Building The Canyon Diablo Bridge

[DKS]

This bridge doesn't look any more difficult to solder than soldering wire feeds to the rails.

Perhaps for you. But I've tried to teach soldering to modelers, and this firsthand experience is enlightening to say the least.

If you can properly build a plastic or wood kit, you can just as easy do a brass model kit.

Seriously? Again, perhaps for you...

I just don't understand this fear of soldering many modelers have.

I don't think it's a fear; when one knows their own limitations, it's natural to avoid those tasks for which one's skill set is not well suited. Plus, there are those who have tried it and simply do not like it. I enjoy home improvement, and I'm good at framing and getting sheetrock up, but I dislike compounding, enough that I'd rather pay someone else to do it.

And now back to the awesome Canyon Diablo Bridge build...

[peteski]

Sorry that I mentioned it Dave.

I just thought that soldering was one of the skills one acquires for this hobby.  It is not requisite to model trains, but I wouldn't consider it brain surgery either.   I wasn't born with a soldering iron in my hand - it took lots of practice for me to get comfortable with it.   But you're right - everybody is different. Bob makes it look easy so when some people expressed doubts in their soldering ability, I simply wanted to tell them that they can most likely learn to solder (of they choose to do so).   But it seems that I'm wrong....

[TrainCat2]

I will say that the level of proficiency to assemble this type of bridge is MUCH lower than the G22b. You really DO want the globs of solder (in the right places of course). There are just hundreds of tabs/slots that must be done. Simple but monotonous.

My first degree was an Electrical Engineer majoring in robotics and built many a circuit board in my time. I own resistance irons and the Weller and will go to the Weller most of the time. I am comfortable using a soldering iron. It took me several tries to figure the method that a modest builder could do very well with. Having the right equipment is a key factor. I would not assemble this bridge with a pencil iron and never without my TIX Flux. There is just not the level of heat control that makes assembly easier.

Working with brass does scare a lot of people since they do not have exposure to it. Human nature is all that is. I was not trying to dumb down the process, just compartmentalize it. You will do the same simple steps many times over. The first few might not look pretty, but as I already said . . don't worry about excess solder.

[Seligman Sub]

Topock and Canyon Diablo bridges?! You sir will be earning lots of my money one of these days! This bridge looks great! Can't wait to see the finished product!

[TrainCat2]

Topock and Canyon Diablo bridges?! You sir will be earning lots of my money one of these days! This bridge looks great! Can't wait to see the finished product!

There will also be the bridge just to the west of Canyon Diablo (have not found a reference to the name yet) as soon as I can get out to it over my winter excursion to AZ. This bridge is a smaller version of CD.
https://www.google.com/maps?ll=35.190671,-111.21814&spn=0.004226,0.008256&t=h&z=18

[TrainCat2]

I created a few drawings so you guys can follow along. The first is a basic structure chart that shows the Chords, Posts and Diagonals and their respective surfaces. This is only half the bridge as the other half is a mirror of the first.


Next is a cut-away at Post5, P5, which is the tallest pier and the attachment point of the Bridge Shoes. Here you can see many things on how the interior of the bridge will be built.


Starting at the top, one should notice that the bridge is decked and the track is on ballast. You can also see that the Canyon Diablo (and Topock) do not have Stringers as most are familiar with. Instead, the Kansas City Steel Company used forged I-Beams resting on top of the Floorbeams and the Top Chords to support the Deck. At the center of the Floorbeam, the Walkway from the adjacent Floorbeam is attached. From the Walkway, two other Walkways went out to the exterior of the bridge supported on Hangers from the Top Chord. To keep the bridge vertical, the Posts are connected with X-Bracing called the Sway Bracing. The size of this Post requires that there are multiple segments. Resting on the Lower Sway Brace is the Lower Stairway that runs the length of the bridge. At each P5, there are Platforms and ladder down to the Bridge Shoes. Elsewhere between each Post, two other Walkways extend out to the exterior of the bridge supported on the Bottom Chord.

Posts P1, P2, P3, P8, P9 and P10 are basically giant I-Beams themselves, P4, P5, P6, and P7  are referred to as Batten Posts where they are constructed of forged C-Channels held together with Tie Plates riveted to the C-Channels. On the bridge model, the Floorbeams have three large tabs that extend into the Post interior. For Batten Posts, that is not a problem since they are hollow. The I-Beam posts presented a challenge. The builder should note that the I-Beam Webs for these posts have cutouts that match the Floor beam tabs and are orientated to the bridge interior. These tabs will fill the cutouts in the Web to make the structure whole when looking at the Post from the side.

[TrainCat2]

Assembly of Truss Posts and Diagonals

Almost always on bridges, you want to assemble all of the Posts first since they will define the straightness and trueness of the Truss Frames. On the bridge model, we must build Posts first since they have small tabs that will go into areas that having the Diagonals in place before the Posts would make it difficult to do. It is best to place the Truss Side on the building surface so the interior faces up. Remember, the attachment points for the Lower Laterals at the bottom of P5 clearly show the builder which side is the interior.


Thing1 and Thing2 greatly assisted in keeping the truss flat. NO POST OR DIAGONAL SHOULD BE ASSEMBLED WITHOUT THE TRUSS FRAME BEING HELD FLAT ON THE BUILDING SURFACE TO KEEP EVERYTHING IN THE SAME PLANE.


Due to the limited space for the Upper D1 Cap ,D1U, must be assembled before P1 is secured in place. There simply is not enough space to wedge the D1 Upper Cap in after P1 is installed. I first tacked the Lower D1 Cap (D1L) in place to get that area rigid and aligned. Then Upper D1 Cap (D1U) was inserted through the P1 opening and tacked in place. Flip the Truss Frame over and tack the other side of D1 then flip over again.


Ensure the interior of the Truss Frame is facing upward and place the P1 Web into the slots for P1. The notches should also be orientated upward to the interior of the Truss Frame. Do not solder yet. Continue placing P2, P3, P8, P9 and P10 Webs in place.

[TrainCat2]

Next up is the Batten Posts P4, P5, P6, and P7. Trust me here . . . these WILL behave differently. The critical thing is still having the Truss Frame held down to the flat building surface when soldering. Insert the Batten Post sides for each Post in place. The part ID that is etched into the part should always be at the top of the Truss Frame. Each Post will have two components. The “A” piece will ALWAYS be facing the Truss End while the “B” part ALWAYS faces the middle of the Truss.

Now it’s time to tack solder the I-Beam Posts P1, P2, P3, P8, P9 and P10. Next, tack each Batten Post side in the middle of the Post.


When all of the Batten Posts are tacked, flip the Truss Frame over so the exterior surface faces up. Since you need to hold the Truss Frame flat on the building surface and the attachments at P5 will not allow it, it is best to let that small section hang over the building surface so the rest of the Truss will lie flat. [REPEAT] The critical thing is still having the Truss Frame held down to the flat building surface when soldering. [/REPEAT] Notice that the part of the Truss Frame in no way looks like it will ever be correct. This is due to minute differences in the building process, but will actually disappear when properly assembled.


I need to restate that any tabs that are positioned at the junction of a Post and Diagonal should NOT be soldered now, but when securing the Diagonal. I have circled two such tab/slot locations on the next image. To straighten out the Post, begin by tacking the ends that do not interfere with a Diagonal. Pick one end and skip a set of tab/slots and work the pieces together one tab/slot at a time. Here, I used an industrial steel tweezers to bring the tab and slot together, apply some TIX and a drop of solder. Don’t worry if the tack will not win a beauty contest. Just get the tab/slot aligned and tacked. Tack the other tab/slot in the set in the same manner. Skip a set of tab/slots and repeat the process. By now, you should have a straight aligned post. Tack the remaining tab/slots.
 

When you have completed tacking all of the Posts on the exterior side, flip the Truss Frame over (interior side) and tack the Batten posts except where the junction of a Post and Diagonal are. Begin securing all joints on the Batten Posts by applying a bead of TIX on the edges of the Post and run a LITE seam of solder along the joint to fill in any gaps and make the structure rigid.

[TrainCat2]

I am at an impasse since I am out of metal awaiting the final artwork tool back. So, I started the clean-up of the Posts and Diagonals. I removed the excess solder with a VERY LITE touch of a cut-off wheel on it’s flat side. Lightly drawing the spinning edge over the metal while moving away from the edge in contact with the metal. Use a file to clean up the solder the other surfaces of the Posts and Diagonals.


Pics of the surfaces once solder removal is complete.

[peteski]

Bob, wouldn't it be safer (and easier) to use Dremel sanding disks instead of the cut-off wheels?

[TrainCat2]

On the chords, YES! Only because you can get the Dremel tool flat. When doing the Posts and the Diagonals, the Dremel needs to be tilted for clearance and then the drum is not flat on the surface. You end up using only the top edge of the drum which will put an uneven finish on the brass. In contrast, the cut-off wheel will follow a flat surface and stay flat. I practiced on the spare brass from the sheet until I felt comfortable after a few passes and a VERY LITE hand. I finished the solder removal in no time flat.

BTW: I also tried a right angle drive to see if I could get closer, and therefore more contact with the metal, to use the drum sander instead of the cut-off wheel. Alas, no such luck.

Edited to correct late nite jibberish . . .

[TrainCat2]

In the meantime, I started building the Lower Sway Braces. These are in two basic configurations; 1) Single Sway Brace where the chord is straight and 2) Multi Piece Sway Brace where there are two Sway Braces in the exact angle as the Chord Knee.

I first built all of the alternating Cross Braces that create the Lattice Web of the Sway Brace by taking two identical multi layered Sides, flip one over so the detail is opposite on the other side. Using a sparing amount of TIX flux on the top and bottom tabs, place a minute drop of solder to hold the two halves together. The finished Lattice Web now shows multi-layered detail on both sides.


Here I am building a Knee Sway Brace. On any bridge, the Lower Sway Brace must always be perpendicular to the Chord, so two Sway Braces will be needed for each angle of the Knee. That means that the two Lattice Webs will be next to each other at the bottom of the Chord and father apart at the top of the Chord. Each pair of Lower Sway Brace Caps have the number of the associated Post etched into one of the tabs. A number 5 Sway Brace Cap will be at the junction of the Bottom Chord and Post P5.

The easiest way to build these are to place the Sway Brace Cap that has it’s slots father apart down on the building surface with the half-etched bend line facing upward. Insert a pre-soldered Lattice Web into one set of slots. Solder the Web to the Cap ensuring the Cap is perpendicular to the Cap. I do this by looking at the two pieces from the end where I can see if they are perpendicular and then touching a small drop of solder on the end tab/slot to hold it in place. Do the same thing for the other end and repeat for the second Lattice Web. Fill-in all other tabs/slots with solder.
 

Carefully bend the Bottom Chord Cap, into the bend line, to the angle of the Chord Knee associated the Post etched into the tab of the Sway Brace Cap. Refer to the TrainCat Web Site for tutorials on how to bend brass. Pinch the two Lattice Webs together forming a V. Place the assembly on the building surface with the Top Cap down. Fit the slots in Bottom Cap onto the tabs on the Lattice Web. The half-etched bend line should face upward where the tabs (when viewed from the side) are parallel.


Tack the two end tab/slot pairs first and then the remaining tab slots. Using a jewelers file, remove the excess solder from the top and bottom Caps of the Sway Brace. I found out (after I made these) that you really should clean these parts with lacquer thinner right after soldering otherwise some oxidation will begin. This pic is only one day after soldering and oxidation is already beginning.

[jnevis]

This is being moved to "Best of Railwire" right?

I may never get the opportunity to actually build it, but this is a great tutorial on bridge construction, model and proto.  Just detailed enough to get the point across and not overwhelming.  Plus a good intor to building with brass, no matter what the subject. Thank you Bob.

[DKS]

When doing the Posts and the Diagonals, the Dremel needs to be tilted for clearance and then the drum is not flat on the surface. You end up using only the top edge of the drum which will put an uneven finish on the brass.

Bob, sanding disc, not sanding drum. The discs are flat like the cutoff discs, and they're flexible so they will tend to run flat against the material even if the Dremel is slightly off vertical. And because they are flexible, there is much less risk of damage.

[TrainCat2]

Bob, sanding disc, not sanding drum. The discs are flat like the cutoff discs, and they're flexible so they will tend to run flat against the material even if the Dremel is slightly off vertical. And because they are flexible, there is much less risk of damage.

I'll try to get some in the next day or two.