Building the Canyon Diablo Bridge

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D&J RailRoad

Professor of HO
#1
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.

[video=youtube;PNhBv7kTJIQ]https://www.youtube.com/watch?v=PNhBv7kTJIQ[/video]

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?



 

tootnkumin

Well-Known Member
Staff member
#3
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.
 

D&J RailRoad

Professor of HO
#4
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.
 

tootnkumin

Well-Known Member
Staff member
#7
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.

https://www.youtube.com/watch?v=nEsAolc_4NM
 
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montanan

Whiskey Merchant
#8
Looking forward to your build of the bridge. This one will really be challenging. Keep adult beverages close at hand. Grin.gif That would be a great addition to you layout.
 

Sirfoldalot

Plucked Tailfeathers
Staff member
#9
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.
 

D&J RailRoad

Professor of HO
#11
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D&J RailRoad

Professor of HO
#13
After viewing this article by TrainCat on the details that are possible for this bridge, it really has put a damper on my plans to build this bridge.
That's so aggravating that a business would hang stuff like that out there but then not have it available to buy. It would be a major undertaking to reinvent all the details, especially when I only have pictures from a distance to go by and no prior experience with brass etching.
 

tootnkumin

Well-Known Member
Staff member
#15
After looking at the TrainCat kit and it's method of construction, it could be best described as "a bridge too far". Even that HO one by Peter Youngblood, is still just a beautifully done representation. To most observers it would be very passable, certainly captures the feel of the structure, but not a rivet counters example (and there sure are enough of THEM in it). It's obviously doable as a representation, just depends how that would satisfy you, Ken.
 

D&J RailRoad

Professor of HO
#16
That's just it Toot. If I'm gonna build something that extensive, I want to put the effort in to do the detail as well.
I'm thinking now, it will take more than a few months to complete.
 

tootnkumin

Well-Known Member
Staff member
#17
I reckoned this would be a very time intensive project to do it to a high standard, or even a not so high standard. Much of the devil in the detail are those rivets, they're literally a "standout feature" of this bridge. I know you can get decals to create the effect, but it would be a lot of decals to apply, just as one part of the build. I would love to see it done and if anyone can, I believe it would be you. If you weren't too concerned about someone looking at it through the window, then I guess only one side needs that much high detail. To do it and do it very well, is going to take a lot of commitment. No-one's going to think less of you if you decide not to take it on.
 

tootnkumin

Well-Known Member
Staff member
#19
I did come across an HO reduced length one that was mentioned in MR mag forum by member Arjay1969, wouldn't let me copy the link, but once again only a representation, all made of I or H section and smooth, no rivets, not much internal bracing detail. If you did it, it would be a first I reckon.
 

montanan

Whiskey Merchant
#20
I can see you giving the bridge project some second thoughts. With all of the fine work you have done on your layout, it's easy to see that you want to get things right. With no accurate measurements and trying to work with new materials, this wouldn't be an easy build by any means. Hoping that in time you can get more information on it and perhaps add it at a later time.

It would be one outstanding feature for the layout, but the time that it would take to build it would be a long process.
 



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