Relay boxes

[phillyreading]

Where can I find just the relay box for use near a grade crossing like what FEC
Florida East Coast Railway uses in O gauge?
I have tried Walthers but to no avail. Other manufacturers if they make one make you buy a complete set when all I want is the relay box.
Please don't tell me to buy the set and sell the other stuff as then I am stuck with over 50 signs or other stuff that I have no use for and nobody wants to buy at train shows either!!
Lee.

[Big_Boy_4005]

You could make your own. Buy one and make resin castings. How many do you need?

[phillyreading]

What are castings? And how would I make one?
My experiance is more toward electrical than engineering.

[Big_Boy_4005]

The jist is you take an original that you like, and make a rubber mold around it. Then pop the original out, and fill the mold with some other material, usually plaster or resin, depending on what you're making. The entire process is a little more involved than that, but it is a great way to make a bunch of something.

[phillyreading]

This may sound stupid but how do you make or put a rubber mold around something?
I mentioned before that me mechanical experiance is very weak.

[Big_Boy_4005]

There are a couple of different kinds of rubber that are used for mold making. There's latex, which works very well for making rock molds. It comes in a liquid form like thick paint, and that's pretty much how it's applied to the original, with a paint brush. After applying a number of coats, and maybe some gauze for reinforcement, you peel it away from the original. The key to making a good latex mold is in the first coat. That is when the detail of the original is captured, so you want to make sure the latex gets into every nook and cranny.

The other type is RTV, which stands for Room Temperature Vulcanizing. This basicly means that it doesn't need additional heat to cure. Silacone caulk is a form of RTV, and can be used to make molds, but it isn't the greatest for this purpose for a couple of reasons. First it doesn't flow to fill in detail, it kind of has to be forced on it's first coat. Second, once hardened, it tears easily. There are a number of different RTV molding compounds available, each with different properties, so you have to choose the right one for your particular project.

Since we are on the internet, with the world at our fingertips, a little research is a pretty easy thing to do. Keywords RTV, Dow, molding, silacone rubber. I tried a little and found a bunch of stuff, it's out there.