my forge-development thread

[jwmelvin]

... I couldn't resist trying. In the as-designed setup, the end of the mixing tube is ~9.5" from the back of the nozzle block. I slid it forward to try a couple alternatives. Maximum extension puts the outlet ~5" from the nozzle block; I adjusted for what I thought looked best and it was ~7" from the nozzle block. I find these results interesting.

[D.Rotblatt]

Looking great!  Good to see another burner with small holes and get some more data about them!

If I read this right, it looks like you have 6 rows of ~22 nozzles each (about 66 holes), at about .11" each.  At pressures over 10lbs it appears to be blowing off the block.  For reference, I have 124 holes at 1/8", much closer together.  I started with less holes, then worked up.  It holds onto the block outside the forge and runs from 0 to 20+ inside with a stable flame.  You may be able to double the number of holes you have.  Possibly more actually as I haven't tried that, I just don't have room on mine for more holes (2.5 x 8" plenum).  Also, blackburn doesn't happen at low pressures on regular burners until they heat up - after about an hour of forging, so you will have to try a long run to see how it works at low pressures (though those size holes may be too small for blowback).

I've got to try that PLA burnout technique. Might be easier then lots of wax sprue in a wood block.

Dan R 

 

[jwmelvin]

Thank you Dan. My first ribbon nozzle has 135 nozzles, each is 3 mm (0.118") diameter. That gives a total area that is ~2.2x my mixing tube, so I thought it would be okay for velocity. My single-outlet nozzle (jet nozzle?) has an area that is ~3.4x the mixing tube but it burns in the nozzle so I knew I wanted it a little smaller. The ribbon flames do seem to blow off the block at high pressures. I couldn't decide if that is a problem, so long as the flame stays lit? 

The current block is 8"x2.5", just like yours. As you say, I will have to try a long burn to see how heat soak affects the burner, particularly for low-output performance. Given how well the PLA core worked, I fully intend to try another block with smaller holes. I'm still a little mad at myself for taking the heat gun to it because it would have been really nice otherwise. I don't think the misoriented outlets really matter much but it does bother me. At some point, reducing the diameter of the outlets will make the core too fragile, but 3 mm was no problem. I think using another refractory mix helped, because it flowed into the mold like magic once I applied vibration. It did take three bags, so it wasn't the cheapest experiment. I wonder if the block could be thinner once the outlets are smaller? Please do try the PLA method if you have access to a 3d printer; not having to build the wood box was also pretty convenient. 

--
I'm confused a bit by the forum rules, so perhaps someone could help me. I received a warning for misusing the quote feature in this thread and perhaps for posting pictures (the latter seemed like a suggestion to do what I already am). As far as I know, I edited the quotes I used, to limit their extent, and didn't quote any pictures. That is consistent with what I read here. In other forms, the quote function is very useful to provide context for a response and also to get an individual's attention. I understand that username tags are disfavored, but I don't understand the idea of avoiding partial quotes. 

Also, regarding pictures, I have been editing my pictures to reduce their size, typically aiming for 200-300 kB. Is that still too large? It seems consistent with the advice given in the thread I referenced above.

I have to admit this moderator warning is a little frustrating. I'm fine with adopting to whatever conventions you have here, but I made an effort to do that and still apparently broke a norm. But I have no way to respond to that to better understand. I spent a lot of extra time trying to document my efforts, and I do it because I have learned a lot from the forum and believe that sharing information is helpful. If I am taking up too much of your bandwidth, rather than a vague moderator warning, would it be possible to get more direct guidance? Frosty has given me some and I appreciate that. 

[Another FrankenBurner]

The one time I had a moderator warning, I was able to respond to the moderator and it was cleared up easily.  I'd be careful about public criticism of regulations/moderators.  On the second post of the site guidlines page mentions contacting the owner(Glenn) to discuss matters like this in private.

[jwmelvin]

Okay sorry. I didn’t want to criticize just don’t understand the warning and didn’t see I could respond. Oh - I can just respond to the email. I’m a doofus, sorry. 

[Another FrankenBurner]

No worries.  I didn't want you ending up in the dog house over a misunderstanding.  Thank you for sharing your information.  

[Glenn]

 The forum is a continuous discussion of the subject at hand. It is un-necessary to quote what we just read. If you are answering or referring to a comment a ways back, please quote enough to remind us of the comment, but not the entire comment as it is not needed.  The quote feature 

Warning is not the word I would choose to contact a member on a low level matter.  The soft wear is limited in ways to notify the member and excessive quotes fall into that area.  We ask that you assist us in keeping the site informative and easy to read by editing the quotes to what is needed.

 

[Frosty]

On 5/17/2019 at 3:50 PM, D.Rotblatt said:

you have 6 rows of ~22 nozzles each (about 66 holes),

6 x 22 = 66     Did you leave your shoes on again Dan?

     

Frosty The Lucky.

[D.Rotblatt]

Hmmmm.....New Math?

DanR

[Frosty]

You too eh? I have no useful memories of "The New Math," let alone skills.

I do recall spending a solid week learning how to multiply with Roman Numerals though. Interesting at the time, no homework but useless, no fractions, nor decimals. Zero, what's a zero? 

Frosty The Lucky.

[D.Rotblatt]

7 hours ago, Frosty said:

You too eh? I have no useful memories of "The New Math," let alone skills.

Yup.  I wasn't together enough to understand what the heck they were doing, but I can read roman numerals.  Thank God I went to a hippie high school which actually taught math - ended up OK.  except for the occasional glitch, like 6 x 22 = 66 

[jwmelvin]

So Dan’s total outlet area is ~982 mm^2 whereas mine is 954 mm^2. Not a big difference. What’s the ID of the mixing tube you use, and what type of inducer? It would be interesting to figure out some differences if the high-output performance seems notably different. 

[Frosty]

On 5/19/2019 at 6:50 PM, D.Rotblatt said:

Thank God I went to a hippie high school which actually taught math - ended up OK.  except for the occasional glitch, like 6 x 22 = 66 

If I were a better student I'm sure I could've gotten a better education but I ignored the wrong teachers. Ahh, I've found mistakes in math books and I make mistakes all the time. I try really hard to keep things simple.

Frosty The Lucky.

[Mikey98118]

What goes up must come down. If you'd got a PHD you would still be at that point in life where it is playing the take away game with you. On the other hand many billions have preceded us into the dark, etc., etc. Relax, have a cookie, and grin

[pnut]

On 5/19/2019 at 3:08 AM, D.Rotblatt said:

Hmmmm.....New Math?

DanR

I remember a big dust up when I was in elementary school about switching to "new math" I don't really remember any specifics of the operations but do have a vague memory of the controversy. This was in 1980 nonetheless and it was still being considered and debated in the KY public schools.

Must not have been a better method as it didn't take. I don't see anyone using it, but the better method isn't always the one that survives as people fear change.

I'm going to look up some info on it.

Pnut (Mike)

I looked up some info and it seems like a poor way to teach children If they don't already have a good understanding of arithmetic.

Edited May 22, 2019 by pnut

[D.Rotblatt]

20 hours ago, Frosty said:

If I were a better student I'm sure I could've gotten a better education

I was a horrible student until I graduated from college.  After a few years I started taking classes just for fun...that's when I started to get good grades!  Liked it so much I became a teacher in my 30's.  The main thing I learned in college is that I can pick up a book and learn anything I want - it just takes the time and will to do it!  Learning was no longer a mystery.  I think I learned just as much at the UCLA research library finding primary sources for medieval metal technologies as I did in any class I took, probably more!

Dan

[jwmelvin]

I rotated the forge a bit so that the burner enters at an upward angle, to help keep heat off the plastic inducer. It seems to work fine that way, as the mixing tube did not heat up at all during operation over a couple hours. 

The ribbon nozzle certainly works but I'm not sure it's working as well as it could. I was seeing ~1700 ºF while running at ~7-8 psi. The flames were generally pretty short and there was a lot of secondary flame, so I guess rich. At times the flames lengthened out to how I've seen them before. I think my taped-together plenum is leaking so I need to work on that. I will probably just go ahead and weld it together.

It seems tough to get sharp pictures from my phone but here's one of the flame size and one of the secondary flame:

I should add that there were no issues with backfiring, but I didn't try to run it down to super low pressures either.

[jwmelvin]

I welded my plenum together, which seems to help it maintain a stronger flame (no leaks):

Here is the ~6.5 psi startup flame:

Once warm, a 10psi flame burns a bit off the block:

There were no issues running at ~2psi.

Oh, I'm curious about what I might expect for being able to get to welding temperature. My forge volume is ~300 in^3, and I'm using something like a 3/4" burner (the mixing tube is larger ID than a traditional 3/4" pipe). Any thoughts as to pressure I might have to run at the gas jet? I.e., is 10 psi typically enough for this sort of thing, or would you generally expect to go higher? I know each burner-forge setup is different so what my setup needs will be different from yours, but having some examples and ballpark ideas would really help. 

[Buzzkill]

You have a unique burner setup and a DIY forge.  I don't think there's any way we can accurately guess (or even ballpark with confidence) the psi you need for forge welding.  I've built a few forges and burners, but smaller than yours and I'm usually close to 20 psi for welding, but each combination was a little different from the others.

If you have forge welded before you should be able to read the visible signs of the steel and flux in the forge to know when it's hot enough (then note the psi you were running at the time for future reference).  If you have not forge welded previously then it would be a good idea to get with someone who has so they can point out to you exactly what you need to look for and help you avoid common pitfalls. Other than that it's reading books and/or watching videos and then trial and error.

[jwmelvin]

Thanks. Knowing that your forge takes something like 20 psi is helpful; I didn't figure you would be able to tell me what I will need in my forge. I have never forge welded so that's (a big) part of the problem. I've only had my forge hot a few times. While I have a thermocouple, it seems to take a while to equalize in temperature and I'm not sure how much to trust it. 

It would be super helpful to work with someone in person; I will try to get to a local meeting to make some contacts.

[Buzzkill]

I'd use the thermocouple in a similar way to the psi on the regulator.   Rather than shoot for an absolute psi or temperature reading, note what both of those were when the conditions in your forge are appropriate for forge welding.  In other words use those indicators for repeatedly creating the correct conditions rather than be concerned about what the actual readings happen to be.  

If your thermocouple reading is off by a few hundred degrees it doesn't matter as long as it is consistently off by the same margin. Once you know when the conditions are right then you know the correct temperature reading in your forge with your burner and your thermocouple.  That doesn't mean it will be accurate for anyone else's setup, but you should be confident that it's right for yours.

[jwmelvin]

Good point, thanks. I put the thermocouple in because it seemed like it would possibly give useful info, so if it can help me repeat conditions that's great. I've been a little tentative to run more than 10 psi so far, but I will do so next time I fire it up and see how things go. 

[jwmelvin]

After my forge sitting idle for a couple years, my sister asked me if I could make her a ladle, so with a purpose, I revised my forge. The 3D-printed air intake was mostly fine when the forge was running and pulling in cool air, but could overheat when the flow stopped, despite sitting lower than the forge body. So remaking that was my task.

The plastic cone seemed to work well for mixing, but there was some discussion on this forum about venturi-type inducers, which use a narrowed area after the gas orifice to accelerate the flow and create a lower-pressure area at the opening to draw in more air. That was my target. 

I have a lathe with a taper attachment, so I used that to machine an aluminum inducer. It's a really difficult task to get in to such a narrow opening (long boring bar, which is subject to chatter), but I just did the best I could with the tools I have. I matched it to the same mixing tube I was using before, which is about 0.8-0.9" ID I think. The expansion zone occurs over about 3 inches, something like 10° included angle.

The air entrance (compression) zone:

The expansion zone:

The burner parts (though missing the centering plug that holds the gas tube in the tube with air openings):

A bench test, using the nozzle on the mixing tube:

In the forge, it still runs the ribbon burner. Seems to work pretty well, and now it won't melt. I'd consider adding some swirl-inducing features, but went with this for now.

[Mikey98118]

People without a lathe can do the same task with a kitchen funnel or wine funnel, and tubing with a matching inside diameter. The right tubes can be bought from online metal suppliers. It is helpful to use a cheap digital caliper to measure the outside diameter of the funnel ext, before looking at available tubing.

[jwmelvin]

I agree you can put together an entrance section, but the expansion zone from a narrowed waist does not seem likely in that regard. To be clear, this is a schematic of my inducer cross section (I did not make it to this exact spec, just went for the most gentle expansion I could and a generally smooth compression):

Edited January 8, 2022 by Mod30
Excessive quoting