modify I think.  I am also assuming you are working in HO.  If I were going to do what you are trying I would make a ballasted deck girder bridge and cut the deck out of something like a 1" x 6" piece of wood and glue false sides on it.  You would be the only one to know it is phony.

[Chessie System]

I want to make something like this kit http://s229.photobucket.com/albums/ee177/turbo231/?action=view&current=mdp79.jpg but I want to have a wooden deck under the track and wooden tiers to support the deck instead of the cheap plastic oned in this kit. I will obviously have to make this myself, I know it may have never existed in real life but I am not going for that.

[ndbprr]

Ok.  That's not what  I thought you asked for before.  You can do that by building a  a series of wood bents to hold the track.  The easiest way to do that will be to buy some strip wood at a hobby shop and stain it all before beginning.  Then  make a jig or fixture to hold the pieces while you glue them together.  After they are glued you can use a razor saw to cut them at the different lengths you need to slip under the track.  there are many case of just such a structure including one outside St. Louis to raise a track up to cross the Mississippi River on the Illinois side. In that case it is called a bridge approach. 

[Autobus Prime]

CS:

A stone arch with a truss at the point where the two tracks crossed would look nice.

Essentially, the over-under kits are trestle bents without the longitudinal deck and stringer members. Trestles aren't very hard to make, if they are a little tedious. You could even use the plastic over-under bents, then put stringers on top to support the track. Place some crossmembers under the track to support walkways on both sides, and most people would probably not notice that you cheated on the bridge ties. I'd let the track start out on an 'earth' embankment until it got about 2" high. While a prototype RR would likely have a fill for the whole thing, they might not. It all depends what was easiest to do at the time. For you, a fill might block a view that you might not want to obscure -- but of course you can also use this to advantage.




http://www.trainweb.org/oldtimetrains/OSR/OSR181_506.jpg



Another option, if your tracks are in an urban area, is to build steel elevated trackwork. This is basically a series of girder bridges on steel towers. Manhattan's West Side freight line was an example of this.

[jwar]

Perhaps Kalmback's Model Railroad Bridges and Trestles would be an excellent read for you. Decide on how high and long and if into scrach building, may I sugest on only using one long bent jig, then you can make various lenght bents and all cross bracing will be uniform. I have scrach built a few bridges and they are a lot of fun to build, especially for that first train over them. LOL...John

[ARTHILL]

There are no curved bridges. There are only series of straight bridges attached at a slight angle to support curved track. With stone arches or wood trestles, these straight sections are much shorter than with the steel versions.

For any curved track on a bridge, the key is to make the straight sections wide enough to hold the curved track. On my curved trestle, I have a straight through truss in the middle and it took some planning to get the bents near the truss wide enough to match up. I found the planning half the fun. Well not half, but some.

[ndbprr]

Many wooden trestles were built that were curved.  It is with the advent of steel bridges that railroads straightened things out.  That was the mistake I made in understanding what is to be built in the original post.  What he wants is a series of wood bents for the bridge approach on either side of a small bridge at the top over another track.

[Chessie System]

I found a how to video to make the wood supports http://video.google.com/videoplay?docid=-8336067635443965466&q=Building_trestles_2b.mov&total=2&start=0&num=10&so=0&type=search&plindex=0

Looks like a good way to get started, however I have to finalize my track plan and start building. I am looking foward to this layout, going to be awhile until it gets started though....