Making your own molds for casting

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Trucklover

BNSF SD70MAC's
#1
Hi guys, im looking for tips on making molds and such.

I was thinking of making some molds for bridges (bridge piers, bridge abutments, and the actual bridge themselves) modeling some modern highway bridges. I know there is stuff like it out there, but there plastic and from what i have found, most of them are not that modern, and only 2 lane bridges (BLMA Modern Concrete Bridge is the only thing moderately close to a nice looking concrete bridge for the modern era for highway traffic in my opinion)

Can anyone point me in a direction on how to cast your own parts? I was thinking of using Hydrocoal to cast parts out of. Yes? No? What would you guys suggest would be good to cast good pieces? I might also try the Anchor Bolt Cement (although the parts may get a little heavy but will be more stronger and durable i think)

Is there any casting tools that i should get to help?

I was also thinking of making the molds from styrene, and making a couple master molds for a couple different style bridges i see on the highways around here. Ay suggestions on other materials to cast parts with or to use to make molds?

Thanks in advance for any help guys, i appreciate it alot
 
#4
How large of a production run are you thinking of making? If you're talking one or two, you'd be better of scratch building each one.

I use Alumilite's epoxy stuff for making molds and resin casts. It works well, but is a bit costly. Rather than resin, for pieces that won't be handled (like scenery), sometimes I use a mix of plaster with white glue and black paint added in place of most of the water you'd normally add.
 

stationmaster

Crusty Old Geezer
#5
To make the molds, the better half found this product at our local craft shop. I don't have a container here and my old brain can't remember what it is called. It is vinyl-like and pliable when cured. I found rocks with character, my term for unique, collected them and used them form the impression of my molds. I use HydroCal for the pieces on the layout. Washes for finish. And an airbrush for highlights.
 

tillerman

retired and lovin it.
#8
HO Molds only

Ok,I'll throw my question up in the air.
Doe's anybody know of any mold suppliers just for model railroading,not just rock molds,but other items,such as figures,statues,building parts.
Thanks
Mike
 
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#9
woodlands scenics has nice rock molds of all diffrent kinds found in the east or west coasts. Small and large. I cast them out of plaster of pairis as they dry in about 15 mins
 

UP2CSX

Fleeing from Al
#11
Tillerman, I'm not aware of any company that makes molds in HO for the things you're asking about. You can use one figure or building part as a master and then use some of the molding techniques already described. I suspect the market for masters is very small given the large number of figures, statues, and building kits on the market.
 

Trucklover

BNSF SD70MAC's
#13
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

How large of a production run are you thinking of making? If you're talking one or two, you'd be better of scratch building each one.
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? I would want something that would not be too delicate, and could handle being shipped to a modeler. I dont want it to cost to much, but i also dont want these to be really delicate and to fall apart easily.....
 

UP2CSX

Fleeing from Al
#16
Since you're talking about making these for commercial use, I would investigate injection molded plastic. The price, even for small runs, has come way down with the CAD tools available and most modelers are already familiar with styrene. My personal experience with hydrocal parts has not been good. They have heavy, cracks easily, and doesn't reproduce details well. There's also a limit to how many molded items you can produce before you need to make a new mold. You can make injection molded plastic from masters almost forever.
 



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