Duplicating custom parts using Silicone Rubber and Resin

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Duplicating custom parts using Silicone Rubber and Resin

Postby DesTROYer » Fri Sep 19, 2014 1:57 pm

Over the last few weeks I have been working on a C-130H Hercules. Im using the Academy 1/72 (Italerai) kit, and as many will be aware, the engine nacelles are too short for the RAAF C-130H, So I set about modifying the ones that come in the kit, and then using it as a mould for casting new duplicate engines. I thought some of you might be interested in seeing how I duplicated the custom part

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Here is a pic of a kit original, the flightpath after market piece that is too narrow to fit the kit properly (used as reference) and my modified nacelle, made by cutting the back and front off of two assembled kit nacelles and joinging them up so they become one longer nacelle closer to the correct dimensions.

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I also added a lip to the lower intake.

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First I made the master mould using a plastic cup, cut in half and sealed to the tile as a smooth base. Using bluetac, I stuck the nacelle buck on to the tile then mixed up equal parts by weight "PinkySil" silicone rubber from Barnes, which consists of two liquids that when mixed form a tough silicone rubber.

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Once the rubber has set, about 20 mins, you pop out the buck and you're ready to pour the mixed two part "Easycast" polyurethane resin, again from Barnes Moulding, into the mould. It only has a two minute pot time, so you need to mix and pour pretty quickly.

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As I said, it cures pretty quick and you can de-mould them in about 10 minutes, then just let them fully cure over the next 16 hours.

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Not bad for two hours work. They aren't perfect, due to some imperfections I missed on the master, but nothing that can't easily be fixed with a bit of tamiya putty. I actually got the mix wrong on the two bottom ones, which makes them a little soft and translucent. but they cured just as hard as the others, just took a little longer. I've since taken the best four and made up another mould up, so I can now pour four engines at once.
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Re: Duplicating custom parts using Silicone Rubber and Resin

Postby bell209 » Sun Sep 21, 2014 5:47 am

Very nice work and much better than the kit originals! Took me a while to make the ESCI kit ones satisfy my eyes, too.
Rob

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Re: Duplicating custom parts using Silicone Rubber and Resin

Postby GeneralJG » Sun Sep 21, 2014 9:17 am

Thanks Troy! That doesn't look too hard at all!

I'd like to have a go at this with 1/48 engines.....
John G.
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Re: Duplicating custom parts using Silicone Rubber and Resin

Postby DesTROYer » Sun Sep 21, 2014 10:00 am

John, its really not. Once you get your master they way you want it, you just have to figure out the best way to cast it. You want to avoid under cuts and deep hollows on the sides. The nacelles were easy as they have one flat side and all the hollows (the intakes) are mainly on the up.

So you mount the flat side to the flat smooth surface of the tile then build your mould box around it. I usually use lego as I can build it to size. I find that 10mm of rubber from the piece to the edge of the mould is good as it helps your rubber mould last longer. Pour the rubber off to the side of the piece in the mould box and let it flow up and into the details. If you pour directly onto the piece, especially if there is detail there, you can introduce an air pocket, which is not good, obviously.

http://www.barnes.com.au/addition-curing-silicone/pinkysil-1591
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http://www.barnes.com.au/polyurethane/easycast-1306
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