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Modeling the South Norwalk Iron Works

By Craig Bisgeier (Modeling by Neil Henning)

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As we have been making progress with the railroad, we need to populate the layout with buildings that will accurately reflect the look and feel of the area in the 19th century.  While we will use appropriate plastic and laser-cut wood kits where we can to fill out scenes, we are going to need to build many scratch-built structures, particularly unique ‘signature’ structures that place a scene geographically.  One such structure is the Norwalk Iron Works that sat near the Housatonic Railroad’s tracks in South Norwalk, CT.  I recently learned that it still stands today, restored, as a part of the Norwalk Maritime Aquarium complex. (See the About Us page for another historic picture of the building.)

A quick look through the Walthers catalog showed that there was no structure kit that closely resembled this large building.  Its simple design and clean lines also made it a natural for scratch-building.  Further, since the long dimension of the building (about 250-300 feet) was a simple repeating pattern, I decided it was also a good candidate for a molding and casting project. 

By modeling and molding the side walls of the building in manageable sections, we can make these walls as long as we want by grafting sections together.  We can also re-use the model in a different location by changing the details and size of the building and get all the advantages of a second scratch-built quality model with little additional work.

I made some rough scale measurements from the photos I had, found an appropriately sized window casting from Tichy Train Group that would work, and built up construction drawings based on those measurements and ratios.  I hope to get a chance to find out how accurate the drawings are this spring, but they seem to capture the size and proportions of the prototype pretty well.

About the same time, my friend and fellow modeler Neil Henning wanted to work on a project for the railroad, and was looking for something to bring home and work on between work sessions.  I had recently finished the construction drawings for the Iron Works, and it seemed like a good match.  We talked over what I wanted the building to look like and how the parts would go together.  Then I gave Neil the drawings and some photos and drawings I had of the building, some styrene brick sheet and other supplies, and let him go. 

Well, within a couple of weeks, Neil was done with his part of the project.  He had cut the brick sheet to the proper dimensions, located and cut all the window holes, added brick relief details and window sills and retaining bolts on the walls.  He also added 1/8” square styrene strips around all the edges and windows to give the walls some thickness, which was going to be important when we set up the mold of each master wall section.

We left off the distinctive window hoods (lintels) because we are going to cast them separately as detail parts, and apply them directly to the model.  This way, when we re-use the basic structure later, we can make and use different hoods to make the structure look a little different.

To prepare the mold boxes, we glued the master wall sections down to a sheet styrene backer panel cut slightly larger than the master walls.  (Note the holes in the side wall backer - It developed a curl during construction, so we had to screw it down to a slab of plywood to flatten it.)  Then we built dam walls around the master using Lego bricks (which the RTV rubber doesn’t stick to -- see the picture of the end wall below), and held it down by running a bead of hot glue between the styrene backer and the bricks.  The hot glue also seals the bottom of the wall to the floor of the mold box preventing the liquid RTV from leaking out.  The dam walls are placed to leave a minimum of ˝” around each edge of the master.


Time to make the molds.  We started with the side wall master.  We mixed equal parts of the A and B components of the RTV rubber and poured it into the mold, trying to minimize the number of trapped air bubbles in the mixture.  I under-estimated the amount of RTV we would need, and it turned out we needed to make three pours to cover the entire master by the time we were through.  It also pooled a bit into one corner, which we may have to try to shave down after the mold has set up – we’ll see.


As it turned out, the side wall mold turned out OK.  We completed that mold, and then the end wall mold and the tower mold.  We actually ran out of the RTV on the end wall mold, and had to make it up with a different type of mold RTV .  It worked, but not too well.  Well enough to pull all the parts we'll need for this project, though.  Within a day or so, the RTV was cured and we carefully pulled it off the master models.  I was really pleased to see they came out very, very well.  almost no trapped air bubbles or blemishes at all.

Pouring resin into the tower mold Teasing air bubbles out of the resin

Now that the molds were done, we wanted to make some parts!  Here you see Neil mixing the polyurethane resin (Alumilite) and pouring it into the tower mold.  This resin had a long working time, so he had plenty of time to tease out the air bubbles that sometimes occur during pouring.  This is done with a strip of styrene or a toothpick.  As a matter of fact, this resin was so slow that we actually helped it along a bit by running a hair dryer over the resin to help kick it over.  In the end though, the parts worked out very nicely.  

We eventually pulled four side wall sections, four tower sections and two end walls for the Iron Works model.  Since the location of the model actually wraps around a corner in the backdrop, and it will be half-embedded into the backdrop, an additional four side walls were not necessary to pull.  After all the parts had been made (plus a few extra wall sections to use up the resin we had) we taped the model together to get a feel for the size and shape, and boy were we happy with it.  It is going to look great on the layout in South Norwalk, it will be a real eye-catcher.

Since the walls were cast as solid panels, the edges which met at 90* had to be beveled to 45* so they would mate with no overlaps.  This was easily done on my tablesaw, but the panels had to be sanded flat first to ensure the saw would cut a straight line.  A bit of shimming with masking tape under some low spots helped, and in the end the walls were fit together very nicely.

Neil brought the parts home and began the assembly process.  Actually there was a decent gap in the time from when the parts were finished to when he got around to starting to build the model, several months really, and in that time some of the parts cast in Alumilite warped a little bit.  He spent some time coaxing them back into shape, and when he did assemble the parts he had to use 1/8" square brass tubing across many of the joints to ensure the walls aligned with each other.  All of it was glued together with epoxy, and this seems to have held up well over the last few months.

As mentioned earlier we did not make the window hoods (called Lintels) ahead of time and include them on the master mold.  This now meant that we needed to make all we would need for the entire building separately.  In the end this would turn out to be more than 150 lintels for  this model alone!  Had I realized that early on I might have included them in the master amd molded them on.  But what's done is done and now I needed to make them separately.  Again, this process ended up taking several months to generate all the parts we would need in the end.

I started the entire process by making one master lintel.  Actually I made it three times before I had one I was happy with.  The master was molded as you can see in the picture below.  From that mold I made five separate castings of that lintel (actually eight after I threw out three that were not good enough).  Those five became the basis for another master mold, and a five-piece mold was made from that.  This mold was eventually used over 30 times to make enough lintels for the Iron Works model.  That was a lot of work -- in the future I'll make at least one more 5-part mold from the same master and cut the work time in half.  It takes no more time to cast 10 parts in two molds than it takes to cast five arts in one.  Or maybe I'll just cast them in place on the master model...

Molds used to make the 150 and more lintels for the South Norwalk Iron Works building

By the end of the summer I'd made enough lintels for Neil to start finishing up the model.  He painted the entire building with brick red enamel spray paint, then painted the window sills and the lintels a stone gray color.  The windows (about 150 Tichy Train Group plastic castings) were painted a brown color and glued into place with CA cement.  Clear styrene glazing was applied inside the model after the painting was completed.  In the picture below you can see Neil's progress with the model just before our open house on October 2005.

I'm sure you can see why I'm so excited about this model!  It is looking great.  

After the open house, Neil got started on the roof of the mail part of the building.  He cut a large rectangle out of .040" styrene and braced it heavily with 1/4" square styrene rod to keep it from warping.  Once it was cut to fit, he scribed lines across the entire surface from side to side, 1/8" apart.  Then he applied Tichy Train Group slate shingle strips across the entire roof.  When all shingles were applied, he painted the roof with washes of gray and blue paint, and streaked on a number of different colors too.  It looks great.


Not too long after the open house, we started thinking about running a freight spur to this building so we could include it in the operations of the layout.  I didn't feel very comfortable with that, the real building was served by rail but on the backdrop side of the building (see illustration at the top of the page), and I had not designed in appropriate freight doors on the model.  The solution, I figured out, was to include another building from the compound.  I chose to make a model of the foundry building seen in the foreground of the sketch, but to move it around a bit to fit our space limitations.  I chose to model the building looking at the end and only model it a short distance to the backdrop, about 4".  I would take the large overhead traveling crane and place it in between the factory (current model) and foundry.

The Foundry building will use wall sections of the factory building to maintain a family appearance, but they will be heavily modified.  It will consist of an end wall and a side wall cut in half to represent two half-length side walls.  All three walls will be cut down in height by removing the first floor, and a wooden clerestory will be built on the top of the roof with windows lining the sides of it.  The attic window in the end wall will be removed and a round brick opening will replace it, and a large industrial fan will sit in the opening.  Fortunately back when we made all the original factory parts, we cast a few extras which will now make up the parts of the foundry.

The table saw once again helped with dramatically altering the castings to make a new building.  We used it to remove the lower floor of one full side wall and one end wall, then we cut the side wall in half to make it only three windows wide.  I got a piece of PVC tubing and used it to mark out a new circular hole over the attic window, then cut it out and inserted a small ring of the pipe to make a round vent window, a fun little project.  Neil took these home along with some extra sheet styrene and larger Tichy windows, and a few weeks later he came back with a finished building.  This looks pretty cool and helps give the whole scene more of a feeling of there being a complex of buildings here, and you can't see all of them.

To help flesh out the scene even farther, we decided to include an overhead traveling crane between the main factory and foundry buildings of the iron works.  A Walthers kit, after close examination, looks pretty close to similar cranes that existed in the period.  We decided to mount one of the supporting girders flush against the foundry building with a supporting girder underneath it, and a little room between it and the other side of the factory.  The crane, of course, straddles the track that runs next to the building so finished pumps and boilers can be loaded out and parts and raw materials can be loaded in. 

One good thing about Using the crane here (and a major reason for including it) is that the crane's traveling beam kind of breaks up the backdrop between the two buildings a bit, making it a bit less obvious the two buildings both end at the backdrop.  On the other side of the foundry we'll place a single large tree next to it, again to hide the hard transition into the backdrop.  It actually works better than I expected it to, which was a pleasant surprise.

In the end (well, there are still many details that need to be completed including the signage) I'm very pleased with the scene and both of the buildings that make up the South Norwalk Iron Works industry.  It was a lot of work that has paid off handsomely for us, and I'm very hopeful that it will be one of the nicest scenes on the layout.   As far as the molds and castings for this model go, we are currently taking some more of the wall sections and cutting them up / changing the lines to model yet another building on the layout, a textile mill for the town of Winnipauk.  The entire model will be highly modified and may not even be recognizable as the same basic model -- which is just fine by me.  I like being able to re-use something that we put a lot of work into and have it stand on its own.  If that model goes well, we'll put up some more pictures and write a page for it too.

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