- Joined
- Nov 11, 2024
- Messages
- 112
- Points
- 78

Note: These guns turned out to be way too big and I end up 3D printing these with normal FDM later in the build. I left this process in as casting may still be a viable option for some folks more crafty than I.
Guns!
So this has proven to be a real challenge. I turned one barrel on the lathe with reasonable success but I know I won’t be able to consistently repeat this with perfect results another 29 times so I decided to go down the road of casting with some very mixed results. Here is the update so far.
I wanted to make my molds with Oyumaru or blue stuff, but I cannot find either in South Africa. So, I went for 2 other options. The first was a 2-part liquid silicon that would be poured around the cannon and then cut away to release the blank and then secured with elastic bands to re pour the liquid resin into it. This did not work at all...
Without the benefit of a vacuum pump to extract all the bubbles it created a mold full of imperfections. The elastic bank required to keep the soft silicon together distorted the mold and therefore produced a frankly, rubbish result. The resin also left flakes inside the mold that would be very difficult to clean and finally the resin itself was very brittle and weak (this is clearly just the resin I used, and I am not judging all resins). Here you can see the results of lots of struggling.
Next up was making molds from thermal plastic. This process involved heating the product in boiling water. Pressing the cannon blank into the product until it was half in the material, then cooling the product in the freezer and then pressing a second lump of product on top of the cannon to make the second half of the mold. Here you can see what this looked like.
I then pressed Milliput into the 2 halves and joined them back together while it set (note the indexing holes and protrusions in the 2 halves of the mold.
This produced a reasonable result as shown below. The issue was that the mold struggles to release the material, and it seems like the quality deteriorates after each attempt as the mold degrades. I do have a few ideas to improve this, and I will report back.
I then made a little jig to file in the notch for the trunnions. As per the suggestion of Marcus, trunnions add an additional layer of complication to casting which I am not able to overcome.
I then added the trunnions and primed the 2-sample cannon with a grey primer.
I then finished them off with some black paint and this is where I find myself.
I did get the feeling that these carriages (built to the specifications mentioned in a previous post) were a bit on the small size. The carriages on the hull model also appear to be proportionally larger but I have also found examples in other research where the ratio between cannon and carriage seems equally disproportionate. Like this example of the constitutions 32 pounders from 1858.
My plan is to keep experimenting and seeing what works. This means:
· Trying to produce a thinner more flexible thermal plastic mold with what i have already.
· Trying to create a better silicon mold by changing the ratios of parts A and B of the mix
· Trying to buy Oyumaru and having it imported into South Africa
· Trying a mold made from other materials like silicone and corn starch.
Guns!
So this has proven to be a real challenge. I turned one barrel on the lathe with reasonable success but I know I won’t be able to consistently repeat this with perfect results another 29 times so I decided to go down the road of casting with some very mixed results. Here is the update so far.
I wanted to make my molds with Oyumaru or blue stuff, but I cannot find either in South Africa. So, I went for 2 other options. The first was a 2-part liquid silicon that would be poured around the cannon and then cut away to release the blank and then secured with elastic bands to re pour the liquid resin into it. This did not work at all...
Without the benefit of a vacuum pump to extract all the bubbles it created a mold full of imperfections. The elastic bank required to keep the soft silicon together distorted the mold and therefore produced a frankly, rubbish result. The resin also left flakes inside the mold that would be very difficult to clean and finally the resin itself was very brittle and weak (this is clearly just the resin I used, and I am not judging all resins). Here you can see the results of lots of struggling.
Next up was making molds from thermal plastic. This process involved heating the product in boiling water. Pressing the cannon blank into the product until it was half in the material, then cooling the product in the freezer and then pressing a second lump of product on top of the cannon to make the second half of the mold. Here you can see what this looked like.
I then pressed Milliput into the 2 halves and joined them back together while it set (note the indexing holes and protrusions in the 2 halves of the mold.
This produced a reasonable result as shown below. The issue was that the mold struggles to release the material, and it seems like the quality deteriorates after each attempt as the mold degrades. I do have a few ideas to improve this, and I will report back.
I then made a little jig to file in the notch for the trunnions. As per the suggestion of Marcus, trunnions add an additional layer of complication to casting which I am not able to overcome.
I then added the trunnions and primed the 2-sample cannon with a grey primer.
I then finished them off with some black paint and this is where I find myself.
I did get the feeling that these carriages (built to the specifications mentioned in a previous post) were a bit on the small size. The carriages on the hull model also appear to be proportionally larger but I have also found examples in other research where the ratio between cannon and carriage seems equally disproportionate. Like this example of the constitutions 32 pounders from 1858.
My plan is to keep experimenting and seeing what works. This means:
· Trying to produce a thinner more flexible thermal plastic mold with what i have already.
· Trying to create a better silicon mold by changing the ratios of parts A and B of the mix
· Trying to buy Oyumaru and having it imported into South Africa
· Trying a mold made from other materials like silicone and corn starch.

