Making your own molds for casting

[Trucklover]

First off, id like to thank everyone for there replies. My girlfriend has been on spring break this past week, so i have not been on the forums all that much, spent practically the entire 9 days with here, going home only to sleep for a bit lol

While RTV moulds are excellent for capturing details, they're probably overkill for obtaining simple geometric shapes. The styrene moulds are quick and easy to build, and probably a lot cheaper, too.
Another avenue of attack might be to skip the mould-making step altogether and simple build the bridges from styrene - probably less styrene would be required than for the moulds to make similar-shaped castings. Moulds are generally used when you want to make multiples of a particular shape.

If you're making something where you need multiples of the same shapes, casting may be worth the effort of constructing moulds. If you need only a couple copies of simple shapes, it's not likely worth the extra work. However, if you simply want to try casting, by all means do so.

Wayne, i had a look at your casting methods with the styrene molds over on the "other" forum, i actually remember reading this, and it was great to re-read it and re-fresh my brain on the subject. When and if you have time, i would love to see this mold making series on the new gauge!!

what i had planned is to make X amount of each casting and selling them as bridge components for modern day highway bridges. i wanna cast the piers, the bridges them selves, and the bridge abutments and concrete embankments that usually lead up to the top of the bridge abutments. I wanna try and make something that can be sorta a module design, meaning that you could buy more then one bridge segment and add onto it making it longer and adding more piers where needed. I was thinking of maybe doing each bridge segment 12" long, and if you need a longer bridge to fit your layout space, then one would be able to buy additional bridge segments and add onto the original kit.

Each kit would contain a bridge segment, a set of piers, and 2 bridge abutments. Expansion packs would be also cast and sold individually and separately. Basically, im looking to sell parts to make a modern concrete overpass found on Americas highways. I could also offer built-up and painted, weathered bridges ready to be fir onto a layout....

So to answer your question about making the bridges from styrene, i would want to make some molds, a separate mold for each piece of the bridge, that i could use over and over again to cast the same parts. I would also like to do a couple different styles of bridges, piers, and abutments, so i would have to make alot of molds for all the pieces. Does this make sense?

Here are a few picture examples that i have collected so far:



This one isnt all that great of an example, but it shows one of the possible bridge pier castings that could be made to go with the bridges. It is a solid wall bridge pier




This one shows the bridge piers as round columns with a solid horizontal block ontop of them supporting the bridge as a bridge pier. This is also a good example of what one of the bridges could look like on the sides if a mold was made to a model of a bridge segment like this one.




Another bridge pier option and shape, this one being a octagonal type shape




This bridge has simple round column bridge piers.




Ive also noticed that some of the older bridges around here have square column bridge piers. I found this one and it would make an interesting model if i could do a mold like this to a similar shape.


In the end, here is a breakdown of what i would like to create in the way of molds:

~~1 Mold for a bridge segment. This mold would be of a generic concrete style bridge, with center and side K-Rail barriers. Thinking of making it 12" long and somehow making it modular allowing the modeler to connect more segments together to make a longer bridge

~~4-5 molds for different styles of bridge piers

~~2 Molds for 2 Different styles of bridge abutments


I still need to do a lot of research on this, not only on the bridges, but the mold making process, and the best material to use for something like this.

Any suggestions on casting materials? Wayne what material did you use to cast your bridge piers and abutments? I would want something that would not be too delicate, and could handle being shipped to a modeler