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As of the last posting, I had connected the drawbridge-style extension and embedded some wires to electrically connect the extension track with the main bridge track.
Now I hope to get a local modeler with brass-etching machinery to produce some embossed-rivet gusset plates for me to use on the visible girder joints. This required me to spend many hours tracing the shapes and [digitally] drawing the rivet patterns, so I could forward these to the brass wizard (whom I'll call "Mike"). Needless to say, I did not accomplish anything photo-visible during that period (about 2 weeks). Also, I discovered another context for that old adage "the devil is in the details". When I printed an enlarged copy of the photo of the waterfront end of the prototype ore bridge, I noticed that some of the bracing was TOTALLY different from what I had first believed! Time to tear apart and reconstruct the top of the extension...
Currently I am waiting for Mike to produce some samples of the gusset plates. His "daytime job" is to manufacture printed circuit boards and, since he has to give those customers priority, it may be awhile before I get those finished plates. So I've decided to focus on other areas while I wait.
One aspect of my bridge that had been neglected was the supporting legs - I still needed to install the diagonal braces on these.
Starting with the simpler rear "inland" legs, I cut sections of 1/32" thick brass strip and soldered these to the inside edges of each frame. Much as I would have loved to achieve perfect 90-degree angle accurcacy from top to bottom, I placed greater emphasis on ensuring that the brace patterns would be symmetrical on both legs. Starting at the top, I soldered each diagonal brace on one leg frame, then positioned the corresponding brace on the opposite leg so that it resembled a "mirror" image of the first, and soldered that one accordingly. Even though the result is not a perfect scale replication, it works for me: ob_model_rear_legs_01.jpg.
Applying the details to the forward (or "waterfront") legs proved to be a much more challenging task.
As I have mentioned earlier, I wanted all of my support-critical junctions to be soldered rather than cemented. Luckily, the forward legs frames were already structurally sound - this allowed me to avoid using a hot soldering iron for the bracing.
On the main bridge body, I had applied all of the girders first, and would cover the joints with gusset plates at a later time. But this approach seemed impractical for the tiny, cramped work spaces of the forward leg frames; I needed to first cut out all the gusset plates and attach them to the outside edges of the junctions, using CA. Once the plates were in place, I placed the diagonal brace sections on the inside surfaces of the gusset plates and secured these with 5-minute epoxy cement.
Photos of the both the side and end views of the finished forward legs are at the links below:
ob_model_fwd_legs_01.jpg ob_model_fwd_legs_02.jpg
There probably is a technical name for the section I will be describing in the following paragraphs, but I don't have the time to look it up (I'm already way behind schedule!) - if anybody reading this knows the answer you may feel free to communicate it to me via email. But I have included an image with the target area circled in yellow so you'll know what I'm working on:
Unlike previous sections of the bridge, the forward "foot" structure contained numerous curved edges and trapezoidal shapes. Furthermore, since this would be supporting the weight of the entire forward end of the bridge, styrene was NOT an option. Thus I spent many hours, and consumed 4 Dremel fiberglass cutoff disks, cutting out the support-critical pieces. (While cutting the trapezoidal pieces, my Moto-Tool got so hot I had to stop several times and give it time to cool! )
The following photo shows the curved pieces with the trapezoidal legs soldered on:
ob_model_fwd_foot_endplates.jpg
I then placed 1/8-inch width rectangular tubing on the trapezoidal legs on one endplate assembly and "sandwiched" them under an opposite endplate assembly. The image below shows a "before" and "after" view:
I needed four 6-inch long sections of 3/32" square brass to connect the end assemblies together - two for the top and two for the bottom. However, since I still don't know what the exact distance will be between each end (I haven't attached the leg frames to the main bridge yet), I needed to cut each length in half and join them in the center with a 1-inch telescoping piece of 1/8" brass tube. This will allow me to calibrate the length when I permanently attach the legs.
I needed some way to ensure accurately-aligned and structurally-sound junctions of the long girders with the end assemblies, yet I lacked the necessary clamp/jig arrangements hold the oddly-shaped pieces together, so here is what I did:
At the 'open' end of each half of the connecting bar, I placed a telescoping piece of 1/16" square brass tube on the inside. On the end assemblies, I drilled holes for .030"-thick brass wire at each point where the connecting bars were to be joined. The wire was slid into the holes, then soldered; the telescoped ends of the connecting rods were then slipped over the protruding wires. The wires are scarcely visible in the photos, but in the second one I have slipped-on a section of the long girder to illustrate the concept:
ob_model_fwd_foot_assy_02.jpg ob_model_fwd_foot_assy_03.jpg
The final two images show the almost completed forward foot assembly (it still needs the diagonal bracing added) and the assembled foot section with the forward legs loosely connected to each end:
ob_model_fwd_foot_assy_04.jpg ob_model_fwd_foot_w_legs.jpg
..and that's "the way it is" on this 20th day of December, 2003.
-KJL
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