Part of air induction is generated by the gas jet, and part of the induction is generated by the flame; this much has solid evidence.

My supposition is that whatever air is generated by the flame through the burner port may reduce the amount generated in the burner. Fact or fiction? I don't know

Twigg: The burner is sputtering because it's igniting in the mixing tube, which kills induction from the pressure of detonation, which starves the detonation for fuel air so induction resumes which allows for another pre-detonation in the tube and so on.

How about some useful information, I have no idea what you mean by holding the mig tip in the fitting threads. How about a pic through the intake ports so we can see the position. 

The way to tune a T burner is by adjusting the distance between jet and mixing tube end. The farther back the more intake air it will induce.  

Don't make us guess, it irritates me and tends to get you guesses as fixes. Your solution should be pretty cut and dry IF we can see what's where.

Frosty The Lucky.

Sorry for the delay, life caught up with me.

Swapping out the mig tip solved the sputtering issue. I must've done something bad to the first one because it seemed  like it was never happy in any position relative to the mixing tube.

I haven't finished fine-tuning with the new tip, but here's a clip of the flame.

Sorry for the frantic/scatterbrained posting on this thread, Frosty. Things have been a little stressful on my end and sometimes I just forget to take a breath.

Looks like the tip will need shortening by 5/16" to begin with, followed by a few thousandths of an inch at a time on sandpaper. Don't forget to clean out internal burrs with torch tip cleaners as you tune the burner this way.

Caught a break to post an update

The mig tip was too loose. I left it finger tight before, once I tightened it slightly more with some pliers, the flame induced a lot more air and was louder. The tuning the position of the mig tip behaves a lot more like it should with this change.

It was hard to get good pictures of the flame because the forge heats up too quick!

I'm not satisfied yet, because with 3/8 to 1/4 stock I'm only getting a mid orange heat. The limit seems to be a stability issue (see video):

https://youtu.be/Rrb_MD0euQg

The flame seems to transition to a less-intense flame when the forge reaches a certain temperature. I'm able to change this by moving the end of the mixing tube further in or out of the forge port, but it's hard for me to tell which was is better. Based on what Frosty said earlier, it looks like I'm still having premature combustion problems.

Edit: am I right to think the mixing tube is heating up and causing the early combustion?

One thing I will say is that I wish I had made the burner parallel to the top face of the forge. I don't know how many times I have to repeat this mistake to realize it's never worth it pointing the flame straight at a wall.

You aren't going to like this, but it looks to me that you simply have too large a burner for the space.

I have to agree with Mike, too much gun. How about adding another IFB? Simply cut one lengthwise into pieces the same width as the sides next to the bore. (forge chamber hole) stack and clamp the forge making the chamber another 2 1/2" wider. This will enlarge the chamber to a more suitable volume for the burner and align it in a way to lower back pressure considerably.

The other issue I see is the flame is aimed straight at the far side of a cylindrical space, almost a cup. You can watch the flame being blown back at the burner outlet. This makes excessive back pressure, further reducing induction. 

I'm thinking a 3 brick forge would work better.

Frosty The Lucky.

Oh sure, Frosty. Go  right ahead NS suggest that he do things the easy way! Now, how do we get him to build a micro "T" burner, huh? It is soooooo hard to have any fun around here

You missed January's payment, Mike. 

Truth is Twigg, Mike's right, you really need to build a micro T burner. Doing things the easy way is for wussies. 

Frosty The Lucky.

Lol! You two are dangerous, putting ideas in my head like that... 

I dunno if I'll be even remotely successful but I'll give it a whirl, since I already bought some EDM tube and it sounds like a learning experience

Does kastolite 30 bond well to IFB? I was thinking of plugging the current burner port with some kastolite, and drilling a new port directing the flame tangent to the "ceiling" of the forge. 

Kastolite sticks to darned near anything. 

Your head deserves idea insertions and we're pleased to serve. 

Frosty The Lucky.

Lol thanks Frosty

I just remembered I have that one 1/2 x 1/2 tee that drilled dead nuts center by sheer dumb luck. I guess the stars are aligning

6 minutes ago, twigg said:

by sheer dumb luck.

Keep talking like that and you'll never make a blacksmith. It took me decades of intense study and training to learn to drill dead nuts. Heck, I was almost 70 before I knew dead nuts needed drilling!

Step up the patter will ya?

Frosty The Lucky.

I won't be throwing in the towel any time soon Frosty I appreciate it

I decided to divide and conquer: I'm going to continue to try and make this forge work but also try making some smaller tee burners. I'll do a separate thread for those.

I'm going to take Frosty's suggestion and go for a third brick in the middle. I'm also going to plug the existing burner hole with KOL 30 and move the burner port to run tangential to the longer side-wall of the ellipse. This will also make the nozzle 50% longer, which I think will help slow the flame down(?). Total forge volume will be 100 cu in with this change.

Hold off on the forge changes until you build the micro-burner. Otherwise you will probably solve all your problems with it, and never build those burners

You underestimate my ADHD Mikey

I got parts to do a 3/8 and a 1/4 tee burner. I bought extra long mixing tubes based on 671jungle's results (I know, different design, but I can always cut them shorter). I'm currently messing around with cutting external threads on mig tips so I can screw them directly in to a 3/8 tee for the 1/4 burner. Just experimenting to see what works. My kingdom for a lathe!

Still waiting on the edm tubes.

Have you followed the threads on using 3D printer nozzles? I think in these small burner sizes you will find them easier to play with than capillary tube gas orifices mounted in MIG contact tips; just a thought.

I read through the relevant IFI content just now and ordered some. The nozzles seem really convenient, but if I end up using them I'll probably end up forgoing the tee design and instead do something with a choke like a Mikey burner, so I can tune the fuel/air without shortening the nozzle like in a tee burner.

As posted in another thread, I did my first test of the 2 bricker with a 3/8 tee burner today. I learned mostly about the burner not the forge, but what I did see was that the 3/8 little dude was hot (I would guess wire color was white hot based on watching the corners where the lining had flaked off). The forge had a large thermal gradient down the long axis (not even red near the exhausts, yellow near the burner) and there was still a bunch of dragon's breath. I'm thinking the smaller burners are a step in the right direction, but I'm also going to need to move the burner port to get more circulation. Possibly go down to multiple smaller burners.
 

 

The 3d printer nozzles are a smash hit. Thanks Mikey and others who posted about them!! I love being able to change orifice size as easy as changing socks.

You'll also love being able to clean them easily. There is more than one kind of Dragon's breath. Have you tried turning your burner down, after the forge super-heats? Because what that looks like is complete combustion in too small a space. And less I forget, congratulations on building one hot burner

Thanks Mikey! Turn it down as in less propane? I don't think I ever let the forge reach max temp last night. Hoping to do more testing tonight if time permits. I was also going to try a larger (1mm) 3d printer nozzle to try and slow the flame down, since I have no problems with getting enough induction.

I take it if it looks like complete combustion in too small a space, then adding another 3/8 burner to even out the heat is not a great idea? Is that correct?

Back from round 2 of testing. Really let it get hot tonight, because I had more time before don't-wake-up-the-neighbors o'clock. At 2psi, it is plenty good for forging. At 5psi, it'll get a piece of 5/16" 1018 round stock to yellow heat (about 1" length to yellow heat), and at 7psi it'll get that same 5/16" rod to white hot (about 1" length to white heat). I'm pretty sure it would've melted the steel at 7psi if I let it be for a bit. I didn't want to find out while I had the forge sitting on my landlord's workbench

As another measure of forge temperature, it is now hot enough that my dumb self stared into the forge for about 10s and then I couldn't see the workpiece on the anvil because I was seeing spots. Time for some goggles (or some brains!)

Next step is definitely modiyfying the forge shape and coming up with some new nozzles. Still brainstorming, but I'm thinking of adding at least a 1" or 2.5" wide IFB in the middle to make it elliptical. I also made a second 3/8 burner to potentially add in (and tested it, it's as hot as the first but with a more stable flame envelope). I have no complaints about the current temperatures, but it's very concentrated in one spot. I figure if I get it to circulate more, I'll need more BTU/hr to get the same temperature over a large volume. This forge would stink at twists right now.

Only other complaint is there's a lot of scale. Flame looks kind of lean. I didn't get to testing it with a larger orifice tonight.

I

think you have arrived at "an embarrassment pf riches," and need a little time to sort out all you can do with your new forge; certainly not a bad place to end up

No, I don;t think that you need a second 3/8". I think you need a,  1/4" burner, but my prejudice should be plain to see
 

As to twisting bar stock; yes, a burner aimed at an angle would lengthen the hot spot. but if you wont to go very far down that path, one or two very small ribbon burners would be hard to beat.

You're dangerous Mikey lol! Well, I already bought the parts for 1/4" burners and was planning on making a pair of them, just wanted to spend some time really getting to know the 3/8" ones first before I get carried away.

One thing that I keep thinking is that if I try to get the flame to swirl, the 2-1/2" diameter of this forge's inner surface looks like a very tight curve for the flame to follow. Are there any known ratios for swirl geometry? Something like length of primary flame / inner diameter of forge?

Ribbon burners are definitely on my very long term to-do list, but maybe not this semester, and I have a lot of IFI reading to do before then.

 If you want a more even heat on a longer area in such a confined space with single flame burners, then two of them on opposite sides of lomg parts, and aimed at acute angles should create twinnning super-heated exhaust gasses down most of the length of that forge. You would probably want to mount them in the far opwning, and stay far away from the other end of that forge, while they are running. Simply aiming your single burner directly down the middle of the forge, from one end, with some stock hitting in it should give you a strong hint as to where you're going...