Bridge on 18" radius curve

[ham99]

I have five curved bridges on my N scale layout. A Walthers trestle is the longest one. You can adapt the kit for straight or curved. The UP still has a short wooden trestle in use not far from here. The other four bridges I made from blocks of wood painted concrete grey. They can be made to any radius. I needed three really sharp radius bridges for sidings, so I traced the track pattern on wood blocks and cut them on a band saw, then sanded them smooth on a belt sander. Finally I glued on thin strips of wood to give them a finished look. E-mail me if you would like pictures.

[nbrodar]

You could also make a concrete trestle. Round styrene tubing for the legs and square or rectangular tubing for the top and cross braces.

Nick

[GMTRacing]

Vollmer makes a curved truss bridge - its in the Walthers catalog and other places. It will work fine if you raise the track up to about the level of the walks on either side of it. Length is 7" aprox through the centerline of the arc. Hope this helps - you're not the only one to work yourself into a corner. [:D] J.R.

[colvinbackshop]

I have a similar situation where a logging shortline (Sawyer Lumber) crosses the Main (DM&IR).
I took an Atlas Warren Truss bridge that I had gotten in a "buy my old layout deal" and cut it in half, down the center. I then measured what clearances I needed on the logging line and widened the bridge to accommodate that traffic, with a strip of .060 styrene.
After painting it all up, adding a strip of "stripwood" as a curb, for a ballested deck bridge, I installed it with the 18" curve running through it. It looks good and works great!

[Anonymous]

If the clearance under the bridge is adequate, I recommend the HO scale MEI 30 ft deck girder span bridge. A steel span suits the era and it can be built with an open deck which the railroad would likely do to save money. If the 30 ft span doesn't provide an adequate span, then look at the 50 ft version. - C-Bridge

[canazar]

If the foam allows yuou to do this and the "canyon is deep enough, I would suggest getting an Atlas plate girder bridge and turnign it upside down and useing that.

They come with a peice of track all ready on the bottom, and it is aroudn 9" in length. But it is close to 3" wide and the bottom of the bridge is pretty smooth. And cut the plastic to fit and even shape. Maybe be the quickest and cheapest fix while keeping something that looks good and modern design.

Hope the idea helps.

best of luck

John

[Anonymous]

A wooden trestle may not be totally out of place on a layout in the mid-90s. Considering you only have a 4x8 layout I am going to guess you are not modeling a Mainline or even secondary route. There are a few branchlines out there today still with wooden trestles and in fact, on the shortline I work on, one of our lines still has two LARGE wooden trestles. Of course if you do use wooden trestles I would suggest staying away from running some of the larger cars or heaviest frieght but.... you can run some heavy frieght IF you were to use "idler" cars. Idler cars were nothing more than empty boxcars or flatcars that railroads would put on a train running over bridges with load restrictions. The "idler" cars would be placed between the loads therefor allowing the train to carry some heavy loads. In some cases the "idler" cars were even placed between engines but, the cars would have the equipment on them allowing the engines to be MU'ed. That being said, most branches using idler cars dissappered in the 60s and 70s. You'll be safe running most 4 axle power and anything below a few coal hoppers if you do decide to go with a wooden trestle. Or go with the idler car idea and add an operational challenge to your railroad

[blubryexp]

Following up on John's comments-There is a triple straight span, curved track , steel bridge about 8 miles from my home. Been there for over 80 years.
Have a similar situation. An older Walthers catalog lists a double track steel truss bridge (#200-764) that you might be able to use. An 18" radius track has about a 9" chord length. The bridge is 16-7/8" long. Maybe it could be modified. Also,use a section of Flex-Track?

Jean B.

[Anonymous]

Have a look at MRR Magazine's "Carbondale Central" Feb 1988 Page 83. They had exactly the same situation with 22" & 18" radii tracks on a curve. The article even has a diagram on the how-too's. If I had a scanner would have posted a link....maybe somebody else can?

Remember...."You ain't stuck.....till you're really stuck"

[John Busby]

Hi all
According to an article in Model Railroader years ago a curved bridge is a
series of straight ones arranged to follow the curve with curved track on it.
So it will need at least one or two piers in the middle and two or three straight bits it
may look a bit strange but that's the way the real ones are.
Remember car over hang when you build it or the cars will hit the sides.
I would suggest one of those 90' monsters as a test car you never know what presents for the train set relatives will buy and you will have to use them when the relatives are around
regards John

[chateauricher]

QUOTE: Originally posted by leighant

Wood trestle is good idea, though not especially modern.

Nothing says you can't build a steel trestle. [swg]

You can follow Harold's (hminky) instructions for building a trestle; but use plastic or brass I-beams from your local hobby shop instead.

Or...
Search out ready-made plastic "steel" trestle bents.

EDIT : Model Railroader magazine is introducing a new book The Model Railroader’s Guide to Bridges, Trestles & Tunnels. So, if you want to get more ideas... http://www.trains.com/Content/Dynamic/Articles/000/000/006/255bazen.asp

[bogp40]

Check into Central Valley and MicroEngineering Plate and Girder sections or bridges. The CV double track plate should be wide enough for single track 18" radius. You can do it as a see through or ballasted deck. These types of bridges would be proper for the 90's era you are modeling. One note about the curved steel bridges. Wood trestles were often built to the curve as are steel bridges and viaducts, however the timbers of the wood bridge are straight same as the girders being straight on the steel. It would be very rare that steel would be bent to a curvature for a bridge. the beam would lose it's strength and have lateral movement.
Bob K.

[leighant]

Wood trestle is good idea, though not especially modern.

Another OLD idea but one from first days of railroading that remains serviceable after more than a century-- the masonry ARCH bridge, which can be on a curve. If you are modeling today's railroading on a right of way built in 1850, this would be appropriate. Concrete rather than stone would be more modern.

Bridge frame can be as wide as it needs to be to support the curve. On a club layout, we once had one end curve crossing another end curve at a shallow angle. No place for supporting pier under the end of the span. We had the end of the span supported by a beam which crossed to lower track to a pier at each end... in effect, it was a crosswise support bridge holding up the lengthwise railroad bridge. Yes, it had to be scratchbuilt.

[ondrek]

Ok, I found the pics of it, if they dont do enough explanation, let me know and i will have to take some new ones after the kids go to bed.

http://www.vermontel.net/~kevin_ondre/HO%20Train/curved%20bridge01.jpg
http://www.vermontel.net/~kevin_ondre/HO%20Train/curved%20bridge02.jpg

Please dont pick on me about how simple the scenery is, the layout was built for my son who was 2yrs old when i built it. at 5 he still uses it.

Kevin

[Cannoli]

Sure, I'd like to see pics of the completed brige.

[ondrek]

I built my son's layout and it has a curved 15" radi bridge.

I took 1/4" plywood, drew out the whole curve and cut it out. I then bought two of the Atlas girder bridges, I did not use the base of the bridges, I just used the side parts. I wamed them up and bent them and with glue and nails attached the platic griders to the sides of the 1/4" plywood. my bridge was much longer than yours, I used two kits. It came out fairly well I think.

I can get pics if you want, I dont have them with me, but i can get them tonight when at home. if interested.

the trestle bridge is a good idea too, but not sure if it would fit in your 1990 era if you are picky about things like that.
Kevin

[Anonymous]

I would either go with the trestle, or build a ballested deck plate girder bridge. Make sure you've got the girder far enough apart to clear your longest motive power and rolling stock, and use a piece of foamcore/cardboard/wood/sheet styrene between them for the deck. You could also use shorter girders, to give the bridge some curcature, similar to what I think selector was saying.

[selector]

Harold has the right idea. Trestles were often curved, probably most of the time in order to follow contours as closely as possible.

A straight bridge over an 18" curve will have to be very wide to avoid collision with longer cars, such as passenger cars. What you might do is cut a straight bridge in two transversely, and then build a wedge into the wide gap if you place the two pieces in such a way that they more closely match the curvature. Use cardboard stock or styrene. Even wood would be great..better than carboard.

[Cannoli]

QUOTE: Originally posted by hminky

I have a short web article about making this trestle at:

http://www.pacificcoastairlinerr.com/4x8/trestle/



Thank you if you visit
Harold

This will work perfectly, thanks!

[hminky]

I have a short web article about making this trestle at:

http://www.pacificcoastairlinerr.com/4x8/trestle/



Thank you if you visit
Harold

[Jacktal]

Curved bridge in kit...I don,t think you could find this,specially so short.Atlas makes small girder bridges this small but they're straight.You'd need to modify your curve both sides to accomodate this.

I've seen pictures showing straight bridges that were wide enough to allow some degree of curved tracking on them.I guess it was for simplified engineering and it gets the job done fine.If you absolutely want a curved bridge,you could build a short threstle or a viaduct.

[Cannoli]

OK so I made a big blunder in my layout, I placed a bridge over a stream on an 18" radius curve. The foam is already cut for the stream but now I'm not sure of what type of bridge or who's kit(s) I should use to build it. It's not very long, about 5" but because of the tight curve I see a challenge ahead of me. I'm modeling the mid 90's but I'm not picky about bridge type. Thoughts?