I wanted a set of pressed steel fox trucks for my coke cars. I was having trouble finding some at a reasonable price so I'll try to bash some together. I started by taking some measurements from a set that I had and made a master.[attachment=5921] I added a set of journal boxes but deleted the pic.

next I pressed it into a blob of Sculpey clay a few times. I wanted to do a few more but wrecked the master after 4 imprints so I hope they work out. Into the toaster oven it went for a few minutes to set.when it was cool I coated the mold with a ""thin"" coat of petroleum Jelly for a mold release.[attachment=5920]
I fond some casting resin at the craft store that dries Cristal clear[attachment=5919]. I experimented with it a few times and am happy with the results.I mixed up a batch and added a few drops of black paint to it and poured it into the mold. thinner castings take a wile to cure completely so I'll demold in a few days.I have to make enough for at least 3 cars so it's a slow process.

I am curious how these turn out for you. Too bad MDC no longer makes Fox trucks.

Oh! Oh! I wanna see how this turns out also! Very cool, and I wanna do some of this casting stuff too!

Damn! It's not like I don't already have enough project on the "Oooooo! Gotta Do This" List! I have copies of Fox Pressed Steel trucks ... Most of the LS&W M.o.W. equipment rolls on them, with a few Arch Bars tossed in out of Operating Department frugality.

I'll have to take a look in the "Trucks" box and see if I can come up with something ... I know I have one pair of Central Valley Fox trucks, but they may be HOn3 ... I'll have to check.

Making patterns, fabricating molds and then casting a run of pieces from the mold was a major project in the Industrial Design Foundation Program during freshman year ... it was great fun ... messy, but fun! Lots of plaster was used!

Good luck on the project ... It looks like you're on the right path for a set of short run production molds ... looking good!

Oooo...this looks exciting. Do keep us posted on the progress.

Out of the mold they came, flashing cleaned and mounted on a athearn truck with the detail filed off.[attachment=5929]

I'm having trouble with air bubbles, but as a first try it shows promise. I'll keep on playing around with my technique till I get it right. you get the Idea of what I'm going for.[attachment=5928]

E-Paw ...

To defeat air bubbles you must first not introduce any into your casting epoxy. Yeah, I know that sounds like a "duh" statement, but it is critical! When mixing the catalyst into the epoxy, stir gently, slowly and mix thoroughly without any undue "splashing." You needn't stir violently to get a thorough mix.

The next step is to eliminate any air bubbles that have joined the party despite your best efforts to avoid them. Then, when you make your "pour," do so slowly and from a height that allows the liquid being poured to "neck down" to as fine a stream as you can. The premise is that any bubble larger that the stream at the point of contact with the mold will break when the stream gets narrower than the diameter of the bubble.

Next, so as not to capture any air which may manifest itself as a bubble on the actual surface of the mold, start your pour in a corner and keep it there, letting the casting liquid spread out across the surface of the mold. When the mold cavity you are pouring fills, quickly move to the next mold cavity and stay in the corner where you begin the pour.

One last thing. Surface tension. Although the use of petroleum jelly seems like an intuitive choice for a mold release, it has "dimension" and may impart that dimension to the finished part, yielding an imperfect surface on the final production part. When I was in design school (in the mid '60's and then again in the early '70's) and taking the class where we did patterns and molds and master molds from which to cast production molds, and then had to produce a run of "parts," we used a solution found in the pharmacy called "tincture of green soap" as a mold release. It had a very low coefficient of friction and was a marvelous mold release. You may find other substances that will work as well (Pam, maybe) but gently brush it on the surface of the mold, paying attention to a smooth surface and no bubbles.

Hope that helps.

Would vibrating the mold help remove air bubbles? That is what the concrete guys do...

After following my other advice, vibrating the mold would be an excellent strategy!

I think the idea of casting your own parts is a great idea, but I saw those trucks on my last trip to the LHS and they were not there on my previous visit. Either they're new stock or part of an estate lot or collection that the store has picked-up, a common practice of that store.

Wayne

An old aquaintance of mine used to take a small coffee stirer straw and blow on the mold from a distance of 3-4 inches or so from the castings while they set up to get rid of air bubbles. As goofy as that sounds, it worked for him.

Thanks everyone... What I found is that I need to use even less mold release and less paint. I did notice what Bil said about the petroleum jelly and using less is giving better results. The paint thickened the mix quite a bit cutting it back to a single drop makes it easier to pour. The last step that I added is to put the mold on my 2 month old's vibrating seat for a few moments to shake out the bubbles.

Here's a pic of a sample from the last batch.[attachment=5930]
Even engineer Fred thinks that I'm getting better at this.

I'm glad some of my freshman year experience from back in the second ice age was helpful!

Much better IMHO.

I second blowing on the casting. It seems to magically make the bubbles rise to the surface and pop. Ditto on the other suggestions, and here's another - try using just paint for the mold release. Paint the casting then make the pour. Now if it does NOT work, you didn't hear it from me. But I have heard this technique espoused before, that the resin will stick to the paint and the paint will release it from the mold. Not sure how it'll work with a sculpey mold, but maybe better on an RTV mold or silicon mold. It could be worth experimenting with after you get a set of castings you're happy with.

Galen