Gut check on D-shaped, single burner forge design

[thecelloronin]

Hello IFI,

I've been lurking these forums for a couple of months now and feel fortunate to have been admitted! While I have not read the entirety of the Forges 101 thread, I have put a mighty dent in it. As such, I have a fair idea of what kind of forge I'd like to build, but there are still some room for some guidance if any of y'all are feeling generous with your time.

First, the burner. I plan to use Frosty's T Burner build. I'd intended to obtain a flare from Larry Zoeller, but it a) doesn't seem like he's in business for those parts anymore and b) seems Frosty himself doesn't use them, but instead uses thread protectors obtained freely from local plumbers. Rank newby that I am, I wasn't sure about trying to sweet talk free stuff, so I bought [a 3/4” merchant coupling] from Supply House. Will it work okay?

Second, the 3/4" burner brings an interior volume of 350 cu inches to forge welding temps. Moreover, y'all seem to really like the oval or D shaped forges for their flat floors and rounded design facilitating the "swirl". I don't pretend to understand fully why that's important yet, but if y'all say it's good I'm listenin. It seems a forge of this shape wants the burner placed at the midpoint of the chamber, than tilted maybe around 11 or 1 oclock so that it doesn't point straight down at the floor. Do I have this correct?

Third, I'm not sure what dimensions make the most sense. I hate to admit I asked the nearest AI bot what it thought, (perplexity.ai, a good alternative to the SEO ridden cesspool that is modern day Google), and it recommended 12" long, 6" wide, and 5", which is a tad over 350 cu in. Conventional wisdom here seems to say "well, we don't know if that's good for you, because we don't know what your goals are", and fair enough, neither do I.

Aside: I'm a rank beginner to both smithing and metalworking, but due to serendipitous circumstances, I was laid off a few months back and picked up work at my buddy's metalworking shop. The minute I was given some basic tasks on the anvil and forge, I was hooked. At this point, I just want a small setup at home to practice basic techniques on, mostly hooks and small decorative items like leaves that I can sell at my wife's booth in the Charleston market. Figure if I need anything larger than a single burner, I have my buddy's three burner forge available; plus a single burner will always be useful even after I do build bigger and better–not to mention forgiving on fuel while I practice.

So, following up on third, is a D-shaped 12x6x5 chamber a reasonable size (I'm of course planning on building the forge larger than this to accommodate the refractory encapsulating this working volume) for general piddling around with hooks, nails, leaves, and small tools?

Fourth, reading Forges 101 might have actually made me a little more confused on refractory than I probably need to be. There's so much good information, but my lack of experience makes it difficult to parse effectively. I know I'll need two 1" layers of kaowool to line the inside of my forge, then some food-coloring tinted colloidal silica rigidizer, then something like satanite or kast-o-lite 30 to coat the outside of the kaowool. This is where my understanding starts to break down; is it either/or with the satanite/kast-o-lite, or do they work in concert with one another?

Fifth, and related to fourth, is the floor of the forge. Much of Forges 101 mentions high-alumina kiln shelf as the ideal solution, but as the thread goes on mention is increasingly made of K26 fire brick.  I'm sure this has been answered directly before, but which is preferable for my application?

Again, I am 100% certain all of the answers are somewhere in the annals of this forum, and trust me I've been doing plenty of site searches (site:iforgeiron.com + keywords). But, I figured I'd get a gut check to break out of analysis paralysis and start making stuff.

I humbly thank y'all for your consideration. I hope to be a productive member of this community in time.

Edited December 18, 2024 by Mod34
Removed commercial link — mod

[Mikey98118]

50 minutes ago, thecelloronin said:

Will it work okay?

Yes; flame retention nozzles, whether flared or stepped, are only necessary, when a burner is being run outside of the forge; in other words, when the burner is being used as a kind of hand torch.

 

55 minutes ago, thecelloronin said:

It seems a forge of this shape wants the burner placed at the midpoint of the chamber, than tilted maybe around 11 or 1 oclock so that it doesn't point straight down at the floor. Do I have this correct?

Generally speaking, you want the burner aimed at the longest distance it can get, before impinging on internal surfaces; this can be further refined, depending on what you use for insulation within your forge. Most forges use ceramic wool insulation, with a 1/2" flame face of Kast-O-lite 30; in that case, you can position the burner low on one side, and aimed upward across the width of an oval or "D" shaped forge interior, so that it takes also takes the maximum distance possible before impinging on your work pieces. The longer combustion is going on before those gases can touch steel the more certain you can be that no single molecule of super heated oxygen will be in them. The advantage here is that you can tune your burner to a completely nuetral flame, without worry over scale buildup. With a lessor distance, you would need to tune your burner to a slightly reducing flame to avoid scale buildup.

 

1 hour ago, thecelloronin said:

it recommended 12" long, 6" wide, and 5", which is a tad over 350 cu in.

I would not recommend a 12" length, unless you are going to run two 1/2" burners, instead of one 3/4" burner, so that you can shut one burner off, and separate the internal area of the forge with a movable internal wall. Otherwise, you will be wasting fuel, during much of your forging.

 

1 hour ago, thecelloronin said:

So, following up on third, is a D-shaped 12x6x5 chamber a reasonable size (I'm of course planning on building the forge larger than this to accommodate the refractory encapsulating this working volume) for general piddling around with hooks, nails, leaves, and small tools?

We usually suggest a two-gallon forge for a first effort. However, a used five-gallon propane cylinder will make you a lovely "D" shaped forge, by the simple expedient of raising its floor level under an extra thick base of insulation. I would suggest that your cut both ends of the cylinder off, and then reatach them with hinges on one side and a latch on the other; this allows you to accommodate the occasional large part, and makes all your internal construction work far simpler.

 

1 hour ago, thecelloronin said:

then something like satanite or kast-o-lite 30 to coat the outside of the kaowool.

 You can look all the way through the Forges 101 thread and never find me recommending the use of Satanite on the interior of a forge. Use a 1/2" layer Kast-O-lite, and then a finish layer of Plistix 900, if you want to be thorough.

 

1 hour ago, thecelloronin said:

Fifth, and related to fourth, is the floor of the forge. Much of Forges 101 mentions high-alumina kiln shelf as the ideal solution, but as the thread goes on mention is increasingly made of K26 fire brick.  I'm sure this has been answered directly before, but which is preferable for my application?

And I still prefere to trap a high alumina kiln shelf in recesses cut into the end openings of a propane cylinder, over a pillowing layer of ceramic wool, for a highly effective forge, that is meant to move around to job sites, etc. However, just because one method is slick, does not make it the only game in town

Morgan K26 insulating firebricks (use rated to 2600 F), and some other newer versions of insulating firebricks make very nice insulation, at a reasonable cost, too. Whatever method you choose will have particular advantages and limits (the kiln shelf can be slid in and out of the forge, for cleaning of welding flux. The insulating bricks are good to several hundred more degrees more than most ceramic wool, and are way cheaper than the ceramic wool in their own heat range).

There is no need for confusion; look for the reason behind the choices.

Just now, Mikey98118 said:

Yes; flame retention nozzles, whether flared or stepped, are only necessary, when a burner is being run outside of the forge; in other words, when the burner is being used as a kind of hand torch.

 

And before I get any flack back from this, remember that I said "necessary": I did not say "undesirable."

[Latticino]

Mike gave you some great guidance, as usual.  A couple of additional points or elaborations:

1. If you are going to cast a forge liner out of Kastolite I find that 3/4" thickness is a little easier to cast and a little more reliable than 1/2" thickness.
2. If you are casting a Kastolite liner you can also use it for the floor.  A removable high alumina kiln shelf is nice, particularly if you are going to forge weld and need a consumable replaceable section, but good ones are expensive and not really necessary.  A possible compromise is to cast a separate rectangular "floor" panel out of Kastolite and use that in place of the kiln shelf as a renewable item
3. Doors are important and tricky to design.  A good door system can save you a lot of fuel and allow your forge to get up to significantly higher heats.  I would suggest copying a proven design.  An approximately 4" square front opening for a forge seems to work pretty well.  As Mike noted a rear "hatch" to be used for longer stock is a great idea as well.  That hatch can typically be smaller (I use a 2.5" square opening).
4. I would recommend a forge internal length of no more than 8" for your first forge and to use as you describe.  If we go with the 350 cubic inch rule of thumb that gives a internal crossection area of 43.75 sq inches (after insulation applied).  That is around a 6.5" square chamber crossection or 7.5" diameter for a circle.  I'll let you do the calcs yourself for a "D" shape.
5. Brick wall forges are easy to construct and flexible in design.  Giberson has a nice one illustrated on his site.  You do need to use the right bricks.  I have had problems with even the better K26 insulating fire bricks (light brick) cracking under repeated thermal cycling.  I feel you need to allow for this and to put the bricks under some compression with the external frame.  Make sure this frame is protected from the combustion exhaust from the forge (dragon's breath) or it will heat, expand and be less effective.

[Mikey98118]

Those are all good points, Latticino. I would not call the thickness of the Kast-O-lite 30 layer a political football, but it is something of a tug-of-war

[thecelloronin]

Thank you guys, great information right off the bat! Few followups...

Mikey98118:

15 hours ago, Mikey98118 said:

in that case, you can position the burner low on one side, and aimed upward across the width of an oval or "D" shaped forge interior, so that it takes also takes the maximum distance possible before impinging on your work pieces.

So if we're using a 5 gal propane tank, what orientation are you talking about here? From the way you describe, it almost sounds like 8:00 or 4:00? Anyway, the rest of this section was very illustrative as to just WHY you angle it in the first place.

 

15 hours ago, Mikey98118 said:

However, a used five-gallon propane cylinder will make you a lovely "D" shaped forge, by the simple expedient of raising its floor level under an extra thick base of insulation. I would suggest that your cut both ends of the cylinder off, and then reatach them with hinges on one side and a latch on the other; this allows you to accommodate the occasional large part, and makes all your internal construction work far simpler.

Okay, so the forge itself won't be D shaped in this scenario, but the interior chamber will be since we're essentially raising the floor somewhere near the halfway point of the circle, correct?

15 hours ago, Mikey98118 said:

I said "necessary": I did not say "undesirable."

So, my merchant coupling is not necessary inside the forge, but is it even desirable? (I doubt I'll be using this as a hand torch.) I already ordered it, but I'll discard it if it will make things worse somehow (nothing I've read so far leads me to believe so, but I might as well ask now).

 

Latticino:

7 hours ago, Latticino said:

If you are casting a Kastolite liner you can also use it for the floor.  A removable high alumina kiln shelf is nice, particularly if you are going to forge weld and need a consumable replaceable section, but good ones are expensive and not really necessary.  A possible compromise is to cast a separate rectangular "floor" panel out of Kastolite and use that in place of the kiln shelf as a renewable item

I like this idea. Would the kiln shelf still be the more durable solution, or is it a tossup? I guess since I'd already have the kast-o-lite, K26 bricks or kiln shelves are an unnecessary added expense.

7 hours ago, Latticino said:

I would suggest copying a proven design.

I'm almost ashamed to ask this, but do you have a specific one in mind that you could link to? I've looked through a few builds here, but never really settled on one.

 

 

[Mikey98118]

3 hours ago, thecelloronin said:

So, my merchant coupling is not necessary inside the forge, but is it even desirable? (I doubt I'll be using this as a hand torch.) I already ordered it, but I'll discard it if it will make things worse somehow (nothing I've read so far leads me to believe so, but I might as well ask now).

The problem is that you are asking a perfectionist that question. For all practical purposes, the answer is NO. Ugh! That sprained my brain. The bottom lie is that burners will run in most forges, without a flame retention nozzle. However, that does not mean it is a good idear to do so. The any flame retention nozzle is considered to be a consumable, because the burner's nozzle will be heated up to yellow hot in that environment. So, a propane flame will slowly oxidize it away. If there is no nozzle to take the abuse, then the mixing tube will start being oxidized away instead. Do you see the point of using a pipe coupling, now?

Lots of people use a stainless steel pipe reducer as a make shift flame retention nozzle. What, as a certified picky-butt, can I say about this deplorable decision? Only that they are cheap, easy, and they work. Double ugh! After that, I need aspirin.

 

My fingers are betraying me all over the place

[Mikey98118]

Ron Reil's forge pages is where I started twenty-five years ago. His burners are quite out of date, but you can find a very nice little forge on his site; it's construction is a little dated too, but it will work.

https://ronreil.com/design1.shtml

 

Gas Burners for Forges, Furnaces, & Kilns is also dated, but since it was pirated, you can find its information for free on the Net. There is a chapter about building a forge from a five-gallon propane cylinder, which should give you all you need to know; just raise is floor, to create a "D" forge. You should also disregard its door, and use a movable brick wall near the forge opening instead.

The are photos of brick pile forges here, and on other websites; they are quite simple to build.

[Latticino]

Sorry I don't have a drawing for you of a door design, at least at hand.  There are a number that are effective.  Some of my favorites are:

1. 4-bar linkage holding an angle iron frame with a 2" thick Kastolite insert (door pivots straight up and down parallel to forge opening).  If you cast the liner a little proud of the forge skin your forge skin won't get burned up.  These benefit from counterweights and really shine with a cable connected via a pully to a foot pedal.
2. Same kind of framed Kastolite hung from a set of pulleys that also run on a track suspended at the top of the forge parallel to the opening.  The door can be tilted out and slid to the side.  Not quite as nice as the 4-bar, but a lot easier to fab up.  That is what I currently use.
3. Similar cast and framed door riding on two parallel vertical rails with the door suspended from aircraft cable that pivots over a frame above the forge opening.  These tend to rack and jam if not well constructed
4. Pile of K26 bricks on a hardbrick shelf in front of the forge is the easiest, but can be a hassle to shift open and closed while forging.  I always seem to drop the bricks and they get so brittle after a few firings...

[Frosty]

Hmmm, once again lots of good advice from the usual suspects I see.  

NO, 12" is way too long. Unless you have a power hammer or roll forge a smith can only effectively work 6" +/- with the caveat some smiths are way more effective at the anvil. 8" is a good length and if you nee to heat a longer piece of stock, say to twist for decorative pickets, fire tools, etc. you pass the stock back and forth through the forge using the doorway and pass through opening at the back.

Aligning the burner for max distance before impinging the work means you don't have to tune the burner as precisely or aim for a slightly reducing flame. In a D shaped chamber I like aiming the burner horizontally just under the top so it impinges the far wall at a shallow angle super heating the forge liner above the floor and then flowing down the wall to the floor and up the side to swirl back over again. All the oxygen will be consumed before reaching your work. 

AND as hasn't been  mentioned yet, propane forges are known as "recuperative" forges. This means the flame does NOT heat the work directly for the main part, it heats the forge walls and the re-radiated IR heats the work. Having the flame directed AT the work actually reduces a forge's effectiveness.

"flame holders" and various flares main values are #1 decreasing the back pressure in the mixing tube and upstream so the burner will induce combustion oxygen at a lower velocity. This lets you use a larger propane jet (mig tip) that provides more propane at a lower pressure and also the flame exits the burner nozzle at a lower velocity so it stays IN the forge chamber for a longer time to transfer more energy to the forge liner to re-radiate onto your stock and work for you.

Make sense?

What I REALLY like about brick pile forges is how versatile they are without having to build new forges to accommodate a different shape work.

A good kiln wash as suggested by Mike is almost always a good thing, adding an additional layer of armor for the liner and re-radiating more IR to your work. It's a different if connected subject. I think getting you going on the basic forge is a good start.

Frosty The Lucky.

[Mikey98118]

On 12/18/2024 at 5:50 AM, Latticino said:

I have had problems with even the better K26 insulating fire bricks (light brick) cracking under repeated thermal cycling.  I feel you need to allow for this and to put the bricks under some compression with the external frame.  Make sure this frame is protected from the combustion exhaust from the forge (dragon's breath) or it will heat, expand and be less effective.

I have worried over this for some years, and decided that the addition of small springs at one end of the threaded rods, trapped between the angle irons and a flat washer would make a valuable addition to this forge design. One aspect of this idea that is pleasant,is that,, so long as additional length for the springs is included in the threaded rod, they can be added at any time.

[Frosty]

The brick pile forges we made at a club forge and burner clinic are all going strong only needing repairs from drops and getting banged around. The K 26 IFBs haven't suffered from thermal cycle damage. The below pic is from the day of the clinic and I didn't make one for myself but they're all the same. The allthread, nuts, bolts, etc. aren't "tight" but there is no slack.

1/2" T burner brought this one to welding temp in under 4 minutes. Pretty typical for the clinic's 21 forge run.

Frosty The Lucky.

[Latticino]

Frosty,

I assumed that by design someone cleverly kept the tensioning members on those forges out of the direct path of the flue gasses.  Yours is exactly the design I would have used if I needed to make another small forge.  Pretty clearly the tension on the bricks is enough to hold them together without crushing and the mobile ones are hardbrick.  Likely not an absolutely optimal design, thermal efficiency wise, but certainly more than adequate for most users - and you can't beat the price or ease of assembly.  If you can source Z channel you don't even need a welder.

[Frosty]

Why thank you.  The only thing I put into the plans they changed is flipping the angle iron the door baffles ride on upside down. It was supposed to let the baffle ride lower and further block the angle iron from the heat. Turned out not to be an issue, the door baffle track(?) hasn't warped from what I've heard.

Frosty The Lucky.

 

[thecelloronin]

Hey folks, just wanted to say Happy New Year and drop in to show I didn't ghost. I'm still assembling everything I need to get started.

I'm currently looking around for sources on ceramic blanket, kastolite, and plistix/matrikote. I'd rather avoid big-box online retailers and give my money to an actual person. Does Wayne Coe still sell such things? His website seems defunct. Alternatively, is there another IFI endorsed human who sells forge-building supplies?

 

[Frosty]

Wayne's been completely retired since before Covid hit. To find out if there is an IFI "endorsed" refractory seller it's your job to look at the site's front page and go to the propane forge supply section and start making calls in your area. It's set up to be accessed like information in a dictionary. Not exactly but there is an index with links.

That isn't to say someone on the forum doesn't sell small quantities of forge supplies I just haven't seen one lately. Someone might speak up.

Okay, I just spent about 30 seconds typing, "refractory suppliers, S. Carolina," and got several hits immediately. Again, it's YOUR job to pick up the phone and ask them.

Frosty The Lucky.

[thecelloronin]

Hey Frosty, I did actually click on the Gas Forge Supplies tab like you said prior to posting, but all I see is an empty forum. I'm guessing you see something I don't?

Re Google: Sometimes, knowing the right keyword makes all the difference. I now see several options near(ish) to me. Thanks for that.

[Irondragon Forge ClayWorks]

35 minutes ago, thecelloronin said:

Gas Forge Supplies

Sadly the IFI store had to be closed when Glenn died.

I can't control the wind, all I can do is adjust my sail’s.~ Semper Paratus

[Frosty]

Sorry about that Ronin, I forgot how much the forum changed when we lost Glenn. 

Glad the search terms worked. Another good place to look for forge refractories is "Kiln Building Suppliers." You don't necessarily want to tell them what you're building some ceramics folk think forges have nothing in common with kilns so it can be hard to talk to them. 

Just ask about the materials in small quantities, refractory ceramic blanket, 3,000f water setting refractory, Kastolite 30 by preference, kiln wash, Plistex 900 is pretty common. 

When they ask, just tell them you're making a small kiln. 

As soon as they think you don't know what you're doing they'll sell you everything they can think of. It's sales job. 

Frosty The Lucky.

[thecelloronin]

2 minutes ago, Frosty said:

As soon as they think you don't know what you're doing they'll sell you everything they can think of. It's sales job. 

 

If you're asking me to play the part of the uninitiated rube, I'm way ahead of you! 

[Mikey98118]

1 hour ago, Frosty said:

Wayne's been completely retired since before Covid hit.

Is that why he doesn't post here anymore? Gone fishing?

[Frosty]

No. PRETEND not to be! <sheesh>

Frosty The Lucky.

[Irondragon Forge ClayWorks]

That and I believe Wayne & Glenn had a little run in about the competition with the IFI store.

I can't control the wind, all I can do is adjust my sail’s.~ Semper Paratus

[Mikey98118]

On 12/18/2024 at 5:50 AM, Latticino said:

• f you are going to cast a forge liner out of Kastolite I find that 3/4" thickness is a little easier to cast and a little more reliable than 1/2" thickness.
• If you are casting a Kastolite liner you can also use it for the floor.  A removable high alumina kiln shelf is nice, particularly if you are going to forge weld and need a consumable replaceable section, but good ones are expensive and not really necessary.  A possible compromise is to cast a separate rectangular "floor" panel out of Kastolite and use that in place of the kiln shelf as a renewable item

We all tend to look for ways to be "first-est with the most-est." The thinner the hard cast refractory flame layer outside of a ceramic wool insulating layer the faster a forge will heat up. And we assume that the only downside is that thinner hard refractory layers are fragile. But, that is only part of the picture. For, the flame face layer has has two sides; its flame side and its far side. If the flame side reaches 2300 F, the far side will likely reach 2000 F--in a one inch thick layer of Kast-O-Lite 30. With non-insulating refractory, or with a thnner layer, the heat of the far side will only increase. So, what? So, the closer your ceramic wool insulation comes to its use-rating the faster it will last.

Lattiscino is also right about high alumina kiln shelves having become too expensive to make a smart choice as forge floors, these days; I just hate this fact...but facts are facts

[thecelloronin]

Hi fellas,

I’m putting in the last orders for what I need to get started on this build. I found an 24 x 48 x 1 sheet of 8# ceramic fiber on Amazon which is quite a bit cheaper than elsewhere online. The seller is “Simond”, which just seems like a reseller of Chinese products.

Is there any practical difference between something like this and branded Kaowool/Inswool? Assuming I’m rigidizing with fumed silica, costing with a 1/2” layer of kastolite, then finishing with plistix as is recommended.

That said, before I buy anything online, I’m going to call a few places locally first. Still, thought I’d ask since a google site search wasn’t conclusive.

[Mikey98118]

16 hours ago, thecelloronin said:

Is there any practical difference between something like this and branded Kaowool/Inswool?

Not really. All you want to look at is how heavy the product rating is; 8 lbs is good. Then look at what its use temperature rating is; I assume that it is 2300F, which is standard, and good enough.