After a year of hard work on patterns, flasks and the rough casting, Tom Ward has returned to Boston. Thanks to him, and the Fulbright Commission, for all he has achieved. We hope to see him back here as the project continues through the winter and into the spring.
The exterior of the gun is now largely cleaned up and needs only some detail work on the coat of arms and final planishing, which is the process of beating the surface with a hammer to harden it. We tried some of this the other night after work, and it soon became a musical evening as we experimented with the sounds different types of hammers and mallets make – the gun rings like a bell! One of the new Fulbright scholars was present and he is studying music. He made some recordings of the results, which he plans to use in a composition he is working on. I guess gunfounding really is an art!
We still have to clean out the bore, as the breech end has remnants of the core as well as a hardened mass of casting dross in it. This will take some boring with long drills and a little brute force. Once the bore is clean, we can build a full-size boring mill to take the diameter to its final 146 mm.
We have also been planning for the wooden and iron parts of the gun carriage, which will be built at the museum, along with the loading equipment – rammer, sponge, ladle and linstock – we will need for the test firing. And since we will need something to shoot at, we will also be building a section of ship, based on the construction of Vasa. This will not only let us test how much damage this gun could do, but also how much of a pounding a ship like Vasa could take.
The cannon blog will likely take a pause for the time-being but we will try to keep you updated on progress in these other projects as they happen.
Here are a few photos of the cannon in its nearly finished state. The gun is around 3M (10ft) long and weighs around 1.5 tons. The bronze is a median alloy of surviving originals of around 93% Copper, 4-5% tin, and trace amounts of Zinc and Lead. The following photographs were taken in the carpenter's shop by fellow Fubright scholar Evelyn Ansel.
Powder pan & touch hole
This is one of my favorite details on the cannon. Its a lion hold fern vines in what is called the vent field, because optionally you can drill the touch hole here.
The end of what is called the crozet, or core support for the mold, its a cross of iron that becomes part of the gun.
At long last on Thursday last week, we got to open the mold! We cut some welds off of the side and began digging! We'll just get right too it, shall we? The first few of these pictures were taken by Helena Jonsson who is the managing director at Tierp.
Success! There is a cannon in the mold! The details look great. However, there was one problem in that the bronze permeated the sand in places in the mold, creating a mixture of sand and bronze that was an exact mold of the surface. This was a little unexpected and something I'd never seen, but apparently with the right heat and pressure, you can force molten bronze in between the air space and grains of sand! Crazy physics, but very annoying to remove.
In places where this was thin, a simple hammer and chisel could be used to remove it, thicker section took a torch and a jackhammer, leading to some errant blows that will need to be repaired. However, all and all, the cannon looks great, the core seems to be able to be removed, and it looks solid. Heres a bunch of pictures of the 30 hours I spent with a jackhammer and one of the biggest air fueled torches I've had the pleasure of using!
When you run a grinder over the surface, it is mostly bronze.
Ladle warming torches are the coolest.
It took me the better part of 30 hours to get to this point. Ooof.
The final pieces of decoration, including the Coat of Arms. It was amazing that that stuff wasn't adhered to the surface, I can thank the graphite coating for that!
Also, we needed to remove the gunhead, the extra material at the end of the gun that helps feed the gun as it cools! After that, they began drawing the core rod with a 100 ton jack, they had moved it about 15 cm before I needed to leave.
With a little bit of luck, they'll pull the core and ship the cannon down to the museum tomorrow or Monday, and I can treat you guys to some nice photos of it before I head back home to the United States for the time being!
Also, a few exterior links from the media and video stuff!
Applogizing for the late update! But we we're asked to wait for the media to publish first! We poured the cannon on friday, first and foremost. We had members of the media and other employees from Vasamuseet present for the event, as well as no less than three crews filming! All of these photos were taken by Evelyn Ansel, current Fulbright Researcher, as I am the former Fulbright Researcher.
Martin Wildman and his camera man from Deep Sea Productions!
Monica and Håkan, you may know them from Vasa's regular blog, they're some of the ship's carpenters!
Thomas Carlsson, the foundry master and Bertil Bjorkman, the head of the Friends of Vasa.
Dr. Fred Hocker and I!
Our materials for the day had to be made, Bronze is a copper alloy and we needed to produce our own. We used pure copper that has been reclaimed from wiring and electronics by the foundry's parent company Lantz Metal, which specializes in this. Then since the alloy we were aiming for requires about 5% tin, 1% lead and 1% zinc, we loaded the crucibile with additional bronze and brass scrap, as well as 90kg of old pewter commemorative plates, some of which even came from our own museum shop in years past!
After a bit of melting, mixing and checking, we arrived at about what we needed. We poured the metal out at a crispy 1200C into the ladle to warm the ladle up, then we pour the metal back into the furnace. We did this process again and while we had the metal out, we poured the lifting dolphins.
At this point, we were ready to pour. We had set up the mold the day before so we could concentrate on getting the metal mixture right, so all we had to do was dump the mold back into the ladle for the 3rd time. This time, however, we ramped the furnace up to 1300C so while we transfered the metal into the room with the mold, it would not drop below our optimal pouring temperature of 1150C! The ladle was skimmed and poured! It went off without a hitch!
After we poured the metal we had a good round of congradualtions, photography and interviews! Then we got to have a mini christmas in opening up the molds for the lifting dolphins! We were a little worried that one of them may not have cast due to a leak in the mold, but they came out beautifully. Johan, one of the owners of Lantz and Tierp was also able to check the alloy with this cool hand held x-ray spectrometer that we suspect could also turn you into the Incredible Hulk, and that was spot on as well!
The failed casting.
The good casting!
Now, Thursday we should be able to open up the mold and see how we did, if the actual pour day is any indication, we should have done very well, but you never know what surprises are in the mold! But knock on wood and hopefully there a beautiful bronze Vasa 24 sitting inside our 7 ton Christmas present on Thursday!