The New Year has given me renewed vigor and desire to see at least one level of my Coquihalla model operational.
On the first level of my model, I have three bridges I must complete in order for trackage to connect. Of the three, I have one completed (the HDPG between the second and third Quintette tunnels), I have another in kit form to make the last Coquihalla crossing just east of CNR crossing that will be kitbashed into the right size and look, and then there’s the pin and eyebar bridge between the third and fourth Quintette tunnels.
I have to be honest. This bridge scares the hell out of me. Look at it. The HDPG that took me a month to build is positively child’s play by comparison. That one had a couple of big girders, some stringers and hangers. Whoopdy doo. This eyebar bridge – well, let’s just say I can see why they stopped building them this way. Lace and lattice, eyebars and rods everywhere. The thing looks like a spiderweb on some angles.
And then there’s the small problem of lacking plans or engineering details. My HDPG came about thanks to an article in a modelling magazine. The kit bridge already mostly exists. But the pin and eyebar? Nada. Zilch. No plans. I can’t even find anyone with good field measurements. I went out there myself, and apart from length, the rest is tricky to divine. Tricky because the bridge is perched between two cliff sides with a river canyon underneath. It’s impossible to measure certain parts, or even see some of them. So there’s a lot of guesswork. This is why I pays to take time. As I’ve learned more about modelling, I’ve learned lots of terminology, but more important, I’ve learned what to look for. What questions to ask. What parts to measure.
The eyebar bridge looks intimidating, and it is, but in reality it’s pretty straightforward. You have four trusses that run the length of the bridge and are its backbone. Components of the trusses include posts, long horizontal stringers, and of course the eyebars.
Sandwiched in between the trusses is what appears to be plate girders. This is what the ties (12 inches thick) appear to sit on at their ends. From my examiniation of various photos, I cannot divine if there are any girders directly under the track. There should be, but it’s not evident in my photos. I suppose it’s possible these massive ties are thick enough to carry all that weight on their own. If so, wow. That means directly below the train is nothing but rails, the ties, some thin floorbeams and a few (torsion?) rods. Impressive.
Now to the build. You’d think a bridge this large would positively dominate the model. But in scale, it’s actually only about 13 inches long and a little over an inch and a half wide. Which makes all those rods, eyebars, channels, etc *very* finicky. Another problem is that 6" plate steel scaled in styrene results in something that has the structural integrity of paper. The little lips on the stringers are so small they’d almost require a magnifying glass to see. Rivets? Yeah, I think we’ll be skipping those.
Anyway, I’ve spent 3 years trying to figure this out. My battle plan is to keep it as simple as possible. First, I printed out a rectangle, in scale, representing the footprint of my bridge. My plan is to build it upside down, starting with stringers and girders. I’ll assemble four of those (to create four trusses). Next, I’ll create posts. The posts are laced on two sides, so that’s going to be tricky. Nobody makes lace that matches the size present on the prototype. Thus, compromise. I found some etched brass in an X pattern rather than the > pattern used on the prototype. I chose that because it’s a bit smaller than the > type offered was, and I can just cut the middle of the X’s to get my > pattern. Probably what I will do is create each post in components – the sidewall, a bit of lip for the lattice to attach to. I’ll get that done and then make a mold of it, and cast it in Alumilite over and over again. I need 40 of them so I’m not eager to scratchbuild each one. The bottoms will have the holes to secure the eyebars. Between each post is four of those, plus a couple that go diagonally from bottom of one post to top of the next one down. I’ll make a couple of each and use alumilite to replicate them also. Once I have the trusses done, I can then install the girders, and then the floor beams and start tying it all together. Detail bits like the rods will be done later. Once it’s steady and strong enough, I’ll flip it over and work on the top deck.
Last night I began working on the stringers. The stringers run the length of the bridge and each of the 10 posts per truss are bolted into them. They have lace on the bottom and plate on top. Immediately this presented me with a challenge – the available styrene C channel pieces were either too big, too wide, or the lips of the C shape were too long. After finding channels that had narrow enough lips, I assembled them on some thicker-than-scale styrene strips. I was pleased to see how strong these work, but dismayed to realize what I had was twice the size of scale. Crap. So I removed the c-channel and found some L shaped styrene and glued along one edge to create the c-channel shape. Still a bit over spec, but okay. It’s not going to be exact. Exact would be so small and weak. The toughest part is keeping this extremely flexible styrene straight and even. It likes to twist and bend. Getting one L- shaped piece in position after pulling the c-channel was about all I could do, but I think it’s looking about right. I positioned two experimental posts I made using the brass lacing in between to check. Those posts are more or less to scale (about 12 inches in real life), so if they fit I should be good.
This is going to be tricky!!!