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Burners 101


Mikey98118

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The problem of hoping for ideal part matches are the fans themselves. You have no way to predict the exact opening diameter from fan to fan; they are designed for a very different use than this.

The way it is positioned to cool computer chips make the exact diameter of their openings irrelevant; this is a typical glitch when retasking parts.

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The outside openings of these fans aren't even listed, as a rule; it has no importance for their intended use. The 70mm that the fan is listed by is its width and length measurement from the outer sides of the fan casing; not the measurement of its blade opening. Thus, trying to closely match such an opening by other than direct measurement is to invite trouble, when you consider that too large a matching hole in the flange area is likely to create a gas leak, while too small a hole will create major back pressure from an impeller blade. Both problems can be avoided by providing room and material in the flange area for adjusting the opening diameter through some minor believing. There is typically 1/16" between the end of the blades and the casing; this is what you are trying to match up with; if you miss it by very much, either way, there will be problems.

"...believing" should be"beveling."

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And in looking at the fans I bought, the case is pretty thin halfway between corners where the fan duct diameter nearly contacts the outside case dimension, so the margin for error is slim.

When drawing up the profile of this funnel piece, the I.D. of the 3/4" pipe mixing tube is .82". You said the maximum ratio of fan opening to mixing tube I.D. should be no greater than 3:1. So .82" x 3 is 2.46" which is 62mm, so I'm designing this funnel based on 60mm fans for a 3/4" burner because a little smaller is better than a bit too big.

And another question that I should have asked some time ago - what size forge would be appropriate for this 3/4" burner we're building? The typical 20 lb. propane tank type? Or would a 1/2" vortex burner be better fitted to the 20 lb. propane tank with 2" of kaowool and 1/2" of kastolite 30?

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It is only thin if the original aluminum fan plate is not cut oversize, which they all are. Leave an extra 1/2" of width and length on the flange area, and you will be well covered.

So, what happened with the wine funnel? it turns out that the Rabbit brand wine funnel has replaced the old one for good (especially for us) reason; they changed its open end, which was cut at an angle, to ninety degrees; this saves us so much work that I have ordered the new one from Amazon.com.

20 minutes ago, John in Oly, WA said:

When drawing up the profile of this funnel piece, the I.D. of the 3/4" pipe mixing tube is .82". You said the maximum ratio of fan opening to mixing tube I.D. should be no greater than 3:1. So .82" x 3 is 2.46" which is 62mm, so I'm designing this funnel based on 60mm fans for a 3/4" burner because a little smaller is better than a bit too big.

Fudge a little and go with 70mm; I do;) Yes, yes, I know...it ain't fair; ya got me.

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So, if the rule of thumb (3:1 maximum) is so important, why is Mikey fudging on it!?! Do we need to get out the tar and feathers?

Both your funnel design and the Rabbit wine funnel afford some leeway because both of them have lowered back pressure AT THE FAN/FUNNEL JOINT. Loads of people are going to end up using sausage stuffing tubes or kitchen funnels that have no change in their angles near their openings, and therefore no lowering of backpressure right next to the fan joint.

This brings up your earlier question about lengthening your funnel design; I don't think it needs it, because you chose to use the typical pipe reducer shape; that gives some parallel area near its large opening; this does more to lower backpressure where you don't want any, then a longer funnel section would. I think you are well covered.

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Ah! A good ol' fashioned tar and feathering. LOL I'll bring the tar. Do I need a pitchfork or torch?

But seriously, what do I know? I'm just asking questions as they come up. Looking forward to making some progress on this build this weekend. I think I have all the parts and pieces. We'll see how good I am at videoing the process. (roll eyes)

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Vortex burner safety

Any powered burner design can suffer a back-fire through the fan, if you block its flame path at the source (ex. allowing the burner to fall over on its flame nozzle during operation); these burners will do so; instantly and every last time! Secure the burner in position before running it. Place your burner opening sufficiently high above a casting furnace’s floor to keep it clear of any spilled metal in case of crucible failure. Place burner openings out of the direct path of heating materials in forges.

    It is necessary to initiate fuel gas flow first, and then ignite the fuel/air mixture from the burner’s forward end (in front of the flame nozzle), BEFORE STARTING THE FAN MOTOR on Vortex burners; these are a combination of natural induction and fan powered burner. Initiating the flame nozzle dynamics first will strengthen the establishment of mixture flow direction; greatly reducing the chance of reversing fuel gas flow from backpressure at the funnel/fan interface, once the fan is turned on. Fans installed on this burner series generate increased back pressure at the funnel opening because they are designed to create a swirl, rather than to create forward thrust. If the normal direction of mixture flow isn’t already established, some fuel gas can accumulate at the fan to funnel joint, instead of all the gas being pushed into the mixing tube.

Note: Fuel ignition follows starting the fan on standard forced-air burner designs, because the fuel in such systems can collect in the combustion area of heating equipment, leading to minor explosions, when it’s ignited; so the fan is started first with those burners, to reduce this possibility. But, on Vortex burners, the fuel-air mixture has no chance to collect in the combustion chamber with the burner lit, nor can starting a weak impeller fan blow out the burner’s flame.

    Close the gas feed, but keep the fan running during Vortex burner shutdown; then it is best to remove the burner from your forge or furnace if it is positioned facing downward. Furthermore, the burners fan should be left running, until your burner is completely cooled down and ready to be stored, even if it is removed from the heating equipment.

 Note: If you don’t already know it, “chimney effect” is caused by a reverse air flow in some heating equipment, once its burner is shut down. What happens is that, when a burner port is placed near the top of a horizontal gas forge, super-heated gases travel up and out of the burner port after shut down because of buoyancy, while cooler air enters into the forge or casting furnace through the exhaust opening to replace them; thus overheating any burner that can’t be completely sealed. Even if the burner could be sealed, delicate fan parts would get too hot to survive.

Caution: The larger the burner the greater the danger from backpressure against the fan, because of the increased air pressure needed to power the vortex. Therefore, blade to mixing tube diameters, funnel shapes, and fan strengths that are safe enough on small burners are not necessarily acceptable on larger burners. You need to keep this in mind when tempted to depart from construction recommendations, or when substituting parts. 

    Running a larger fan than recommended for a given mixing tube diameter (greater than a three to one ratio between blade diameter and inside diameter in the mixing tube) increases back pressure beyond acceptable levels, thus escalating the danger from ignoring the safety procedures given above. The smaller the burner the less sensitive it will be to funnel shape in creating back pressure through the fan. Therefore, the larger the burner the longer its funnel should be. Double curved shapes, such as found in high quality butt-weld pipe reducers (ex. schedule #10 stainless steel) also lowers backpressure at the fan/funnel interface, as do kitchen funnels that have a parallel section between the funnel’s angled section and its large opening (ex. the Aozita stainless steel spice funnel from Amazon.com).

Caution: Even when back pressure is kept to a safe maximum, some of the fuel/air mixture can escape at the funnel to fan interface if sealant, such as thread locker or gasket sealant, isn’t provided at this joint; it then will be drawn into the fan, to create a flashback hazard.

    Any burner can be snuffed out if it is placed in a vertical-down position, facing at a steep enough angle; what causes this is spent exhaust gases (which rise through buoyancy/displacement), and enter the burner’s air intake.

    It is safest to install Vortex burners in horizontal tube forges with the flame nozzle angling upward.

    Vortex burners used in any position other than the horizontal need ball-bearing axial fans. Motors with sleeve bearings are only meant to run in a horizontally placed burner, so that their bearings are positioned vertically; otherwise, their lubricating oil will seep out, letting the bearings run dry and seize up.

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I think after reading the last post from Mikey, I will live with my current Vortex burner minus the fan and plan on a ribbon burner for my next revision. Thanks for sharing that background Mikey. Opened my eyes to a scenario I had not considered

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Anytime safety procedures are openly discussed--without a fig leaf--the subject is going to sound scary. I consider myself to be in the information business; the good and the bad; pretty or ugly. I've seen a lot of people hurt by happy talk. The bill for obfuscation always comes due eventually. Whatever you choose, I want you to do it with your eyes wide open.

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The second video shows the burner's flame to be off angle, which weakens burner performance. The burner also sounds as weak as it looks. The pipe reducer it uses as an air scoop is too small, further weakening the burner. None of this prevents you from mounting it in a forge, while you work to improve it.

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I made some progress on the vortex burner build this weekend. I'm making one with the SST and one with the concentric reducer. Both are taking quite a bit of work to get the ends to fit the mixing tube and the fan. I think I need to put the aluminum spacer block (3 pieces of 1/2" stacked up between the fan and the SST)  for the SST build on a metal lathe to get a nice smooth transition. The concentric reducer will take some hot forging to get the larger opening to the right size for the fan.

At the same time, I'm going to print this on my 3D printer in wax and set it up to cast in aluminum. If I can get the dimensions dialed in, it should be a whole lot easier than the SST or the concentric reducer. Just bolt the fan on one end and the 3/4" pipe mixer tube on the other. Fit the gas inlet tube and away you go.

 

Funnel v4.jpg

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There is no doubt that 3D printing could do a fantastic job, as could conventional casting, and even lathe work. When I wrote my instructions it was plain that those who could pull off those techniques would also understand this. Basically, I write for beginners, whose dreams far exceed their reach :)

This doesn't mean that I and others here won't greatly enjoy seeing what you make with advanced methods.

So for the slow reply; there is something very nasty going around; took the wife and me down for three days.

That should have read "Sorry..."

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Sorry to hear you and your wife haven't been feeling well. Hope you're both on the quick road to recovery.

I'm just going through the processes of building and trying to find the easiest ways to do it. The SST and concentric reducer are showing their difficulties. The wine funnel with the newer perpendicular large opening cut may be the easiest way to go. Of course, if I bought a smaller diameter fan, I wouldn't have to enlarge the big opening on the concentric reducer to fit the fan I have. But sometimes I just get stuck trying to make something work, and in my determination to achieve a set goal, I stop thinking sideways.

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Actually, I think hot forging, or even cold hammering, on a stainless steel reducer fitting is well within the capabilities of even most newbies for up to 1/8"  increased diameter without complications; stainless steel is just as much work to cold work as mild steel, but less effort; it moves so much better.

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The Rabbit wine funnel

The Rabbit wine funnel finally came from Amazon.com today. I was right; it is an updated version of the old Metrokane wine funnel, with the one change that it has a standard opening, changing out the biased cut of its lip. This will force me to change sections of my 3/4" burner chapter; it has gone from a very good part option to a perfect part choice. I rarely get to feel so pleased with a new part. Also, the large opening is now 2-3/4" inside diameter; also just perfect for a 3/4" pipe Burner size :D

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The Aozita 18/8 Stainless Steel Spice Funnel

Is a cheap and serviceable funnel choice on 3/4" Vortex burners, which can be pushed into a 3/4" pipe, and has just enough of a flange to serve; it has a 1" wide parallel portion before the angle portion of the tunnel begins to help safety by keeping back pressure some distance away from the fan, to add to the thickness of the fan plate. The funnel's large opening is 3-5/8" diameter, which is too large for safety, but nothing prevents you from cutting a smaller hole in the fan plate.

But you will need to mount a fan with the most powerful motor you can find to keep all that ease and safety from weakening the burner's performance; nothing's for nothing :) 

 

And of course, the larger funnel only helps the performance of the burner for as long as you use it as a simple linear burner...for those who don't want to make the journey all the way to Vortex burner in on long go.

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The Aozitafunnel comes with a handle, as many kitchen funnels do; you don't want to cut it away. Your burner will end up with a length of copper fuel gas tube, some 12V wires, and a speed control, all of which will benefit from something to mount them to.

So there you have the Formula One path, and the jalopy path; which is better? That's a personal question; you must answer that one for yourself.

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Standard 1-3/8” diameter stainless steel (long) hip flask funnels have limited ease for mounting on small burners (1/4” or less); they are available through Amazon.com (refer to alternate sellers at the bottom of their page for better prices and shipping costs). Hip flasks have all the mechanical features, flanges, parallel sections, and exit tubes that make an SST very handy for use on larger burners; you can also find them for sale through eBay.  The limits of their utility comes not from any mechanical lack of features, but simply from the problems involved in working with small parts. The "long" in the part description refers to the parallel section between its flange and the beginning of the cone section on this part, which is twice as wide as the distance on a standard flask. This added distance between the cone's backpressure will end in a safer burner.

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Kitchen utensils, including funnels, come in either 18: 8 or 18: 10 series stainless steel; the second number denotes the amount of chromium present. The lower chromium content of 18: 8 is better for silver brazing, so choose the “cheaper” 18: 8 material whenever you can.

Cake decorating tips are the best general source for long funnel shapes on very small burners (all sizes up to 1/2”); they require brazing to coupling tubes, and to flat washers (as flanges) but are a superior shape to almost any other funnel source in these sizes, with the possible exception of the long cone side of Japanese style double jiggers, which only come in sizes for use on 3/8”, and 1/2” burners (see.

Cake decorating tips (AKA tubes) are elongated metal cones; stainless steel air funnels from this source come in several sizes according to their small openings; the smallest hole is a #0, at 5/32”; a #1 is 3/16”; a #2 is 1/4”; a #3 is 5/16”; a #4 is 3/8”; a #5 is 7/16”; a #6 is 1/2”; a #7 is 9/16”; a #8 is 5/8”; and #9 is 11/16”. Base diameters (large openings) vary according to small hole size; rims are minimal, complicating fit-up a bit, but decorating tips are able to exactly line up with a variety of desired burner sizes.

 

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The exact sizes of hip flask funnels can only be measured once a particular funnel comes, but in general, they are about 1-5/16" inside diameter in the large opening to 5/16" outside diameter on their small tubes.  Odbiouslythis is over the strongly recommended 3:1 difference.  What to do? nothing forces you to match its large opening with the fan mounting plate; that and the parallel portion of the funnel will protect any burner made with these flask funnels from over high back pressure.

The real limit for these parts is that they are only a practical part for 1/8" burners, but for this size, they save a lot of work. For other miniature burners, cake tips may be indicated.

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I've been lurking quite a while soaking up info.

My goal is to build a forge, using pretty much materials on hand. The burners I am working on are a bit of a couple ideas and principles... we will see what insisting on making my own mistakes (HAH! Like I'm the first!!) will produce. Scavenging and fabricating with basic stuff has been challenging, but fun.

Then I came to the flame nozzles...... Stainless is obviously the way to go...but there I am in short supply...My design is based on a 1/2" mixing tube. Searching recommendations - the step nozzle seemed the best way to go... but what to use??? I kept digging into corners, piles, parts... and then it hit me - well - fell on my foot honestly...I spilled an old box of spare sockets - doubles/triples, rusted, etc...I think it may work. For the 1/2" burner, the 13/16 fits nice to the pipe. So I cut the bottom off it, drilled it to set screw, and then used the same in an 1-1/16 to slide over it. This is giving me a strong 3/4" deep flare a 1/16" over 2x the dia. of the tube. I can adjust this length by a 1/4" or so - inside and outside. Let's assume everything else will be operating as it should, what guesses do we have that this will function up to snuff?  The only other issue - I hadn't seen much about I was questioning,  is the safety of this tool steel - they aren't plated -so I assume there's no issue - but would LOVE to be warned if I am wrong.

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To begin with, Burners 101 and Forges 101 are written with the expectation that you will go your own way; This is why there is so much written about the why of things, rather than just the how-to of things:)

How well will your flame nozzles work? Light them up and send us a photo.

 

BUT, you should know that the cost of stainless tubing parts from metalsonline.com depend on size; the larger the costlier the smaller the cheaper; a 1/2" burner will have cheap parts.

Stainless steel pipe is cheaper than stainless steel tube. Use a 1/2" schedual#40 pipe from your hardware store for the burner's mixing tube, a 3/4" pipe for the spacer tube, and you can then buy a 1" stainless steel pipe dirt cheap for the flame nozzle. All three parts will fit together with minor power sanding. You may decide to slit the spacer tube for convenient fit-up.

Furthermore, most of their supplies can be cut to size, saving a lot of money on both parts and shipping.

 

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I have been trying my best to keep constrained on building a jewel. This 1/2" burner - a pair actually, came to be because I just happened to have some bells and pipe I scored for free while cleaning a shed for a lady. I was going to do a 3/4, but would have had to buy those...They are a 1/4" undersized from ideal - but I think I have that figured... other than that I have committed to using only stuff I have on hand to build it. I DO have a considerable and eclectic pile of stuff to draw from.

So far, the ONLY parts I have invested cash into are the gas supply parts - valves, regulator, fittings, I have some old stuff, but this isn't a place to apply old propane hoses or fittings. 

I can't overstate how grateful I am to have found this forum. The knowledge, discussions, and just plain sharing here is a resource second to none. Thank you to all - even the "inquisitive idiots"- for expanding the discussion and access to such a wide range. 

I am putting together a picture package, I hope to post once things are coming more together. I haven't even gotten to the refractory parts yet. ... although I'm tempted to try the flame thing on video and picture shots... I really don't know yet....

That said for now, just because you don't see me here, doesn't mean I'm not following you..............that's not creepy is it??

 

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