Andy98

For anyone interested, this is the 3/4" version running with the PC fan at full (the last batch of videos were the 1/2" version). I don't think I can run the PC fan less than about 70-80% and still maintain the necessary output velocity. I believe the 3/4" works better.

Wayne, Buzzkill and Frosty I see I have argued and speculated you all past your tolerance levels (not to mention having hijacked the thread). I do totally accept the stated benefits of ribbon burners and although I see that my first post here does read a lot like I was rejecting that information. It does also make intuitive sense to me - at least I did say that somewhere above. ...but I do also want to understand the mechanics of why they are better. I don't see that as a bad thing, and I don't apologize for that. I realize that some people find theoretical discussions annoying, and I do apologize for being annoying. Frosty: I think combustion is voodoo. I don't think I have the vaguest idea of how it works. I do think I have my fluids right (although I'm less sure I have expressed them clearly) but would welcome being told if and where I've gone wrong so I can get it right next time. I'm not surprised burning outside the forge is wasteful, but I am surprised mixed gas/air could get all the way to a forge exit before burning completely (I thought it must mean there wasn't enough oxygen in the forge). I would love to experiment more but I have family commitments that prevent that.

Hi - In both cases the burners are required to operate with the gas/air velocity at the nozzle exit being at least the flame propagation speed. That means that a single-large-burner running at the minimum will have the gas/air exiting at the same total (stagnation) pressure as the many-small-nozzles also operating at it's minimum. The fact that the small nozzles are diffusing the flame is probably important. It's also possible that the many-small-nozzles allow ribbon burners to run closer to their minimum? For all I know my burner is dumping fuel/air into the forge at several times faster than the flame propagation speed. Playing this thought out: On surface area a ribbon burner with 26 x 5/16" ports is like a 1.6" single port burner (26x5/16=2sqin, which is the same as a 1.8" diameter circle). Most people don't have 1.8" diameter burners, they have 1" or 3/4". The real world will be more complicated than this, but if a ribbon burner was running at the minimum then a 1" burner would have to run at 2.5x faster flow rate to push the same amount of fuel/air. So that seems like it would mean the single larger burner will have a lot of cool, unburned gas in the forge, and it would make sense that would be bad.

Hi - Thanks! I saw your post in the other thread with the actual fuel consumption estimations too. Interesting stuff.

Is it your belief that the dragon's breath is caused by gas that didn't have enough time to burn in the forge? I always assumed it was completely caused by fuel that didn't have enough oxygen inside the forge, and thus burned on exit into the atmosphere. I think this is the real reason. If you think of the "surface area" of the flame itself, lots of little flames will have more surface area than one big jet. So I think the gas at the centre of a small jet will both slow down more quickly, and heat up faster, thus burn sooner. Total guess. If your belief about dragon's breath being related to time is true, then this would be the second part that makes it make sense (to me at least). Your other points about pressure and exhaust exit velocity I'm not sold on, for reasons that would take lots of paragraphs of tedious explanations that would just annoy people reading (but if you're interested I'm happy to go on and on and on about it).

All I know is what's in the video. He uses a thick wood board placed on his anvil, and just for the initial setting blows. Second heat onward are directly on the anvil or powerhammer. He was using it for welding an oddly shaped billet made up of many pieces of cable, hence my initial assumption it was for stability. But he also does it when setting the welds on more uniform billets as well. Most of the comments on the video are in, I think, Russian - so I couldn't gleen anything there (admittedly I didn't try that hard). I might comment and see if he replies.

I think that is the autoignition temperature, not the flame temperature. Per this link the flame temperature in the "continuous" part of the flame is around 1500F and Wikipedia states it as ~1800F. So not welding heats, but surely hot enough to significantly reduce the rate of cooling. Combined with the insulation effect of the wood, and the helpful pressure distribution the wood would give when you land the tacking blows, that seems useful...

I'm confused by this. Why would the flame speed be any slower? Ribbon or not, burners generally run with the gas/air mix exit velocity at close to the flame propagation speed. No? I'm also not clear why people believe ribbon burners will waste less heat. I'm not saying the do or don't (especially since I've never even seen a ribbon burner in person) but if I input X cfm of unburned gas/air it'll produce Y cfm of exhaust gas, and thus the same exhaust flow velocity regardless of wheather that input was via a single nozzle or a ribbon, right? So unless the ribbon burner is actually running at a lower cfm, I don't understand how the belief that the flame has longer time in the forge can be true. I guess what it boils down to is if slowing the flame down to keep it in the forge longer works, then why would I not get the same effect turning down a regular burner? Every way I puzzle through this leaves me stymied - although the idea has some intuitive sense. The more even heat distribution makes total sense. I wonder if people with ribbon burners run then at lower cfms because of the distribution alone?

Are you judging efficiency just by psi? That doesn't tell you the full picture. You need to know flowrate (by mass or volume). Your low-input-pressure burner might have a big orifus and thus still be delivering a high volume of gas.

Hi, continuing my practice of vicarious blacksmithing, I came across,this video: In the video, the blacksmith sets the initial weld with the workpeice resting on a wood block (happens in the first minute). I assumed this was for stability, but thinking about it more (while watching Mark Aspery's scarf welding videos) it occured to me that the wood would also help insulate the work piece from the heat-stealing anvil. Further, since that wood is burning it might actually heat the metal and reduce oxidization. Is that a crazy thought? Has anyone ever seen this approach before who could explain it?

I couldn't find this posted here before, so I thought I'd post it up. From Lewis Razors: He has a build video too, the most interesting step of which is hammering the brass (copper?) tube to narrow the ID sufficiently to hold the mig tip. Cheers.

Exciting updates: I tried a few new configurations: 3/4" burner, fan attached to the "drop" of the T, natural gas attached to the "run" of the T. Air-rated stop valve added inline with shutoff ball-valve. 1/2" burner, gas via the "run" and air via the "drop" 1/2" burner: 3/4" to 1/2" reducing T, 1/2" mixing tube approx 4" long, air into the 3/4" run, and NG via stop-valve through the "drop" of the T. Results: All 3 are successful! In all 3 cases I could turn the burner up high enough to make it stutter a bit, but it never burned in the mixing tube. Having the NG feed in through the run (rather than through the drop) definitely increased the airflow. I assumed it would increase the velocity by about 10% but I think it did more than that. Configuration #2 would feed gas/air fast enough that I'd get a cold spot on the impact wall, whereas #3 did not have a cold spot. This is configuration #3: Configuration #3 is running pretty well at the top of it's potential, as far as I can tell, in this video, and seems to stutter just a bit but remained cool. This configuration was sensitive to the backpressure created by the firebrick doors, so I had make sure I didn't restrict the airflow too much. In this configuration I was able to successfully weld this steel. I say successfully, in the sense that 1/2 the weld worked and the other 1/2 failed and I think that's my fault. This is my second ever organized attempt at forge welding, so lots of potential error on my part. Question: It's not conclusive, but it seems to me that the stop valve is making the difference (and for that: Thanks everyone! I frankly never would have bothered without everyone suggesting this). I don't understand why it is helping (and would happily take an explanation if anyone has one). I assumed/thought that for any arbitrary position I put the stop valve in, there would have been an operationally equivalent position on the ball valve. Yet, all 3 configurations above worked successfully with the stop valve. Technically, I've not done a fair comparison (none of the 3 configs above were tested without the ball valve - I'll try that on another date). Without the stop valve, there were occasions where I smelled unburned NG escaping the forge. So the only guess I have is that I had too much NG all along and the extra pressure drop caused by the stop valve is helping..?

Ok, so I got a chance to run the thing again yesterday. Now that I have a better idea what I'm looking for, it was easier to recognize what was going on. Here is how it's behaving: State 1: Hot forge Gas set low. I set the fan at 100% Result: I can get a good roaring burn with no visible dragon's breath (to me, in dim-ish daylight). State 2: From State 1, I increase the gas: As the gas quantity increases, the flame goes from roaring, to sputtering, to (I believe) burning in the mixing tube. Result: The mixing tube gets hot. The burner is very quiet (but what roar there is has become higher pitched in keeping with the idea of burning occurring in the tube). Lots of orange flames come out of the forge openings. When this is occurring, if I blow into the back of the PC fan then the flame goes roaring again but only while I am blowing into the fan. State 3: While in State 2 Back down the fuel again. Result: The burner continues to act as if it is in State 2. If I blow into the back of the fan, it will toggle back into State 1 and stabilize there. So this is the state that confuses me. I don't know why the flame position is changing the richness of the burn. I can guess that the flamefront position is affecting the backpressure felt by the fan. I guess if combustion is happening in the tube, there would be a marked increase in backpressure and thus less air from the fan? Perhaps when I have a roaring burn in the forge I'm actually getting some air induction? I figure that States 1 and 2 could be explained purely by richness changes - but that State 3 cannot. So in combination, I feel like I've confirmed that the air/gas velocity is not sufficient. Determining this was my immediate goal, since I do have the option of upsizing the fan. Side Note: I believe I've confirmed that burner position doesn't seem to matter (I've upgraded my burner mount so I could move the burner around better).

Yes - that's what I was getting at with the momentum thing. I'm picturing that pressure wave going backwards to the PC fan. I figure for lots of reasons (momentum, flex, etc..) that PC fan will be less capable of keeping the air pressure steady than a bigger blower. Plus, I figure that the more pressurized air (e.g., in the supply duct) the more the pressure drop would be diluted. Kinda like a pulse jet effect. Anyway, half the time when I think about this it makes sense, and the other half of the time it seems crazy.

Apologies if it appears I have ignored this advice. I haven't - I have been looking into it quite a bit, trying to see if I can find a good and reasonably priced option. I assumed, perhaps incorrectly, that the recommendation to go a needle or globe valve was to help me adjust the flow more easily and not because it would actually meter or regulate the gas flow any better (once set) than the ball valve. I've assumed it I actually want any improvement in regulation, I'd need an actual regulator. Do I have this wrong? All the fuel gas needle and gate valves I can find are in the $30+ range. There are $7 Water & Air rated stop valves at my local homedepot, but I've assumed it would be unwise to use them? There are cheap valves on ebay that claim to be gas rated, but I half think the "air" rated HomeDepot valve might be more trustworthy than something random and unbranded on ebay.