Mikey98118

Burners 101

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You are close to dead on point, Frosty.

I'm not only aware of it, but it is deliberate policy. the older we get the more we all search to "find our thing." My thing is excellence in tooling. I have come to appreciate that other people have different needs and goals; so I'm pleased to point out that my way isn't the only way, or even the best way for others; this is only fair; that said, I'm going to go right on "doing my thing," and depending on you to do your thing too. Others should benefit from meaningful  choice.

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Hi. I m new to the forum. I would like to ask a question if I may.  What is the most efficient burner I can use in a medium sized forge? I'm looking to use the least amount of  fuel as possible. Fuel conservation is a top priority for me.

 

This forge (see link below) boasts of being the among the most efficient but it has a hefty price tag, and I'm a DIY guy anyway, I prefer to build my own. I do like the design of this forge though, and if its as good as they say it is, then maybe I can build my own version of it. What kind of burner is this? It has a tapered gas line running between the burner and forge. Is this for mixing the gas and air?  

http://www.hypona.com/forgeeng.html

 

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Yes, that's a commercially manufactured propane burner, not only are they more efficient they're much less susceptible to back pressure or breezes. They cost plenty, efficiency costs more up front but it will pay for itself in fuel use and lost time eventually. YOu may be able to build a burner as efficient but it'll probably be after building many many burners.

What shape forge you need depends on what YOU want to use it for. It's common for new guys to build forges WAY larger than they need try to avoid that. The rule of thumb that works pretty well is: one well tuned, 3/4" dia. burner for every 300-350 cubic inches of forge chamber. Commercially manufactured burners will heat a little more volume.

Frosty The Lucky.

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I looked at the hype, and failed to find any solid FACTS behind it; they are actually bragging that they have internal metal surfaces showing? One of of the guys on here already measured temperatures in my old forge design that would melt stainless steel, if it was to be used that way. Furthermore, the photos show an orange interior; not high yellow, let alone white. I would like to see a match between this forge and Ron Riel's old Mini forge for efficiency, or half the knife maker forges out there for that matter.

Maybe it actually is a good forge, and they just screwed up by trying an empty headed sales pitch, in stead of laying out a sound set of detailed facts, but I wouldn't spend good money based on the BS I saw. Also, if someone is going to pay a lot of money for a commercial forge, we wouldn't they just buy a proven brand like Chile Forge? If they are going to bet on a dark horse, why not start with one of the forges offered on eBay and spend a small fraction of what regular commercial forge makers ask to buy and upgrade it?

I'm not saying these guys are all that is evil. I'm just asking "where's the beef"?

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Yes, that's a commercially manufactured propane burner, not only are they more efficient they're much less susceptible to back pressure or breezes. They cost plenty, efficiency costs more up front but it will pay for itself in fuel use and lost time eventually. YOu may be able to build a burner as efficient but it'll probably be after building many many burners.

What shape forge you need depends on what YOU want to use it for. It's common for new guys to build forges WAY larger than they need try to avoid that. The rule of thumb that works pretty well is: one well tuned, 3/4" dia. burner for every 300-350 cubic inches of forge chamber. Commercially manufactured burners will heat a little more volume.

Frosty The Lucky.

Thank you for the reply. I use to think I needed a huge forge, you are correct. However after I built a small forge I saw how much propane they used, and that's when I decided I needed something efficient. I could build 2 forges, a small one and medium sized one, I guess. I was wondering if the design in the link I posted might be good. I want to forge odd shaped things such as rings for example. I'll need something more than just a small blade forge, I need to build it myself too. I would love to talk with someone who has a really good burner design that he would share with me. I also would love to know how small I can safely make the forge openings. I believe much fuel is wasted as the heat rushes out the from of the forge. I know there is a safety concern here but I saw a good thread written by a gentlemen on this forum which seemed to suggest that small openings are better because you don't need to use as much heat that way. I would have asked him questions but I don't think he posts here anymore.

 

I looked at the hype, and failed to find any solid FACTS behind it; they are actually bragging that they have internal metal surfaces showing? One of of the guys on here already measured temperatures in my old forge design that would melt stainless steel, if it was to be used that way. Furthermore, the photos show an orange interior; not high yellow, let alone white. I would like to see a match between this forge and Ron Riel's old Mini forge for efficiency, or half the knife maker forges out there for that matter.

Maybe it actually is a good forge, and they just screwed up by trying an empty headed sales pitch, in stead of laying out a sound set of detailed facts, but I wouldn't spend good money based on the BS I saw. Also, if someone is going to pay a lot of money for a commercial forge, we wouldn't they just buy a proven brand like Chile Forge? If they are going to bet on a dark horse, why not start with one of the forges offered on eBay and spend a small fraction of what regular commercial forge makers ask to buy and upgrade it?

I'm not saying these guys are all that is evil. I'm just asking "where's the beef"?

Amen brother, that's what I'm saying. Where's the beef? I want to build a really efficient forge. Not to have the greatest forge around, but because the cost of propane is a big concern of mine. I need super efficiency. A small blade forge will be ok for some things, but I need a more versatile forge as well. I'm looking for a good design to mimic.

 

 

 

Did I accidentally merge our replies? Or is that a default thing that happens? If it was my fault, I'm sorry.

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It's not the burner Mike though I  have to admit all I did was look at the pictures I didn't need to see more. It's only at orange heat because for the most part farriers don't need hotter. It's the forge and how much gas they're giving it. I think we've had the same conversation about every farriers forge someone has posted here.

The cast burners aren't as efficient as the old, the interiors are too rough. The tube length taper of 12:1 max. is exactly what all the old papers I collected talked about for efficient induction. Just putting a flare on the end was something Robert Grauman did after we talked, he misunderstood what I said. I almost hit send on the Email reply I wrote telling him a flare wouldn't work. Happily I looked back at the pic he sent with his post and decided a beautifully shaped flame was good enough. The other misunderstanding we had led him to mount the T sideways and thus was born the "Sidearm" burner.

One of these days I'll locate those pamphlets and papers and post some info direct. Well . . .  maybe, you'd have to see our basement to know how unlikely it may be.

 

Someguy out there somewhere: I spend a lot of time trying to make my forges versatile and it's always a dice shoot. Making small burners for small spaces is a good idea. However if you're mostly doing jewelry you will save time and fuel by using a fuel air torch rather than a small furnace/forge. A jewelers oxy, hydrogen torch is excellent for small work and you can generate your own gas with an electric oxy, hydrogen generator.

About most home made forge burners blowing excessive flame out the openings you're right it's wasted fuel. There is one and only one reason a LITTLE dragon's breath is a good thing, it shows there is NO unburnt oxygen IN the forge to generate scale on your steel/iron.

Balancing the burner size to the furnace volume is important but getting a home build's nozzle velocity down is another story. Recently guys have been talking about and building "ribbon" burners which is a final nozzle into the forge made up of a LOT of smaller openings. This does a couple things, it spreads the flame evenly in the furnace and more importantly a well built ribbon has a nozzle velocity JUST above the rate of propagation of the gas air flame so it can't back fire. (burn back up the nozzles into the plenum)

This is a popular burner design with glass blowers but can be over done easily. Blacksmiths are sort of known for getting carried away.

About your quest for "THE most efficient gas burner". Join the club, every furnace, torch, etc. manufacturer on Earth is actively working on improvements in their labs every single work day. They have staffs and labs doing it.

Frosty The Lucky.

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10 minutes ago, Frosty said:

 

Someguy out there somewhere: I spend a lot of time trying to make my forges versatile and it's always a dice shoot. Making small burners for small spaces is a good idea. However if you're mostly doing jewelry you will save time and fuel by using a fuel air torch rather than a small furnace/forge. A jewelers oxy, hydrogen torch is excellent for small work and you can generate your own gas with an electric oxy, hydrogen generator.

About most home made forge burners blowing excessive flame out the openings you're right it's wasted fuel. There is one and only one reason a LITTLE dragon's breath is a good thing, it shows there is NO unburnt oxygen IN the forge to generate scale on your steel/iron.

Balancing the burner size to the furnace volume is important but getting a home build's nozzle velocity down is another story. Recently guys have been talking about and building "ribbon" burners which is a final nozzle into the forge made up of a LOT of smaller openings. This does a couple things, it spreads the flame evenly in the furnace and more importantly a well built ribbon has a nozzle velocity JUST above the rate of propagation of the gas air flame so it can't back fire. (burn back up the nozzles into the plenum)

This is a popular burner design with glass blowers but can be over done easily. Blacksmiths are sort of known for getting carried away.

About your quest for "THE most efficient gas burner". Join the club, every furnace, torch, etc. manufacturer on Earth is actively working on improvements in their labs every single work day. They have staffs and labs doing it.

Frosty The Lucky.

Thanks Frosty. I am considering a ribbon burner. I'll check out that  little dragons breath forge too.

I'm not into jewelry, so a torch wont work for my forging needs, although I have an oxy/propane torch for cutting thick steel and heating as well. I did see the hydrogen torch though, on youtube, and I wondered if a hydrogen burner would heat a forge. If it would it might be a good fuel  source. However I could blow myself up too because I have no idea about hydrogen gas. Any idea if its possible to use hydrogen to heat a forge? You could generate your own hydrogen with a generator and electricity, I know that much

 

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I don't know of anybody using hydrogen for a forge fuel, a forge needs a much larger quantity of fuel than a torch. Currently gas forges are "Reverberatory" furnaces. This means the flame heats the interior of the forge and the radiated heat from the forge liner is what heats the work. Large industrial forge furnaces are cycling a LOT of material and time is money so their furnaces are lined with heavier refractories for the thermal "mass" it can transfer more BTUs faster without losing so much heat the next work takes longer to come to the desired temperature. Of course anything the flame touches will be heated by the flame but that isn't the main manner of how a gas forge heats.

This isn't much of a factor for most small scale blacksmiths so we operate by a different philosophy. An insulated forge liner with a relatively thin hard flame face heats up to a higher absolute temperature in minutes and requires much less fuel. However if you're working a lot of pieces you might notice piece #3 or 4 taking longer to heat than #1&2, this is because the first pieces took the heat.

Not having a LOT of dragon's breath is a good thing unless you're heating your garage too. Dragon's breath is a factor of gas forge operation just like smoke is for a coal forge. It isn't a type of forge it's just a thing that is.

Frosty The Lucky.

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2 minutes ago, Frosty said:

I don't know of anybody using hydrogen for a forge fuel, a forge needs a much larger quantity of fuel than a torch. Currently gas forges are "Reverberatory" furnaces. This means the flame heats the interior of the forge and the radiated heat from the forge liner is what heats the work. Large industrial forge furnaces are cycling a LOT of material and time is money so their furnaces are lined with heavier refractories for the thermal "mass" it can transfer more BTUs faster without losing so much heat the next work takes longer to come to the desired temperature. Of course anything the flame touches will be heated by the flame but that isn't the main manner of how a gas forge heats.

This isn't much of a factor for most small scale blacksmiths so we operate by a different philosophy. An insulated forge liner with a relatively thin hard flame face heats up to a higher absolute temperature in minutes and requires much less fuel. However if you're working a lot of pieces you might notice piece #3 or 4 taking longer to heat than #1&2, this is because the first pieces took the heat.

Not having a LOT of dragon's breath is a good thing unless you're heating your garage too. Dragon's breath is a factor of gas forge operation just like smoke is for a coal forge. It isn't a type of forge it's just a thing that is.

Frosty The Lucky.

Thanks for clearing that up. I kind'a began to understand that dragons breath referred to "flames and heat" instead of an actual forge. I began to understand this as a read another topic on this website not long after I posted my last comment. I'm now understanding that small and well insulated is better, and that small forge openings are better, but I'm not sure how small I can make those openings and still maintain safety. If I use a ribbon burner will this mean I can make smaller openings in my forge without worrying about some kind of safety hazard? I guess I just need to know what kind of burner will be efficient, (if there is a burner that's a cut above the rest), and I need to know how small I can make my forge openings.

 

 

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It's all a balance, combustion gasses being HOT take up a lot more space so what you can shoot into a forge through a 3/4" dia orifice is going to want a 2" dia exhaust port or it'll make detrimental back pressure. This is exactly why a lot of guys have doors on their forges they can adjust, sliding soft bricks are popular and work well but the high temp soft brick is more expensive.

Currently I've been experimenting with making my own partitions and baffles rather than destroying soft fire brick. What's available to us are 2,200f soft brick and our forges get a LOT hotter than that so soft brick only lasts a couple firings before it starts breaking up. We'd have to special order 2,600f. soft brick so we're trying other things.

Check out what Mikey has been saying about building forges, especially what he has to say about baffles and how they work.

Frosty The Lucky.

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33 minutes ago, Frosty said:

It's all a balance, combustion gasses being HOT take up a lot more space so what you can shoot into a forge through a 3/4" dia orifice is going to want a 2" dia exhaust port or it'll make detrimental back pressure. This is exactly why a lot of guys have doors on their forges they can adjust, sliding soft bricks are popular and work well but the high temp soft brick is more expensive.

Currently I've been experimenting with making my own partitions and baffles rather than destroying soft fire brick. What's available to us are 2,200f soft brick and our forges get a LOT hotter than that so soft brick only lasts a couple firings before it starts breaking up. We'd have to special order 2,600f. soft brick so we're trying other things.

Check out what Mikey has been saying about building forges, especially what he has to say about baffles and how they work.

Frosty The Lucky.

Well at least that 2" exhaust port gives a little better idea of what I might expect. Thanks. I'll check out Mickeys posts, as you suggested.

On ‎5‎/‎8‎/‎2016 at 4:47 AM, Mikey98118 said:

So, going on about funnel shape fittings on the end of linear burners, and its effects:

Swirl isn't the only advantage that they can provide. If an impeller blade is attached at the large end of a funnel or pipe reducer at the burner's year end, a stronger vortex can be produced at the fitting's small end. The  impeller blade doesn't even need to move to get the effect, although a weak fan motor will work wonders.

It is a given that a fluid running through a round restriction will form a vortex, but usually so weak a one as to make no practical difference, so that the term swirl or  is more appropriate.

But, for every minor increase in power added to a vortex its swirl and other benefits are greatly magnified. What other benefits? Increase flow of incoming air simultaneously with a large drop in air pressure in that flow; a magic combination that can be found in no other way. And with that we can move on to jet-ejector burners and their air openings.

To begin with jet-ejectors induct more air into a naturally aspirated burner than can be found from a linear style with a rear funnel, unless it is equipped with a fan, and then it is no longer naturally aspirated, even if it is an impeller blade fan.

The way a jet-ejector's multiple air openings create swirl is from twisting into a small part of a turn, as air travels into the burner, just ahead of its mixing tube area; that my be found as part of a single tube shape (Mikey burner), or within a larger area built up in part from a reducer fitting and a larger diameter tube section (Hybrid burner). It can be made up as  two opening on a pipe fitting ("T" buner), or even from a single opening (Modified Side-arm burner); all are examples of jet-ejectors.

One fact of life we have to address is DRAG, which is the arch enemy of mixture flow. Any opening through which air flows creates drag as it passes by the air opening's edges, by creating eddy currents. Curved edges create more eddy currents then straight edges; the stronger the curve the greater the eddy currents. Can you think of anything worse for creating drag than lots of little holes? Thus the advantage of just two larger holes in a "T" burner is far superior, and even the offside single hole of a Modified Side-arm burner trump them; this is despite the fact that both of the latter two burners have threaded openings that air must pass through, which threaded side holes don't! Do we begin to appreciate how powerful eddy currents are at creating drag?

Moving in the opposite direction, Rex Price, while still studying burner design with me, sent his version of what he thought he had learned of my ideas; his burner used slots for air openings, instead of my rows of holes, thus combining straight with curved edges; the improvement was remarkable. So I came back with rectangular air openings to remove all curves from their edges, and beveled forward and rear edges for good measure. Such a boost in performance was gained that a radical new step stye flame nozzle became possible.   

 

   Ok Mickey, this is all Greek to me. I am very interested in what you say about the swirling action of the gas and air mixture. That's why I posted that link with the expensive farriers forge, because it seemed to have some special plumbing after the burner. You words reminded me of that and so i posted it hoping to get an opinion on the burner design. I'm just looking for a good design.  Do you have an schematic or picture of a properly built burner that I can see? I would like to see these ideas you are referring to.

 

Quote

 

 

 

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Ok, I'm going to stop using the quote feature. I hate that messy quote merge thing.

 

Anyway, Mikey, after reading your first few posts in this thread topic, this sounds all Greek to me. I am very interested in what you say about the swirling action of the gas and air mixture. That's why I posted that link with the expensive farriers forge, because it seemed to have some special plumbing after the burner. You words reminded me of that and so i posted it hoping to get an opinion on the burner design. I'm just looking for a good design.  Do you have an schematic or picture of a properly built burner that I can see? I would like to see these ideas you are referring to.

 

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Did I misunderstand the "swirling" thing? Were you referring to the flame inside the forge swirling, or were you referring to a vortex inside the gas and air mixing chamber? Or both? I'm confused. I don't have your book, but if you wouldn't mind sharing some schematics or pictures it would be appreciated. Thank you.

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What mike was referring to was the fuel and air in the burner mixing tube. The commercial burner is able to drive the fuel air mix around a couple 90* bends because the burner tube is tapered. Mine won't turn a single 45* angle without the extra lengths of pipe and my burners are pretty decent for home builds. They're easy and cheap.

Mike and I sometimes wander off into burner talk we've both been studying on for a few years while most folk out there just want to build one. I've been reading and fiddling with the things since the internet went public around '86 and I get silly giddy when I up efficiency a little bit. Heck I was dancing a jig when I figured out an easy way to jig a plumbing T so folk could accurately drill and tap them without a lathe.

Anyway, Mike and I sometimes get talking and folk don't even suspect we're in the midst of a fundamental disagreement, not a fight, an argument. World of difference you know. ;)

Frosty The Lucky.

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Frosty, I suspected that there might be some competing innuendo in this thread. That's ok. I just thought I might pick your brains for a bit.  Look at this image, do you see the tapered pipe in the plumbing between the burner and forge? Does this serve a useful purpose or it is cosmetic only? Does it serve to create a vortex in the gas air mixture? Can you explain why this forge is plumbed this way? Or can you show me something similar so I can understand this concept better?

 

forgeopen01.jpg

I just love this forge. I love the design. I want to build my own, only use ceramic wool or ceramic insolation board, instead of whatever they are using for insulation. I'm trying to understand the burners design better though.

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The tapered section IS the burner tube and what I was describing as available inn commercially manufactured induction devices, these things have been around since long before Bernoulli penned  his laws of fluid dynamics, Venturi simply restated one of Burnoulli's laws to explain what he'd observed in a specific situation and it has been remembered as Venturi's law.

There is no dueling innuendo that I know of I'm just not as articulate as I used to be. I'm a TBI survivor and Mike is a stroke survivor so we sometimes get too involved trying to describe what's in our heads and only confuse things. Mike and I make burners with a different philosophy, MIke wants to squeeze the best performance he can He calls them Ferrari burners. I'm the guy building plain Jane pickup truck burners, easy to make and tune and they work well enough for most purposes. Mike's burners require good shop skills and an ability to read, comprehend and follow instructions. Mine do just fine with basic shop skills and if a person doesn't understand the directions I'm usually around to answer questions. Heck if someone doesn't trip my curmudgeon button I'll talk the clueless through construction and tuning step by step.

About that forge. If you want one like it I'd recommend buying one. Making a burner like that one isn't something a person can do unless you have a lathe and want to machine one from billet. If you wish to do this let me know I'll lay the industry standard ratios on you and send you sketches of what one looks like in cross section.

If you wish to use a typical home made burner you'll need to mount it vertically on top. A home made burner just isn't a robust enough inducer to maintain a flow around two corners and that length of straight pipe. There's nothing wrong with doing this, I mount mine on top. You'll need to take into account the chimney effect, when you shut it down heat will rise up through the burner by convection and it WILL get HOT. The way to take this into account is use non flammable fuel lines to the burner itself. I use copper tubing on mine.

I don't know the volume of the forge in the pictures so I can't say if one 3/4" burner is sufficient to bring it to welding temperature. Welding temp is sort of a benchmark goal most guys try for. I weld in mine occasionally so it's important for my forges.

That particular forge is purpose built for heating horse shoes and you don't typically need more than medium orange heat and significantly less for hot fitting. This means that a forge with different temperature zones is a benefit. As you can see in the picture the only spot approaching low yellow is directly under the burner, the rest is orange diminishing with distance from the center of the burner flame.

If this temperature pattern is what you want then you'll be time and money ahead buying one. There are other farrier's forges with a long history and factory support. The Whisper line: Whisper: Baby, Momma and Daddy are all superior farrier's forges with 1,2,3 burners respectively and a number of door configurations. These are popular propane forges for general blacksmithing as well. I know for a fact they will hit welding temps. Majestic and Forge Master are two more top line propane forges, don't forget Centaur Forge, they carry forges and tools.

Then there are propane forges coming onto the market recently that are well made and excellent performers judging by the reports we hear on Iforge, The Chili line is one of them.

Frosty The Lucky.

 

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4 hours ago, Frosty said:

 

Sorry Frosty, I guess that was a poor choice of words on my part, and I misunderstood what you were saying too.

Anyway, that forge is over $800 and i cant afford it. Thanks for your time

 

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Nothing to apologize for, we talk for a while on subjects to get a good idea of what the other guy means and I'm not as articulate as I used to be. Not understanding me is a pretty normal state for folk. There are other folk following along too, it's time well spent. ;)

Frosty The Lucky.

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2 hours ago, Frosty said:

Nothing to apologize for, we talk for a while on subjects to get a good idea of what the other guy means and I'm not as articulate as I used to be. Not understanding me is a pretty normal state for folk. There are other folk following along too, it's time well spent. ;)

Frosty The Lucky.

Thanks again.

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It is just incredibly easy to confuse similar, but very different ideas; this is why I only use the term vortex when speaking about parts of a certain type of burner these days, and only use the term swirl when speaking about how to aim the output of a burner in a forge. That doesn't mean others will use the terms thus, nor that I always used them thus in the past; confusing isn't it?

I don't think you actually love that forge. I think you are excited about something in its design; something that you need to think about a little more. There is a book called "Gas Burners for Forges, Furnaces, & Kilns" which has a similar but far hotter forge in it; one which you may be able to adapt to your wants by down sizing it, and its burner, once you have read far enough to understand their underlying principles. You can build that forge to work with horse shoes or quatrifoils, which I think is actually what you're after. But if I'm wrong, it will only take some of your time.  Input the title on a search engine to find a free pirated copy to satisfy yourself about what you really need to do to find the forge you want.

The slickest design for a small forge I've seen is an oval forge made from part of a car muffler. That doesn't mean it will be the forge of you dreams; their are lots of reasons for different forge designs.

Ron Riel shows how to build a knife maker's forge, which he calls his Mini Forge; you can find all the particulars in his burner pages.

As to ribbon burners; they do the best job possible at slowing down very hot flames for maximum "hang time". BUT, they aren't the best design for having a lite small highly portable forge. There is no such thing as the perfect burner, or the perfect forge. The best burner in the best forge for you is as good as things get; you get there by spending more time learning about your choices before rushing off to build equipment;)

 

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Thanks for the reply Mike. You're right Mikey, I don't love the forge I just love the way it looks. Its cool looking but also it looks like it might serve my needs. I was just going to mimic the design and build it out of a scrap propane bottle. Will it work good? I don't know. Will I actually build it? I don't know. I understand my search for perfection isn't so simple to answer. In the end however I just want to use the least amount of gas to heat the most amount of steel. That's all I really want. I don't care if the forge looks like work of art or a POS. I just want efficiency.

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If you like that shape you may want to look for a non-functional oiless or "pancake" compressor that has a tank you can repurpose.  They are fairly cheap compressors and therefore people tend to toss them out and buy a new one rather than repair them when something goes wrong.  Since all you need is a shell to hold insulation and refractory it doesn't even matter if the tank still holds air.

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11 hours ago, Buzzkill said:

If you like that shape you may want to look for a non-functional oiless or "pancake" compressor that has a tank you can repurpose.  They are fairly cheap compressors and therefore people tend to toss them out and buy a new one rather than repair them when something goes wrong.  Since all you need is a shell to hold insulation and refractory it doesn't even matter if the tank still holds air.

That is a good idea, thanks.

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I hadn't thought about that one Mike, I rarely use Vortex to describe anything but flame pattern in the forge when talking forges. The most desirable flow pattern in the burner tube is more a toroid like a tube long smoke ring. I don't have a good term so I just call it "good turbulence" and it isn't really turbulence. I think. :unsure:

In the earlier days of the internet I recall guys making forges by plastering inflatable balls with refractory leaving a hollow sphere when deflated and cut out.  Sawn in half they made early version clam shell forges.

Frosty The Lucky.

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Someguy writes "...I don't love the forge I just love the way it looks. Its cool looking but also it looks like it might serve my needs. I was just going to mimic the design and build it out of a scrap propane bottle. Will it work good? I don't know. Will I actually build it? I don't know. I understand my search for perfection isn't so simple to answer. In the end however I just want to use the least amount of gas to heat the most amount of steel. That's all I really want. I don't care if the forge looks like work of art or a POS. I just want efficiency."

Using a small hot high speed burner, or ribbon burner, located in the bottom half of such a forge shape, and penetrating a round kiln shelf (hole made by a cheap carbide encrusted hole saw from Harbor Freight), and aimed upward at the ceiling, will provide you with a nice long guide path for exhaust gases, as they bend around a partial hemispherical ceiling and back down again before and exiting out of the front opening.

Round high alumina kiln shelves are dirt cheap and very tough. Under such a floor you can place all the high temp insulation you desire for little money. The top half of the forge can be made with rigidized Kaowool, and finish coated by one of Frosty's favorite kiln washes; also for very little money.

Furthermore, the burner can be made anyway you like (ex. "T" burner) and traded out later for a ribbon burner...

A vortex feeding into a mixing tube will create that exact phenomenon:)

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