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Casting parts

In keeping with this issue's "theme" of looking outside the box for ideas, our Tip of the Month is one we uncovered while looking through some old model-railroad magazines. It involves casting simple parts with automotive body putty.

With this technique, you can make a simple impression and cast the parts in a material that can be sanded, primered, painted, or plated, along with your other model car parts.

You'll need to take a trip to the craft store for some Fimo or Sculpey modeling clay. It remains flexible until it's baked, and it doesn't shrink.

The simplest way to make a mold is to knead a substantial wad of clay in your hand to soften it, then press it onto a flat surface into an oval shape that's thicker than the "master," which is the piece you need to reproduce.

Press the master into the clay. (This technique works best when the master has one flat side, and no undercuts - like a valve cover or oil pan - that would inhibit the master from being removed from the clay. After you've made the impression, carefully remove the master, so as not to disturb or distort the clay. Following the instructions on the box, put the mold in the oven until it hardens.

When the mold is cool, coat the inside with a mold release such as vegetable oil, mix a small batch of automotive body putty (a two-part polyester putty, such as Evercoat, would be perfect) and squish it into the mold cavity.

When the putty has hardened, the new part can be carefully removed from the mold. This is the tricky part; the hard, baked mold may not want to give up the master without a struggle.

As a worst case, if you have to break the mold, at least you've duplicated a part, which may be all you need if you can only find one of that perfect valve cover for your next contest model!


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