Firepot depth?

[2dollarhammer]

'bout how deep should the firepot be? I know in our current forge setup, we're having a hard time heating longer stock. Do we need to make the fire pot shallower? It would be easy enough, but if it's as simple as just making the fire differently, I'd like to know.

The problem is, the center of our fire, is below the rim of the bowl, and as a result, we can only heat the tip easily. Is there any good was to raise the center of the fire without cutting the bowl to make it shallower?

I'll get some pics of our forge up in a little while.

[Sabre]

well how deeps your firepot now?

i wiuld say it should be 3-5 inches

[tetnum]

you could use a bullet tweer wich will rase the fire a few inches

you can put more air in wich will have the same effect but use more coal

or you can use charcoal wich needs a deeper firepot

[UnicornForge]

The depth of the firepot is for the purpose of creating a neutral zone where a rod inserted into the coal would end up just above the firepot. The area of the length of the heated area will be determined by the length of the firepot.

The purpose of the neutral zone is to have an area of the fire above the over oxygenated area, and below the over-carbon area of the fire.

One way to have a long area in a coal fire is to run a pipe along the floor of the forge with air slits in it for the air to be distributed over a longer area. For a large iron tire/hoop, memory tells me someone built a large circular forge with an air pipe, with holes, circling the forge under where the round tire would sit in the coal.

In most applications the smith heats and works on one area of the iron at a time, limiting the size of the heated area to the area he/she can practically work on before it cools to the point that it has to be returned to the fire.

[2dollarhammer]

Not trying to heat an entire stock bar. Just trying to heat different points on long stock, but I think my firepot's too deep because the heart of the fire is at such a point that to heat the metal effectively, it has to be actually in the bowl, not over the rim. Time to do some cutting I guess...

[UnicornForge]

Before cutting I would humbly suggest comparing the size of your firepot to either a Champion firepot or a cast firepot offered by a vendor such as Centaur Forge. The danger is to decrease the depth of the firepot so much that you raise the over-oxygen rich area above the surface of the forge, in which case you are then blasting your iron with too much oxygen.

If I remember correctly, the excess oxygen accelerates the conversion of the iron piece to scale. I don't remember what the excessive about of carbon does to the iron. Perhaps someone else here remembers. I'm a bit sleep-deprived.

The Champion firepot is a very good size, in my opinion. ;-)

Originally Posted by 2dollarhammer

Not trying to heat an entire stock bar. Just trying to heat different points on long stock, but I think my firepot's too deep because the heart of the fire is at such a point that to heat the metal effectively, it has to be actually in the bowl, not over the rim. Time to do some cutting I guess...

[Arbalist]

I'd like to see some pics of your Forge as this is a concern of mine as well. Many Forges often seem to have deep sides as well making it virtually impossible to heat up anything but the end of a bar!?

I think my next Forge may be something like this: My Portable Forge

[UnicornForge]

Here is an old "semi-portable" Buffalo forge with its original fire pot. I humbly feel that it is a good example of a basic forge. The forge surface is about 24" square allowing coal to be moved in from the sides as the coal cokes.

Note that both the firepot and the sides of the forge have indentations that allow iron to pass through the forge and over the firepot. The Civil War era Traveling Forge above also has that cutout in the side to poke iron into the hot spot while having sides that reduce how much coal falls on the ground. Coal has a tendency to fall out of these cut-outs.

Flat tables are great, I have seen a couple of very nice ones at museums. However, they had surfaces large enough to enable the coal to stay on the forge.

Still with this forge as with other forges with firepots, the hot area is in practicality limited to the length of the firepot. If you want long heated areas, then you will likely need multiple air sources such as a pipe along the bottom with multiple openings.

The sides of the forge are there to simply reduce how much coal falls onto the floor.

I hope that answers your question.

Originally Posted by Arbalist

I'd like to see some pics of your Forge as this is a concern of mine as well. Many Forges often seem to have deep sides as well making it virtually impossible to heat up anything but the end of a bar!?

[John B]

Have attached a picture of a solution I use on small portable forges, this one is approximately 20" square x 3 1/2" deep ( it also used to be a standard fitting on larger industrial (including side by side) double forges)

The one in the picture gives you a couple of options, at one side you have one plate that can be removed to give a low setting (Level with the base of the forge), at the other side, there are two plates that either one or both can be removed to give you a half depth setting, By removing the larger plate, and substituting one of the other plates, you can get access right through the forge on this half depth setting which leaves a fair depth of fire under the workpiece should you need it

The plates consist of two large plates sandwiching a smaller plate slightly thicker than the wall thickness of the forge so they form an H section that can be easily slid in or out of the gap left in the wall sides of the forge.

They can be taken out when required, then replaced when not needed, this helps to minimise the fuel being used spilling out over the sides

[Arbalist]

As 2dollarhammer says, it not about long heats, rather selective heats on a long bar. I've tried to heat the middle of a 20 inch bar in a chip forge at work and even though the table is flat I can't get the bar low enough to get a decent temperature on the middle. I'm planning on building a charcoal forge with a flat table (like in the link) but I'm a little worried if I make the fire pot too deep I won't be able to get enough heat in the middle of a bar and if I make it too shallow the metal will over oxidize?! I'm not worried about losing fuel over the sides of the table as I'll just place fire bricks round the edges if I need them. Sorry to hijack your thread (a little) 2dollarhammer!

Originally Posted by 2dollarhammer

Not trying to heat an entire stock bar. Just trying to heat different points on long stock, but I think my firepot's too deep because the heart of the fire is at such a point that to heat the metal effectively, it has to be actually in the bowl, not over the rim. Time to do some cutting I guess...