Small bridges for many applications

A man after my own heart; - as my personal belief is that our scale models should be viewed at eye level for maximum visual impact and not from the more frequently seen “helicopter” point of view.

(Unless perhaps should you be modeling the Tehachapi Loop.)

Most all my past layouts were constructed with a grade lever of 55" or higher.

San Diego Model Railroad Club/Museum - Balboa Park, San Diego:

Tehachapi Loop Division and environs.

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That is interesting. If true with all evergreen, at some point soon you (general modeler) might need to do real engineering work to keep that all together me thinks. Regular Tamiya glue and slapping bits together won’t work or work well for long.

WOW! This mega-model structure is clearly ALL scratch built and I suspect the fellow that built it knew a thing or two about actual, real life, bridge design. (Or at least he did after finishing this project.)

I’m not suggesting this could have been put together out of a pile of HO Atlas truss bridge kits. This project is way beyond all that! What I am actually trying to do here is to inspire more (and more accurate) scale model bridge building.

Just trying to get people to observe all the many impressive engineering projects (large and small) seen all around them in everyday life and have those observations be encompassed into their model building.

We are all good. It was a general comment and admiration of that build. It’s one thing to build something static to look at but to be “used” having to support actual weight and other stresses would require more thought then me building a ladder on a whim is all.

About the relative strength of thin material.
I built a charcoal storage building for a H0 (1/87) layout. It was fairly small one, 10 inches wide and maybe 30 inches long (a small real one could be 400 feet long and 100 feet wide).
A railroad track leads in to the upper level, the wagons are winched in (do NOT want a steam engine in there and the slope can be steep)
image

The track rests on a trestle bridge inside and the wagons are emptied down into the cavernous space below.
The one I built in 1/87 scale had an internal bridge very similar to the one in the photo above but I used diagonals from the feet of the vertical pillars to support the track between the pillars instead of the heavy beams in the photo above. It was all wood except for the roof (corrugated aluminum) and the railroad tracks.
The largest “timber” I used was 3 mm diameter rods and 2x2 mm square.
Just for the fun of it I balanced one of my 7,8 kg (17 pounds) dumbbells on the end of the bar on top of the track, between two pairs of vertical pillars.
This general type but mine only have two disks

The construction squeaked and flexed a little but it held. I’ve got a photo somewhere …

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*Scene from the intro to the movie “Days of Heaven”.
(Real Train NOT Digital.)

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Please find the photo. I love such images.

You can click your way around the layout here:
https://www.smj.org/ekensholmsbanan/info-in-english-36809859
Swedish with Google-english …
Bildgalleri = Image gallery
The charcoal shed is located in Bångfors
https://www.smj.org/anläggningen/bildgalleri/vy-4,-mh-bs-37099569

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Relating to Robin’s comments about building and testing his bridge reminded me . . . .

One of our early assignments in design class was to use only 6 balsa wood 1/4" x 1/4" x 36" sticks and two large sheets of thin paper to build a bridge that spanned 30" and supported 25+ pounds.

On another note:

As said earlier bridges don’t really have a “scale”.
A thru plate girder bridge in a smaller scale easily becomes a deck plate girder bridge for a larger scale when turned upside down.


Thru plate girder bridge

ME75151
Deck plate girder bridge

A thru plate girder bridge is usually employed where there is insufficient height clearance below to allow for a deck plate bridge. (which is cheaper to build) This most frequently occurs when a railroad passes over a highway.

Deck plate bridges don’t usually have that little curved end so just cut off the last plate panel at each end for a slightly shorter but now squared off plate girder.

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Also plate girder bridges are rather easy to custom build today using Evergreen sheet plastic and their various sizes of “angle iron.”

I built my first one about a 100 years ago using card stock cut from a Manila file folder and some bass wood angle held together with Elmer’s Glue.

images

Heavier rail loadings may require one or more additional girder plates added between the two outer most plates. If it is a 5 plate bridge that doesn’t necessarily mean you have to model all five - unless you want to!)

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426482-M
Thru plate girder bridge with concrete or stone abutments.


Deck plate girder bridge with wooden support pilings that have had their header beams replaced with concrete and steel.

Pilings settle with age and header beams are usually the first to rot out so some replacements were installed here and some jacking up of the bridge height was necessary

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Model photo found just recently on line. A mix of a steel girder deck bridge with wooden trestles for the supports and the approaches.


(Modeler/photographer Unknown)

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*All Photos by Corey Vernier via Facebook:

Here is a lovely 1889 thru truss bridge in Blevins,TN built by the narrow gauge East Tennessee & Western North Carolina Railroad aka the ‘Tweetsie’. It’s still being used as a roadway bridge. A sister deck truss bridge a short distance away is not in great shape.


Modeler’s Note: Something a little different in this unusual underslung quasi deck truss/through truss bridge design. (Last two photos.)

An HO through truss bridge could be easily repurposed into a similar underslung bridge design as the one seen just above in either O scale or Military Scale.

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Similarly designed truss but used here as a full deck truss:


Photo property of the Cumbres & Toltec Tourist Railway ~ Used here for discussion purposed ONLY.

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High Bridge, Kentucky on the Norfolk Southern just South of Lexington, KY.
(Approximately 275 feet above the water’s surface.)

In 1911 the new double track replacement bridge was literally built around the old single track (built 1877) deck truss bridge without hampering the then current day rail traffic. The line was closed for less than 48 hours to make the transition to the new bridge. The old bridge was then slowly dismantled from within the new structure.

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Young’s (Tyrone) High Bridge; located on the road between Versailles and Lawrenceburg, KY
As seen from the Wild Turkey Distillery Visitor’s Center.

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Bridge Diorama in Military Scale:

This will be a rehash of the original post, now still to be seen in the archives, that started this thread in the first place.
I feel this model can offer much “food for thought” for bridge dioramas done in O, F as well as in “Military Scale.”

Bridges really have no scale. A large bridge in HO may be used to represent a smaller bridge in the larger scales. Possibly only the size of the rivets giving away the difference. The rivet sizes can be corrected or (quite honestly) simply overlooked.

Warren Thru Truss Bridge by Atlas. Available in N, S, and O scales. (Also available in a Deck Truss Design.)

The Original bridge concept was to use a single HO span to make a short bridge in “Military Scale”. (1/35th)

However, this design was deemed as being impractical, as being too short by my brilliant Army Corps of Engineers niece. (Two Tours in Afghanistan) She pointed out that at this short length, they would have simply used a short girder bridge as being smaller, lighter, cheaper and easier to build

So a longer, spliced bridge requiring two kits became necessary.

*Now here is the key: The wide thru truss bridge (in HO Scale) serves very nicely as a Deck Truss Bridge in the larger “Military Scale”. It simply has to be rotated UPSIDE DOWN!

The current status of the diorama build as seen below:

The trackage is from Trumpeter with the rails and ties painted and stained. The flatcar is Dragon and the Pz. III is from Tamiya.

Even as a young child he wished all his toys could be in the same scale.

The bridge abutments are a combination of the Trumpeter track bases for the top and some 1/2 inch scribed “Evergreen” sheet material. The abutments are painted with a light gray “crackle finish” garden spray paint from “Home Depot” to add some concrete/stone texture.

Rule of Thumb: My niece also tells me that a “rule of thumb” with such bridge structures is that the depth of the web, (height of the truss structure) should be no less than 12% of its’ length. Fortunately for me this bridge works out to be right at 12% of the length.

________________________

For the 1940’s wartime era, my bridge would be considered as being light to medium duty load bearing but there are larger and more massive bridge moldings available from some of the European Model Railroading manufactures. ~ If you should want something more massive such as that seen below!

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Michael, you’re in the catbird seat with a niece who knows engineering. That 12% rule will be very useful, or at least cool knowledge.

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