Monday, December 23, 2013

087 The Navajo Mining Railway - Building an Ore Car Fleet #2

When designing a fleet of cars, you have to figure out how to manufacture them.  I've made kits before, and the process is very similar with the exception that you don't have to write instructions or consider packaging.

Let's go through the steps!

First, we need a prototype.  We are using the Gilpin Tram ore cars, Phase 2 and 3 as the starting point.  This is an imaginary railroad, but we want it to be prototypical enough that the car makes sense.  Otherwise this one would be a hot tub and beer car.

Next, I grab the sketch pad and start drawing.

I've got a ton of sets of Grandt Line On30 SR&RL type trucks, so we'll use those as they have a small profile at 22", which adds to the eye appeal of the mining line.  Smaller is better.  This also helps save money since I already have them and will just have to pick up a few more sets.  They are $12.50 each when I last bought them.  Actually, they are very close to the prototype.

I keep a small sketching set in my desk.  This consists of 9 x 12 sketch pad, an assortment of drawing pencils with different lead hardness, pencil sharpeners, erasers and other sketching tools.

First, I really want to understand the model.  Sketching it gives me a quick feel of the model and how it would go together.  I can already see that we really only have two pieces to cast: the ore bin and one car side as they are mirror images of each other.

While I'm not an artist, I can sketch well enough to give me what I need, and can do this in two minutes.  Now let's take a look at molding the pieces.

For the ore body, I can see a two piece "squish" mold.  This is a mold where you pour an amount of resin in the bottom and then insert the top part and squish the resin out of the evacuation ports.  Special steps have to be taken to get it from warping during the squish, but it will be good enough for our project.  I'll put in special "markers" to help line up the car side pieces so that it is all straight.

The car side is a bit tougher.  We'll have to lose the bottom board under the coupler, so we'll plan to mold it separately.  The first pass I did wouldn't work as it would trap the evacuation gate in the middle of the mold.  So I redesigned it so the gates are where the mold sides meet.  The gates will hit the casting at a place where they will not be seen (next to the ore bin) so we can sand them flush.  That will work!  This is just planning at this point!

I put all my sketches and print out in one folder for easy use, as I'll have other projects laying around at the same time.  The next step...CAD drawings!

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1 comment:

  1. is another that keeps a Gilpin style box on a steel frame.

    Bill Uffelman

    On Tuesday, December 24, 2013 12:50 PM, William Uffelman wrote:
    Might want t look at the "modern" ore cars in this thread. While these are 1/35n2 they could be done as On30 too.

    Bill Uffelman


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