Friday, October 22, 2010

Cutting Plastic: Carlaw build 1

This is actually big news for me, this cutting plastic business. I've been researching the R Street corridor for years, planning my layout for just as long, and getting lost on historical journeys that sometimes last months at a time.* Drawings and cardboard mock-ups have been produced for a variety of buildings, but cutting actual plastic with the intention of making an actual finished model hasn't happened.

Until now.

So this is my first scratch build project.  For it, I'm using a technique I first saw in a clinic by Jack Burgess, and he has since published it a couple of times in the hobby press. Basically you start with a CAD drawing with an imported prototype photo used as a reference. (Jack uses Photoshop I'm using Sketch Up since it's free and its designed for this sort of thing.) You print out the walls in your modeling scale, use a spray on adhesive to stick the drawing on to your wall material, and just cut on the lines. I'm oversimplifying, but that is the essence of it. Jack goes so far as to subtract the thickness of the plastic sheet he uses from one set of walls to keep the prototype dimensions accurate. I didn't do that this time, but it would be easy enough to do.

I started with my Google Sketch Up model of the Carlaw Brothers Polishing/Blacksmith shop building to make cutting templates. The model is based on a much clearer version of this picture from the Center for Sacramento archives.  I altered my Sketch Up model to have cutting guides for window and door castings.

On two of the walls I have good photo evidence of window size and placement.  On the other two walls however, I have zilch. As a guy who leans heavily on the prototype for inspiration, imagineering window and door placement feels dangerous. I figure as soon as I finish this model, historic photos of the mystery walls will suddenly appear, which wouldn't be such a bad thing.

Here is a picture of me trying to figure out which workshop door I should choose on one of the walls - this is where having a cardstock mockup is a help.

I then used my digital caliper to figure out the hole needed to accept the various castings.  I measured in millimeters then divided that number by 3.5 to get the size in HO scale digital feet. Since my Sketch Up model was drawn with full scale dimensions I just used the rectangle tool and entered the dimensions in digital feet.  I printed the walls out in HO scale, cut out them out and used a spray on temporary adhesive to stick on a piece of Evergreen sheet styrene. I feel compelled to mention that it's important to have good ventilation and to wear a decent respirator when working with spray adhesives.  I used V-Groove 100" Spacing, .040" thick sheet styrene which appears to be a perfect match for the clapboard siding on the original building.

I'm hiding the front wall as it still has a piece of the hi-res image from the Center for Sacramento History on it and I don't have rights to distribute it.  Once the plastic piece is cut out and my template removed, the wall will be revealed.

After cutting out the wall sections, I borrowed another tip from Jack by using a nibbler to cut out the window holes. I also used a small flat file to fine tune the fit.

   One of the nice things about leaving the template on for a while is that it does provide some protection against errant knife cuts.  Although it's not total protection from my honey glazed ham hands. I had to redo one wall already because of an unsightly scar.

More soon.

* And enjoying every minute of it.

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