Forge

[Hibernicus]

We've made ourselves a portable forge for events

And a very functional bellows... not knowing what a proper Roman bellows looks like for large scale heating... we chose one that has proven itself.

Set up at The Muzeo in Anaheim Calif

Unfortunately the "structure" the museum is building to house and secure it was not finished. The walls will be plastered and the back side festooned with grafitio

The bellows is a double chamber... two intake valves and one transfer valve allowing air to move from the bottom half into the top. By lifting the bottom half, the top half fills. Gravity lowers the bottom (filling it) and the top (emptying it). On each action air is pushed threw the tube to the forge.. a steady stream of air. More vigorous pumping created a 12" to 15" spout of flame! We even melted off the tip of a pilum!

We've also decided to build a piston bellows. Roman had pistons to pump water.... Why not air? Besides, wouldn't that be cool to see!

The bellows skin is pig. Its 42" (106cm) long and 34" (86cm) wide and when fully inflated it's 24" (60cm) and weighs about 75lbs

The bellows will be further supported by a frame to increase the operator's leverage.

[Comerus Gallus]

Nice I need a babe like that in my back yard...

[Carlton Bach]

Way cool.

On the subject of bellows, a late antioque ivory from the museom of applied arts in Milan swos bellows that work on the 'accordion' principle - pulling up and pushing down what is basically a corrugated tube. They are for a small forge, though, I don't know how they would scale.

[Gaius Julius Caesar]

What about wind or water powered bellows, bet that would be an efficient setup with that bellows you guys have there Hibs....

[Magnus]

Hey Sean, 2 questions.

1. What kind of charcoal do you use, and does it have a high sulfur content?

2. Could your design utilize some type of electric powered blower instead of the belows?

[Hibernicus]

Magnus...

We use real charcoal.. and because it's readily available in 40lb sacks we use mesquite. A bag retails for $15 and in a day of demonstrating its real easy to go through a whole bag.

Electric... yeah, mulled that one over. Had a back up in case the Bellows of Supposition didn't work. An adjustable speed hairdryer mounted inside .... do not want to/do not want to... I'd rather explain the use of a later period bellows than the use of electricity, the one being plausible.... and then there's the cord.... and the safety tape securing it to the ground....

Used a small double pump iron age style bellows some years ago.... great for small work... melt some lead, cast some bronze, work a knife.. but for larger work like making a dolabra... we need more air

Now tha we have this set up I really really want a piston bellows. Using known Roman technology to pump air instead of water will be easier to explain than using known later period technology.

[/i]

[Magnus]

Yeah, the reason I asked about the electric pump (ironically i was thinking hair dryer as well), was for a non-roman related forge. I may try that next year sometime.

I heard that certain charcoals were not good for forging because of the impurities they leave behind in the steel you are working with. Any experience with this?

Is your charcoal made with hardwood? I'm not sure what mesquite is, aside from the style of cooking. 8)

[Caius Fabius]

A heavy duty hair dryer or a vacuum sweeper motor with a rheostat control, like a light dimmer switch, makes a modern forge blower that is adjustable.

Make the inflow through the bottom of the fire area and use a grate on the inflow point, and use metal hose for the first few inches, or when hot embers drop, as they always do, they'll melt through plastic hose.

[Gaius Julius Caesar]

Where do you get fire bricks from....and what are they made of? That looks like the answer to my problems as far as building a forge goes..I will sacrifice authenticity for the sake of an electric blower...and possibly the option of using gas or charcoal.....weather permitting of course!

[Robert]

Oh well, so much for trying to get things "right" or trying to create any resemblance of "period.
Magnus, charcoal makes a very clean forge fire. It can even be used for forge welding. The major problem is not brushing of the iron scale which covers the iron when you take ik out of the forge and start hammering away straight off. You will hamer this oxide (scale) into the iron, not a good thing. I am just getting into smithing, having a small forge and anvil, and have found neither coal nor charcoal will mar the iron, but scale will.

[M. Demetrius]

To save your helper's knees, many an old time forge had an attached rope to the bellows handle, and a simple frame with an overhead pulley, so the helper can stand, and simply pull the rope to run the bellows. Just a thought.

That used to be the job for the pre-apprentice boy in the smithy, they say. At least from his vantage point, he could see the work in progress (and there wouldn't be much else to do...) and get a million questions answered before they were asked.

[Caius Fabius]

I have photos of reconstructions of a Roman bellows (from Germany and Switzerland) and the relief that was used as a model (from Italy). It was built in a stationary wall like support and the operator would be standing. The forge was also raised. I can give you a little help for both, BUT if you want to go make a modern forge, that's easy.

Actually, on the farm, we don't forge weld with charcoal, it doesn't usually get hot enough to weld, and the local coal has to be turned into clinker, and the bellows has to be really adding air (oxygen) to the fire to get up to welding heat.

We heat (cook) the local coal, and burn off the sulfur, then save the purified 'coke' (heat treated coal?)

Simple metal heating and shaping is easier, but the actual heavy duty stuff such as welding just won't happen with normal store bought charcoal without a whole lot of extra effort, when 'coke' and a steady stream of air will give a hotter fire, much hotter.

On the other hand, if your fire is too hot and you'll start losing the carbon from your iron / steel and burning your iron-metal. You do not want your iron metal to get 'white hot', so you need to keep an eye on the color all the time. If you get distracted, you can ruin a piece of metal.

Maybe this makes sense, maybe not, but you never know how much steel is in your iron metal unless you buy it from a store. Around where I am, we use a lot of recycled stuff, old tools, bailing wire, scrap 'iron', old nails and fittings, even rusty old horseshoes, to make our 'new' stuff. :wink:

And people wonder why I don't do any of this for reenactment? Well, if you have to do it at work, why would you do it for fun? :lol:

[LUCIUS ALFENUS AVITIANUS]

Only a suggestion. The below don't have to be so big!. You can get a better aireation using two little belows, used alternatively. When one below is taking air, the other is giving air to the forge. African people use in that way, to make a continous aportation of air, so the temperature increases quick and high.

[Gaius Julius Caesar]

Interesting information......never thought about burning iron/steel.
Just goes to show it was an art.

[Robert]

Salve Caius Fabius Maior, greetings Charles,

I am very new to smithing, and have a question on the clinker issue. I have fired up the forge a few times now, and as the coal burn a while, it formes a kind of bonded, slag like product in the forge. This is very hot and glows bright yellow in the airstream. When cooled, it has a metallic kind of feel to it and is heavier then the sulpherous coal I started out with. This clinker, as you call it, is described in my book on backyard smithing as an unwanted product, to be cleaned from the fire (or I am confused as to the appearance of this byproduct and breaking up the wrong stuff). If you have any pointers, I would be most interested to learn from a pro I sometimes use pure wood charcoal (not the useless bonded brickets for the Bar-b-q) and this gives the iron a good heat as well, but I churn through a lot in a short time with the blower on moderate airsteam. A simple circular valve in the tube regulates my airflow, no elaborate controls, its an old furrier set.
The book "the blacksmith's craft" by C. McRaven has some good pointers and a blow by blow foto series of making a small forge from a cast iron brake drum from a truck or large pick-up. For period appearance, even common well fired brick not directly in contact with the blaze seem to work fine, no real need for those non-period looking firebricks. You will crack the odd one, but they are easily replaced.