Model resin casting starter kit options?

[John]

Yeah, lots of new words here that I've never heard before.

You guys did accomplish your mission of dissuading me from even attempting, LOL.

Thats the RW way .. although I think you might be able to pull off the method described with Oyumaro and jbweld .. it would be a 2 part process -- make a mold of the back side - then when thats dry, do the same thing for the front side ..

Take a look at this .. its a little long but it explains mold casting nicely .. you can find all the stuff at hobby lobby or michaels

[Dave V]

Yeah, sometimes this can be a really helpful place to ask questions. But not always, LOL.

[Spades]

Probably the easiest cheapest way, but it takes a few tries. 

How to cheaply cast miniatures or plastic models - new version

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If you are going to go the traditional route. BJB Enterprises has great videos on how to make the molds and galley ways. I just use a an unmodified paint pot to de-gas the resins.
They are great people to work with.

https://www.youtube.com/@bjbenterprises/videos

There's 3D printing.  Alot of people can produce a dimensionally correct part, but it takes an artist to make a really good looking part, I think of Gary Hinshaw tank car end platforms. He is in the Artist class.

[Dave V]

Probably the easiest cheapest way, but it takes a few tries. 

How to cheaply cast miniatures or plastic models - new version

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This may be sufficient for what I'm doing. The part is purely cosmetic so there's no worries about strength. Since it's in shadow under the carbody it also doesn't need to look perfect.

I don't own a 3-D printer... I thought about purchasing one years ago but I don't think my occasional need for a part would justify it. Also not clear on how easily I could translate an actual tiny part like this into a 3D design for printing.

[Chris333]

Not too different than this : https://www.printables.com/model/528925-toma-model-works-porter-brake-shoes-hon30

[Dave V]

Not too different than this : https://www.printables.com/model/528925-toma-model-works-porter-brake-shoes-hon30

I would disagree though. Quite a bit different from the wheel spacing and diameter of the brake shoes to the spring types and mounting and yeah... actually other than that these are wheel brakes for a self-propelled thing, they have nothing else in common, LOL.

[Chris333]

Just sayin' it would print.

Since you have detail on the front and a press fit tab on the back you would need a 2 part mold. They are twice as much fun as a 1 part mold.

[Dave V]

Okay, I did find my digital calipers.

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[peteski]

Yeah, lots of new words here that I've never heard before.

You guys did accomplish your mission of dissuading me from even attempting, LOL.

If you don't care about the detail on the back (so you can use one-part open mold), here's an example of what can be done with no pressure or vacuum pot, and a simple resin/RTV rubber kit. https://www.therailwire.net/forum/index.php?topic=28541.0

Since the piece you are duplicating does have some detail in the back, you could use the same open-mold process to separately cast that mounting "doughnut", then glue it to the back of the brake detail part.    But the smallest hobbyist (sample) kit you can buy is I believe 1lb. so you will end up using about 1% of the kit and dumping the rest (unless you find some other uses for the resin before it becomes unusable).

I just reread that entire bumper car thread (it was 10 years ago), and I do mention there that I did vacuum the RTV rubber, but it really wasn't required. I was just trying out my new toy (vacuum pump and a home made vacuum chamber made from a small thick aluminum pan and a cover made from a piece of 1/2" thick acrylic).

[Angus Shops]

I recommend Smooth-On products. I use resin casting a lot in my model building and have used it to build a variety of Canadian Pacific prototype models (rolling stock and structures), other structures, details and almost anything else I could possibly need more than one of. I find Smooth-On to be the most reliable products - I’d recommend Smooth-Cast 300 (their fastest curing resin the pot life of only a couple of minutes and can be removed from the mold in about 1/2 hr) and one of the Mold-Max tin cure silicone rubber options.

In my climate (PNW) the resin products have shelf life of only a few weeks after opening (bubbles as described by others and spotty uneven curing) so I like to plan my projects in batches so I use up the supply of resin inside that time frame. I buy the “trial size” packaging - it’s really quite amazing how much casting will result from this. I have a few molds of items that a) use up a measurable amount of resin per copy, and b) I can use in multiple places on the layout (the solid body of a tool shed and lumber stacks are two that spring to mind) so I can use up the full volume of resin without waste. So, in addition to your tiny part, I’d advise you come up with a couple of other larger items that you may also be able to use on your layout(s).

[daniel_leavitt2000]

I did a full write-up on casting almost 10 years ago:
https://www.therailwire.net/forum/index.php?topic=37486.0

This part would be difficult to make, but not impossible. It might be easier to have someone make a 3d printed version. Casting resin is usually soft unless you add additional catalyst. When you do that, you have very little working time - sometimes seconds. There are hard resins out there - https://www.reynoldsam.com/ has a few. Wow - they closed the Boston location. Bummer...

[C62-2]

I Santa Fe-ized some steam locomotives by making castings of the sand dome on the locomotive to get a second matching sand dome. I used stuff available locally in Tokyo, so the brand info won't help you in Colorado, but I'm sure the same stuff exists as a different brand. For the sand dome, I made a one piece mold, since the side of the dome that faces the boiler needed to be a different shape than the original, since it goes on a different part of the boiler. You could also do a one piece mold of the part, and add separate pins to the back, or do a two piece mold to get the whole thing.

The kit comes with two colors of putty-like stuff that you knead together until it becomes one color to make the mold. In my case, I just pressed the mold material around the original, and let it dry. In your case, press the part into the material so it makes an impression of one side plus the edges. Once the mold is hard, carve some grooves into it for indexing with the other half. Make the second half by kneading up some more material and pressing it onto the mold + part so the part is now completely surrounded (and the second half of the mold has parts sticking out to go into the index grooves in the first half. When hard, separate, and carve a pathway down to the open part chamber so the resin can get in.

For the sand domes, this got me parts that were 95% of what I wanted, a bit of filling and sanding got me a part that is indistinguishable from the original. This method would not be adequate for producing something like a car body or other detailed large highly visible part, but it would work well enough for something that's going to be painted black and not the center of attention on the model (and it worked well enough for sand domes, which are somewhat prominent!).