Making your own molds for casting

[Trucklover]

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

[upnick]

Hi Josh,

Not sure about supplies over there but a guy over here might have a distributor <!-- m --><a class="postlink" href="http://www.tiranti.co.uk/index.asp">http://www.tiranti.co.uk/index.asp</a><!-- m --> the mouldmaking section should give you some ideas.

I have seen a guy make a moulding box from LEGO bricks to the size required and the tiranti products latex/resin. <!-- m --><a class="postlink" href="http://www.modelrailforum.com/forums/index.php?showtopic=1033">http://www.modelrailforum.com/forums/in ... topic=1033</a><!-- m -->

[MasonJar]

doctorwayne did a series over on "the old site" about casting piers for his high steel trestle. DOn't have the link on hand, but a search might turn it up. I'll see what I can find.

Andrew

[doctorwayne]

It took some hunting (I thought that I had started the thread, but couldn't find it. ) but I finally tracked it down HERE. You'll need to scroll down a bit to get to the mould making/casting process.
This is one of several that I plan on re-doing here, when I get some spare time.

Wayne

[upnick]

Hi Wayne,

Excellent article on the supports many thanks for finding and showing us all .......... now can i fit in a bridge on the layout Josh has started something here now

[MasonJar]

It took some hunting (I thought that I had started the thread, but couldn't find it. ) but I finally tracked it down HERE. You'll need to scroll down a bit to get to the mould making/casting process.
This is one of several that I plan on re-doing here, when I get some spare time.

Wayne

Thanks Wayne for tracking that down...!

Andrew

[nachoman]

Have you considered RTV molds?

[doctorwayne]

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.

In this view, all of the bridge piers and abutments are plaster (Durabond) castings, while the tunnel portal is styrene - I think that if the colour on the portal were improved, it would be indistinguishable from the others:
[album]863[/album]

In these two shots, all of the piers and abutments are made from sheet styrene (the piers are stacked .060" sheet, filed to shape, then carved to suit the terrain. Again, the colour needs to be improved:
[album]864[/album]

[album]865[/album]

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

[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

[doctorwayne]

Josh, I made my moulds from .060" sheet styrene - look in the Yellow Pages for a plastics supplier, as it's much cheaper buying it in 4'x8' sheets than as small sheets from the hobby shop. For casting, I used a product from Canada Gypsum called Durabond. U.S. Gypsum has the same stuff, under the same name, too. The name is followed by a number, which represents the setting time, in minutes. I used Durabond 90, the same stuff that I used for my landforms and rivers on the layout. It sets in approximately 90 minutes, at which time you can remove the mould. When fully cured, it is extremely hard and durable. Various setting times are available, as quick as 20 minutes, and it can be had, I think, in 2 and 5 lb. boxes, or in 33 lb. bags - the bigger the quantity, the lower the cost per pound. It will set no matter to what consistency it is mixed, although very thin mixtures don't seem to be quite as strong. When fully hardened (it depends on the thickness), it is difficult to file or sand, although, when first removed from the mould it can be carved or scribed to represent cut stone. It takes water-based stains reasonably well, although it's best to use a fairly wide brush to apply it, in order to avoid blotchiness - use a thin mixture and make several applications, as required.
I used vegetable oil, applied with a paper towel, as a mould release, although my moulds were very simple shapes - it didn't seem to affect the plaster's ability to take a stain.
To make the bridge spans modular may be as simple as casting a "key" (a simple protrusion) extending across one end, with a corresponding keyway (depression) in the opposite end. Since some modellers may wish to shorten their spans (a mitre saw - hand-powered or hacksaw should work) I'd leave placement of the piers up to the individual. You could build the abutments with a "seat" to accept the end of the spans, though, which would both support the bridge and prevent it from moving sideways.
To join the spans to the piers and abutments, white glue or yellow carpenters' glue should work well - I used yellow glue to glue the footings to both the Durabond scenery and the plywood riverbeds.

Wayne

[Trucklover]

Josh, I made my moulds from .060" sheet styrene - look in the Yellow Pages for a plastics supplier, as it's much cheaper buying it in 4'x8' sheets than as small sheets from the hobby shop.

This is somthing i always forget about when i buy sheet styrene lol. Thanks!! This will save alot of money buying in a 4x8 sheet lol

For casting, I used a product from Canada Gypsum called Durabond. U.S. Gypsum has the same stuff, under the same name, too. The name is followed by a number, which represents the setting time, in minutes. I used Durabond 90, the same stuff that I used for my landforms and rivers on the layout. It sets in approximately 90 minutes, at which time you can remove the mould. When fully cured, it is extremely hard and durable. Various setting times are available, as quick as 20 minutes, and it can be had, I think, in 2 and 5 lb. boxes, or in 33 lb. bags - the bigger the quantity, the lower the cost per pound. It will set no matter to what consistency it is mixed, although very thin mixtures don't seem to be quite as strong. When fully hardened (it depends on the thickness), it is difficult to file or sand, although, when first removed from the mould it can be carved or scribed to represent cut stone. It takes water-based stains reasonably well, although it's best to use a fairly wide brush to apply it, in order to avoid blotchiness - use a thin mixture and make several applications, as required.

I know exactly what you are talking about When i worked at Lowes, we had this stuff down the DryWall aisle and it was next to the Mud. I used to hate stocking the pallets of this stuff, because we had to get 3 pallets in an 96" beam opening in the racking which is almost impossible because each pallet seemed like it was 3' wide but really only 2' something (they were odd sized small pallets and always stacked horribly which also did not help when stocking the pallets and shoving them into place), and almost everytime, no matter who put the pallets in there with the forklift, bags would tear and it would just absolutely make a terrible mess all over the aisle that would take about an hour to clean up LOL. I think we discontinued and stop stocking the 5 and 90 minute, but i know for sure we had the 20 and 45, the 45 should be fine for me

I used vegetable oil, applied with a paper towel, as a mould release, although my moulds were very simple shapes - it didn't seem to affect the plaster's ability to take a stain.
To make the bridge spans modular may be as simple as casting a "key" (a simple protrusion) extending across one end, with a corresponding keyway (depression) in the opposite end. Since some modellers may wish to shorten their spans (a mitre saw - hand-powered or hacksaw should work) I'd leave placement of the piers up to the individual. You could build the abutments with a "seat" to accept the end of the spans, though, which would both support the bridge and prevent it from moving sideways.
To join the spans to the piers and abutments, white glue or yellow carpenters' glue should work well - I used yellow glue to glue the footings to both the Durabond scenery and the plywood riverbeds.

Thanks for the tips, this is what i was thinking for the bridge spans, something like you mentioned. I was thinking that i would leave it up to the modeler to cut off the key whole or connecting piece on each span if it was not needed....

Having the bridge spans sitting in the bridge abutments is a great idea, and i will definitely have to do that, it will also make it look alot more realistic

And i agree with you, the placement of the piers would be up to the modeler and his/her scene. I really wanna come up with at least a few different style of bridge piers, i think more choices will be the best, since there are such a variety of them i see just around here in Cali on the highways

[MasonJar]

Josh, I made my moulds from .060" sheet styrene - look in the Yellow Pages for a plastics supplier, as it's much cheaper buying it in 4'x8' sheets than as small sheets from the hobby shop.

This is somthing i always forget about when i buy sheet styrene lol. Thanks!! This will save alot of money buying in a 4x8 sheet lol

If you have public transit in your town, you may be able to get heavy styrene for nothing. I got a sign off the side of a bus for nothing... It was about 2x6 before I chopped it up. Required a quick wash before it was useable, and only one side is good, since the sign is on the other (although the vinyl letting could be removed).

Hope that helps.

Andrew

[Russ Bellinis]

Josh, for concrete freeway type overpasses, scratch build your "bucks" and use styrene to make molds. They are all simple poured concrete shapes with no fine detail. If you want to make something with more detail like some of the art deco concrete arches seen in downtown Los Angeles or San Diego, to name a couple of cities not far from you, then you wold need to make models and use silicone molds.

[MountainMan]

Depending on what I am casting, I make molds either out of RTV Latex (room temperature vulcanizing) or a two-part acrylic casting mixture. With the RTV, I cast the sections of stone wall out of Hydrocal. The acrylic molds is make using the LEGO trechnique and then use them to cast resin parts. For smaller molds, I just use a plastic parts drawer from one of those multi-drawer small parts cabinets, set the part face up and slowly flood the drawer with RTV compound until the detailed face of the positive master is well covered. This works well for walls, flat panels and such where the detail is essentially on one face and the sides and top. After it dries thoroughly I remove the mold, flex, peel and remove the molded copy. I then return the mold to the drawer to keep it flat and refill it, or leave it stored flat until the next time. Casting is a useful technique for mass producing some items that you will need a lot of. I found a site belonging to a guy who casts freight car bodies, something I'm working my way up to, long with two-part indexed molds. Much to learn. :?