Car Casting Question for the Experts

[Morpar]

I have been doing some thinking, and have decided that I need a whole fleet of Virginian style 105 ton gondolas. I have an article from the October '74 MR on building a close version from 2 Athearn quad hoppers. Considering that I would like to have 30-50 of these cars, kitbashing that many would be expensive and time consuming. My thought was to cast them, just like in a January '83 MR article. I looked back in the forum and found the thread about this article, but there wasn't any newer information. My question is what is available now that is as good or better than what was available in '83? Has anyone else tried this? Is the cost going to be so high that I don't really have any interest in this idea? Where would I get the resin and the mold materials? Any input would be appreciated. Thanks

[dehusman]

The hard part would be a two part mold to make a one piece body. The alternative would be to make a series of flat castings: a bottom/underframe, 2 sides and 2 ends. The sides could be identical, but the ends would have slight differences due to A/B ends. You could do it with some careful engineering of the masters. If you used Athearn body shells for the masters you could make as many as you liked, but you could run into legal trouble if you tried to sell them.
The whole trick is in making a good set of masters.

Dave H.

[Anonymous]

If you can pull off making a 2 part mold, it is doable.

Figure if you were going to buy 50 cars at $7 apiece, that would be $400.

I spent that much making something out of resin that weighed 8 or 9 lbs, and I didn't spend that much.

I would go with a good quality silicone rubber. The good thing about silicone is that you don't need a mold release when you make the resin duplicates.

I THOUGHT I didn't need a mold release for an original piece, but I had problems with the rubber sticking to my master on a few pieces.

Silicone rubber comes in several "flavors" - from really stiff to very flexible. If you use something more flexible, you don't have to worry about undercuts (as long as you exercise some caution in demolding).

I would think a "squish" mold would work best. Then, you have the bottom half of the mold, you fill it with some resin, and then put the top half on, squishing out the excess resin.

There are several different resins. They have different hardnesses, and setting times. For something that size, I'd go with something that sets up in 3 - 7 minutes. It doesn't take that much time to make a copy, and you'll appreciate not having to wait 60 or 90 minutes to de-mold.

A recommendation - use some talcum powder and a small makeup brush (the kind that comes in a lady's compact) to VERY LIGHTLY dust the interior of the mold. This seems to break the surface tension of the resin, allowing it to flow into fine details.

If you work carefully, you don't have to worry about vacuum degassing anything or pressure casting anything.

It IS difficult to paint the resin afterward. You will need to lightly rough up the surface of the casting, and make sure you prime it well.

If you have any questions, please feel free to e-mail me - Rob(AT)sandcrawlerworkshop.com

replace the (AT) with @

Rob

[Morpar]

I just thought of one other question I forgot to ask before. Will I be better off trying to cast an entire car (like in the Jan. '83 MR) or just the individual parts? If I cast the entire car I will still have to pour the frame separate to prevent it from getting locked in the mold. If I pour the car as parts, I will have more work to do. I really want to pour these as a unit, not parts. Is there any problem with embedding weight in the resin? I am planning to leave areas that can be filled with lead shot to add weight while pouring. Any thoughts on this? Any other suggestions? Thanks for the input!

[Anonymous]

http://www.mgussin.freeuk.com/1-32BerlinettaBoxer.htm

[dehusman]

For the type of car you are planning I would either have two molds, one for an underframe and one for a body and sandwich the weight between the two or a one piece and make the weight the bottom of the gondola well.

You could cast the the gondola as a one piece casting. Its more complicated, you will have to simplify the underframe to make it work (no H section crossbearers and sills). If yo are will ing to maybe have to toss a couple molds and castings, go for it.

Dave H.