I'm in the process of installing new benchwork on my layout, but I want to include some bridges, and wonder how to go about the benchwork under them. How did you do it on your layout?
Modeling the N&W freelanced at the height of their steam era in HO.
Daniel G.
Some would depend on the location you are modeling and how far above the "bottom" the bridge is.
Carving down into 2" foam would do fine for something not far above the river. If you dug all the way to the bottom, you'd be about 14.5' of clearance.
For something with deep canyon, Rocky Mountain type terrain, I have seen benchwork built to drop the scenery base, some go nearly to the floor.
Something in between can be done by cutting out the surface to the benchwork, then attaching supports that drop the base as far as needed to give you the height.
Good luck,
Richard
CR&T is employing cookie-cutter on plywood, grid-benchwork, and elements of L-girder between the grids. Also, due to traction, the base will be plywood to properly attach the traction poles for live overhead. Foam will be used as a scenery supplement, and not the layout base.
Thus, what goes under the bridge, may be applicable to any of the above benchwork scenarios, and adjusted thereto.
For example, in one CR&T community, plywood cookie-cutter (supported underneath by grid-benchwork) is called for over some trackage -- Where the traction mainline wraps a balloon-loop over that those lower tracks into a reverse loop ()another type of balloon-track) -- And only after the supports under the bridge ends are securely fastened, will the space be cut away, to put in the overlying bridges and piers.
However, other bridges will employ techniques better suited to "open-spaces" spanning L-girder benchwork supports. Each scenario will have a bearing on how you approach each bridge's construction, and what goes underneath be it rivers, switching yards, a mainline, a highway, etc.
Sometimes, a bridge across the shelf-width, is a type of scenic block, over a switching yard like -- Rix concrete highway overpass -- Mostly placing the bridge on top of the layout table. Dave Vollmer's N Scale Juniata Division bridges are photo-documented -- Note the highway overpass -- Over the Enola Yard.
What are each of your specific scenary scenarios? Thus, it really depends on...
Conemaugh Road & Traction circa 1956
Here's how I did the bench work for a bridge over Hammer Creek. DJ.
Finished scene.
It really depends on how high you want your bridges.
I wanted to model the CPRs Stoney Creek Bridge which is 300'+ high. I am really happy with the progress I am making on it. It is a canyon that drops to the floor. In the first two photo's you can get an idea of what I am doing. The long piece of unsupported spline will be cut out to accommodate a steel arch bridge at some point. I have an Exactrail girder bridge for the lower track. I built the section of bench work to accommodate my needs but it is essentially an upside down grid style of structure.
Elsewhere on the layout I used 2" foam over open grid. Depending on how deep the cut you want, 2" of foam may be deep enough, so that's easy. Just gouge out the foam.
I am planning another creek on this part just to the right in this photo. I will cut out the spline for the upper level and put in a bridge and dig out the foam under the lower track and do the same.
On most of my layout just cutting out the foam will be deep enough, but when I built the benchwork I put it all together using Lap Joints. It is so sturdy I can cut out a chunk of it anywhere and it won't affect its strength. Just in case I want a deep ravine somewhere else.
I am modeling the Rockies and there are creeks, canyons and lakes everywhere in the real Rockies. I wanted to leave my options open.
Good luck.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
First off, my basic benchwork is classic Linn Westcott L-girder design, which means I can go down to the tops of the L girders between joists at the L-girder line, or even lower closer to the aisleway. The terrain in my modeling area can best be described as `broken,' aka somebody stood the world on edge. On one stretch of mainline short bridges alternate with shorter tunnels along a slope steeper than most staircases. While the fascia profile will be interesting the basic benchwork is absolutely standard.
I do have one really tall concrete arch on a curve planned for a specific inside corner. The lower abutments and the valley floor will be carried on a sub-base suspended below the regular benchwork and the bridge itself will cut the corner outside the joist-end lines for a right-angle turn. I may have to trim one joist to fit, or simply omit it.
Track is laid on cookie-cut plywood, with thin extruded foam carved into roadbed caulked to the top. Where the planned bridge has a concrete deck (the corner arch) or is intended to be a deck girder (the local standard) the extruded foam is replaced by plywood (for the arch deck) or straight 1/2" square wood (for the deck girders.) Girder bridges simply have a detailed girder fastened to the wooden core. Under the usual bridge ties and walkway planks, it's all but impossible to tell that the blackness barely visible under the woodwork is a wood surface painted flat black, and that there is no backside girder.
I didn't just decide to include some bridges. I'm basing my modeling on some very specific prototype locations and situations. Fortunately, L-girder design and cookie cut plywood subgrade on risers makes the modeling easy. Of course, for my modeled terrain (think of the depths of the Grand Canyon covered with a cedar forest) a flat table top, or even a hollow-core door more than 14 inches or so wide, one each on a layout that fills a double garage, is a non-starter.
Chuck (Modeling Central Japan in September, 1964 - on steel stud Westcott-pattern benchwork)
I've got a pair of truss bridges and a bascule bridge on my layout, both supported by piers.
Rich
Alton Junction
I have 3 bridge areas on my layout. Two are shown in the photo attached. The triple curved chord one in the foreground has two support columns and spans a river. The one in the background is a 150' CV kit and the subroadbed was installed in two pieces, clamped to a longer board to keep them in the same plane. Once the supports were mounted, the long board was removed and now both ends of the bridge line up and the track flows across without any dips or kinks.
-Bob
Life is what happens while you are making other plans!
It really depends on what type of bridge you're shooting for. Are you passing over a highway? A small stream? A vast and deep gorge? Maybe a low bridge over a broad river? Give us a little more information, and we can help you a little more specifically with your question.
Lee
Route of the Alpha Jets www.wmrywesternlines.net
In addition to something things similar to the above examples, we have some track that wrapped up and around mountains from one to another. No cutting of benchwork in that case. Planning for the net elevation change from track level to the feature and then feature elevation in relation to the floor is where I start. Basically you have three elevations to begin with, the floor, the feature and the track (you could have multiples of the track and feature of course, but this is the basic idea). Once that's calculated, then I build accordingly.
Since I built the Yuba River Sub on a stacked extruded foam base, I measured the height and depth I needed for my bridges, built the bridges, cut the foam out, and kinda/sorta 'dropped' them in, connected the track and I was in business.
The Deer Creek Viaduct:
Buillards Bar arch bridge:
I followed suit on the smaller bridges (I have about 8), just cut into the foam roadbed and installed them.
It's pretty easy with a foam based-layout, I didn't have to cut into the benchwork at all.
Tom
Tom View my layout photos! http://s299.photobucket.com/albums/mm310/TWhite-014/Rio%20Grande%20Yuba%20River%20Sub One can NEVER have too many Articulateds!
Alot is going to depend on what is under the bridge. I had a layout with 2 bridges on it and one had stuff under the other did not. Here are the pics.
This area of the layout was supposed to be a walk through to the closet behind. My benchwork was free standing and it made keeping the tracks aligned in the removable sections very difficult so I mounted the bridge and removable section perminatly.
This was a bridge that was built over a opening for an abandoned tunnel. There is benchwork under it and if the scene had been finished there would have been a work crew pulling up the old tracks.
Massey
A Veteran, whether active duty, retired, national guard, or reserve, is someone who, at one point in his or her life, wrote a blank check made payable to "The United States of America" for an amount of "up to and including my life."
Carved into foam, built up forms and structolite, used real stone. As others have said it depends on the bridge and the height.
A few ideas ...
http://stremy.net/SRA/Tips/Old%20Trestle/Trestle.html
Look at real bridges, lots of them and you will get a feel for it.
The mind is like a parachute. It works better when it's open. www.stremy.net
All my track is on 2" foam risers above an extruded foam base, which sits on the benchwork. This gives me plenty of vertical distance to deal with the shallow gorges and gullies created by streams in New England, where my layout is set.
Depending on your materials and where your underlying supports are, you can always simply take a sabre saw or hobby knife and carve out a deeper area underneath the bridge. Just make sure that you take this into account when designing the benchwork and substructure.
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