i’m thinking of casting freight cars and locomotive shells using resin
is it difficult to do? Any pointers would be appreciated
scott
Scott,
Numero Uno: Do what you have to do to make sure you are well ventilated!
Tom
What scale? From what I’ve seen, If you want thin walls you have to deal with warping.
First you have to want many copies of what you are making. If you want just one or two shells, then scratchbuild them. If you want 25 then cast them in resin.
Second you have to be able to make a master to reproduce, so your modeling skills have to be able to make an original copy of whatever you want to make in enough detail and clean enough that you will want to make copies of it. The RTV rubber you make the molds from is fine enough that it will pick up the difference in sheen where you got a little too much liquid plastic cement on a surface.
Third be willing to invest in some equipment. You will need to make molds. You will need a balance scale to measure the RTV and resin amounts. You will need a compressor and pressure chamber to cast the resin without bubbles. If you are making small flat castings that won’t be necessary. If you are making complex castsing such as engine shells, you will probably neeed it. You will need something to warm the resin while it cures to make sure it cures completely.
Fourth you have to be willing to invest time. Casting isn’t a fast process. It might take 30-40 minutes, start to finish to produce a set of castings from one mold. Expect that you will have to redo your masters a couple times to get one worthy of making a mold from. Expect to have to revise your processes to get an optimal casting sequence with your equipment. Expect to have to remake some molds it there is a bubble or defect in one. Expect to have some castings be defective (bubbles, too thick, too thin, resin didn’t cure, you took them out too early and they warped, you took them out too late and they cracked)
Fifth be willing to invest some money into the process. There is a lot of up front costs before you cast your first car. The cost to make the masters, the cost to make the molds, the cost to buy the resin, the cost in equipment and supplies. I have
If you don’t have any experience doing this type of work, I would suggest starting with something a bit easier. This will require a multi piece mold most likely and getting these to work right is a bit of a challenge especially if you have to account for shrinkage. Start easy with some simple open pour molds to make some small detail parts and then work your way up. Also, buy a couple of resin kits to see what is involved. Funaro and Westerfields both make nice kits from resin. and you can get a good idea of how they do this by looking at their parts
Dan Pikulski
HO scale CSX Coke Express hoppers
thanks guys for your input
I do resin casting.
You could get away with casting a boxcar in two parts plus details: The top box shell, and the chassis. Hoppers are especially tricky. I do a TT scale hopper and there are about 7 parts to cast not counting the details. It also depends on the types of parts that have to be cast. Take a 55 ton coal hopper: I do it by casting the two sides, the two ends, the bottom with the slope sheets, and the frame in two parts.
As for equipment, I have a vacuum chamber and pump, and a pressure pot and compressor. To get bubble free castings, you need to vacuum the RTV after mixing and before pouring the mold. For casting, I cast under pressure so bubbles won’t form. There are other ways of doing it, but they will not yeld perfect results.