enginear joe Posted July 1, 2016 Share Posted July 1, 2016 Ahhh, I got the master to reveal his secrets! Just kidding with you. Thanks for sharing. I was trying different methods to reduce trapped air bubbles on my O scale pilots. After a few attempts I found that the molds had them too. The areas around the small steps were good at first and then tore away revealing small holes from the trapped air. I never remade the molds. I got frustrated at the expense and labor involved in the learning curve. I will try again someday soon. I learned on the last attempt not to cheap out and skip the proper mold release!! Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 1, 2016 Author Share Posted July 1, 2016 Yes, I have found out the hard way, not to skip any steps, when I do, things go wrong. I have learned to, like I said before, to provide an escape for the air and plastic, this step has worked well. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 1, 2016 Author Share Posted July 1, 2016 Some bubbles occurred in the last pour of the cab, so I added some some relief channels to the upper most part of the mold where the bubbles occurred, "V" channels, cut with an Xacto knife, so I hope this cures the problem, I will know later on today, and also I have been taping paper, with vinyl caulking, since the tape won't stick to the waxed wood, to make the cleaning of the molds easier, works good. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 1, 2016 Author Share Posted July 1, 2016 OK, done for today. I poured a cab, a heavyweight chassis, heavyweight roof. I put quite a few relief channels in the roof mold, so we shall see if they work. The experts say that I can de-mold after four hours and while you can, the plastic is still soft, so if you did, after that time, you would have to either put it back in the mold or make sure you put it on a flat surface so that it wouldn't deform. I prefer to wait 24 hours and then it is hard. Bob. Quote Link to comment Share on other sites More sharing options...
Jerry B44 Posted July 1, 2016 Share Posted July 1, 2016 Bob, there are some of the round window frames, none for windshields. Were a few pieces I fitted into that cab, not sure of anything else. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 1, 2016 Author Share Posted July 1, 2016 That's fine Jerry, and thanks for looking. I think what I am going to do is cut a mold of some windshield frames on my mill and cast them in plastic to get the correct profile. I think that I have close to the correct profile on my cab, so I will have to somehow have to bash them into your cab, and a bunch of other stuff. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 1, 2016 Author Share Posted July 1, 2016 I couldn't wait, so I pulled the parts out of the molds, the chassis and the roof came out perfectly, but still having some small bubble problems in the cab. None of the bubbles are bad enough that they can't be repaired, but I would like a bubble free part, here are some pictures. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 7, 2016 Author Share Posted July 7, 2016 Just an update. Poured another 15 lbs. of urethane today for another heavyweight side, some parts for the truck, pilot for the cab, and reduced a three part piece for the truck to one piece, starting the mold today. I keep forgetting to tell you this. I don't know how many of you are using urethane, but if you do, this procedure was recommended to me by the seller. Part A, that is the hardener, to keep water vapor in the air isolated from the urethane, after opening, a shot of nitrogen should be shot into the bottle to preserve the hardener and to give it more shelf life. I found out the hard way, without that shot of Nitrogen, the hardener will gel much faster. The part B doesn't need this step. When they ship it, a shot of Nitrogen is already in the bottle, but once opened, you have to do it again. The Nitrogen is heavier than air, so it isolates the urethane from unwanted moisture in the air. Urethane, in contact with air, causes the moisture to get into the urethane and causes air bubles in the urethane, just something that I had to find out the hard way. Bob. Quote Link to comment Share on other sites More sharing options...
enginear joe Posted July 7, 2016 Share Posted July 7, 2016 It was suggested to pour the stuff into the molds in a vacuum to help release trapped air. I did get a plastic bag for a chamber. I never tried it as it seemed to be a hassle or just one more thing to deal with while hurrying to pour. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 9, 2016 Author Share Posted July 9, 2016 Joe, I have seen videos of people, after mixing the urethane, set the bucket in a vacuum chamber to expel the bubbles from the urethane, but I haven't had any problem with the materials that I am using, so I wouldn't worry about bubbles. The best environment for pouring urethane is a dry atmosphere and that means air conditioning, and that is how I limit bubbles in my pours. The above procedure using nitrogen is just for storage. Bob. Quote Link to comment Share on other sites More sharing options...
Jerry B44 Posted July 9, 2016 Share Posted July 9, 2016 Sure a nice looking roof casting. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 10, 2016 Author Share Posted July 10, 2016 Thanks Jerry, it did come out excellent, I believe because of the added overflow channels, no bubbles. Here are some more parts for the truck, still mocking up. I combined the spring cross bars with the mounting plate, so it makes it a little easier to assemble. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 11, 2016 Author Share Posted July 11, 2016 After 5 attempts at producing a flawless pilot, I discovered that one half of the mold had a pocket molded into it that was trapping air. I am filling that area with clay, and I think that will correct the problem. I just poured one with the clay, so we shall see. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 15, 2016 Author Share Posted July 15, 2016 Yep, the filling of the void in one of the mold parts with clay solved the problem of inducing air into the part, so the pour is bubble free. Still cloning parts for the truck and adjusting the design to make it better. Hope to have one fully finished shortly. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 16, 2016 Author Share Posted July 16, 2016 The mock up is finished, here is the truck. Bob. Quote Link to comment Share on other sites More sharing options...
enginear joe Posted July 17, 2016 Share Posted July 17, 2016 Looks great from here! You have skills! (as the kids say) Now how about the modern ones..... Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 19, 2016 Author Share Posted July 19, 2016 Here is an MTH passenger truck that I stretched out 1/2 inch to make it more prototypical. I might redo this project to make it better, someday. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 21, 2016 Author Share Posted July 21, 2016 I have been trying to get the perfect shape for the F cab windshield and I made a pattern for a mold. The shape has been scaled from the full size to 1:32 and is made with the seal. Here is the beginning of the operation. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 31, 2016 Author Share Posted July 31, 2016 Here is what I have been doing in the last few days. I made a mold of the heavyweight doors so that they will open and be a split door. I am still trying to make the perfect E and F series windshields. I am trying to make the windshields, so that I may retro fit them into any one gauge E or F series loco. I am designing them so that when installed in the loco, there will be no glass to make it easier for painting and then there will be a ring in the shape of the windshield, to be installed from the inside to hold the glass in. I am using .020 Lexan for the glass, also making the side windows for the loco, and here are some pictures of the patterns and molds. Bob. Quote Link to comment Share on other sites More sharing options...
enginear joe Posted July 31, 2016 Share Posted July 31, 2016 Yeah sure. Perfect the E series. Like we're not drooling already! Just kidding. Thanks for sharing the process. Someday, I will attempt one. I have a long list that keeps growing faster and I've stalled. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 31, 2016 Author Share Posted July 31, 2016 Well what is said while flying and close to a stall, push forward on the stick and get flying again. Bob. Quote Link to comment Share on other sites More sharing options...
enginear joe Posted July 31, 2016 Share Posted July 31, 2016 Well, not to distract any farther from this post, I will just say I did keep busy trying to keep my trains running while acquiring several new pieces that needed work. It's tuff when almost everything made, has some kind of flaws that show up when put to a heavy test. It does justify spending extra time and effort, making your own product. Having that stand up, is proof that you've accomplished something special. I look forward to completing a rolling stock list, that all has dependable coupling and smooth rolling for my bigger trains. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted July 31, 2016 Author Share Posted July 31, 2016 In this hobby, it is never ending. Well here are the glass panels. I cut them with a tool that I made, a vinyl cutter. This tool was made to cut just .005 material, but I ran it through twice and it scored the .020 Lexan enough so that it broke away clean. They came out just like I wanted them to. I have to draw just one more part to complete the assy. then I will attempt to install them in an MTH cab and the other cab that I made the mold for. Here are some pictures. Bob. Quote Link to comment Share on other sites More sharing options...
rbrown7713 Posted August 16, 2016 Author Share Posted August 16, 2016 Just an update as to what I have been doing in the last weeks. I have been working on the elusive shape of the F cab windshield shape and after two molds and patterns, I think I have it. I now have to make an entirely new mold for the cab.. I also, have been working on the heavyweight doors and splitting them and also hinging them. Also, the wind wing on the F cab, I am trying to slant it open, and also the side window will be half open, might help for ventilation for the electronics. I also have been removing grass for the layout, and almost ready to lay some concrete. The layout will be abou 160 feet long and of course the viaducts will be laid for that entire length, so that is what I have been doing, boy, it is sure hot here in Florida, Bob. Quote Link to comment Share on other sites More sharing options...
enginear joe Posted August 16, 2016 Share Posted August 16, 2016 7 hours ago, rbrown7713 said: Just an update as to what I have been doing in the last weeks. I have been working on the elusive shape of the F cab windshield shape and after two molds and patterns, I think I have it. I now have to make an entirely new mold for the cab.. I also, have been working on the heavyweight doors and splitting them and also hinging them. Also, the wind wing on the F cab, I am trying to slant it open, and also the side window will be half open, might help for ventilation for the electronics. I also have been removing grass for the layout, and almost ready to lay some concrete. The layout will be abou 160 feet long and of course the viaducts will be laid for that entire length, so that is what I have been doing, boy, it is sure hot here in Florida, Bob. Is that all! Quote Link to comment Share on other sites More sharing options...
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