Hello everyone, i am hoping someone here can help me decide on a couple of bridges i want to put on my layout. The first bridge will be over another lower track and be around 12" long. It will be single track but i am looking for suggestions as to a decent looking bridge based on the 1970's through the 1980's east coast and that will accomodate the 12" openning i have made for the bridge. The second bridge i am looking for suggestions on will be a crossing over a deep river canyon sort of. It too will be single track and something that you might have seen during the above mentioned years as well as locale. As for length i have not decided yet so thats no problem. I had considered a trestle kit but i have never built anything that complicated before. Both bridges are N scale and will be 4" above either the track under it and the river floor. The river floor could be made to be a bit deeper due to me using 2" foam for my sub road bed. Anyways, any help and suggestions are greatly appreciated.....Thanks!
These would be 160-ish feet long. A girder bridge would probably need an intermediate pier, but a Truss bridge (you'd want the through truss variety), can cover that length rather easily and not need a pier.
https://ftp.dot.state.tx.us/pub/txdot-info/library/pubs/bus/bridge/span_tables_i_girders.pdf
There is lots to know here. For example, what will the load be? It would take some doing to place a girder bridge where you need it cheaply and easily. In fact, it could not be done practically. What will the load capacity be of the bridge? It might have to be huge in order to support the train's weight mid-span. As the table at the link says, at the bottom, lengths of girders beyond about 150' are problems due to the ease with which they can be transported and set in place.
I'm sure more knowledgeable people with some engineering background will help you out soon.
Trainzman2435the 12" openning i have made for the bridge.
I'm not an engineer, though I started out to be one, but I'm not an accomplished bridge scratchbuilder either.
If you are not a scratch builder, I don't know why you would pick the span before picking the bridge. That said I think everyone needs a Truss bridge. They have been in use for decades. Get the modern bridge if you run modern height equipment. The Central Valley bridge in N is 11.25 shoe to shoe. The Atlas is 10" Walthers has bridges, and I'll give you the link and you can do the research.
A 80' microengineering deck girder bridge is 6" so two with a central pier ought to fill your span.
Henry
COB Potomac & Northern
Shenandoah Valley
It's hard to figure specs from text.
One thing I pride myself on is expertise in the bridge field.
Pictures on your situation would be very helpful.
There is no such thing as an area where a solution cannot be found.
The bridge is removable from its supports, I got that one from Wayne. His advice and guidance was much appreciated!
It just takes some time.
TF
Track fiddlerThere is no such thing as an area where a solution cannot be found.
TF,
Thanks for showing that bridge. I was impressed the first time I saw it, but after studying it again, I have a much better appreciation of how well it was designed to fit over the tracks below. The support posts fit perfectly in between the lower double tracks, and they are also positioned perfectly on the four corners of the middle span above. That must have taken a bit of thinking!
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Thanks Dave.
You put a big smile on my face this morning. A nice complement is always appreciated.
You are right, it was quite tedious and time-consuming. It took way more than one try to get there but I didn't give up
A cardboard mach up was constructed to determine the support placements in relation to the bridge corners.
It just takes some time
Track Fiddler
That's a nice looking bridge model.
Paul Mallory's book Bridge and Trestle Handbook is old but still has valuable information about why certain types of bridges are used in given situations. It also has a section on bridge and trestle engineering "impossibilities" that are common on model railroads but should be avoided by modelers. I do not know if it is still in print; over the years various publishers have picked it up.
Dave Nelson
Hello All,
In it's simplest form a bridge can be defined as a structure, supported on both ends, to span a gap or obstacle.
That structure can be as basic as a plank or as complex as a bascule, draw or lift type.
Gaps can be as simple as a ditch or stream to vast valleys or man-made depressions.
In addition to the questions posted by others, my question is how simple or complex do you want to get?
Do you want to be "realistic" (prototypical) or do you just want to fill the space with something aesthetically pleasing?
There are many resources available to help you in your decisions.
In my library I have three (3) books that have helped me shape my decisions as to what structure is most appropriate for my given situations.
Even though the first two are out of print they still can be found on auction sites like Amazon and eBay.
In the world of modeling we have the luxury of creating structures without regard to redundancy, material limitations and external forces.
In deciding what type of structure you want, can the structure be supported mid-span or do you want a freestanding structure?
On my pike I have spans that vary from a curved aqueduct on a 3% incline to a skewed, curved arch-truss, to a spiral trestle and several elevate unloading platforms.
Simply asking, "Looking for bridge ideas please!" isn't a simple answer. There are many factors to consider.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
I like Bridges but as you will notice the upper part of the bridge needs to be toned down with thinner pieces of styrene.
Then it will look better.
It's still a cool Bridge though, it just needs some paint.
And I do need a Canadian fishing trip in the spring.
Thanks everyone for all of the great suggestions and ideas, i really appreciate them. For the larger bridge i need i decided to modify the gap a little and go with the Walthers Cornerstone Arched Pratt Truss Bridge pictured below. The 2nd bridge i need will fit a gap of approximately 9" and cross a river. Thanks agaoin for the help!
Can you get to a train show or a large club's open house? It would be good to take a look at a number of bridges in the flesh.
I have a few bridges. My favorite is my Central Valley Pratt Truss bridge. I model in HO, by the way. I have a much older and more simple Atlas Chord bridge, plus a short Atlas girder bridge. I see all of these as enhancements to my layout.
Don't be in a hurry. Enjoy the selection process and get the bridge you really want.
It takes an iron man to play with a toy iron horse.
MisterBeasley Can you get to a train show or a large club's open house? It would be good to take a look at a number of bridges in the flesh. I have a few bridges. My favorite is my Central Valley Pratt Truss bridge. I model in HO, by the way. I have a much older and more simple Atlas Chord bridge, plus a short Atlas girder bridge. I see all of these as enhancements to my layout. Don't be in a hurry. Enjoy the selection process and get the bridge you really want.
Thanks for the advice but there is not any clubs close to me unfortunately, i checked already. As far as the bridge i really want, that would be a nice curved wooded trestle bridge if i could find someone to pay to build it for me lol. But i see what your saying, thanks!
Try a Google image search for N scale railroad bridges. Maybe something will come up that you can track down as to where it came from.
Kind of hard to pick your mind and start from scratch as to what you want. Search around, find something close to what you want, and track it down.
Look at all the manufacturers out there, wooden bridge kits should be easy enough to find.
Mike.
My You Tube
Okay, i have another bridge related question....As i said above, i went with the Walthers Single Track Pratt Truss bridge shown above. In the description it says that the bridge is 14 3/32" in length. I also ordered the walthers bridge abutments for it. My question is: What length of span do i need to leave open in order for the bridge and abutments to fit correctly? I want to continue on with my track and roadbed laying while i wait for the bridge but i want to be sure to leave a big enough opening for both the bridge and abutments to fit correctly. Maybe someone can explain how i would go about figuring this out or does it need to be exact? I am using the Woodland Scenics risers and incline/decline set to create my elevation. Thanks for any help!
See the flat plate "shoes" on each end of the bridge? Those sit on the abutment walls.
Look at the picture of the bridge abutments, it shows the bridge sitting on them.
Real easy.
I'd wait until you have the bridge and the abutments in your hand. Then you can measure everything. If you make the gap too big, you will have to decide how to fill in the empty space. If it's too small, you will have to make it bigger.