If anyone has the Walthers Cornerstone Arched Pratt Truss Bridge, eithter the single track or the double track version, can you tell me if the center segment is perfectly level flat on the top?
Being that it is an arched bridge, the remaining segments on either side slope a little, but is that center segment perfectly level on the top of the segment?
I ask because I am thinking about kitbashing this kit, so that middle segment needs to be level flat on top for the kitbash to work.
By the way, it will be either Item No. 933-4521 or Item No. 933-4522.
Kit bashing a real bridge is beyond most of our budgets or expertise. I think he means this one.
Edit I misunderstood and thought Rich meant the piece connecting the left and right sections, but he means the the side piece over the X, which in the photo doesn’t look flat.
I think that is an illusion of the photo. Foreshortening is the photographic word for it and is the result of a wide angle lens. The bridge is symmetrical but the impression is that everything to the right of that X in the bridge is longer. It wouldn’t make any kind of sense to have a model that inaccurate that the segment would be curved or on an angle.
Ed, thanks for posting that diagram. I had downloaded the instructions and studied that diagram, and it does appear to be flat - - which is what I am looking for to do a successful kitbash.
By the way, how do you know that the left and right sections are 60/40 and 40/60?
The center section is level and perpendicular to the bottom, actually the main stress point of the entire bridge. That is why it has an ‘‘X’’ brace in the center. The others also are flat on top, but not perpendicular to the bottom. That is a riveted bridge, all the girders are straight, but angled when constructed. A welded bridge will have some pre-stressed curved girders.
Ed Pullman is just about correct in His assessment.
Electrical/Machine/Structural Design Draftsman…before I got drafted in 66’…
The bridge that I am thinking about modeling is the PRR vertical lift bridge in downtown Chicago. It is actually a Parker Through Truss which is a modified Pratt Truss. It is illustrated in the drawings from that link as a Parker “Camelback” (Pratt) Truss, which is the Walthers model.
I ordered two of the Walthers kits and they arrived today.
The good news is that the center section with the X-bracing is perfectly rectangular, so it will be geometrically possible to add one or more additional center sections to increase the length of the bridge span.
What I fail to understand though is why the kit was designed with that 60/40 arrangement. That complicates the insertion of additional center sections. So, I need to further analyze how to pull this off. I invite all comments and suggestions in this regard.
Like I said in My PM…The X sections are the main vertical stress part of the bridge. The 60/40 arrangement was to offset the stress on the X sections where the girders would meet, instead of having them directly over a joint, like in a hinge. Sort of like a reversing section on track where they tell you to stagger the joints…not directly across from one another.
What You would do, is add an X section to bridge part 4 and 2 or two X section per part. Then You would reinforce the bottom deck with full length I- beams for the deck as I also suggested in My PM. Don’t over think this…It’s not that hard.
