Naturally Aspirated Ribbon Burner. Photo heavy.

[Frosty]

I didn't know what 2cash meant by "struggling with scaling" so I watched the videos. As usual they jitter and the angle changes constantly so you only have a couple seconds to try and evaluate THE ONE THING that matters. If I'd gone by his observations my suggestions would have been way different. In fact I don't know why I suggested filing the jet diameter larger. Probably because I didn't really trust the videos. 

The importance of a good balance between inducer and outlets is why I asked him how many outlets there are in his burner block. The flames are all lifted off the block by quite a bit and that says to me there aren't enough outlets. If following my original NARB plans did NOT include making wood test blocks before casting one from refractory then it was a crap shoot. 

I almost never differ enough to matter with your observations and burner advice, I get to go other places on Iforge. I was surprised this time that's why I asked you directly about your evaluation of the flames.  

2ndcashboy: Please post still pics of the flames, one in the opening before the forge warms up and another after. One from the side so I can see what the exhaust looks like coming out the door, one hot one before it's hot.  

I'm not giving you a hard time when I say my build plans are only guidelines if you built just like they're laid out then good luck. Currently I have 8, 3/4" T burners working, four of them (on my way too large and fancy shop forge) were built on my lathe and are as close to identical as I could make them and not one has the same burn characteristics. One almost casually vitrifies then melts a puddle in the 3,000f split hard fire brick floor. The other 3 happily bring the various chambers to welding temps but not nearly as hot. three of the four will melt steel left too long to their gentle mercies. The coolest will melt steel but you have to turn it up higher.

I tune the burners before I screw them on the plenum. I've observed tuning after they're installed has almost no effect. 

The way I tuned the ribbon burner was by making wooden test blocks until I arrived at THE number of outlets that worked best with a tuned T inducer. Screwing one on then trying to tune it didn't work. Once coupled to a plenum the whole is incredibly stable.

 Frosty The Lucky.

 

 

[the2ndcashboy]

I'll get some still pics when I make it to my weekend. I work nights, and pictures of the forge taken during the day won't tell you much due to all the ambient light. 

As far as the flame liftoff, I don't know if its as bad as it looks in the video. I still get the below-10psi "flutter" when the forge has been running awhile, and from what I've seen in this thread, the solution to that issue is to plug outlets and get air speed up. It also seems like if it's too restricted, I'd get a richer mixture as I increase psi (like buzz was saying), but I really don't seem to. The thing runs remarkably consistent no matter what variables I change.

 

I guess all this is just the hazards of learning something new in isolation. I don't really have anyone in my area that I can go to and say "how does this flame look to you" and trust their answer. The internet is great but no substitute for in person experience. I appreciate you attempting to help me bumble through. 

[Frosty]

Just don't back light the pics. 

Are you STILL assuming your burner is running lean? Am I wasting my time?

 Frosty The Lucky.

 

 

[the2ndcashboy]

I'm not assuming rich or lean at this point, I'd just like to know what it is so I can work from there.

[Buzzkill]

Well, since the main reason we generally like slightly rich flames is to avoid scale formation inside the forge, that's where you should focus. If scale is forming on your pieces while inside the forge that's a good indication of a lean flame - unless there is direct flame impingement on the stock.  If scale is not forming on your stock while it is still in the forge then you most likely have a neutral or rich flame.  The richer the flame is, the more CO will form and also the cooler the flame will be.

So, imho the first order of business is to start with a shiny piece of steel and observe what happens to it when heated in the forge.  Once you have that information you can move forward.

[the2ndcashboy]

I have seen scale form on the stock while in the forge, but it's mostly when I have the doors open all the way I think. Its not something I've been particularly concerned about until I've started forge welding.

I've probably hijacked this thread enough at this point. My on-topic original question has been mostly answered (FAM on the NARB is primarily determined by the interaction between the size/number of outlet holes, and the hole size of the mig tip. Mig tip length has little to no effect). I probably should make a separate thread for tuning my particular setup.

[D.Rotblatt]

Teaser: just completed a build of two NARBS (for double burner) with 200 holes at 3/32” using brazing rod as the cores. Filmed the whole process (a little boring during the three days the refractory is setting up). Simple technique to get the refractory between the cores, using Mizzou. Need to test more, but so far very stable at almost 0psi to 20psi+. Occasional organ sound, but not often. I just need a to cast two burners to run them, but I’ll scavenge a couple to test. 

[Frosty]

Sounds good D., where are the pics? We'll believe it when we see some. 

Did you use a release agent on the brazing rod? I've considered pulling metal cores after the refractory sets but before it cures and fully cements itself to them. 

**********************************

2ndcashboy: I don't wish to come across like I'm giving you a hard time but you aren't interpreting things correctly. FAM is NOT primarily determined by any of the things you list. Effected yes but not determined. You are combining to many different potential causes and solutions. 

It's not a fault thing, you're just painting the same corner lots of folk can't get out of on a problem. The answer reverts to one of the fundamentals of trouble shooting anything. "Change ONE thing at a time, test, observe and take notes."  Changing more than one thing at a time  increases uncertainty of cause and effect exponentially.  

Slow your roll a little please. I'd love to help you get your burner working but I can't really start without a couple good pics. You have at least two issues that don't directly effect each other too significantly but you need to deal with them individually. The best I can offer are educated guesses and that's flirting with chaotic results.

The "fluttering" you're getting is just the nature of naturally aspirated multi outlet burners. By their nature they have to balance between enough Flow to keep the blocks cool enough it prevents preignition and flowing so fast it blows itself out. 

I can't see well enough to evaluate how your ribbon is burning with any degree of certainty. What I CAN see are the flames standing off the block significantly. This is caused by a too FAST flow. The block is cooled by flow volume, NOT velocity. Reducing the velocity while maintaining or increasing the volume it is the answer AND the flames will burn closer to the block so doesn't blow out. It could well lower back pressure against the T inducer and MIGHT improve the FAM ratio.

This is a MAYBE and to test you need to increase the number of outlets in the block. ONE AT A TIME between tests. Unfortunately you've already cast the block in hard refractory and drilling outlets in set refractory is problematical as smooth outlets makes a real difference.

Until then put that short jet back in the T and leave it be. Moving the jet farther from the mixing tube WILL increase air intake. This is a KNOWN. Just because it doesn't do what you think it should has no bearing on the induction properties of jet position. 

I suspect that reducing back pressure with another outlet or two MIGHT PROBABLY lean out the flame. 

I don't know how much of my NARB lives posts you read but getting the right number and position for the outlets took quite a few test blocks. That's why I made the test blocks from wood. Spending a couple days for refractory to set, dry and cure so it would survive firing for experiments was bad on all fronts. Those plenums just screwed to the wood blocks and changed out in seconds. WAY better than just tossing the whole unit if it didn't work, the plenum isn't a complicated labor intense component but it still takes time and materials and they're bonded permanently with a refractory block. 

If I've created too many questions, let me know I'll try my best.

 Frosty The Lucky.

 

 

[the2ndcashboy]

Ok, I took some pics after work this morning. This is a 3/4" Frosty T with a standard length .035" mig tip, 19 crayon-sized holes in the burner block. I couldn't get any dragons breath with the forge cold unless I closed the doors completely, and even then it was faint. There was a bit more with the forge up to temp. The standoff on the burner pretty much goes away when the interior starts to glow.

1st pic: Cold start, 10psi

2nd pic: Cold start, 10psi

3rd pic: Most of the way up to temp (low orange), 10psi

4th pic: Most of the way up to temp (low orange), 10psi.

 

[Buzzkill]

FWIW, if the forge interior in the last picture appears the same to you in person as it does in that pic and you aren't getting scaling on stock while it's in the forge I would just use it as is.

[the2ndcashboy]

The color is pretty accurate, at least on my phone. YMMV of course. That's not completely up to temp, probably 1800-ish degrees. It will easily peg a type K thermocouple (2300) at a very bright yellow color. You can't really see the burner flame anymore at that point though, that's why I took the pics at a lower heat.

[Frosty]

That helps a lot, thank you. The flames aren't as rich as I thought but still a little. The distance they're burning off the outlets is still a problem and no it doesn't show when hot. The NARBs I built balanced at 19 crayon diameter outlets but your's needs one or two  more to get the flow velocity down while keeping the volume high enough to keep the block cool enough. 

The dragon's breath  looks better than most. The orange flame is probably caused by calcites in the refractory oxidizing and not a problem. 

From what I can tell scale shouldn't be forming in the forge with the openings closed partially to limit or eliminate ambient air being drawn in by flame currents. 

All in all I think your problem welding is a matter of getting a handle on a new tool rather than a flaw in the forge. It's normal for a propane forge to not produce the kind of temperatures found in solid fuel fires, you need to be more patient, allow more soak time before setting the weld.

Make sense? 

Other than maybe adding one or two ore outlets I don't see a major problem with your burner, it looks to be burning a little richer than it should but not a lot. 

Looks plenty hot to me. Good job.

Frosty The Lucky.

[the2ndcashboy]

Ok, good to know. I kind of suspected it was a combination of me leaving too much opening on the forge and also my lack of experience forge welding. I just wanted to make sure it wasn't a FAM issue so I didn't chase my tail excessively. I've known since I built the forge that it gets plenty hot enough to weld in. The pics are after less than 10 minutes of run time, it gets much hotter. Like I said in my reply to Buzz, I took the pictures at a lower heat because the flame is pretty much invisible at full heat. I'll put the shortest mig tip in and do some testing next time I get a chance to actually do some forging.

[Frosty]

If it's getting hot enough now don't mess with it. Ever hear the old adage about not fixing something that isn't broken?

Frosty The Lucky.

[JHCC]

If it ain’t broke yet, it will be soon!

[Frosty]

If it ain't broke yet I'm not finished.

Frosty The Lucky.

[the2ndcashboy]

I always thought it was "if it ain't broke, fix it til it is". 

[Frosty]

A better philosophy than, if it ain't broke fix it till you are.

Frosty The Lucky.

[ThomasPowers]

"If it aint broke---why are you messing with it anyway?"

[Frosty]

What else is stuff for?

Frosty The Lucky.

[ThomasPowers]

Your stuff has to justify it's existence?!   Heresy!

[Frosty]

It is. 

Frosty The Lucky.

[D.Rotblatt]

On 6/2/2020 at 11:16 AM, Frosty said:

Sounds good D., where are the pics? We'll believe it when we see some. 

Did you use a release agent on the brazing rod? I've considered pulling metal cores after the refractory sets but before it cures and fully cements itself to them

Pics coming. Was working on the burner lines today. 
 

I used lithium grease first time, and A&D (a bottle of diaper ointment I found in the back of a cabinet...my son is 17yo now   It’s basically Vaseline, wax, and lanolin). They pulled out easy like they were greased   
 

DanR

[D.Rotblatt]

OK...I took a video of casting the burner head, but when I try to download it I'm getting a -200 error immediately. I know I can't put a youtube address, but you can look on my website listed in my profile in the "Studio Tour and Video" section. 

The new burners work like a charm.  The front one has a large baffle, the rear one doesn't.  I think on this design a small baffle would have been appropriate - I went the two extremes.  Either way, they both work.  I haven't run it for more then 30 minutes or so, do I don't know about backfiring when it gets hot. The plenums get a little hotter then expected, almost too hot to touch in 30 minutes. 

Less of the "organ" sound on these.  Only happens when cold in a narrow pressure range.  They seem much more adjustable to lower temperatures then my smaller 1/8" ribbon. 

Check out the video!

Pics

The mold with metal 3/32 rods.

_______________________________

 

The head after demolding.  I've already pulled some of the rods out.

_______________________________

 

The Frankenschtein forge set up for a test run.  The two burners are different, the closer one is my best cast burner so far, the rear is an earlier iteration that doesn't work as well.

_______________________________

 

First burn.  Not tuned.  the rear burner is much more rich, but it's a reject burner.

_______________________________

      

Low pressure test.  Works perfectly down to under 1lb.  Gets really rich at low pressures since it's not pulling in much air anymore.  No backfire!

_______________________________

 

After running for awhile.  At 3 lbs pressure.  Looking really nice.

_______________________________

 

 

Left the window open....when I went to work on my mill I found a nest in my tooling rack.  This is after about 3-5 days after hatching. 

_______________________________

[Frosty]

Looking good D. Looks like some sort of difuser might help even the flames but all in all it looks really good. 

Frosty The Lucky.