May 7, 2012

Spin casting

Vulcanizer, melting pot and spin caster set up in my shop
First rubber mold



(For some unknown reason Google has been deleting images from my blog. I do not know why this is happening. Sorry for the inconvenience.)

Last year I ordered a spin casting set-up from Conley Casting Supply, in Warwick, RI. It took several months for the machines and supplies to be delivered. Then I had to make some master parts to try to cast, which required a new Sherline lathe and drill press. Last weekend I finally got it all going making my first mold and cast parts.

The mold process went well. The silicone rubber cures at 300 degrees, so it is possible to use acrylic masters.

I made three types of cannon barrels: 12 pound Napoleon, 3 inch Rifle, and a 10 pound Parrot rifle, a set of cannon wheels and stanchions for my model of the Ironclad Passaic. I added some of my PRR signal targets as I am out of stock of my brass ones.  I also put some out of production parts from other manufacturers in the mold to see how they worked out. These were wooden barrels, a switch stand and a figure.

Once I had the rubber cured, I inspected the mold and removed the masters.  I had a little rubber stick to the hub area of the wheels, but otherwise it worked great. I made a mistake and forgot to insert the center plug for the pour hole when I set up the mold. That was a minor problem that I corrected by cutting the pour hole. However, it did leave the mold thinner and therefore weaker and the rough bottom of the cut out area created some turbulence that affected the mold filling.

Then came the tricky part of cutting gates and vents. I tried cutting the gates on the bottom and the vents on top, but that was much harder than I expected as I inadvertently ended up with some gates crossing over vents,

Next I melted some pewter. I loaded the mold in the spin caster and poured the metal. At first only one cannon barrel filled. So I cut some more gates and kept pouring. As the mold warmed up, I got better yield. I also increased the spin speed. After about 30 pours I have the parts in the photo above. The pour hole of the mold started breaking up and the fill rate was not as good, so I may need to retire this mold.

Overall there was almost no flash and the the shrinkage was negligible. There was some squash distortion.  I never did get the PRR signals to fill properly. The parts are just too thin. But everything else worked pretty well.  The cannons had the best yield. They had direct gates. The side loading gates did not fill as well.

All in all a good first test. The cannons will be an Alkem Scale Models product. As no one currently makes true 1/48th scale ACW field artillery. The chassis will be laser cut wood with separately applied detail parts.  Here is a photo of a pilot model gun in a revetment at Potomac Creek. I still need to do some tweaking of the details.



8 comments:

  1. Do you know of anyplace that sells O scale muskets?

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  2. No, not to my knowledge. However, I am working on it.

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  3. Great work. I have all but given up trying to model a M1841 6 pdr in O scale. Was looking to build a Confederate monument on my On30 layout, showing the tube being yanked away for a WW2 scrap drive to show how much history got melted down for pretty much no constructive purpose. It never crossed my mind that nobody makes a good representation of civil war field guns in that scale!

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  4. Alkem Scale Models has O Scale artillery cannons for sale. See www.alkemscalemodels.com

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  5. I tried that site. You can't get to any items available, it never gets beyond the title page. You can get to the order section but if you can't see what there is to order, that's a moot issue.

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    1. To which site are you referring? Conley Casting merged with TekCast last year. They are still in business AFAIK.

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    2. I'm refering to www.alkemscalemodels.com. No matter what scale you click on the front page, it doesn't go anywhere. I've tried at my home and work computers and my cell. You can't anywhere to see what's available from your home page there.

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