[abrasive]

I'm re-working a forge I built many years ago. It's been great for general forging, but I want to start welding and it's just not hot enough here at altitude. (Salt Lake area)

The forge body is 8" pipe, 17" long. Two layers of 1" Kaowool all the way around, and a piece of kiln shelf on the bottom. Net inside diameter is, taking into account the non-round shape, about 5.5". So we're looking at around 404 in3. I made a little movable wall out of satanite-and-itc100'd kaowool. Oh, and ITC-100 on the Kaowool, though that needs to be re-coated.

Single 3/4 "Reil EZ burner dead center, i.e. 8.5" from each end at about 10:00 pointed in so the flame hits the wall and swirls. If I were doing this over, I'd place it closer to the front - that's where all the heat goes. The back stays pretty toasty.

I am looking at two improvements: adding a second burner, Porter-type, and upgrading the old burner to a Porter-type.

My burner holder is 1.5" pipe welded into the forge body. Really not looking to cut it off and move it. I am thinking of adding another burner between the existing burner and the front - maybe 4" OC from the existing burner. Is that too close? Can I go closer? I really don't want the additional burner right in my lap... Or should I bite the bullet and move them both? Or just weld up a new forge body - I think I have the cutoff from that 8" pipe around here somewhere...

I've already plumbed ball valves for each burner, so I can run them individually. Same pressure to both, though.

Any advice welcome!

Thanks,
Dave

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[reefera4m]

abrasive, on 02 February 2010 - 01:14 PM, said:

I'm re-working a forge I built many years ago. It's been great for general forging, but I want to start welding and it's just not hot enough here at altitude. (Salt Lake area)

The forge body is 8" pipe, 17" long. Two layers of 1" Kaowool all the way around, and a piece of kiln shelf on the bottom. Net inside diameter is, taking into account the non-round shape, about 5.5". So we're looking at around 404 in3. I made a little movable wall out of satanite-and-itc100'd kaowool. Oh, and ITC-100 on the Kaowool, though that needs to be re-coated.

Single 3/4 "Reil EZ burner dead center, i.e. 8.5" from each end at about 10:00 pointed in so the flame hits the wall and swirls. If I were doing this over, I'd place it closer to the front - that's where all the heat goes. The back stays pretty toasty.

I am looking at two improvements: adding a second burner, Porter-type, and upgrading the old burner to a Porter-type.

My burner holder is 1.5" pipe welded into the forge body. Really not looking to cut it off and move it. I am thinking of adding another burner between the existing burner and the front - maybe 4" OC from the existing burner. Is that too close? Can I go closer? I really don't want the additional burner right in my lap... Or should I bite the bullet and move them both? Or just weld up a new forge body - I think I have the cutoff from that 8" pipe around here somewhere...

I've already plumbed ball valves for each burner, so I can run them individually. Same pressure to both, though.

Any advice welcome!

Thanks,
Dave

I posted a thread of my venturi forges a while back that had some photos on two different burner placements. Both forges are 12" long & 8" in diameter, and insulated with ceramic wool, refractory cement and ITC-100.
On my first forge I placed the two burners on top of the forge equal distance apart. They tend to create twe distinct 'hot spots'. On my second forge I kept the same distance between the burners but mounted them on the sides of the forge (one on each side 1/3 of the way down the side). This arrangement causes the flame and heat to 'swirl' around the inside of the forge and heats it much more evenly.

However, I must admit that although the 2nd forge heats more evenly the heat doesn't necessarily get transfered to a blade evenly. Blade geometry plays an role in how the steel heats, the tip and edge will always get hotter faster - just due to the lower mass. So I still have to move the blade around in the forge occasionally to get the blade to heat evenly. Bottom line - offset/canted burners help even the heat but you still have to pay attention.

The real key to burner placement is the lenth of the steel you'll be heating. For an small billet it makes more sense to concentrate the heat near the billet. Heating the back of the forge is inefficient to some degree. For longer blades/billets it is better to distribute the heat as evenly as possible throughout the forge. I find concentrating the heat is even more useful in welding as I don't try and weld very large billets and it is much easier to get to and sustain welding heat in a small concentrated area. Just my .$02 cents worth.

[abrasive]

Thanks for the input!

It's looking more and more like a rebuild is in order. I have learned a thing or two since I built the current beastie.