After abortive attempts at overthinking, we settle on a nice rivet forge

[JHCC]

All history is living for the Irish.

[Frosty]

Thomas: did we go to the same Boy Scout camps? Or maybe it's a common thing to learn in boy Scouts. Our summer camp had a shard of granite about the size of a saucer stuck in a live oak 8-10' off the ground about 30' from the fire pit. Every single time we camped there we got THE TALK about fire rocks while looking at that shard.

I agree, a mafic or ultramafic is usually pretty safe still, it only takes a tiny fissure. A good way to test is get a good deep bed of coals in a pit, toss the rocks in and cover it with soil. If one explodes the dirt will act as a scatter shield.

I still get the willies around stones and fires.

Frosty The Lucky.

[JHCC]

Okay, Frosty, a serious question.  I was under the impression from our previous discussions (and from my reading elsewhere on IFI) that for forging with charcoal,  you need about a six inch diameter fireball: smaller will not get enough heat, and larger will just burn up fuel. The profile of the clay that I just put in and fired yesterday for the first time was basically intended to be a circular version of a Tim Lively-style oval tub forge, and was sized to hold a fireball about that big. It may not have been a classic duck's nest (and that term may well not have been appropriate for what I was building), but is there a problem with this design and construction for what I'm trying to do?

Edited August 28, 2015 by JHCC

[JHCC]

 

(I'm also getting the feeling that I need to break my charcoal into smaller lumps before lighting it, but that's a separate issue.)

[JHCC]

Some heavy gauge wire makes a nice tool rack.

Edited August 31, 2015 by JHCC

[JHCC]

Fired up again last night. Real bear getting a fire up to forging temperature; not really sure what the issue is. Part of me is toying with the idea of tearing the clay out and building some kind of piping arrangement to convert it from bottom-blast to side-blast, something like this:

(Not to scale. The crosshatching indicates clay, and isn't intended to indicate the actual profile of the firebowl. I'm open to suggestions there, too.)

Edited September 1, 2015 by JHCC

[Frosty]

I've never used a forge configured like yours. I don't know about what size fire ball to use I judge my fire by how it's burning and what I need. I've never had anyone tell or show me how to use charcoal, I just mucked around till I figured it out.

What I was saying about a duck's nest is what works for me and in general what I've seen. Were I to need to design a fire pot like you have I'd model it with fire brick till I found a shape that worked then copy it in clay.

My rivet forge is a bottom blast but most of my charcoal forging has been in camp fires occasionally with a side blast either by funneling a breeze or a 12v inflate all blower. I had pretty good luck with a trench forge dug into a steep embankment and covered with flat slate. The natural draft was pretty impressive I can see how they made pretty good smelters and foundries when scaled up.

I don't know how to answer some of your questions but what I'd do. Please believe me I don't intend any as challenges.

Frosty The Lucky.

[JHCC]

Thanks, Frosty. I think I'm going to post this over in the Solid Fuel section to see what folks there might suggest. 

By the way, speaking of charcoal and rocks in fires, the last time I fired up the forge, I found an egg-sized chunk of sandstone mixed in with the charcoal. Glad I was breaking up the lumps into smaller pieces; I don't like to think what would have happened if it had gotten into the fire. (Although I suppose that if it went through the charcoal making process, it was probably already pretty dry.)

 

Edited September 2, 2015 by JHCC

[JHCC]

As chronicled elsewhere, I've been experimenting with forging in a charcoal-fired rivet forge with a fairly deep duck's nest built up from clay and sand. Here's what it looks like right now:

 

I've been having a hard time getting a good fire that will get steel up to forging temperature in any reasonable amount of time; I have this weird feeling that I shouldn't be spending only a tenth of my time actually hitting metal. So, in reading around IFI, I see a lot of recommendations that side-blast is a lot better for charcoal than bottom-blast, which is the current setup. Part of me is toying with the idea of tearing the clay out and building some kind of piping arrangement to convert it from bottom-blast to side-blast, something like this:

(Not to scale. The crosshatching indicates clay, and isn't intended to indicate the actual profile of the firebowl. I'm open to suggestions there, too.)

I'm thinking that if I do this, I can pipe the air directly from the blower to the tuyere, bypassing the ash dump, which is leaking air anyway.

Thoughts? Suggestions?

Edited September 2, 2015 by JHCC

[Charles R. Stevens]

Easer to make a 55 sideblast alla Glenn's blue prints and adapt the blower to fit it. 

[Frosty]

Yeah, a person needs to keep an eye on what comes in their solid fuel, finding rocks is pretty common with coal.

I forgot your question about breaking up the charcoal, YES. The smaller the pieces the more surface area so the more space to react with oxygen. This does two things that are important forging: First it makes more heat in a smaller volume and the covering fuel contains it better. Secondly It consumes the oxy more thoroughly making it easier to keep your steel from scaling or burning in the fire.

Breaking the fuel up also makes it easier to find foreign . . . stuff.

Frosty The Lucky.

 

[JHCC]

It consumes the oxy more thoroughly making it easier to keep your steel from scaling or burning in the fire.

Yes, I was pleased to note how very little scaling there was this last time. 

[JHCC]

Looking at some of the other threads about charcoal, I'm wondering if I've got too much of an opening in the tuyere. There's a central hole surrounded by smaller ones, certainly more total than the 3/4"-1" diameter I see recommended. Let's see if smaller charcoal and a smaller opening make a difference.

Edited September 3, 2015 by JHCC

[j.w.s.]

Why don't you first get all that clay out of there and build a trial fire just to see what you can actually get out of it?

J

[JHCC]

I decided to try some inexpensive anthracite from Tractor Supply Company (as discussed here), but discovered that the hand-pumped blower wasn't giving me enough of a blast to get up to forging heat or keep it there. Then I remembered the electric leaf blower...

Total success. Plus, the look on my wife's face when I told her I'd decided to stick my blower up the ash dump was priceless.

Edited September 19, 2015 by JHCC

[JHCC]

Since I don't think I'll need as deep a duck's nest for coal, I've carved off some of the extra clay.

[Charles R. Stevens]

Ok, fallow my reasoning (note this may be "B"lack "S"mithing)

in a side blast forge, the air comes in, is broken up by the fuel and the opiset wall aof the fire bowl, the air must now turn 90 degrease to excape. Their is a lot of turbulance as the air goes up, down and sideways. 

This takes time, giving the air more time to interact with the fuel. Wile a bottom blast the air goes strait up, their is some turbulance as it tries to make it past the fuel but not near as much as in a side blast. 

So, tho get the same "dwell" time you need a deaper fire bowl for a botom blast, were as a side blast can be only 3-4" deap (with 3" of fuel on top) a bottom blast needs to be 5-6" deap. Now we are talking about charcoal, as cola is much denser and can deal with more air flow, this efect isn't as significant. 

[JHCC]

Aaaaaand the leaf blower crapped out. Switched to the shop vac.

Edited September 19, 2015 by JHCC

[Charles R. Stevens]

Anothe issue often pointed out by TP is the fact that to much air flow will cool the fire, cause fire fleas and or blow the hot coals out of the pot.

[JHCC]

Charles R. Stevens, I totally get that. However, switching from charcoal to anthracite has changed things up considerably, and this setup is working a lot better than what I was doing previously with charcoal.,

[Charles R. Stevens]

Glad to hear that. The forge is desighned for coal, but you wont be the last new guy to read this thread. Nor, do I think It will be the last time you play with charcoal

[JHCC]

Much later addendum: this setup has been working well with nut coal (anthracite from Tractor's Supply Co), and I'm now trying it with the TSC rice coal. One VERY key detail is setting the blower to almost totally blow past the air intake; it takes startlingly little air to work well.

[7A749]

On August 28, 2015 at 10:57 PM, Frosty said:

Be very VERY careful, any water trapped in the stone will make it explode once it hits 212f. If it's been laying on the ground get it off the ground and let it dry for a few days, then maybe light some charcoal briquettes and let them gradually heat it up.

Sandstone is generally safer than say granite because there is a lot of room between grains to let steam escape, just don't take any chances, there could be a mudstone or shist lens hidden in it.

Frosty The Lucky.

Seen that first hand in scouts back in the day. 

First time it happens, it'll scare the living heck out of you. A clean your drawers out type of experience for sure..

Cool forge. A real coal job is next on the list.

[SReynolds]

I drove up to Bellevue (Ohio) to work a bit with the smith at Lyme and he had a cold fire. It was Tractor Supply hard coal. He had some soft coal I had arranged for him to buy from Yoder's Supply near Mt Eaton but wasn't using that. He was attempting to heat 1/2 stock and was taking quite a while. he threw in some soft coal, cleaned out the tuyere  holes and was forging.

Hard coal may work better if the tuyere holes  wouldn't plug every three minutes. I don't know what it looks like as he always has a fire in it. Night and day. It's the Champion Whirlwind Blast Fire pot, but hard to say what it looks like today.I can poke a length of 1/8 x 1/2" flat stock through the clinker breaker. (which does nothing by the way)

On 5/30/2016 at 0:11 AM, JHCC said:

 One VERY key detail is setting the blower to almost totally blow past the air intake; 

What does that mean?

Say hello to my little friend. This Champion 145 and Eureka Blower will destroy steel stock. I use it as is. Just pour in the coke and coal and fire away. I use only soft coal as my hard coal experience was an embarrassment in front of a live studio audience. For real.

[JHCC]

1 hour ago, SReynolds said:

On 5/30/2016 at 0:11 AM, JHCC said:

 One VERY key detail is setting the blower to almost totally blow past the air intake; 

What does that mean?

When I first started using a powered air source, I simply jammed it into the air intake, where the blower would normally go. (Actually, that's not precisely what I did, but it's easier to explain this way.) I found out pretty quickly that this was too much air, that the blast was cooling the fire. However, my blower (that is, the exhaust from my shop vac) is not variable speed, so I can't change the volume of the air by changing the speed of the fan. By offsetting the hose from the blower from the air intake, a portion of the air blows past the intake rather than going into the tuyere. Changing the offset changes the proportion of air going into the tuyere and around it.

Allow me to demonstrate with coffee cups. The cup on the bottom represents the blower, and the cup on the top represents the air intake. In this photo, they are perfectly aligned, and the entire blast goes into the tuyere:

In this photo, the offset is about 1/3 the diameter, so about 1/2 of the air is diverted outside the tuyere:

In this photo, the offset is about 2/3, and only about 1/4 of the air is actually going into the fire:

This last setting is pretty much the sweet spot for nut coal, and I suspect that something close to it will turn out to be the sweet spot for rice coal as well. However, it's been a couple of months since I was able to get into the forge, so I haven't had the chance to experiment. 

Does that make more sense?