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  • Simple body casting

    I don't know if this info is really needed, but if anybody is thinking of trying this, I want to explain how simple it is to make nice bodies without using expensive equipment. All you need is the silicone, resin, scales, and some mold box material.

    You have to kind of think backward making a mold. Start with the body you want to make and fill it with clay, the cheap Ben Franklin clay works fine for me. Let the clay extend about 1/4- 1/2 inch past the bottom of the body. Mount the body to a flat piece of plastic with screw up thru the bottom and into the clay.

    Use your glue gun to fasten the sides of your mold box around the body. Use heavy cardboard, thin wood, any stiff plastic, old corrugated plastic election signs. Just be sure to seal all corners and seams so rubber can't escape the mold box. Usually about 1/2 inch clearance is enough on all sides of the body and the top. You only use this box one time, so it doesn't need to be fancy.

    Using a cheap jewellers scale from Harbor Freight, You can set the scale for grams and mix rubber in disposable plastic cups using a plastic spoon. If you have old molds, cut them up in small pieces before you start and use them mixed in with the fresh mixed rubber as a filler. Pour the rubber into the edge of the mold and let it run up over your body.

    When the rubber is cured, cut the mold box apart and pull out your mold. Remove the body and clean out the clay. With a NEW blade, use the Exacto to cut a ledge around lower body edge of the mold. Make the front cut different than the back so thee is noticeable difference between the ends. Notice the ledge cut around this mold for the Lotus 38.
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    After the body is cleaned up, put it back in the mold. I use the Alumilite silicone mold release in the white bottle to paint 2 coats over the inside of the body and the mold box. When that dries, a couple hours, you can pour silicone inside the body and mold box. Just pour enough to keep it level with the top of the mold box. You want it to be flush with the top of the mold.
    Click image for larger version  Name:	P1010007.JPG Views:	0 Size:	151.2 KB ID:	92161Let the rubber cure and then pull the body and inner plug from the mold mold box. Remove the body and the mold is ready to use. You may have to experiment on how much plastic to mix up and how to insert the inner mold to slowly shove the air out. I have added holes into some molds to let air bleed off the sides of the body so there are no areas where air keeps plastic from flowing. This Lotus 38 mold is easy to pour. The rear of the plug is inserted first and the rest of the plug is slowly inserted working toward the front. You can see a hole in the front of the plug. This lets the air escape and allows the front to be fully cast. Click image for larger version  Name:	P1010004.JPG Views:	0 Size:	109.8 KB ID:	92162It's not very expensive to do this simple casting. Experimenting will show you ways to make your bodies and not have air bubbles and get solid body. Adding vents to let air out is simple to do and gluing some plastic rod to lower body edges is a sure fire way to let air out of the mold. With the plug poured to be even with the top of the mold box and the ledge you cut into the edge, the plug can't be inserted too far and all the castings will have even wall thickness.

    More coming
    Last edited by mattb; April 6, 2021, 12:21 PM.
    Matt B
    So. In
    Crashers

  • #2
    I've been told a mix of mineral spirits and petroleum jelly also works as a mold release between silicone. I haven't tried that. I do think an open wheel or roadster body is much simpler than a hard top body to mold and cast. Open wheelers are a good place to start.

    Many parts can be made with simple mold where the back side is glued to a mold box and is unfinished. Many parts can be cast in two parts and glued together to make a nice 360 degree part. Some parts can be completely covered with rubber, than slight cut open to remove the master part. This split mold can then be spread open and plastic poured in. allowed to close and cure and you can have a replica part.

    With 3D and so many guys making bodies, probably this info isn't needed anymore, but if anybody wants to pursue it, it is fun to see what you can create. I can answer specific questions and show more info if anybody is interested.
    Here is a Brawner Hawk made from a simple two part mold. Over the years, it has had a decal malfunction.
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ID:	92172 The 1951 Belanger Special. This is a mold made from a Monogram 1/18 scale midget that I cut and sectioned and used a lot of body filler on to get a body to fit the original scale plans.
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    Matt B
    So. In
    Crashers

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    • chappyman66
      chappyman66 commented
      Editing a comment
      Like someone once said.....it ain't rocket science.

    • mattb
      mattb commented
      Editing a comment
      That be our buddy Jack!

  • #3
    One more thing is I never use mold release on my molds to make it easier to remove the cured body. I've had too many paint problems with mold release and long mold life isn't a big deal. I even believe sometimes the mold release is absorbed by the resin and you can never get rid of it.
    Matt B
    So. In
    Crashers

    Comment


    • Kevan
      Kevan commented
      Editing a comment
      Silicone is insidious, you can't get rid of it.

  • #4
    Thanks for sharing, good info.
    Mike
    Oz

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    • #5
      Thank you for posting this info. Just getting into the hobby and not sure if I will get a 3d printer so this gives me info that I have been wanting to learn. Thanks again.

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