Hammered Copper

What's wrong with soldering?

Are you envisioning a pretty wheelbarrow that will sit idle, with a couple of flowers in it, or something you can mix concrete in?

Hand-hammering a deep form out of a single piece of sheet requires raising (hammering from the outside) not sinking or stretching. Raising is incredibly time consuming and very difficult with anything heavier than

18ga. Also, you would need large stakes and the arms and hands of King Kong. If you're interested in how the coppersmiths did things back in the day before the industrial revolution, find a copy of "The Art of Coppersmithing", readily available in paperback reprint copies ( check Centaur Forge )

If you really want to do it right, you'll need to learn how to cramp the edges of copperplate together and learn the fine art of forge brazing. Haven't you always wanted to learn how make spelter?

Check out an old copper cooking pot ( a real old one, not a repro ) and you'll be able to get an idea of how the thing was made.

I suspect that it might be possible to make it in one piece, but it would be very difficult. To get a sense of how difficult, start with a flat sheet of paper, and try to bend it into the shape of a barrow. You will end up with lots of extra material at the corners. If the front is rounded rather than squared off you could shrink the edge rather than cut out a piece, but that is tedious and requires some skill.

is a good site for information on how something like this could be done. Since the bottom of a wheelbarrow is flat, you probably don't want to stretch that area, unnecessary work, that is why it is easier to shrink the edges or cut out a piece, and leave the bottom essentially untouched. A wooden hammerform might help with the edges, etc.

If I wanted to do this, I would cut material out at the corners and then weld it back together. You could do this with TIG or oxy-acetylene welding, although copper is not easy to weld. I tend to get porosity in my welds, so they don't look that great even after being ground smooth.

As far as thickness of material, I would use 0.040 inch (1 mm) thick material or thicker. That is workable, and reasonably substantial. You might check the thickness of the steel of a real wheelbarrow, and try to match it, especially if you plan to use it rather than have it only for appearance.

One challenge is that when you heat or weld copper, it gets very soft, so you need to work harden it back to a more usable hardness. The yield strength of work hardened copper is close to that of steel.

I have done several sculptures in copper, so I have some experience from which I speak. I am reworking my website, so only have one sculpture on my website right now. This is a three foot birdbath made of copper about 0.040 inches thick.

Richard

haywyre wrote:

Richard Ferguson wrote in news: snipped-for-privacy@omitthisatt.net: snip

Hey Richard, is that a Reil design burner on your forge? Nice work on that Birdbath BTW.

granpaw

Just curious -- how are you planning to attach it to the frame?

Assuming you want flat sides and a flat bottom, I would suggest trying to keep these flat throughout the process by clamping supports to them (think flat plates -- metal or wood) while bending them in (that is, support the flat sections, leave the bends and corners unsupported). Bend all four sides up a little at a time. You'll end up with excess metal at each corner, which you can eliminate by using raising techniques, which will essentially reduce the area by making those sections thicker. Then bend the sides up a little more, and repeat, until you get the desired shape. With this approach, the answer to your second question is that it won't stretch at all; it will shrink a little at the corners.

Of course, you'll need to anneal the sections to be raised (the corners) frequently to avoid cracking. If possible, you want to avoid annealing the remainder of the piece. You could try attaching some kind of heat sink (maybe some thick aluminum plates) next to the corners to prevent the heat from traveling too far (copper is an excellent heat conductor, as you may know). But you'll need a good heat source to bring the corners up to annealing temperature quickly before the heat sinks loose their effectiveness. Any areas that are annealed will eventually need to be work-hardened (generally done by hammering) if you want maximum strength.

As for the thickness of metal to use, it all depends on how big it will be, how it will be supported, what kind of loads it will have to carry, and whether you care if it gets a little out of shape. To take a wild stab, I would guess you'll probably want at least 0.060".

Bert

Richard,

I've wondered how bird-friendly copper birdbaths are. Most copper compounds are at least slightly water-soluble and are somewhat toxic as well (at least to humans; I assume they don't do birds much good either), especially cupric acetate (aka verdigris), which is a key component in the aqua-colored patina of weathered copper. I've seen copper birdbaths before, so maybe it's not a problem, or maybe it's just a case of the toxicity not taking effect until after the birds fly away! Anyway, I was just wondering if you've looked into this issue at all. If so, I'd be interested in what you found.

Bert

Could the shape be cut from sheet, brazed together, and then hammered to final form?

I have some Sil-Phos copper brazing alloy. It's a good color match. Can it be hammered without cracking?

I'd be happy to send you a stick. It cost around forty dollars for a pound or whatever, in a tube about the size of your thumb, maybe 18 inches long. Each stick is like 1/16 x 1/4 inch.

It would be particularly convenient to send two half sticks in a first class envelope with a little carboard.

Yours,

Doug Goncz ( ftp://users.aol.com/DGoncz/ ) Student member SAE for one year. I love: Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically. I drive: A double-step Thunderbolt with 657% range.