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Styrene Sheet Rod & Tube etc. - Grade Info. Uses & Techniques
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 Posted: Fri Jun 27th, 2014 07:07 pm
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844Fan
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Will do Herb will do.

Thanks for linking me to your site Ray. 
I looked it over and it has amazing detail for Poly building.

By the way have any advice on how to make molds like you did for the brakes on the RS-3 Conversion? 
I plan to have my buffers 3D printed and then like you did make them as needed.

I hear Latex is a ok way to go on making the mold if you use Resin but I'm not sure.

Thanks again everyone,

Joey


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 Posted: Sat Jun 28th, 2014 12:22 am
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Herb Kephart
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Latex is too limp and flexible. What you want is RTV- Room Temperature Vulcanizing rubber.

You can get small quantities from http://WWW./micromark.com/ 
But their stuff is high priced, and has very poor shelf life, even in un-opened containers.
Same with their casting resin.

Much better quality and price, but you have to buy larger quanities--http://www.smooth-on.com/

I have used RTV that had set on a shelf for 15 years--little hard to stir up, but still worked. 
Micro-Mark goes bad in a little over a year.

Read the ''how to use'' stuff on the Smooth-on site

The fun is just beginning, Tigger  (Pooh bear, when he first saw a little female bear)

Herb





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 Posted: Sat Jun 28th, 2014 12:44 am
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844Fan
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Thanks Herb

I'll look into RTV indeed since I'm going to be needing to make molds. 
What category would be the best from Smooth-on? 
I just wanna make sure I'm looking at the right stuff.

Nice shelf life for that brand.

"Please read the enclosed instruction book." (Mario - Hotel Mario) :thumb:

"You got that right!" (Phil Hartman)

Joey



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 Posted: Sat Jun 28th, 2014 01:29 am
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Herb Kephart
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The stuff that lasted a long time for me was Dow-Corning.
(probably only available to commercial users)

The Smooth-on site tells you what to use for what. 
Lots of info.

Herb





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 Posted: Sat Jun 28th, 2014 04:16 am
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Ray Dunakin
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I like to the "Oomoo 30" from Smooth-on. 
It's mixed 1:1 by volume so you don't need a precision scale, and is pretty forgiving if you're off slightly. 
You can also get it from some art suppliers, such as Dick Blick:

http://www.dickblick.com/products/smooth-on-oomoo-30-silicone/#items

For resin I like Smooth-on's "Smooth Cast 300", for the same reasons.

Both of these products have a pretty short shelf life once they've been opened. 
However, you can prolong it considerably by getting yourself some of that "canned air" used to dust out keyboards, cameras, etc. 
Before resealing the container, spray a little canned air into it. 
This displaces the "real air" and humidity.

Most of the things I've molded and cast were pretty simple one or two piece molds, 
and I just used foam core art board, scrap styrene, or whatever else was handy to form a dam around the master.

When I made a mold of the brakes for the RS-3, it was a two piece mold of an irregular shape. 
I filled the bottom half of the dam with modeling clay, and embedded the master halfway into the clay, 
building up the clay as needed to fit the shape of the piece. 

IMPORTANT: 
Make sure you use a modeling clay that does NOT contain sulfur, as this will react with the silicone mold compound!

Disclaimer: I'm not an expert at mold making or casting. I'm just relating what has worked for me.




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 Posted: Sat Jun 28th, 2014 12:57 pm
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Herb Kephart
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If you elect to do a two piece mold of a part, press a couple of cone shaped holes into the clay, 
to form keys so that the two mold pieces come back into register.

Don't forget to put some kind of of a release on the first mold half before pouring the second, so that you don't bond the two halfs together.  
I always used a light spray coat of Krylon.

Better to do some open, or flat back molds first, before you get into this.

When I was running the model shop, we had done a wooden model for a customer, of a corporate jet that they were dealers for. 
They liked the model, which had about a 20" wingspan, and asked how much an additional 3 would be. 
We took the original, made multiple piece RTV molds backed with plaster (without harming the finish on the original) and cast 3 more. 
Made the fuselages hollow to cut down on the weight (and the amount of resin). 
One of those jobs that you wonder if you can do, after you commit to doing it.

Herb





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 Posted: Sat Jun 28th, 2014 10:04 pm
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Ray Dunakin
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When I made the mold for the RS-3 brakes, 

I forgot to use a mold release between the two halves, and ended up with master embedded in the middle of a solid block of rubber. 

Had a heck of a time cutting it out.





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 Posted: Sat Jun 28th, 2014 10:25 pm
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pipopak
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Had a heck of a time cutting it out.

Model railroading if fun.

Model railroading is fun!

Model railroading is #$%** FUN!!!

Cheers!

Jose.





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