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Thread: Building the Canyon Diablo Bridge

  1. #1

    Default Building the Canyon Diablo Bridge

    I am starting this thread as I suspect there will be a lot of activity in the construction I am undertaking.
    I have a section of my empire that was designed to have a bridge installed. At the time of construction, I didn't have any idea of what kind of bridge I was going to put there. The following video shows this gap.



    The scale gap is a little over 500 scale feet or actually about 74".
    As I have looked at quite a few designs, I have ruled out the truss type bridge because of the expanse of the canyon. I wanted something more substantial than viaduct type bridge. I happened upon the Canyon Diablo bridge one day and knew that was what I wanted to build.


    I have found just about every picture and video on line about the bridge and have read about the history of the area from numerous perspectives. I've seen the N scale version of it that was built by an NMRA member but can't reach him for any details of his measurements or construction technique.
    I am venturing out on my own to make estimates based on the available pictures and videos.
    At first look, you would just assume this is all I beams, but look closer. You will see that all the beams are rectangular stock. Some completely closed like the main arch is and some with oblong holes or square plating riveted along the open sides.

    So far, I have estimated the main arch beam to be a scale 1/2" tall and 3/8" wide. I can only figure this by comparing the arch beam to a locomotive that is passing over the bridge with pictures like this one.



    The only choice of material 1/2" X 3/8" to build this bridge will have to be solid brass stock for the main arch. There is no source for hollow rectangular brass stock in the estimated dimension. Plastruc tubing is to flimsy and there is no such thing as solid plastic stock in the required dimension. I don't trust wood enough for this, plus it just wouldn't have the appearance of steel beams. There is aluminum stock but it will be difficult to weld. I'm not going to try glue on this nor will I use out of scale pins.

    I ordered a 12" section of solid brass to do a scale comparison by. It took a few weeks for it to show up which kinda alarms me if I need additional stock after I start the project. My luck, the stock I receive is the last that they made in that size but you know the vendor won't tell me that in advance.

    OK, I painted the solid brass and put it up near the gap with a loco in the picture to compare. Does this size stock look close enough to the real picture to use as scale size stock for the arch beam?



    Ken
    When ya absolutely positively need model railroad fun, choose the D&J Railroad.


    Visit the progress of the construction of the D&J Railroad at:
    http://www.modelrailroadforums.com/f...-From-Scratch]

  2. #2

    Default

    This is a video of the bridge with trains running on it.

    Ken
    When ya absolutely positively need model railroad fun, choose the D&J Railroad.


    Visit the progress of the construction of the D&J Railroad at:
    http://www.modelrailroadforums.com/f...-From-Scratch]

  3. #3
    Join Date
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    Caboolture in SE Queensland, Australia
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    Default

    Going purely by eye Ken, of that pic with the train on the bridge, my guesstimate would be that the vertical height of the section is very close to the distance between the railhead and the underside of the loco's walkway. Interestingly, the walkway up and over that bottom chord appears to pass through the upright bracing. IIRC the N scale one had it as an outboard walkway.

    I know that you've gone and lashed out on some of the brass stock, but looking at it now, you might be better off building all those rectangular hollow sections from flat sheet styrene. As far as the load carrying capability is concerned, you should be able to use the ply deck you have, beefed up with shallow aluminum top hat section, or channel along it's length, screwed up underneath. That would relieve the the substructure from contributing to the load carrying.
    CONVICTED SERIAL KIDDER

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  4. #4

    Default

    Yes, that is the same reference point that I used for the arch beam thickness. That comes out to right about 1/2". One of the videos is of a walk along the maintenance walk way under the bridge. A perfect shot of the width of the arch beam can be seen which is narrower than it is high. That's where I get the 3/8 width.
    Ken
    When ya absolutely positively need model railroad fun, choose the D&J Railroad.


    Visit the progress of the construction of the D&J Railroad at:
    http://www.modelrailroadforums.com/f...-From-Scratch]

  5. #5
    Join Date
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    Default

    This vid, taken close by, seems to show a mixture of I beam and hollow section steel used in the verticals. I beams where they're shorter and rectangular hollow with square cutouts for the taller. Good views of the deck supporting beams also
    CONVICTED SERIAL KIDDER

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  6. #6
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    This one with better lighting on the verticals, confirms from about 1:30 that the short ones at the ends and in the center span are indeed I section RSJ

    CONVICTED SERIAL KIDDER

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  7. #7
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    Default

    Don't want to overload the page with similar vids, but here's one with the sun at a low angle showing the bridge decks thickness and it's relationship to the top chord beam of the actual steelwork. Sort'a blows the suggestion of having the plywood as the top chord, eh.

    Last edited by tootnkumin; 12-19-2016 at 06:37 AM.
    CONVICTED SERIAL KIDDER

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  8. #8

    Default

    Looking forward to your build of the bridge. This one will really be challenging. Keep adult beverages close at hand. Name:  Grin.gif
Views: 625
Size:  166 Bytes That would be a great addition to you layout.

  9. Default

    You would think with as many video's as there are of trains xing the bridge that someone would have concentrated more on the bridge and not the trains.
    Would have been nice for someone to have taken a few measurements of things.
    BTW - KEN, That;s going to be awesome looking.
    **********
    Sherrel
    'I survived Charles Tillinghast & Carl Ican
    Every day I beat my previous record of consecutive days I've stayed alive!

  10. Default

    Here's a thread by someone building it out of brass. Don't know if it has anything new or helpful or not. I believe it's in N scale.

    http://www.trainboard.com/highball/i...by-step.72496/

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