I have to scratchbuild a bridge

Hi All,

On my N-scale layout I need a curved bridge located where the double track starts with an easement to a 19" curve.
This bridge includes the easement and half of the 19" curve.(length about 1/2')
Guess I have to build this one myself.
Any ideas ?

Paul

 

Paul Templar builds some spectacular scratchbuit bridges and trestles (curved as well as straight). That would be the man to talk to.

 

Correction :The length of the 19" curve is 15° not half an 19" curve.

Sorry to mislead you,
Paul

 

Hi Paul,
If you need help with the bridge, just email me and I will let you have the drawings for a jig.

 

Hello Paul,

I tryed to E-mail you but that didn't work.
I got a message that the E-mail adress is not valid.
I will explain here what I want.
The question was clear I think, the only thing I did not mention was the Era.
I model the late seventies, so I think concrete or steel should be the way to go.

Thanks for reply and please keep all of us informed of your new layout as you do now, because it gives us a great inspiration and encouragement to go on with or less soffisticated layouts.

Paul

 

Hi Paul,
Sorry, only ever built Wood Trestle bridges not concrete or steel.

 

I have one suggestion. Use Micro-Engineering flex track for bridges. This track has the close tie spacing used on all open bridge structures and brown ties as a bonus.

 

Nuts:

Looked up curved bridges in my "Bridge and Trestle Handbook" (Carstens Publication). I found the book a great source for bridge building.
Book notes that there are no actual 'curved' bridge structures in railroad usage. The bridge should be straight in construction between the supports and the track on it curved. Which means a wide enough deck to handle the curve spacing and locomotive overhang.
The track runs left corner start, outside edge center and left corner end. The book also shows this idea on both a wood deck as well as a steel Truss bridge.

Not sure if this will help with your ideas.

....Eddie

 

I can name two famous prototype curved bridges, specifically the wyeat Keddie on the WP and the wye onto the Celilo Bridge on the BNSF (ex BN, ex SP&S ex OT). I'm not as familiar with the Keddie wye, but the Celilo bridge is built on a series of short plate girder spans. Thats one way to do it is to cut up some Atlas girders and piece it together. There are also several commercially made curved bridge sections in the Walthers catalog. Take a look at the Faller ones on page 505 of the 2002 walthers catalog and also the Kibris on page 588. I also know of a guy on eBay who scratchbuilds custom bridges and I can get you in touch with him if you would like.

 

Thanks for reply guys.

Reading all of your comments I came up with the idea of using pertinax.
It is the stuff hobby electronic guys use to build their circuits on. It is 1.5mm thick and very stiff. It is easy to cut.
One or both sides is covered with cupper.
If I use this for the dek of the bridge, I can solder small pieces of the same material on this dek so it should look like a plate girder bridge.
The bridge can be easely painted to look like a concrete bridge or plate girder bridge.

Just another idea,

Paul

 

Hi,

Found this while looking on Google for bridges.
I think you might be interessed.
http://ghostdepot.com/rg/bridges/plate/plate.htm

Hope this works,

Paul

 

Hi Paul, if you want to use what we call PC Board stock (Pertinax) you could actually layout the outer edges of the bridge spans, and the rails where they need to be, and all the ties and crossmembers. You would want to be sure you cut a tiny gap in each crossmember and tie, between the rails, to prevent an electrical short. Stagger the gaps and they are not as visable. After you solder the rails in place, paint can help hide the gaps. A gap of one mm is enough. Works well on turnouts too.

 

Thanks for the tip Watash, maybe I can use some of your ideas.

Paul

 

Paul,

Follow me: Place a large piece of paper on a flat surface, lay a piece of curved track on it. Use a ruler and pencil, and mark off scale 40 foot spans ONLY on the inner rail for three spans. Connect a pencil line from the center of radius out to each of the three marks, and extend these lines beyond the track about three inches. Replace the track, you should have 4 lines fanning out from center. Now connect each mark to represent where each of the 3 spans will be. (You are drawing the cord of a radius).

Now place your longest car on the track, and follow me step by step. You will get the hang of it soon, if not already.

When you have the PC Board stock acid etched, only the copper will remain, which will corrode rather quickly, so ask them to "TIN" (solder plate) the copper for you. They will run it through their wave soldering machine, both sides, and you may then easily solder your rails and wires to it where needed. Best to use nickle silver rails.

Trim off excess board carefully, and sand it smooth. The fiberglass fibers will stick into your skin and fester! Best to paint these edges with a good lacquer to seal them.

A side note here:
Somewhere out of sight, or away from view, drill a small hole through from the right hand rail's copper stock, then solder a stubby piece of wire top and bottom. The copper on the bottom will act as a hidden wire to carry the current across this bridge as well as the rails, and only two wires will be required, which can be hidden under the roadbed. Jumper wires may be soldered from span to span this way also on the bottom. Keeps it neat.

Back to our project:
Remember the inner girder is always shorter than the outer girder, and they are both straight and parallel to eachother. The Pier, or bent will bisect the angle between the first girder pair, and the next girder pair, and so on around the curve. The center line of each pier is also the long lines you drew fanning out from the center of radius, see?

If you follow the "book", your bridge will look fine, but your radius may not be the same "Scale" as the real one, so do consider the over-hang of articulated engines, and long cars such as the 86 foot diners, and long freight loads.

Consider this:
On the outer girder span, the front of most articulateds may clear over the top of a short span, or it may not, as on a Through Howe or Through Pratt truss type, but the CAB may not!

To insure that adequate clearance is provided for an articulated engine, (say on a left curve), push the engine katty-wompas (twist it clockwise), until the the right front driver flange (of the rear driver set) comes to rest against the right hand (outer) rail, keeping the right front of the boiler at the mid point of the span. (Halfway between the second two pier lines from center). Hold that, and push the left rear driver (of the rear driver set) against the inner rail of this curve.

You will now have ANY engine located in the greatest missalignment relative to this curve, it can get, without derailing. Called "Hunting" the rails.

At the widest point of the right front corner of the boiler front, and your bridge span, clamp a block representing the span in place just touching the boiler temporarily, and parallel to the two marks of this #2 span. Mark the block at this touch point, and down at the two lines from center. Mark each end of this block on the paper, on the rail side. Draw a line across, and remove the block. Measure 1/4" away from the rail, and make another mark parallel, and clamp the block here temporarily. This will represent where the inner most surface of the outer span can be. But this may NOT be enough!

Here is why:

Move the engine on around the curve until the right rear corner of the cab ROOF is at the original mid point of this span. You may find it touches, or that you may have to move the span away some more than the 1/4". Surprise!

The other side of the bridge:
Where two inner spans rest on the same pier, locate the longest car or engine so the mid point of the car rests centered between the span's and centered on the pier. Again, allow 1/4" to clear here. This will be the closest point relative to a long car creating a "cord" across the radius of this curved rail.

Remember, the spans are always parallel to eachother, the outer one will be longer, and spans from pier to pier may vary in length as required.

The engines and cars CAN rock as they pass these points, so without adequate clearance, your bridge, or rolling stock CAN be destroyed in a flash when you least expect it. This usually happens before you have scenery in place to prevent your rolling stock from diving to the floor, so plan ahead, and use yours!

Working on paper first, is always safer than re-building a bridge! I lay mine out full scale on my cad system, plot it out, and have a true to scale full sized template to work from!

 

Great Watash.

This is wath I call a very detailed explenation.
I hope to start with the bridge next week-end and I will print your recommandations to read it a couple of times.

This is a great help.

Thanks again

Paul

 

Paul, I deleted that double post for you. OK?

If you get into a problem, email me and I'll help you out. Click on the icon above that says "email" then copy the address on a scrap of paper, then get out of TrainBoard and go to your email and type my address in to a NEW email. I will get it that way. Email direct from the TrainBoard sometimes fails, but will be fixed later.

Another thing I do on bridges and trestles, is:

after I have marked up my paper template, I cut it out and paste it onto a piece of 1/8" or 1/4" plywood, then copy the pier center lines, and track center line onto the wood. Then I cut it out along the straight marks that are the final clearance for the girder spans.

Then I can drill two holes 1/8" diameter through the wood on the center lines of each pier. Drill these holes about a half inch in from the edge. You can use flathead wood screws to mount the piers later and have each one aligned perfectly.

I place this wood on site at the proper location and fasten it to the abutments with a screw at each end, so I can remove and replace it as needed. I usually set the top surface of this piece at the level the ties will sit on, then the bridge spans will cover the edge, and be fastened to this wood after mounting all piers.

I use some sewing thread and a small plumb bob in each of the drilled pier holes to locate the spot directly below, so I can prepare for the pier's footing block. It makes fitting the piers easy with flat surfaces to work with, even if they are all different lengths. It works the same way on trestles too.

(I made small plumb bobs by drilling a tiny hole through a B-B, inserting the thread, then gluing the thread into the hole.) By carefully raising a Testor's tiny open paint bottle with some color of paint, up just until it touches the bottom of the B-B, I can then lower the B-B until it touches the canyon wall, and I have my mark made precisely.

Don't bury the B-B, too much paint will run!

When you carefully drill straight down through the scenery on your dot, it will align the pier block, so you can mark around it to cut out, or build up to support the block and pier. By centering your pier foundation blocks over the two holes, all your piers will stand up straight.

Let me know if you need help. OK?

[ 09 January 2002: Message edited by: watash ]

 

Thanks again Watash,

Sorry for the double post.
You can count on that if I need help, I'll be there to ask.
But I think most things are very clear now, just hope to find time next week-end to start the project.

Paul

(I will buy a Digital camera before summer and will post pictures of the result )