kcrucible

Basically it's a multi-jet buner drilled out of fire brick. Given the lack of straight flow from the air/fuel input to the burner inlets, I can see why that design NEEDS a blower. Without signifigant pressure it just wouldn't work. Pretty cool though. This is basically what Grant was doing with his stainless steel rosebud bottom port. Maybe I'll have to do something like this to create a blown glass glory hole. :)

You and Robert Simmons have the same problem... an oxygen starved atmosphere. Hmm. Given a scarcity of oxygen in a given volume I can see the problem of introducing the propane molecules to the oxygen so that combustion can occur. I'm pretty sure this problem is directly related to your oxygen content. It's a special case. The longer it takes to introduce all of the propane to the proper number of oxygen molecules the longer it takes to burn. The higher the gas velocity, the shorter amount of time that it has to combust completely. It's a problem that isn't generally addressed by the atmospheric burner community because most don't live in that environment. I had found an article describing a home-heating adjustment for high altitude use (posted a link in the forums as a reply to Robert Simmons, but can't find it anymore.. youre welcome to look Basically they reduce the nozzle size to limit the amount of fuel to match the oxygen content. The smaller jet will be moving faster for a given quantity of propane, which will have the ability to generate a better vacume to pull in more air too (assuming sufficient intake area... I had to increase my area signifigantly from my initial build.) Note that for this, the tube dimensions stay the same, so that fuel/air speed is slower on exit, providing more time to fully combust. That can be adjusted by other means as I indicated above, and the tube can be lengthened to promote mixing. Any reduction in maximum power comes via increased efficiency by getting a better burn. If that means that you need 2 burners to get enough into the chamber at that altitude, that's just the way it is. I remember driving a "lowlands-tuned-car" over the continental divide. It was having a MUCH rougher time of it, barely crawling, than a local car that was tuned for higher altitude This is a general combustion problem, not just with regards to forges. The canonical burner design isn't designed to be used in the rockey mountains. The "rules of thumb" are incorrect for the environment. Ah, but that isn't actually true. Smaller mig tips will put the same quantity of propane into the forge with higher pressure, and larger tips will put the same quantity of propane into the forge with lower pressure. Smaller tube diameters will increase pressure, larger tubes will decrease pressure. The "flare" that I use increases from 1" to 1.25" in a short distance (much faster than the 1:12 ratio generally suggested) and the air at the edges hit the threads and generate turbulance which migrates inward to lesser and lesser degrees. I like to imagine it as causing the turbulant air to be forming the proper 1:12 ratio. Sure, tuning in fixed hardware is not instantly variable, but your environment doesn't change rapidly. Once you tune the burner for your area then it doesn't need to change. The "rules-of-thumb" were designed for sea-level to plains. The charts I've seen give a range of tip sizes for a given tube diameter to accomodate altitude no doubt. Being at sea level, I used the largest tip. If I was signifigantly inland I might use the smaller listed. If I were at high altitude I'd consider dropping back to the top end of the smaller burner. I like the reducing flare as a way to promote mixing and generating a stable flame. You may want to try it.

It also signifigantly increases surface area. :)

My "flare" seems to go a great job of mixing and slowing right at the tail of the burner. So much gets burnt right then and there that there's not that much left to burn after the fact. Huge turbulance inducer via the threads at the end that could be used by pretty much any burner. (I actually ground them down somewhat to get smoother operation at low pressures.) Because the turbulance is generated at a much larger diameter than the burner tube itself, no signifigant backpressure is created. When I tried a flame holder at burner tube diameter bad things happened.

I'd say that you don't have a large enough exhaust for the amount of gas and air that you're pumping in. If the doors and burner inlet aren't airtight, all of that heat is trying to escape from the cracks, and heating up your metal shell. If they WERE airtight, then the pressure would increase and shoot out in a very hot jet through your tiny exhaust. Basically, I wouldn't be closing down that flap door unless you've got the air cranked WAAAAY back... maintaining heat, not at full burn.

Very nice, edge. I tried a ring based flame holder with my atmospheric and it did not work well at all because of the back pressure killing the venturi action of pulling in combustion air. The blown shouldn't care about that. Just found another link that documents several forges/burners, including some blown ones. http://forgegallery.elliscustomknifeworks.com/ Indian George's and Michael Birche's look useful to you. Sorry I can't post direct links.. they're doing some funky html stuff.

Not a whole lot of that that I can see. I guess they're so easy to get running that no one bothers documenting things in detail. You can eyeball some people's works though. http://www.jamesriser.com/Machinery/GasForge/PropaneForge.html http://elliscustomknifeworks.hightemptools.com/burners.html

Is this inside or outside the forge? It means the velocity of the exhaust is too high when you crank up the pressure. You could try dialing back the air pressure and see if it stabilizes. Sounds like your fuel-air ratio is ok-to-too-rich as it is though, so even if it's interesting from an experimental standpoint it'd just be wasteful and wouldn't increase temperature anyway (all the extra fuel is going to burn OUTSIDE the forge.) You could always try adding a flare to the burner output to slow down the gas, but I don't think that's common with forced air, particularly inside a forge. If your burner inlet isn't expanding as it enters the forge, you could always dremel out a tapered cone. This would serve as a functional flare, and should make it easier to get a stable flame at the higher velocities. If you're trying to keep your piece from oxidizing rapidly, yes, I think that's what you're looking for. There's not enough oxygen to fully combust. Ideally you want just-a-little orange/yellow if you're trying to maximize fuel-efficiency though since the longer the yellow flame the more fuel is leaving the forge without getting combusted, basically pushing the heat to the outside air instead of in your forge cavity. No idea. For #5, I don't think it really matters a huge amount on a blown burner. I think your B position is just fine... I've seen other schematics that do that. If you push it too far in you're reducing the cross-sectional area that fuel-air can occupy to get into the tube. Too far back and you may have a harder time getting them mixed. Orifice doesn't matter except as it may block off some pipe depending on positioning, etc. You're just dumping propane into the tube. Volume and speed of propane is dictated by the regulator and blower vs tube diameter. The larger the pipe is for a given quantity of gas/air, the slower the gas moves. At a given magic-velocity your flame stabilizes. Going up to a larger pipe would slow down the gasses exiting from the burner, making it easier to get a stable flame. You should probably experiment with different tube diameters. That's functionally what the flare is doing, but again, as a blown burner the dynamics of the tube are a lot less important. maybe start with a reducer jumping up to 1.25" and see how that changes things. But again, I'm no expert... just my understanding of things. I'm happy to be corrected in the particulars!

The flame should already be properly mixed and ignited. But I think the last point is probably the correct one... additional surface area. Massive increase in surface area to transfer more heat from the air to the insulation rather than being expelled to the outside as exhaust. Massive increase in surface area to radiate the heat back into the cavity.

Easy to make, and pretty decent performance. http://ronreil.abana.org/design1.shtml So, Ron's a fan of Larry's work.

I tried looking it up online... no mention of propane usage that I can see. Looks more like an air-regulator. Propane/acetylene can corrode seals unless it's made of the proper materials. I wouldn't recommend it! If you're looking for something cheap, this seems to work pretty well... http://www.amazon.com/Bayou-Classic-7850-Adjustable-High-Pressure/sim/B000VXEW4G/2 or get the whole kit and caboodle w/ optional pressure gagues, etc. http://elliscustomknifeworks.hightemptools.com/propaneregulators.html

No, not at all, I just wasn't sure the nature of your castable. As I was trying to illustrate, there's a huge difference in performance possible, and outlined one method to turn non-insulative castable into highly-insulative castable yourself... no need to buy it. Here's one group working on creating low-tech insulative bricks by hand to aid villages that could use better cooking stoves, etc. http://www.bioenergylists.org/stovesdoc/Still/VC%20Stove/vcstove.html When you're pouring castable, you're basically making your own custom-shaped bricks. Whether they're insulating or not depends on the composition. (and how high a temperature they can take before breaking down also.) The point still stands though, that you may want to ask your supplier for the insulation specs on the cement and compare to the two I listed. If it's edging toward the first, then it is going to take a lot more heat than the latter. If you have half insulative brick, half no-insulation concrete, the net effect is roughly half insulation of the brick. But if you're confident that energy loss isn't the problem, then you can move on to other things. Since you suggested the idea yourself I thought I'd give you some things to consider/research. Best of luck! I know very little about blown burners, so can't be of much help there. Miscommunication here I think. He means anything that would restrict the gas flow, like a mig tip. My 1" atmospheric pipe burner uses a .045 tip, just for reference. .02 is way too small for that (and apparently isn't needed at all for blown burners anyway... no point in accellerating the gas to draw in air, etc.) This could be the problem... I think .02 tips are in the 1/2" burner range and heat-class. Sounds like you may just be able to pull the tip out and try it there.

That's not a good assumption. many people combine a solid refractable over wool, etc. For use in furnaces just means that it can take the heat. The fact that it contains "heavy furnace bricks" makes me think that that it's not especially insulative. Heavy bricks mean a lack of air pockets that give insulative firebricks their qualities. I can't find your brand online to look up the specs. For comparison though, here's a vendor that sells 3 different castable refractories. http://elliscustomknifeworks.hightemptools.com/castablerefractory.html The top is basically not insulative.. - Density = 141 lb/ft^3 - This material has a thermal conductivity of 7.4 btu-in/hr-F-ft^2 at 2000 degrees F The lower is called "insulating castable" - Low thermal conductivity = highly insulating compared to Mizzou - Density = 90 lb/ft^3 - This material has a thermal conductivity of 4.54 btu-in/hr-F-ft^2 at 2000 degrees F and conducts almost 40% less heat through the forge shell at 2000 degrees F! Much better than the top refractory at retaining heat. You'll notice that it's much less dense. The reason that this is so is that the insulating refractable includes elements that will burn up when you fire it, leaving air pockets that increase the insulative qualities, that also makes it less dense. You can take a "non-insulating" refractory and add your own bits that burn out (foam beads, sawdust, small fibers, etc.) I've heard a 3:1 ratio of insulative volume to refractory is good, but can't vouch for it myself. I did an experiment (click here to read more) where I added additional shredded styrafoam and sawdust/coffee grounds to the already insulative one, and so far it seems fine though I haven't brought it up to max temperature yet. I did this at both a 2:3 and a 1:2 ratio in various parts. They both worked, but 2:3 required a lot more post-cast doctoring by "glazing" it with more binder so I'd recommend 1:2. In my own furnace I'm surrounding this mixture with ceramic wool also, to further improve heat retension (when the heat soaks through the castable it'll hit the wool and slow down even further, keeping the heat in the center.) The ITC-100 reflects heat, so that less enters the refractory to start with. Try cranking it up and see what happens. I suspect it'll improve things. If so, then you can consider whether you want to redo it with more insulative materials to cut down on gas usage.

As long as they're outside, and leave me alone, I agree with you.. inside spiders and *shudder* scorpians have violated the armistice! (yes, I have a thing about scorpians... They're the devil's pets. The most unholy looking creatures imaginable. They give me the heebie jeebies, and it hasn't been helped by some video games that I've played or mories I've watched!)

What castable? Is it insulating? Is it backed by wool? Do you have ITC-100 on the face? Have you tried going up to 10 psi? Heat build up is determined by how fast you add BTUs vs how fast BTUs leak through your insulation. If it's poorly insulated then you need to supply more heat. Firebrick has better insulation value than insulating castable from what I've read. Backing the castable with wool would have slowed down the loss too.

I agree it's not that unreasonable given the amount of work it takes to approximate. It comes down to time vs money really. I had rounded slot ends on my burner when I was having trouble. As one of many simultaneous changes (more intake area, tapered inward on the inlet cuts, and I made it squared off at the same time) the problem was reduced with the square end. I was having burnback issues, so I could see the behaviour of the air/flame at the end of the slot. Porter is right in that things were a LOT rougher with the rounded edges. If I wasn't having burnback that doesn't neccessarily mean that it would have caused any problem though... I think slower velocity but better mixing. It could be that Trex uses the better mixing to generate a shorter tube and makes up for the velocity loss in other ways. I'm using the 045 with a 1" burner. That thing screams.... or more accurately, whistles. Haven't fired it up inside the forge yet... I should finally have time tomorrow! I'm glad that you enjoyed my site. I enjoy the experimentation and trying to understand how it's all working, why it works, how it might be improved, etc. While I don't ave access to CNC equipment, I figured someone else may get some use from the engineering drawing. Apparently the original was linked here from some user's site and it's never online.

Maybe it was to carry spare blades, not to fit over the tool itself. The notch at the end lets you see if it's "loaded?"

Thinking about the original question though... you may want to consider a bottom-feed forge. I know that Grant was developing one. Here's an example of what is known as a "vertical forge." http://www.alchemyforge.net/smithy.html http://forums.dfoggknives.com/index.php?showtopic=786 That's basically what I've done with my furnace... input on the bottom , forging ports in the side for a 3" by 5" entrance. If I need more volume, I can put spacers under the lid to lift it up and create a higher and wider entrance. It will never get to HUGE dimensions, but I think it should handle a decent size of item. You generally only need one section of metal hot at a time... you can only work so fast. If you're not concerned with melting metal for casting, then the lower dimension can be much smaller obviously.

Not really a reply concerning top burners, but regarding the extra air, etc, if I remember correctly you were inserting air via the second port because if you did it "inline" it was causing the burner to blow itself out due to the velocity? If you're starting over anyway, I'd recommend that you try a reducer on the end as a turbulent flare. It does a heck of a job as a flame holder in my experiance. The stepdown at the end of the burner tube transitioning to threads + threads at the larger output end generate a lot of turbulent flow which locks the flame in place no matter how high the velocity, and most of the combustion takes place within a few inches of the flare, which could be helpful if trying to use a really small chamber to extract all of the heat. In fact, it's so turbulent that at very low pressures it was actually causing backpressure resulting in stuttering until I tapered the end threads up (barely changed the outermost threads, the innermost mostly gone) using a dremel with a grinding wheel. Now I have great performance over the entire range... at very low pressure (picture not shown) it's like a blue butane lighter... gentle and wavey. The reason I mention this is that if you can simplify the burner to one tube, that will make the variable dimensional forge much simpler to impliment since you'll only have a single required point. A sidearm burner would probably be the best implimentation since you can hook up a blower (or not) to the air inlet as the case dictates. Regarding top mount heat, given the pressure of the jet the accumulated heat should be constantly pushing AWAY from the burner and toward the exhaust. The burner inlet should be the coolest place in the forge I'd think. Making sure that you have an exhaust large enough to handle the burner would be important. I've heard some say 4x the inlet diameter(s) to avoid backpressure, some did 7x.

hey, he was only off by 80%. What a deal!

Even if they came into it with the lowest-bid mentality, as soon as you start asking what they expect and what they want to pay for, they're likely to use the same criteria to compare your work vs your competitor's work. If you just charge more for a given class of work there's nothing we can do about that. But if the other guy has a lower bid because he cuts corners, doesn't do the detail work, etc, then introducing the customer to the REASONS that a bid can be lower can only work in your favor because it will cause them to question WHY the other guy's bid is lower. It will force apples-to-apples comparisons. If nothing else, the whole thing opens up the lines of communication and turns the process into a dialog of wants vs needs vs price where the customer is an integral part at all levels.

Not really based on blacksmithing pricing, but in my line of work we have a fair amount of flexibility in pricing and items that can do the job. What we TRY to do is approach it like this: "You know, there are a lot of ways to approach this problem. If you could give us an idea of what you're prepared to spend we can find the best solution that can fit within your budget." This has the advantages of: 1) Letting them know that you're flexible and what they want is important to you. You can do "not top-of-the-line" work if it meets their needs and aren't just going to try to bully them into spending more. 2) Implies that top-of-the-line work is pricey, and worth it, but they may not be able to afford it. It reinforces the "you get what you pay for" idea that everyone already knows, but lets THEM dictate what they want to pay for instead of presenting it as a "take it or leave it" scenario. For example, with the gate, you may mention that by reducing the number of bars, you can cut material and labor costs dramatically, while still retaining the "feel" that they're looking for. It doesn't always work... some people feel that you're trying to squeeze out as much money from them as possible when you ask for budgets, which is true, but what they don't realize is that if they told you their budget it'd probably work in their favor... you may throw in some freebies and still keep the costs the same, etc.

I guess I just have pristine-anvil-envy. Alright... you've all convinced me. As it happens, it turned out to be a 162 lb anvil, not the 120-140 it was initially billed at. Score!

As far as I know, the Trex is basically just a pre-fabricated Porter burner. They worked in collaboration. http://www.hybridburners.com/new-vertouri.html The Trex is machined to precise specifications, so it probably gets a minor boost from accuracy in construction and repeatability/tweaking that most people won't be likely to get into off-the-shelf plumbing parts. That's not to say that you CAN'T do it, it's that it would take a great deal of effort for the small incremental improvement. As one example, the ratio between welding tip orifice and burner tube diameter... when we're dealing with a static pipe dimension we choose the closest orifice that we can find to get the width that balances proper mixing with maximizing velocity. Since the Trex machines its own tube, he can pick an orifice and construct a burner tube to optimize for it. Michael Porter's jet ejector and the Trex are basically a refinement of the Ron Reil's Mongo. Scaled down, larger air intakes, etc. Ron mentions many of the adjustments that you can make to the Mongo in text, that Michael Porter impliments in his book. Ron deserves a huge amount of credit for initial concepts, which the other guys then refined and developed into an excellent technology. Someone sent me a link to what is supposedly an engineering schematic of a version of the Porter design, in case anyone has CNC equipment, etc. Scroll down and click the prov burner link. http://kcrucible.wordpress.com/gallery-of-fire/

For the record, here's the anvil...