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Structures on th LP-and-N RR, vol.4

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  • Carl, Mike, and Jerry, thanks for your posts, much appreciated.

    Carl, you have a point, they are expensive. However, I have checked around on sites to order

    parts and wow, they are really expensive, especially 1/24 scale parts. Not only am I

    casting parts that are of my own design and requirement, not available for purchase, but

    when I divide the cost of resin by the number of parts I get per bottle it turns out they

    are quite cheap in comparison.



    • Thanks Bob, the tutorials help me to understand the process, however, it looks very challenging to me!


      • Thanks Dave. Maybe someday you will find the need to reproduce a number of your details.

        I started to take some photos for the next step but developed a problem with my camera

        (it is real old), the fitting for the USB cord seems to have broken off inside the

        camera, that may delay my postings.

        Anyway, the next process is to start resin casting and there are some things you should

        have on hand beside the liquid resin. Lets deal with the one piece mold first.

        Guys who want to go full steam will need such things as a pressure pot and a source for

        pressure/vacuum but this is not intended for them, it is for the guy who just needs to


        I recommend that you wear gloves and you will need a lot of newspapers to protect your

        working area. Cut something FLAT to just over the size of your mold, I use Gatorboard but

        flat plywood would be OK too. Next you will need a sheet of something that resin will not

        stick to, I have heard that some plastic wraps work ok but I always use the paper that

        is left from a sheet of labels or stamps, that non-stick side works great. You will

        also need some sort of weight to press the flat board down to seal the casting while it

        sets. Machine shop weights, wheel balancing weights, or bottles or bags of lead shot, or

        anything that's heavy.

        We will pour resin on the next post.



        • Now is the time to start casting, we will deal with the one piece mold first.

          Some folks apply mold release to the mold and let it dry, I normally do not require this

          step, it's up to you. Your mold should last longer of you do so.

          With the mold face up on your newspapers, slowly pour you resin mix into the parts

          until it SLIGHTLY overflows. Then take the non-stick paper and starting at one side lay

          it over the mold and sort of roll it over the rest of the mold pushing excess resin along

          with it. That helps to push any air bubbles along instead of trapping them in the mold as

          would happen with simply laying this down without rolling. Then quickly lay the flat

          board over all and apply the weights to hold it down and force out any remaining liquid

          resin. Let it set for whatever time your resin instructions say, I usually wait about a half hour.

          Then remove the weights, the board, and the paper and pick up your mold and carefully

          remove the new resin part. There will be a thin film of resin around the parts but it is

          usually thin and easily removable with a hobby knife and sanding sticks after breaking

          it away by hand. I did not get a photo but will posting one with the two piece mold

          write-up. If this film is too thick and hard to remove you can usually fix that by adding

          more weights to press down on the mold.

          Here are the first two castings on this project. Any little air bubbles that might

          remain can be filled with hobby putty.



          • Bob, your first castings came out looking just perfect, but that's what we've come to expect from you now isn't it.

            Greg Shinnie


            • Bob,

              The castings came out beautifully. Your description of the squash method is going to be very useful to me when I get back to resin casting.

              I was given a sheet of glass with rounded edges a couple decades ago which makes a great work surface. Residual resin can be removed with a razor blade.

              Thanks again.


              Not everything that is faced can be changed, but nothing can be changed until it is faced. James Baldwin


              • Greg and Mike,thanks, I appreciate your posts.

                There is a little step that I do without thinking so I forgot to mention it.

                Right after you pour the resin into the mold I take a toothpick and just dab it into spots that

                could hide an air bubble. That includes closed protuberances such as the hub of a wheel, or

                small thin sections such as the bracket arm at the front. That will release any small

                trapped bubbles.




                • Splendid casting results Bob! How long have you been doing casting with resin? If you want to make multiple castings, like your meter boxes, do you cast one at a time or make many masters to cast?


                  • Good morning Dave, I have been doing resin casting for about as long as I can remember.

                    What has changed is the fact that RTV rubber and resins have improved many times over.

                    I'm not sure I understand your question about multiple castings. If you just need several of the

                    same casting I simply pour one, work on something else for about a half hour, pop the

                    casting out and pour another. etc. etc.

                    If you need MANY castings you can make multiple molds from the same master or cast a few and

                    then use them to make a mold with several mold cavities. In either case pouring many castings

                    at the same time.




                    • Bob that came out perfect!! A master at mold making for sure!

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


                      • Thanks Jerry.

                        Here's the first casting from the two piece mold. Scary isn't it?? Not too bad, perhaps a

                        little more weight will make that web even thinner.

                        Here are the same wheels with the web quickly removed. Now all that is needed is a clean-up with

                        the #11 hobby knife and sanding sticks. A little work but nowhere near the work of making another

                        set of wheels from scratch.

                        I had a reason for making the sides and the wheels first. I have a lot of other parts I want

                        to make masters for but in most cases I needed these parts to measure against so further parts will fit properly.




                        • In a traditional two piece mold you cut a gate into the molds so that while holding the

                          two parts together you pour the resin into it. However, without the pressure/vacuum

                          equipment there is always a problem with getting the resin to fill the mold completely. In the

                          squash method you lay the two mold pieces side by side face up and pour resin into both

                          molds then pick up one of them, quickly turn it over and place it on the other mold, the

                          keys will line it up OK. On top of this you place the board and weights to hold then

                          together until the resin hardens.




                          • Hi Bob,

                            You answered my question. Since drying time is fast, the one at a time method would be a good choice for this novice.



                            • I cut a floor and the divider at the back of the cab area from .060 styrene and assembled the

                              wagon so far. Again, this was so I could measure and judge the sizes of additional pieces and

                              know that they will fit (hopefully!).

                              This switching back and forth between making masters for parts and making molds, and

                              casting parts, all keeps you from becomming bored and removes the idle time waiting for resin to set.




                              • I guess this is as good a place as any to tell you my philosophy on moving parts for

                                models that are to be part of a static display on a model railroad. I am against it. If you want

                                to make all the wheels turn and the duflinkies move back and forth and either

                                never show it off or pick the model off the layout to show visitors how everything moves,

                                that's up to you. I do not like to do that and I also think that it encourages visitors

                                to see which parts move and which break off. You are the model builder and the railroad

                                boss so do as you please but I wanted you to know why nothing is made to be movable on

                                this wagon.