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structures on the LP-and-N RR vol. 5

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  • Pete, Carl, and Rich, thanks for your posts.

    Rich, No mold box required, that photo of the blue rubber mold is all there is. It lays flat, face up, on a pile of
    old newspapers (you will need them, it's messy) and then pour the liquid resin all over the mold helping it spread with a wood stick.
    If you have any small deep areas that collect air bubbles you can quickly poke them with a toothpick
    to release the air bubbles. I had only two areas with this mold and that was the two doorknobs.

    Next I lay a sheet of release paper face down over the resin, not plopped on to trap air bubbles, but sort of rolled
    on starting at one side, rolled to push excess resin off the mold instead of trapping it. Many papers work
    for this but they must not stick to the resin. I use the backing sheets from mail labels or stamps, non-stick
    side down to the resin. Next goes a sheet of something flat, I use a piece of Gator-board.

    Then quickly top this off with weights, the more you use the thinner the flash. I use a couple of 1-2-4 steel
    blocks but anything works.

    At this point I go do some other work and in about a half hour I come back to remove the casting from the
    mold and start over with another pour.

    Click image for larger version  Name:	DSCF4578.JPG Views:	0 Size:	87.7 KB ID:	1009445

    This is what the casting looks like. Don't worry, all that "flash" areas between parts is very thin and breaks away easily.
    Follow that with a hobby knife to easily clean up the edges. If your flash is too thick you need more weight. If it is uneven,
    OK but thick in only some spots, you need a flatter top board under the weights.

    Any questions?

    Last edited by sgtbob; 09-12-2022, 05:57 AM.


    • Thanks for the How-To, Bob. I'm surprised that the weight on top didn't spread the edges of the mold.
      But your results are proof: nice straight sides!


      • Great how-to Bob, Thank you.



        • Thanks Bob. Nice castings and mold. I never tried mold casting thinking it is expensive and difficult to do. What's your take on cost and difficulty?


          • Bill, Rich, and Dave, thanks for your posts.

            Bill, I guess you could have too much weight and distort the mold but I have the outside borders of the
            mold (alongside the walls), at about 1/4 to 1/2 inch and that seems enough to keep from squashing the mold
            out of shape. I guess what I'm trying to say is when you set the walls for the outer edges of the rubber mold do
            not make them too thin and weak.

            Dave, that all depends on you, the modeler. sometimes it's the only way to get the castings you need at any price
            and when you compare it to the costs of 3-D printing it is really cheap. I watch Model Expo for sales and that helps.
            It also helps to not waste too much of either rubber or resin but that seems to come with experience and that is if you
            will be needing many castings, it would not pay to buy a whole set of materials and then only use a tiny bit. I use it
            enough to always have some on hand, even for small projects.




            • I am just about finished with casting parts for this structure, I have all I need plus a few extras in case I mess something up.

              That's all except the corbels which I will need a ton of each. I simply pour resin into the few parts I still need and build up my stores.

              With this type of mold you do not need to cast every part, just the ones you want.




              • Bob, your castings look wonderful!
                Looking forward to seeing them all come together!



                • Bob,
                  Thanks for the mold making demonstration!
                  And thanks for answering the resin question.



                  • Looking good, Bob!!


                    • Greg, Scott, and Fred, thanks for you posts, much apricated.

                      I thought you might like to see how the walls will look, the left one is the left wall. The others will make up the front wall.

                      The right wall and the rear wall are both mostly straight brick and I don't have any of them done yet.

                      All these walls will be taller, the structure has another section with molding above and below and I thought it would

                      be easier to model as a separate section. More cleanup required.

                      Click image for larger version

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                      • Wow Bob! ...Awesome work....


                        • Very nicely done, Bob! Inspirational! Keep going!

                          in Michigan


                          • Bob,
                            Thanks for answering my casting question. I guess it's time for me to smart small and try my hand at casting.


                            • Talk about perfection! Just awesome work!

                              "And in the end, it's not the years in your life that count. It's the life in your years." A. Lincoln


                              • Wow, Bob that's looking terrific!
                                You clearly have thoroughly addressed your Gettysburg Station project details