Having spent a lot of time on designing the trusses, deck, swing structure etc. the bridge’s complexity kept growing. But the more I added, the more I realized that still a lot of details had to be added.
The pedestrian walkways on Third Avenue Bridge were not really part of the bridge’s core. Existing high resolution photos from the NYC Dept of Records website gave me a good idea how they looked a hundred years ago. Rather, they were attached on the outside. Even though I lacked the details of the construction in reality, I could guess how this was done based on those photos. I did not include the walkways in my original design, but I was able to add them to my model without major modifications to the bridge design.
Walkways
I ended up constructing them as completely separate structures made of .024″ lazerboard (with .035″ supporting brackets), a lot of .0208″ x .0833″ basswood strips for the planks and metal etched railings. A 2.4 mm styrene angle between the posts on the outside of the walkway mimics the construction and the aesthetics of the prototype. The lazerboard turned out to be strong enough so that the walkways could suspended on both ends. Still, I designed them such that the additional deck brackets (under the bridge) made from MDF would also support them. For the railings I used a product from N Scale Architect for the first walkway. I later found a better looking product that was closer to the original Art Deco style railings of the bridge. That product was the SNCF Fencing from Scale Link (a UK company). To facilitate the integration of the metal etched parts with the lazerboard, I also created a supporting structure just with the guardrail posts and the outer edge of the walkway. This also allowed me to cut that beautiful ornamental joist on the outside of the walkways. The resulting walkways with railing (specifically the second version) looked pretty amazing.
The photos also show that additional walkways can be found around the operators house. Access to those is from the pedestrian walkway up a stairway. For the their construction, I designed a basic frame of lazerboard that I could attach underneath the operators house. I’d cover the structure with wooden planks made from basswood strips. For the grates, the handrails and the stairs I used these amazingly fine and realistic looking etched metal products from Gold Medal Models. To get the correct height of the stairways I had to solder several stairs that are connected with intermediate landings, again made from the walkway grates. For the handrails I used brass wire. The soldered wire also improved stability of the complete 3-inch long stairway.
Bridge Roofing
With high resolution archive pictures exclusively based on terrestrial photography, we have very little details on how the real roof of the bridge looked like. We know that it was one big round shaped cover over the four trusses like a dome. But that’s it pretty much – at least to my knowledge. In my design, the roof had not only to be visually close to the prototype. It also has to function as a bracket that holds the 3 segments together (mind you that I still haven’t glued the 4 trusses and the 3 segments of the operators’ house together – and I very well might never do that).
Some relatively small dimensions of the roof parts translates into very delicate pieces in N Scale. Creating a web of brackets with 1/8″ MDF oriented in multiple planes helped making the roof base structure sufficiently stable. The roof is made of a single sheet of .024″ lazerboard Once glued to its base, it was surprisingly strong. Regarding the painting and weathering of the roof, I could only make guesses. On the existing black and white photos, the roof appears uniformly gray, suggesting it is a metal roof. To make it a bit more visually interesting, I decided to make a copper roofing. I added standing seems and air-brushed it with acrylic copper paint. Then I slightly weathered it with a black ink solution.
Lateral Bracing
One of the last challenges in completing the bridge was designing and constructing the struts and lateral bracing on both sides of the operator house. They hold together the top chord. I didn’t really include them in the design of the trusses so I had to design them as independent additions. My first attempt was to use styrene parts but the result looked inadequate (photo 1 of 3 below).
Again, the better solution was to use the lazerboard. In the meantime, I had enough experience with that material so I designed a separate component that would sit on top of the chord and between the trusses. I extended them over five members. I used the lazerboard again in the horizontal as well as in the vertical plane so that interlocking members would form proper (and very robust!) 3-dimensional braces. Having my own Beamo laser cutter and engraver in the meantime definitely helped me to improve and optimize the design. The six separate components fit well between the trusses and don’t even have to be glued down, at least for now. To close the roof and lock it down to the trusses, I used string magnets on each corner. This also gives me the flexibility to remove the roof for adding lighting, for instance.
Almost Done
In a separate blog post I’ll discuss the integration of the bridge in a diorama. That will require some further adjustments and additions. But apart from that, my Third Avenue Bridge is nearly complete now.
