Casting AC&Y 3900 Series 50' SS Box Car

[SAH]

The AC&Y bought a lot of second hand equipment.  Some of these came from MP or T&P (we think) to haul tires.

http://www.rr-fallenflags.org/acy/acy3943jwa.jpg

I'd like to have a half dozen or so.  Walthers produced a pretty decent model of the double door version some years ago.  They may have arrived on the AC&Y as double door cars and rebuilt with single 10' doors.

So I have a bunch of the Walthers models, two as undecorated kits fortunately.  I say fortunately because the glue used to secure the doors to the model warped the doors and the body in some cases.  I've chopped up a few of the models to get what I hope will be enough parts to make a master for resin casting.  It looks like my photo was clipped, but you get the idea.



Now, I've never cast anything in resin or any other material for that matter.  I read the Resin Casting thread a few weeks back and am intrigued.  I don't think I'm ready to make a run at a one-piece body casting (note first sentence in this paragraph) but am wondering if flat casting would offer a reasonable chance for success at a first attempt.  I'll use the Micro-Mark starter casting set.  Any tips related to flat casting or should I be starting with a simpler project?  Your thoughts are welcome.

Thanks,

Steve

[chessie system fan]

If this were my project, I'd cast the shell as one piece.  Two-part molds aren't too difficult (with practice), so why make more work for yourself assembling a flat kit when you don't need too?  Granted, this is a bit ambitious for a first project.  I'd practice casting with other items first.  You need any extra door styles or covered hopper hatches?  Those or any detail parts are great places to begin.

And get a pressure pot.  In my experience, you're wasting your time without one.

[LV LOU]

If this were my project, I'd cast the shell as one piece.  Two-part molds aren't too difficult (with practice), so why make more work for yourself assembling a flat kit when you don't need too?  Granted, this is a bit ambitious for a first project.  I'd practice casting with other items first.  You need any extra door styles or covered hopper hatches?  Those or any detail parts are great places to begin.

And get a pressure pot.  In my experience, you're wasting your time without one.

I'd say just about the same thing.Castings don't really glue well,and casting thin parts without warping is a bit of a crapshoot.There's no downside to casting the whole car in one piece,you'll end up making a hundred castings,glueing them together,then,end up having to add weight to them because they're too light.  And +1 on the pressure pot,first time I used one,it was a magical experience,LOL!!

[bbussey]

Huge plus that you procured two of the undec unassembled version of the model.  Assembled ones are hard enough to find these days, especially with usable doors, as you mentioned.

I concur that one assembled master for casting would be better.

[Chris333]

Me like, when did AC&Y buy these?

All I can say about the micro mark resin kit is that at certain times of the year the parts come out like crap with the resin not fully cured so it is all sticky. It may have something to do with the humidity. At other times of the year it makes great castings.

I have 3 of the Walther's cars and had to brace the doors from inside to push them out and flatten them. 

[bbussey]

I'd like to bash one of the shorter 40' prototypes at some point myself.  I wonder if the Youngstown doors from the InterMountain AAR 40' boxcar could be substituted for the warped Walthers doors?

[DKS]

FWIW, I would not try this as a first casting project, especially as a two-parter. I'd do something a little simpler, like maybe just some doors to get used to working with the materials, because it does take practice.

Also, I would not use the Micro-Mark starter kit, because you can get much better materials than what they supply (notice Chris' remark about his results).

I'd recommend getting Smooth-On products. They sell sample sizes of most everything they make, which will help you get your feet wet. Their product range is quite extensive; I've selected some middle-of-the-road materials as a starting point.

Get the sample size of Mold Max 30 here: http://www.smooth-on.com/Silicone-Rubber-an/c2_1113_1135/index.html?catdepth=1

And get a sample size of Smooth Cast 305 here: http://www.smooth-on.com/Urethane-Plastic-S/c1120_1209/index.html?catdepth=1

Although I rarely use it, I'd recommend getting a spray can of Universal Mold Release: http://www.smooth-on.com/Release-Agents-for/c1123_1169/index.html?catdepth=1

The rest of the items you'll need you can get from local shops. Get a package of popsicle sticks for mixing, some plastic cups, and a bottle of rubbing alcohol for cleanup. You don't really need graduated cups, but it helps. If you use regular cups, then just mark them with a Sharpie at the same depth so you can measure out equal parts of casting resin. Also, you should get a postal scale (they're pretty cheap) so you can accurately weigh the mold material. You can get a Smooth-On mold-making product called Oomoo that is measured 1:1 by volume, like the Micro-Mark stuff, but it's kind of funky to work with; you're better off getting the good stuff.

Finally, if you have access to a pressure pot, your molds and castings will improve 1000%. Barring that, just be sure to mix things thoroughly but slowly, so you don't create too many bubbles when mixing. Use the mold release very sparingly on the master only. The mold will take about 12-16 hours to cure, and Smooth Cast 305 takes about 2 hours to cure.

Good luck!

[up1950s]

To all casters & manufactures , SS boxcars of any road and any length are wanted by me .

[haasmarc]

David,

Is that the rubber you use (Mold Max 30)?  How many castings do you get per mold?  My buddy bought some rubber from Smooth On but he only gets about 10 castings per mold and he is using mold release.  These are two part molds with casting in a pressure pot.  We used to use Visilox 240 and could get 3 or 4 times the castings.

[DKS]

David,

Is that the rubber you use (Mold Max 30)?  How many castings do you get per mold?  My buddy bought some rubber from Smooth On but he only gets about 10 castings per mold and he is using mold release.  These are two part molds with casting in a pressure pot.  We used to use Visilox 240 and could get 3 or 4 times the castings.

The number of castings per mold varies highly, depending on the shape of the object being cast. Some of my molds have yielded over a hundred castings, some only 20-30. I don't use mold release for castings, and I use it on the master for making the molds only occasionally.

Mold Max comes in a range of hardnesses, and you need to match the hardness to the type of object you're casting. For example, if it's just a one-part mold of flat building sides, go with a harder rubber like 50 or more. If you have a highly-detailed master with lots of undercuts (like my crawler), you'll want to use a softer rubber. I use Mold Max 10 for the crawler, and I'm averaging about 20-25 castings per mold.

I'm sure there are better materials than Smooth-On, but I find it more than adequate for my needs.

[jimmo]

All I can say about the micro mark resin kit is that at certain times of the year the parts come out like crap with the resin not fully cured so it is all sticky. It may have something to do with the humidity. At other times of the year it makes great castings.

Chris, in my experience the most likely reasons your castings came out sticky or oily are that either the resin was past it's usable shelf life (most of these casting resins are only good for about 3 months), or the part A was not mixed thoroughly before combining with part B. Uneven amounts of A and B will also cause similar results (voice of experience).

[JoeD]

I agree with David.  Smooth On products are the best.  I've used other's in the past and for finish and consistancy, you can't go wrong with them.  Also, the larger the mold the fewer parts you are going to get beacuse of the heat generated by the fast cast materials.  If you want to solid cast a freight car, you have to go with slow cure, generally filled resins or epoxies.  They make a number of different materials that can be used.  I have some of their metal powder filled epoxies for making spin cast and v-form masters and have found very little shrinkage or cupping over large sections.  It takes 12 hours to set, but the results are worth it.

Joe

[DKS]

Chris, in my experience the most likely reasons your castings came out sticky or oily are that either the resin was past it's usable shelf life (most of these casting resins are only good for about 3 months), or the part A was not mixed thoroughly before combining with part B. Uneven amounts of A and B will also cause similar results (voice of experience).

+1 on all points, also based on experience, particularly with respect to thorough mixing.

Joe also raises a good point on the various casting materials. The Smooth Cast product comes in a range of setting speeds. The pot life for 300 is less than one minute, and sets in a half-hour, whereas 310 has a pot life of about 15 minutes and sets in a few hours. I choose the resin type based on two criteria: the rate at which I can load a mold, and the volume of the mold. If it takes time to load the mold (for instance, if I must use a syringe to ensure it's filled properly), or if it's a large-volume casting, then I'll go with a slower resin like 310. For molds I can fill quickly that are relatively small, I'll use the faster resin. 305 is a good in-between resin that I use most of the time.

[JoeD]

I used to produce 1/700 resin ship kits (Jag Collective) and we mixed the 300 and 310 cataylist 50/50 to get a mid range set.  We had to do a lot of bubble picking on the smaller sprue's and found this mix gave us a little bit more time to work the molds and cut down on reject rates.  They also make a range of metal powders you can add to get more weight or fillers to lighten things up.  I have some Feather-lite stuff they make and the castings will float in water.  I used the material to cast Orange Trees with green pigment added.  Lots of trees on the layout and almost no weight added.  Very cool in smaller scales.

Joe

[DKS]

I also use a lot of the Smooth-On additives. In addition to their So-Strong tinting dyes (do not under any circumstances buy the coloring agents from Micro-Mark--they are worthless), I use their powdered metals, not only to add weight but also to create metal-like effects, as well as their weight-reduction fillers--they have one that makes the resin look like wood. Their product range is quite extensive and they have a lot of interesting stuff. I've ordered a sample of nearly everything they make; they have a sculpting material that looks similar to Sculptamold (haven't had a chance to open the container yet).