Greetings!

I'm planning out a new forge, smaller (and hopefully hotter) than my current 3/4 NARB powered forge. I'd like to be able to forge weld with this one, as my current one just doesn't get hot enough.

What I've got planned so far is a 2 1/2 inch radius tunnel forge with a flattened bottom about 9 inches long. Insulation will be 2 layers of 1 inch 8# ceramic wool and 3/8 inch of kastolite 30. For a shell, I'll be using some steel sheet I've got kicking around pop riveted together.

Some back of the napkin math tells me the inside will be around 175 cubic inches, so I'm planning on a 1/2 inch Frosty T burner. First question for the people who know, I've seen Mikey post in Forges 101 that two smaller burners is more efficient in this kind of forge than one larger one. Is there a tried and true 3/8 T burner orifice design I can copy without needing to order specialty parts?

My second question is about kiln washes/ IR radiators/ IR reflectors. I was able to find some kiln wash at my local refractory supplier for $5.80 per pound consisting of:

ZrO2       55.0%
SiO2       35.4%
P2O5      4.5%
Al203      1.2%

Does anyone see any benefit to this, or will I need to source some Plistex?

Here is a quick sketch on my table of what I'm planning, including approximate burner angle:

That's a proven, sound forge design, it'll work well for you. The jet diameter in T burners is directly related to tube diameter. Sooooo, a 3/4" T requires, 0.035 J. a 1/2"T requires, 0.025"J. A 3/8"T jet is close enough to the same ratio as to make no real difference.

I don't have it written down anywhere and rarely do math for folks. As short a time as we've been acquainted I feel confident you aren't special needs so I'll leave it to you.

These things aren't over complicated you don't need special tools or math so don't sweat it.

Lastly, there was no reason to start another thread, we could've talked about this just as easily on the one I just replied to. more easily actually.

Frosty The Lucky. 

Thanks for bearing with me Frosty. My previous interactions with forums being what they were, I figured It would be best to keep the forge stuff in the forge thread, what for searchability reasons and easy moderation, but going forward I'll keep that in mind.

One comment on your drawing based on suggestions given to me by Jerry and Mikey....  Move the burner to 2 o'clock aimed just short of the far wall instead of at 4 o'clock.  And Do NOT aim it directly into the corner.  I suspect you had the same thought process I did when I posted a similar proposed burner angle, keep the flame away from the work longer and induce swirl. But Mike pointed out that the longest flame travel path is pointing the flame at the floor an inch or 2 away from the far wall and let it induce swirl.

   I haven't put the refractory in my forge yet.   Other projects got in the way of time and then the temps plummeted.  I'll have to see if I can get everything moved into a warm place to get the castolite work done soon.

 

It's just part of the learning curve on Iforge, don't sweat it.

Good catch Brian, thanks for bringing it up. I THINK Ben just laid the burner there rather than indicating where he thought it should go. Still you're right about burner orientation. I don't know if the one you mentioned will work well from the text description. One serious factor is NOT to aim the flame into a corner so it doesn't develop excessive back pressure and inhibit burner performance.

Bummer about the cold snap, we're enjoying a run of subzero weather ourselves. It's been a few years since we got real cold and I'm getting too old for this.

Frosty The Lucky. 

 

Actually, I did lay out my burner with my planned positioning, and I'll explain why I put it there and not the conventional top down sort of angle.

From my understanding reading forges 101, the reason we are encouraged to point the burner at the floor is because of the chemically active propane flame. Pointed at the floor like that, the part it is impinging on is the thickest, most durable refractory. My planned forge will have the same thickness of refractory on the 'walls' as the floor.

 

The second reason is so I can avoid pointing it at a corner. The tunnel being what it is, the only 'corners' I have are on the floor. So if I point at the floor short of the corner, the only place for the flame to hit is directly on my work.

 

The final reason is that with my burner in the 4 o'clock position I have the longest unimpeded flame path before hitting something. That something being a nice sloped wall.

 

If I have misunderstood something, please educate me. I want to know the whys and wherefores of this design before I start.

Not bad though some things have changed. Part of the problem from out perspective is the burner in your photo is a bit more than 2x the diameter of the one you wish to use so it looks like worse orientation.

IIRC you plan on using Kastolite 30-li which is a high alumina refractory and much more robust remaining concrete strong at propane forge temps. The kiln wash you describe above containing a respectable % of zirconia flour further armors the liner from the propane flame. 

Kastolite being what it is can be troweled in much thinner, no need for a thicker floor. Lots of guys are using 1/4" and less even with good results. My issue with applying Kastolite is the crushed aggregate in the mix. Being crushed it keys together which is a major factor in how tough it is. Unfortunately the downside is keyed aggregate means it doesn't move easily for a visual example think of a bag of jacks versus the same bag of marbles. You can easily move the marbles in the bag by squeezing the outside but the jacks are all locked in position and only want to poke holes in your hand. They "Key" together. It's an old term I used working in the state highways soils lab pertaining to how well a road bed resists moving under moving loads.

Anyway the technique that worked best for me was to roughly spread the refractory on the rigidized ceramic blanket and using a piece of round steel rod tamp it flat. Not tamp it end on but lay the rod flat on the "JUST moist enough to move at all" Kastolite and sort of slap it till it's smooth. Don't slap it hard enough to compress the ceramic blanket, the movement will cause liquefaction of the kastolite, just like wet ground in an earthquake. You also need to be careful not to shake it of overhanging surfaces in your forge. Mix up smaller batches and let one side set before mixing up the next batch and applying it. Kastolite is REALLY sticky stuff so you don't need to do anything special to get good stickchion between sides, walls, etc. Kastolite has a limited working time and can not be revived by adding water or more stirring. It'll set in just a minute or two after you stop mixing or working it. It only has a few minutes working time so do NOT dilly dally, plan what you're going to do and have the tools laid out BEFORE mixing it with water

Properly built and tuned, T burner's real charm is having a low velocity flame which means it requires less distance in the forge chamber to complete combustion. Secondly the flame remains inside the chamber longer allowing it to transfer more energy to the flame contact face to be re-radiated as IR to your work. Dragon's Breath is the orange flame blowing out forge openings, the less the better. Mike is much better reading dragon's breath than I am.

Do NOT be surprised, the first time or two you light your forge the freshly laid Kastolite WILL make significant Dragon's Breath. Don't worry it is just the calcite binders in the Kastolite "calcining" and is part of the program, it will resolve after a little while, 2-3 firings to welding temp usually does it. Calcium, oxidizing burns with a vivid orange flame. Check out videos of oxygen lances burning through concrete for an example. OR you can just trust me on this one. 

One last. Kastolite 30 does NOT NEED to be cured by fire. It DOES need to cure in 100% humidity for a day or two, just like Portland cement concrete. They both have the same set and cure requirements even though they are as different as day and night. 

The easy way is to close the whole forge up in a plastic garbage bag with a couple WET rags in the forge and leave it set for a couple days.

Kastolite is darned forgiving though so don't sweat getting it perfect.

Make or model a couple 3/8" T burners and then play with orientation in the forge. We'll help you tweak orienting them. 

Frosty The Lucky. 

 

Alright, I've made a 3/8 T-burner and mocked it up against my drawing:

The smaller burner sure does look more proportional. =)

That looks better though you might want to move the burner port farther up, less junk will fall into the burner. 

What are the dimensions of the T on your burner? I know the perspective really changes on smaller burners but the air intake (run at the plumbing supply) looks huge. I'll be looking forward to seeing it burning.

Frosty The Lucky. 

The Burner dimensions are:

T: 3/8 X 1/2 x 1/2

Mix tube: 3/8 x 3 

And the coupler is standard size, but I used a carbide to remove the threads on one end.

The flame is pretty... fluttery. It might be that I wasn't precise enough when drilling the T, or any number of things.

 

 

Shouldn't have removed the threads. They lower the friction as air passes over them just like the air passing over the top of a wing. Expanding the diameter causes too large a diameter increase the step causes bad turbulence.

How did you drill the T for the fitting? The jet is off center, you can see it's aimed towards the lower side in the last picture.

Why did you trim the mig tip already? And what's it's diameter? 

The flame is rich. Did you pick up more mig tips? Try a longer one, adjusting the air fuel ratio is most easily done by changing the distance from the tip of the jet to or away from the beginning of the mixing tube. The easiest method is start with too long and slowly trim it back till it's right. 

Start with a full length mig tip from the package screw it in and light it. If the flame is off center then it is the hole in the T that's off center. You might be able to correct it by GENTLY prying the mig tip into alignment. Remove the propane hoses and hold the burner at arms length sighting down the mixing tube from the outlet end towards a light. The bright spot of light shining through the mig tip should be centered in the mixing tube. Don't do this like looking into a telescope do it at arms length. You aren't looking for a clear view, just the relation of the light spot in the mixing tube.

Done right a T burner doesn't need a choke. That's a sign of someone who doesn't know what they're doing. A properly built and tuned T burner having a slow flame has a very flat induction curve over it's full stable propane pressure range. from so Low it burns back into the mixing tube to so high it blows off the nozzle. 

If there is a real plumbing supply near you see if you can get them to give or sell you "Thread Protectors" for 3/8" pipe. Before it changed management the local plumbing shop about 2 miles up Vine road from me gave me a good 35+, 3/4" thread protectors and a bucket because they weren't worth the hassle of scrapping.  

I doubt that's true anymore but couplers like you used are WAY too expensive, especially if you make a mistake like cleaning the threads out of the nozzle end. So if you can get thread protectors grab as many as you can. They WILL wear out, heat from the flame WILL eventually burn them up so having extras on hand is a good thing.

Mike Porter uses a different method. He makes a step nozzle that telescopes on the end of the mixing tube and is held in pace with a set screw. The step in diameter from the ID of the mixing tube to the ID of the step flare makes a perfect "flare". Flame holder isn't actually appropriate but lots of folk call them that. 

Anyway, you can tune the flame's fuel air ratio by moving the step nozzle in or out lengthening or shortening the effective length of the mixing tube. How it works is, as the high velocity flame from the mixing tube enters the larger ID of the nozzle it has to expand to fill the space. This does two good things, first it reduces the velocity of the flame. Same amount of flame in a larger volume means it MUST go slower. Yes? 

Well, as it expands to fill the larger volume of the nozzle the pressure drops in the mixing tube as well which enhances combustion air induction. 

The method and machinery is different but we both tune a burner the same way. We both did some head slapping when we stopped arguing about it. By argue I do not mean fight, we'd make a statement present our reasons (Arguments) then the other would poke holes in it and present our arguments. 

We made a lot of progress darned fast. Remember someone saying, "No you're wrong." is not an insult. Being wrong is in no way being stupid. Einstein was wrong more often than he was right. Edison failed at least 10,000 times before his first successful light bulb. 

Sorry, I can get carried away. I'm not as good at explaining things since the TBI.

Frosty The Lucky.

No worries on the long explanation! I'd rather have more to go on than just guessing what you might have meant.

In order:

I drilled the T on my drill press, but the threads for the branch off of the T are not very straight to the part. I did my best.

I Trimmed the mig tip (.023) because it was running so rich. Having trimmed it back this far, I suspect I'll need a thinner jet, or I'll need to come up with a better nozzle. And I do have extras tips, no worries about that.

Although the picture shows the flame running along one side, it actually jumps all around the nozzle. When I sight down the mix tube on this one the jet appears to be in the center.

The coupling I used as a nozzle was 99 cents at the local big box store, so I'm not too upset. The nearest dedicated plumbing supply I've found on the internet is about a 30 minute drive, and they're only open bank hours, so I'd have to take off work early to get there next week.

The reason I cleaned out the threads on one end of the coupling is because I couldn't get the coupling to hold a flame any easier than just the mix tube. (Maybe I was just trying to give it too much gas?)

Having typed all this out, I suspect the vozzle is the main contributor to my problems. I'll pick up a couple more couplers. (ha! A pun!)

Here is a picture with the new coupler and a new mig tip:

In order to keep the flame on the nozzle, i had to turn my regulator WAY down. Still running very rich to my eye, but much more stable.

 

A note about the jet being centered. I did notice that after changing jets, it was no longer quite right, so I took your advise and gently moved the mig tip a bit at a time. More than anything else, I think that stabilized the flame... which means I'll have to drill and tap another T.

 

Oh well, I'm learning and I enjoy tinkering just as much as swinging hammers. I'll come at it tomorrow with fresh eyes.

Mr. or Ms. BFancy,

Burners change when they are put into a container called a Forge. Running it on Empty proves nothing (to me anyway).

Happy New Year, Neil

Thanks for the input Neil.

I am aware that burners have different characteristics when inside a forge, but seeing as the forge currently looks like this:

That might be a bit difficult.

 

My goal here is to get a pair of 3/8 T burners in tuning range, so when I get the forge finished I can do just that. However! At the moment, I'm having some trouble inducing enough air, without the added back pressure a forge would provide.

 

And Mr. Fancy is fine. 

 

Happy New Year, Ben

Neil is right, you can't tune it to run IN a forge, outside a forge. It's a back pressure thing but yours is running so rich  it's not close enough to matter anyway.

A 0.023" mig tip is suitable for a 1/2" burner, certainly NOT a 3/8" burner. 

Did you calculate the ratio between mixing tube and jet diameters?   A .035" mig tip is approx. 0.04666 the diameter of a 0.75" mixing tube. A 0.023" mig tip is approx .046 x the diameter of a 1/2" mixing tube.

See a pattern there? Do NOT bother measuring either plumbing pipe or mig contact tips, the sold as ID is NOT the actual ID. A T burner has enough built in slack a couple thousandths here or there is easy to tune out. 

I'm not good at math at all but I love ratios and have been able to do an awful lot with nothing more than simple multiplication, division and fractions. Heck, I've had a TI scientific calculator for 30 years and never used more than the basic arithmetic functions and clear button. I've never even been able to figure out how to use the memory.

Thomas Powers and I had a good laugh over that one after he used his example of buying a dump truck to go grocery shopping. We exchanged a bunch of PMs citing the times we'd both done the same sort of thing. 

I REALLY miss Thomas. Absent companions.

Frosty The Lucky.

You know Frosty, I was good at math once... looks like those days are past now though. 

I redid my calculations and it looks like I need a jet of about 0.0175 inches for my 3/8 burner to keep in line with your ratio. Unfortunately that brings me square outside of using MIG tips, as 0.023 is the smallest they go. I think I saw somewhere on here people using 3d printer nozzles for gas jets.

Some more math, (wrote it out this time!) Tells me that a 0.4 mm printer nozzle is close to what I need, though I might need to open it up a couple thou. We'll see.

Knowledge is like a garage, it's common to start doing something without remembering you have the tool you need in the other corner behind the Popiel pocket baler.

Ayup, 3D printer nozzles are perfect, I wish Mikey would speak up, he does a lot with small and smaller burners but he doesn't spend much time online anymore. Heck he might even have found something better than 3D printer nozzles. 

Frosty The Lucky.

The 3D printer nozzles are a winner for sure!

The 0.4 mm nozzle was too small - not surprising, the math said I might need to open it up a bit, but I bought an assortment, so I figured I'd try the 0.6 mm and it worked fantastic! For those following at home that's 0.0236 inches, which I expected to be too large, but if it works, it works.

Another note about these nozzles is that they screw in with an M6 shank, so they matched my existing holes for the mig tips. The m6 x 1.0 thread means I can tune very easily by just screwing the jet in or out. I added a bit of blue threadlocker to keep it from moving and to give it a minor seal, though I might need to change that in the future if the propane starts eating it.

The nozzle had to heat up a bit for the flame to stick, but that won't be an issue in the forge. Now I just need to figure out how to mount it before I start adding the kastolite 30.

Frosty, when you suggested I move the Burner further up so less junk falls in it, did you mean something like this?

Looking good, that's well within tuning range. I like it.

Are you planning on using copper tubing between the burner fitting and propane hose / shutoff valve? Maybe you're planning copper tubing to a manifold then to the hose?

If not, lose all the extra fittings, the closer you can connect to the hose the better. Propane is NOT clean gas it carries the waxy compounds of the mercaptan odorant and  moisture. Propane is very chemically active and WILL turn the odorant and moisture into sticky gunk that will condense on all the surfaces it comes in contact, come loose and plug the jet. Rubber propane hose tends to be resistant to condensing the waxy gunk because it is naturally insulated and just isn't conducive to this type condensation. 

The burner position is better but debris WILL still fall in, especially when you shut it off and things cool. Brittle stuff like vitrified slag, old flux, etc. will spall as it cools because it has a different COE. (Coefficient Of Expansion) Were it my forge I'd mount the burner horizontally so the flame impinges on the top of the chamber tangentially. 

This gets the burner nozzle and port away from debris and farther from the hard turn at the bottom corners. The last may not be much of a factor but my thinking is flame turning a relatively tight corner develops higher pressure against the surface that is turning it. However towards the circular surface close to the top the flame is traveling along a curved surface and Mr. Bernoulli says the flame WILL accelerate and generate lower pressure on the contact surface. The same thing that makes aircraft fly. 

Near the top the burner port in the refractory the flame fires through is undercut where it enters the chamber so any debris that gets maybe popped off something is most  likely to hit the overhang rather than enter the port itself. It isn't proof flying debris from hitting the burner but it tips the odds in the burner's favor. 

If I were to put the burner port in the side I'd maybe split the difference from where you show it and the top horizontal I like.

On the other hand because I haven't made this confusing enough already one of the guys in our club has 1/2" T burners mounted vertical up against one wall in a D shaped forge. It's literally in the floor aimed straight up. Happily T burners are so easy to make he just replaces it when it gets gunked up with vitrified debris, flux, etc. regularly. I don't know how often, we don't see each other very often but he used to carry a couple extra burners when he demoed at meetings.

I think I've yakked enough for now. Later

Frosty The Lucky.

Just a few thoughts. First, I just LOVE small burners, and eagerly await you and Frosty ironing the kinks out of yours 

Second, completely aside from the original reasons why I recommended a top down burner orientation at two o'clock, and aimed just short of a forge floor's far corner, you need the height to keep the flame well away from work pieces in a small diameter forge.

I am not doubling down on my original advice. In fact, after a few years I came to agree that four o'clock was superior; but that was in much larger forges than yours, which of course provide more height to the flame crossing over work pieces. So, two o'clock is my advice for your case. "Circumstances alters cases." And advice must keep that in mind.

Finally, I hope you are leaving room between the edge of your forge's end plates, and the inner edge of your refractory flame surface. Otherwise that steel will warp in no time at all.

Good luck.

BTW, I just love small forges too  

Looking over you forge design, I think you are a minimalist; someone who well understands what an engineer means by the term "elegant solution."

Frosty would be the first to say "that certainly ain't me." But if it were, I would recommend that you drill holes for your burners that are about 3/16" larger diameter than their flame retention nozzles, right through the steel shell, insulation, and refractory (with a hole saw) after it  has had time to set up completely, but before it is fired. Then secure each burner into its opening with a simple angle bracket, on either side; it is simple easy, and cheap. It is oh so not the Mikey way, but it is an elegant solution.

On the other hand, if you want to leave design elegance behind, I will be happy to show you, step by step, how to do things the hard way; it is wanna my favorite things...

Alright, I've got an update on the actual forge this time instead of just the burners. Mikey, I did the work and went to bed before I saw your post, but I (almost) followed your hole saw instructions before you gave them!

I ended up taking Frosty's suggestion (I hope) of mounting the Burner up top at a tangent to the inside of the forge, which makes sense to me.

So these pictures are not fantastic (nevermind the cluttered bench), but I hope they show what's going on well enough. This first one is after the rigidizer with the burner laid on top to show angle of the ports.

This one is in process of applying the Kastolite. If you look close, you might be able to see the burner holes.

And here she is wrapped up wet and about to be covered in a blanket to stay warm.

Mikey, you hit the nail on the head I think. I do love an elegant solution. So I have to ask, when you say an angle bracket on either side, do you mean 2 brackets per burner or something like one bracket holding a burner with the burner affixed to the bracket with a hose clamp?

I've got to stop or I'm going to keep saying bracket.

All the burner mount is, is something to hold it in position and support the weight of the propane supply line, bracket is sort of what folk started calling it whatever it is. 

IIRC Mike showed folk an adjustable burner mount made from a piece of pipe larger than the burner's OD with 3 threaded holes equidistant so the alignment of the burner can be adjusted.

 Me, liking the simplest device that does the job disdaining bells and whistles, used a clamp and short length of 1" angle iron, positioned the burner where I wanted and welded the angle iron to the forge shell. Later I discovered I had a stick of 3/4" angle and a length of flat stock would've served but required 2 clamps to prevent it shifting. 

And the clamp itself, I made it with a U-bolt and piece of flat stock welded to the angle iron. 

I'd aim your flame down a LITTLE bit more. When I said level I should've said close or about level. There are few absolutes when making your own propane burner though lots of guys lose themselves "researching" scientific papers on flame chemistry, induction, jets, bla bla bla. 

I spent too many years as an exploration driller for Ak Highways making bricks without straw or frequently clay. When you're 30 miles from the closest road and something breaks you start looking for things you can scrounge, cut off the drill abandoned  equipment, etc. to make a splint. 

Gets to be a habit though Dad got me started being almost driven to figure out how a thing does what it does. 

About the refractory and warping shell. Wrap the refractory farther on the end  as far out as reasonably possible. 

When you put feet on the forge so it's not resting flat on it's bottom make the bottom lip of the opening high enough you can extend a 3,000f split brick laying flat for a front porch. it's length across the whole bottom of the forge. You'll use it to support fire brick for a thermal baffle (Mike's bailiwick) and a place to rest longer stock.

I probably won't be spending much time online for a few days, yesterday's 3-4" snow forecast is currently at least 14" on the ground and still snowing with todays forecast saying 10"+ with more fronts blowing in from over the pole. Woo HOO!

Later,

Frosty The Lucky.

 

 

5 hours ago, BFancy said:

Alright, I've got an update on the actual forge this time instead of just the burners. Mikey, I did the work and went to bed before I saw your post, but I (almost) followed your hole saw instructions before you gave them!

Be sure to describe your solution for how to mount the burners, because this is a point of anxiety for many builders. We cannot have to many choices on how to go about it. Anxiety stops more people than any lack of tools.