Report on my 2nd Casting attempt

[blacksmithn]

I am pleased to say that my second attempt at casting the railroad flat car went much, much better than the first attempt. I actually was able to cast two flats and they came out in one piece and are what I had expected-- not perfect, but good enough. I'll post some pics later, after I get home from work, but I was pleasantly surprised-- again-- by the level of detail and the ease of production. I did learn a few more things.

1) Using advice gleaned after my first attempt, I included a second pour tube running down the side and into the bottom of the mold. That worked LIKE A CHARM! The only issue is that I used rolled clay to form the tube prior to casting the silicone, and that made the tube a bit too large. That isn't an issue that effects the casting of the resin, I'm happy to say, but due to the size there's a lost of wastage of resin, imo. I have some 1/4" (approx. 6-7 mm) copper tubing I want to try as a form for this pour tube.

2) Somehow, and I'm not too certain how exactly, I managed to put a small round indentation about 5mm in diameter in the top of the flat car deck at one end. It's a flaw that is present in the mold itself (due I'm sure to operator error). Were I to use these cars, I'd need to find some way to conceal that.

3) I used a resin with a 6 minute cure time, which was optimal. Although it said it could be de-molded after 1 hour-- and it could-- the resin took a lot longer to fully cure and was VERY pliable for several hours. Not an issue, but something to note. Overall, I'm very happy with the resin I chose.

4) You can never have too much banding at the bottom of the mold form to hold everything in. I sandwiched my mold between two 1x6 inch boards and secured this together with six bungee cords evenly space. This resulted in leakage from the bottom on my first attempt. However, an extra two cords at the bottom fixed the problem entirely and no leaks were present thereafter.

Overall, I am very happy with the outcome of my second try, but already am making plans for a third mold that will address the issues of the too-wide pour tube and the mysterious indentation. Third time's a charm!

[mangozac]

Progressing nicely by the sound of it!

1/4" copper pipe should be a good diameter for the pour tube.

Can you see the indentation in the mould itself? It sounds like there's a big air pocket in the silicone behind it or something...

[blacksmithn]

Yes, it could very well be a bubble! Didn't think of that.

Here is a pic of the bubble-- you can see it on the left of the pic, near the end of the deck:



Here is a view of the entire top side of the mold:


Here is a top view of the two cars, indentation on the right:



Here is a side view of the first car:



Here is a bottom view:



As you can see, quite an improvement from the first effort. Is there a way to try and fix that bubble, or should I just figure on a new mold?

[mangozac]

You should be able to fix the bubble by cutting in from the outside of the mould to release the pressure.

That is indeed an enormous pour channel!