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Dummy Radial Question

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Old 01-10-2014, 03:20 PM
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Default Dummy Radial Question

I just received a dummy radial casting through Bob Dively and will be using it in an Aeroworks Cessna 195. The casting is ABS plastic and is fairly strong, but I am thinking of adding to its strength by pouring casting material into the hollows of the cylinder heads on the backside. Doing this will also provide attachment points around the circumference for mounting and add strength when I cut out the shape of the engine. I could use normal resin casting material, but it is made to release and I want the material to become part of the back side of the cylinder heads. Can anyone provide me with what material I should be using?
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Old 01-10-2014, 03:36 PM
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5-minute epoxy & microbaloons?
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Old 01-10-2014, 04:54 PM
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Well, I have nothing against that, but have not used micro balloons. What is the benefit of adding them to the epoxy?
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Old 01-10-2014, 05:52 PM
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Quote:
Originally Posted by hookedonrc View Post
Well, I have nothing against that, but have not used micro balloons. What is the benefit of adding them to the epoxy?
When the epoxy kicks over, the heat expands the beads. I think they are un-expanded styrofoam beads. 5-minute epoxy kicks over fast & makes more heat so it is prefered type.

What you end up with is an epoxy/foam that is light, but fairly tough. It will expand so one doesn't fill all the way W/the paste. The resulting over expansion is easy to sand.

I have built up wing fillets & such this way.

You can vary the density of the expanded foam. More beads = more expansion/less density.

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Old 01-11-2014, 03:10 AM
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Quote:
Originally Posted by hookedonrc View Post
I just received a dummy radial casting through Bob Dively and will be using it in an Aeroworks Cessna 195. The casting is ABS plastic and is fairly strong, but I am thinking of adding to its strength by pouring casting material into the hollows of the cylinder heads on the backside. Doing this will also provide attachment points around the circumference for mounting and add strength when I cut out the shape of the engine. I could use normal resin casting material, but it is made to release and I want the material to become part of the back side of the cylinder heads. Can anyone provide me with what material I should be using?
I installed a Dively 7 cylinder radial; in my Cessna Airmaster. I supplied additional strength and a mounting method, by the addition of a ring, cut to the inside radius of the cowl. The ring is apporimately 1" wide, and was glued to the back of the dummy radial's cylinder heads. I used Goop to attach the ring inside the cowl.

I didn't feel any more support was required. If you will require nose weight, pouring resin inside the cylinders is a good idea. Be careful what you use, though. Any resin that disperses heat, like epoxy, may deform your piece.
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Old 01-11-2014, 03:14 AM
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Pushrods make a big difference.
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Old 01-11-2014, 06:34 AM
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LOL....I was wondering about the pushrods. I like the ring idea since I don't know what the initial balance will be. I have seen other installs where a disk is epoxied to the back. There a few spaces between the cylinder heads are left open to direct cooling over the engine. I may start with that then I can add the micro balloon mixture to each cylinder as required.
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