Bridge help

[izzy]

I've tried scratchbuilding a bridge on a 18" radius curve. I use wood but have no idea how to form it to the curve. Is there a way I can do this or do I need to buy a kit.

Thanks

[IRONROOSTER]

What type of bridge are you modeling? Many curved bridges actually were made up of small straight sections.
Enjoy
Paul

[frisco kid]

I have had the same problem and solved it by scratch building with wood for the base, deck, floor portion or whatever it should be called.. I used a couple of sections of  18 degree sectional track as a template to cut the wood in the proper radius. I then laid my cork roadbed down and then the flextrack. I am using WS abutments and another supplier, I can not recall right now, for other detail parts. There is a article in the last issue of MR, October I believe, that gave me some help. I used the sides of a couple of Atlas thru girder bridges and yes they don't curve perfectly but by using two pieces it looks ok to the untrained eye. Good luck

[ARTHILL]

Iron rooster is almost right, there are NO curved bridges on railroads. They are all short straight bridges connected together at a slight angle. The trick is to make the straight sections wide enough to put the curved track on top. Thus on the ends, the track in on one edge of the bridge section and in the middle the track is on the other edge. The shorter the sections, the less extra width you have to add. To use a good flexible bridge track gives a very nice look.

For stringers, the same applies, short straight pieces angled to simulate a curve. Then the track lays on top. Kalmbach's bridge book gives some prototype ideas, but I just use short sections butted together, for that part doers not show unless this is for a contest.

Good Luck. Show us what you get.

[E-L man tom]

A few years back, I scratchbuilt a plate deck bridge on wooden stringers and bents. What I did was take the two stringers (in this case, wooden strips cut to length). I wet the stringers and bent them, keeping them in that "formed" position until dry. I was then able to glue the stringers on top of the bents. I then placed the deck over the stringers. For the curved track, I took a piece of flex track and removed the ties where it was to go over the bridge, bending the track to the desired curve and glueing the rails ro pre-placed ties made of strip wood. Use an NMRA track guage to get the guage right before the glue dries. CA glue works the best, I have found, only you have to work fast. Good luck!

[Pruitt]

Iron rooster is almost right, there are NO curved bridges on railroads. They are all short straight bridges connected together at a slight angle.

Not totally true, Art. While most bridges are as you describe, one stand-out exception is the stone arch type of bridge. These are true curved bridges, as you can see in this example: http://maps.google.com/maps?ll=44.980833,-93.253611&spn=0.01,0.01&t=k (the bridge is the narrow one in the center of the view. It curves at the left end).

[ARTHILL]

Brunton, you are of course right. We have a wonderful example right here in Minneapolis. The Twin Cities Club has a fabulous model of it on their layout  and it is shown in DPB vol 5. There are also hyway bridges with curved concrete spans and I assume that sooner or later they will try one on a railroad.  My error of course was to not consider a stone arch viaduct a bridge. My error.

[dknelson]

Actually the Walthers catalog shows several bridges, some of them European, intended for curves.  I suspect some of the actual wood craftsman kits would be a challenge for a beginner, but the plastic Kibri or Faller or whatever bridges should be pretty simple. 

Dave Nelson

[tgindy]

This month's October 2006 Model Railroader has an article called "Bridge Basics" that outlines this specific subject among other bridge topics. There is a nice picture showing a curved track with many connected (tangent and straight) through-girder bridges.

This is only four sentences from the six-page article...

[1] "You must support both ends of a beam."

[2] "Beam supports are where too many model builders get it wrong."

[3] "Each end of each girder on a through truss bridge must be connected to a cross member that is, in turn, tied to the main truss at the end of each panel."

[4] "The rails on a curved bridge can't arc outside of the supporting beams or girders placed under the ties."

There is a section on "modeling bridges" and suggestions of materials, models, and how to connect the bridge components. This issue with 13 diagrams/pictures is still on the newsstands.