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I Forge Iron

Andy98

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Everything posted by Andy98

  1. 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.
  2. 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, an
  3. 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 f
  4. Hi - Thanks! I saw your post in the other thread with the actual fuel consumption estimations too. Interesting stuff.
  5. 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
  6. 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.
  7. 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...
  8. 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
  9. 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.
  10. 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 b
  11. 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.
  12. 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. Hav
  13. 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
  14. 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.
  15. 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+ r
  16. New information: I did try augmenting the blower with a hairdryer. It clearly increased the airflow, but didn't change the sputter. It was a short test, and it was done while the mixing tube was overheating, but my conclusion at the time was that the extra air didn't help at all. Random chatter - might be super boring to others: I know the burner can produce gas flow rates both above, and below, the flame propagation speed outside of the forge (when I ran it flareless, I couldn't get a sustained burn but I could clearly get it to point where it was too fast and would blow out m
  17. I agree with everything you've said, and the course of action you have suggested. It'll take me a while to progress it. It occurs to me that we do have one more piece of info: The burner performance with the draft inducer (from my Feb 28 post's video) vs the PC Fan. The draft inducer appears to be running sputter free (to me). That is a single (but big) variable change: same burner, mounting, and forge - different blower.
  18. I took some of the earlier videos and watched them frame-by-frame and it does look like the flame front is spreading backwards, but it's hard to tell because it happens it happens in just two frames. I did, however, just discover that my phone will do 240fps high-speed video so I should be able to get some good slow-mo of the flame front next time. So I think you're right - but I can't riddle out why the burner wasn't getting hot in those original videos. In all those videos I posted, the burner stayed nice and cool (with one brief exception). It wasn't until a test run on Sunday, video
  19. Good suggestion. I don't have a usable flare at the moment, which is annoying. I did try lighting it without the flare, and I could not get a sustained burn (no surprise) but it did make me realize that at low fan speeds my gas velocity is below the flame-speed and the flame front moves into the mixing tube, while at high fan speeds I can easily blow out the flame (without a flare). I presume that's normal for blown burners? The burner gets crazy hot if the flamefront is inside the mixing tube. Would a more typical blown burner have a minimum blower speed that is always above the flame sp
  20. Unfortunately that's easier said than done. I have to change out the burner support holder - the 3/4" pipe is just slightly too large to fit, so it's pushed in as far as I can push it and that makes the end of the mixer tube end about 1/2" into the outer layer of kaowool.
  21. Oops! That gave me a good laugh. Of course I'm looking for opinions but will take onions if they are offered. Yes, understood. When I did adjust the gas a bit to see what effect that had on things, but that gas ball valve I am using needs two hands to make a small adjustment, so I didn't get that on video. I was trying to get a handle on what adjusting the gas does to the performance, and then separately what adjusting the air does to the performance. Once the forge was hot, I did fiddle with trying to get the forge into a good operating mode. I think I can forge at that low idle
  22. I was able to put all the pieces together and give it a run today. Bright sunlight out, so hard to see what's going on. My synopsis: Success! I don't think I need a stronger blower. I don't understand why it's sputtering. I think/guess I had it too lean with the blower too high. I think the sputtering is due the gas velocity being too high. Apologies in advance, I took a lot of video. First the good: Here is the forge running at a really, really low setting. The noise on the video that sounds like high-rate-gas-flow is actually the fan. The NG flow noise is u
  23. Yes - good point! My burner is side mount, so that should be somewhat helpful. I'm also not going to put an off switch on the fan it, so that should help me remember to do something smart to keep it from melting before I shut off the air. I probably will end up removing either the entire burner, or the non-metal parts of the burner, after use. Should be straightforward, if a little annoying. Hopefully this week will be test run #2. I also wanted to say that Digikey is awsome: They will happily either ship me a replacement fan, or refund me the cost of the fan. I have found
  24. I've also made progress on the electronics front to control the fan speed. I had two viable solutions: Approach #1: Off the shelf parts Note that R1 in there is really a 0-5k pot, but LTSpice doesn't model that. That circuit will produce a 25kHz PWM signal with a duty cycle between approx 5-98%. To get it to 100% you'd need a trim pot and tweak the R2 resistance up. The trick is making sure you don't get something like a 110% duty cycle, because that will actually cause it to produce something like a 12.5kHz PWM at ~50% duty cycle. It should be relatively easy to tune when
  25. The fan is here. I'm not saying they lied about the specs, but they are at least extremely optimistic.There may be one of these fan units that produces the specified fan performance curve but the one they shipped me does not. I purchased an "R" class fan, and it performs like "P" class curve (the fan is labelled as being an "R" unit): In my burner, I measure the unit as producing ~6cfm - spec curve suggests more like ~16. I also measure the fan to produce a static pressure of ~1inH20 - spec says 1.8. All that said, the fan is still sufficient - at least according to measurement
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