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Burners 101


Mikey98118

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17 minutes ago, Mikey98118 said:

"...compared to fan impeller super chargers."

Nuts! Now we need to note that the kind of impeller screw used to create pressure is far different than "an impeller type blade" on a computer fan, before some guys go right off the rails:unsure:

Ayup you're catching my drift about talking super chargers with folk. I mean, heck a Champion 400 hand crank forge blower is by definition a "fan impeller super charger." Coal doesn't burn hot enough without an air blast and not many forges are built so the draft is strong enough to do the job so they have to be super charged. . . Blown.

I can't get very many people to believe a jet ejector or linear inducer isn't a venturi.

What do we want to call the parts and functions for the purposes of discussion? It just isn't possible to get picky about "proper" terms, we just need good working ones.

Frosty The Lucky.

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Heck, I've given up on proper terms, and have settled just for getting the point across half the time. I learned that lesson in my old age; within five years of publication my high speed tube burners had, by popular acclaim, become known as Mikey burners, and nothing I thought about it could sway public opinion; so I  bowed to the readers. Sometime after the next publication my Vortex burners will probably become Swirl burners or maybe Twirly burners  :P

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I so dub them Electrically turbulated twirly burners! :D I gave up, people want to call it a Frosty T? . . . Okay. Sort of a pitiful 15 minutes of fame though.

I've stopped really caring what the masses call things. I'd just like to discuss the things with you without having to define every other word over and over.

Lets see if I have a picture here. You're using a low output blower, fan, whatever, to enhance the vortex generated by the conservation of angular momentum as the air flow is constricted through a constriction in the pathway. (see water flowing down a drain) Close?

Frosty The Lucky.

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For a Vortex burner  I  use a low output axial computer fan, with impeller style blades to form a powered vortex at the entrance to a funnel, thus causing a much stronger  vortex  to be generated than any other kind of fan (even a powerful one) could provide.

If you look up these fans, the first thing you will notice is that they were designed for maximum cooling with minimum power use by flinging incoming air toward a chip's periphery, getting heated air flung away from the part while inducing a greater amount of incoming air than could be done by pushing the air directly at the part. You must understand that it is entirely because of blade geometry  that this is possible; such fans are designed to fling the incoming air toward the blade's outer tips.

So, when such a fan is mounted on a funnel entrance there is precious little forward motion and very high circular motion against the funnel wall. This is what I meant in stating That the fan is meant to power vortical flow--not forward flow. In fact, these blades have such a profound effect in promoting vortical flow that you can see a big increase in burner performance, even when the fan is still!. Of course airflow through a round constricted pathway will cause vortical flow without any other help... but when you power up a vortex, and send that through the constriction...we ain't talking formula anymore; we is talking nitro dragster.

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Got it. Are you using a plumbing bell reducer or have you made up something that'll work better? An impeller sometimes called a centrifugal impeller works by throwing the air/water from the center to the circumference. Directing the flow is usually done by the shape of the shell rather than the shape of the blades. The outlet on a hand crank forge blower for example. If anyone has noticed it doesn't matter which way you turn the crank they still deliver an impressive volume for the effort.

Now I have to try and remember where I put that last computer cooling fan or go bum one from my go to computer guru friend. It wouldn't have any application on the Ts of course but it really has me intrigued.

Cool beans. :)

Frosty The Lucky.

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For a ribbon burner propose use of a small squirrel cage fan in the entrance of a much smaller gentler constriction in order to provide better gas/air mixing, while allowing a very minor air push, for the purpose of allowing gas and air control to be fine tuned, because they are no longer completely tied together.

 

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On 10/8/2016 at 5:13 PM, WayneCoeArtistBlacksmith.c said:

Frosty, the fluxless weld is practical.  There is no flux to cause inclusions.  As a flux insurance some of the guys do dip the billet in kerosene to further aid in no oxygen to cause scale.  I think that the fluxless welds are also easier to do.

Sorry Wayne I didn't mean to ask you a question then ignore your answer. Mike got my attention and I was off and imagining. It's Mike's fault.

I've only done billet welds a couple times and have never noticed inclusions. That doesn't really mean a lot, not being a bladesmith I don't grind through layers so it'd be easy for small inclusions to slip past.

I've welded with a couple drops of 3 in 1 but haven't gone so far as to dip in kerosene. I don't worry about free oxy in my forge, I've tuned my Ts to burn a little rich so scale isn't an issue. I go so light on flux I almost weld fluxless as it is. I don't get flux squirting out between layers, not in a long time. UNLESS I'm welding something dirty or scaled up already that I can't sand or brush shiny.

I'm still messing with the NARB I'm making baffles right now but it's starting to get cold enough it takes a day for things to dry enough to do a preliminary heat cure. I'll see how she welds once I get her closed in.

Wouldn't it be a corker if I went to the expense and hassle of finding and applying a high alumina refractory only to discover it doesn't need to be flux resistant?

Frosty The Lucky.

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To answer your question about  what to mount the fan on for a Vortex burner; I prefer to use funnels, as they give often provide a longer distance for the constriction to work in; Length of the constriction is important because, creating a vortex just beyond the fan creates an outward push in the wall, which is surrounded by a partial vacuum. Such a setup invites the smallest pressure imbalance elsewhere to gack some of the mixture up into the fan--not good at all! I take a lot of care to design the safest equipment possible, before recommending it to the general public. A lot of decisions go into separating a proper design from the typical junk burner. That said, I started with bell reducers and they work just fine; but, old doc Frandenburner is always looking for that little something extra.

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Personally I like layers:

Gas forges: Burners--> blown -- ribbon

                                      -->  NA -- T ,  mikey  , ribbon

just an example, but I was wondering how  you guys browse and what makes sense to you. And yes Wayne please enlighten us.

Frosty , Mike, Wayne, Thank you for your guidance so far.

 

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So, if I truly like ribbon burners soooo much, why am I preparing  to trot out still another new  tube burner design? Let me state still once more that there ain't no such thing as the ultimate perfect burner. For instance all of the various pipe and tube burners have a huge igvantage over every ribbon burner; they are interchangeable, so that different sizes can be used in a single forge, to get a perfect match for various tasks; not to mention that older burners can be updated with newer burner models without rebuilding the forge. That said, I'm a big fan of ribbon burners, and an even bigger fan or free choice.

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Mikey, as to where to view the information on Ribbon Burners people can go to the Forge Supplies page at www.WayneCoeArtistBlacksmith.com and view the attachments there.  The first one, "Build a Gas Forge" is how I like to build a good, efficient, long lasting forge.  I wrote that tutorial back when I was still using venturi burners.  You can still build a forge using those plans and just adapt it to accept a Ribbon Burner.  The second attachment is titled "Ribbon Burner".  This first contains John Emmerling's raw data for the "Hammer's Blow" article from the Winter of 2006 issue, as well as a lot of additional information that I have gathered from forums and other places.  I am presently waiting for Frosty to get his information in final form.  When he forwards that to me I will then make an additional attachment for the NARB.  I hope that Frosty will also submit that to the "Hammer's Blow".  Maybe they will re-publish John's article and Frosty's article in a single issue.  That way all of the Ribbon Burner articles will be in that one place also.

39 minutes ago, Mikey98118 said:

about Ribbon Burner, see Mikey's post above for more.  "so that different sizes can be used in a single forge, to get a perfect match for various tasks..."

Maybe the Ribbon Burner will fill the space for "various tasks" because the Ribbon Burner can be controlled to match any heat and atmosphere needed.  Well, unless you wanted a hot spot and uneven heat.

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Introduction to Vortex Burners

(Taken from my book notes)

Hobbyists have constructed forced-air gas burners for decades; typically employing squirrel cage blowers. During R&D for a genera reference work on powered burners, I discovered the performance that can be gained from powering air swirl, instead of air push at a burner’s air intake, and had previously gained the experience needed to see what the difference changed to performance.

I promptly discarded prevailing views that the best purpose of a fan is to push more air through a burner; starting from such a premise, you’re not going to get very far. Why? Because the more forceful the output of a burner is the more its output must be turned down to keep the flame from being blown clear off the burners end, and snuffed out; pretty counter productive, wouldn’t you say? Of course, flame nozzles can be used to ease the problem, but stopping the prodlem at its source is even matter. 1Unfortunately, this idea pf pushing burner air is so entrenched that the other popular terms for powered burners are “forced-air, and fan-blown” Standard forced-air burners still have a place, but it isn’t on compact high efficiency heating equipment.

To begin with, let’s clarify just what is meant by the term vortex burner; technically it’s any burner that swirls the fuel/air mixture at some point; so technically, every stable fuel/air burner would qualify—even some Bunsen burners. Often, the term vortex burner is granted to those that swirl the flames they make. But, causing a flame to swirl happens way too late in the process to provide more than minimal benefits; applied this way the title is total hype.  

Forcing an air current directly at the funnel wall of a linear burner will create a weak vortical flow, but at the cost of also increasing air pressure at the passage source. The special fans on these burners are used to power up an otherwise passive vortex by creating lateral spin—not push at a funnel entrance; thus, all the energy is spent strengthening vortical flow down the funnel transit, which then reduces incoming air pressure, while speeding up mixture feed and spin rate, all the way through the burner to the flame nozzle, where pressure is reduced still further. Positive pressure in the gas/air mixture severely limits how much a flame can be strengthened, so deliberately powering up the vortex instead of creating air push results in much larger and faster flames than are attainable with a standard forced air burner.

Every part of a Vortex burner is designed either to enhance, or benefit from, the principles of vortical flow; so the name Vortex burner is utterly relevant—not just something that sounds impressive. 

Once you construct a burner that can produce a compact (nearly all combustion in the primary wave front) neutral flame from LPG fuels, it would seem that's the most you're ever going to get. So, if the safety cautions to follow make you nervous, why would you go on to build this kind of burner? 

The truth is that performance involves more than complete and compact combustion. Further improvements can still be, like: Much greater flame variance (turn-down range); more powerful flames from smaller burners; and the ability to simply change out flame nozzle diameters on a single burner, rather than switching between two or three separate burner sizes; all of these advantages are very much missing in all other fuel/air burners, including my own previous designs.

Vortex burners are quieter than other turbulent flame burners for the same reason that their flames are incredibly stable; because of more thorough air/fuel mixing. I believe they come as close to the silence of linear flames as turbulent flames can get. Vortex burner designs can be used for the same stable performance on the smallest burner you can construct.

In miniature burner sizes (1/4” and under), the available turn-down range from a perfect flame can be increased by more than an order of magnitude! When it comes to jumbo size burners (1-1/2” and larger) that extra flame stability happens to be very comforting; if you’ve ever run one of those monsters, than you know just how desirable a smoother flame is.

Note: flame noise is generated by flame variance from millisecond to millisecond during combustion; that variance is mostly the product of imperfect fuel/air mixing; improved mixing results in increased flame stability, and therefore in reduced flame noise.

It should be noted that, since this is the first text on Vortex burners, it can’t possibly be “the last word” on this subject; that will take several years and thousands of burner builds to establish, if. For instance, I’ve concluded that a 3:1 impeller blade to mixing tube diameter is the highest ratio that can be safely employed, but what is the best ratio; or, the best ratio for each burner size and fan power? What are the absolute best proportions on a cone shape? What motor and control refinements are optimums for each funnel size and shape? Such particulars can only be established with feedback from many people over several years.

Safety

It is a given that any type of properly constructed, fan-blown burner will always have a slightly greater risk of backfire than an equally properly constructed naturally aspirated burner does. If you want the increased overall heat output of a powered burner, some increased risk goes along with it. By understanding and applying the operating principles given here, you can greatly minimize that risk, in these burners only.

Vortex burners have important differences in proper safety practice from forced-air burners; this is due to their ultra-low mixing tube pressures, and must not be ignored, lest a fire ball from burn-back should exit through your fan motor; because of this difference, be sure to keep the area behind the fan clear; stand beside—not back of it.

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 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 induction and power burner, and initiating the flame nozzle dynamics first will strengthen the establishment of flow direction; greatly reducing the chance of reversing fuel gas flow from backpressure in the funnel after the fan is turned on. Fans installed on this burner series create some back pressure in the funnel opening, which can pick up fuel gas, if the normal direction of mixture flow is allowed to reverse.

Note: Fuel ignition follows starting the fan on standard forced-air burner designs, because 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 them, to prevent 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. Furthermore, the fan should be left running, until your burner is completely cooled down and ready to be stored.

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 safe on large burners. You need to keep this in mind when tempted to depart from construction recommendations, or in substituting parts. 

Running a larger fan than recommended for a given mixing tube diameter (greater than a three to one ratio) 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.

Backfire photo here

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/displcement), and enter the burner’s air intake.

To safely install Vortex burners in horizontal tube forges, they must, at the very least, be aimed with the flame nozzle angling somewhat upward. Never install a Vortex burner facing downward, as the plastic fan can too easily be overheated when the fan isn’t running.

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 its bearings are positioned vertically; otherwise their lubricating oil will seep out, letting the bearings run dry and seize up.

It isn’t legal anywhere in the U.S. to leave combustion equipment running unattended unless it is fully fitted out with an automatic fuel shut off system, which has first been inspected and approved by your local fire department.

Originally, flame safety systems were activated when a burner system’s pilot flame blew out. Pilot flame safety systems don’t work properly with Vortex burners, or with any high speed burner, because the burner’s main flame tends to blow out the pilot flame. An efficient induction or powered burner system requires, at the least, a flame rectification safety system if the operator isn’t going to be present at all times; see more information at: http://wardburner.com/burnersparts/rectifiedburners.html   

Caution: Even with a fully approved fuel shutoff system installed and inspected, I don’t recommend ever running any kind of heating equipment without an operator present at all times.  

A fully charged water hose, chemical fire extinguisher, and cell phone for emergency calls are absolute necessities; have them present and ready for use before attempting to do any kind of hot-work; including welding. A carbon monoxide monitor is also highly recommended. Further remarks on safety are made in appropriate book sections.

Warning: Always provide adequate powered ventilation when running heating equipment indoors. Improperly constructed and/or tuned burners can expel carbon monoxide. Even properly tuned burners still use up oxygen, while expelling carbon dioxide and nitrogen oxides into your work area.

Safety starts at the fuel cylinder, and what choices you make there. The only fuels you should be concerned with are propane and propylene; they are both LPG (liquid petroleum gas) fuels, and are both heavier than air. Propylene makes a lot hotter flame than propane and runs a little higher cylinder pressure at any given ambient temperature; therefore, propylene cylinders have a thicker wall than propane; outside of these differences, you’ll find that safety regulations are pretty similar for both fuels. If you follow the well published safety codes for propane, you’ll more than cover most requirements for propylene, but its higher flame temperatures will call for special flame nozzles when burners burning it are placed in equipment interiors; furnace walls may also have to be upgraded over what you’d normally choose for a refractory hot-face.

Never use an LPG cylinder out of positioned. You can end up drawing liquid fuel instead of gaseous fuel that way, causing a dangerous flare to occur in your burner. The pressure relief valve on your fuel cylinder, is set to release gas into the air if heat levels cause internal pressure to rise too high on hot days; if that valve is below the liquid fuel level, it will spew a large amount liquid into the air, instead of a small amount of compressed gas; that liquid immediately expands a minimum of 270 times in volume, creating a major ignition hazard.

Propane cylinders are required to have internal OPDs (over-fill protection devices), to prevent the cylinder from being filled to more than 80% capacity.  Furthermore, cylinders are required to be safety tested at least every ten years in most areas, and tanks are not allowed to be dinged, or rusted.

The fuel cylinder is to be physically separated from ignition sources; it must be stored and used outside of any building where you are doing hot work. If you are working outside the building, both fuel and oxygen cylinders are required to be placed a minimum of twenty-five feet away from your work, or any other ignition source (ex. electrical outlets). Most local codes also require the fuel cylinder to be set on a concrete pad above ground level (to protect it from rusting). It is recommended that the cylinder be in a locked but aerated enclosure (ex, heavy gauge wire cage). In nearly all areas oxygen and fuel cylinders are required to be physically separated from each other by a concrete wall or a minimum of twenty-five feet.

Note: torch carts on field sites are an exception to this rule. Using such a torch set-up in a shop actually violates safety codes in most places, in spite of its being common practice.

The department of transportation safety regulations forbid carrying a propane cylinder inside of a vehicle’s passenger area, or in a closed trunk; furthermore the cylinder must be securely fastened in an upright position during transport.

Never store or use propane gas cylinders larger than one pound (in other words, disposable canisters) inside of a dwelling (house, apartment, trailer, tent, etc.).

Never transport a cylinder by rolling it, or lift it by the valve. Never drop or bump a cylinder.

Before use, any propane heating system is supposed to be inspected by a certified professional for leaks; this is usually done by pressurizing the system, and using soapy water (dishwasher liquid (or some other cleaning product that contains laurel sulphate), and looking for bubbles, which indicate gas leaks. But “drop testing” can also be required; this consists of opening all valves except the final valve on the burner, and then closing the cylinder valve; while watching the regulator’s pressure gauge for a drop in pressure over a given time period.

When not in use, the fuel cylinder valve should be capped, to keep it clean, and clear of insects, spiders, etc. If the cylinder is attached to a piping system, a flexible hose section protected by braided stainless steel “armor” should be employed between the outdoor section of pipe and the cylinder, to prevent gnawing by mice, etc., which can be attracted by the smell from minor leaks, and from bottle changes.  

Propane is heavier than air, which means it can collect in low areas, gradually making its way to an ignition source, like an electrical outlet. If you smell propane, the proper procedure is to clear the area, shut off the valve on the outdoor fuel cylinder, and call your local fire department.

Regulators, fuel hoses, and fittings

 

We want be getting into regulators, fuel hoses, and fittings at this time.

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Principles and construction details

Vortex burners unite naturally aspirated linear burners with low voltage direct current impeller blade axial fans—never squirrel cage nor flat bladed fans—in order to achieve superior results from burners which, nevertheless, involve less work than my high speed jet-ejector burners to construct; you could think of these as linear burners of steroids.

Four aspects of vortical flow, which make it a dynamic “motor” for burners:

(1)  Fluid movement through a restriction (ex. a funnel) will create a vortex.

(2)  The forward motion (linear velocity) of a vortex tends to reach about one-half its rotational speed (angular velocity).

(3)  When a fluid (liquid, gas, or plasma) is forced to spiral down a circular reducing passage ( such as a funnel), rotational speed increases more the smaller the restriction gets, because, in a vortex, angular velocity (spin rate) increases the closer a spinning fluid is forced to its center of axis; the opposite result of spinning a solid. Thus forward motion is quite rapid at the funnel’s small opening.

(4)  BUT, fluid pressure drops at the same time; an ideal situation for fuel/air mixing, high feed rate and especially for maintaining a very low pressure feed into a burner’s mixing tube and flame nozzle.

So, if air pressure from an ordinary axial fan, or squirrel cage fan, will contribute to vortical flow, why insist on impeller blades? Direct air flow from ordinary fans has to be turned almost ninety degrees before it makes a positive contribution to air flow in a restricted shape like a funnel, losing a lot of its energy in the motion; impeller blades fling most of their air against the funnel wall almost parallel with it, contributing much more energy to vortical flow, without raising air pressure at all. In fact, since the air is first slung toward the tips of the blades a low pressure central area is created at the fan, forming a vortex right at the funnel opening, which only increases in power as travels down the funnel wall, instead of forming part way into the funnel.

Placing a pressurized gas stream just before the mixing tube entrance (near the funnel’s small end) creates even more mixture acceleration, while only minimally increasing flow pressure (Bernoulli’s principle); this synergistic “double motor” effect constitutes a peerless way to feed an air/fuel gas mixture into a gas burner’s mixing tube.

A vortex burner employs a modified cone or bell shape, on which an axial fan is mounted; because they are also gas-jet powered (induced), they will run in both powered and naturally aspirated modes, although not with as much output, without the fan running. But the unique difference in a vortex burner is that its fan features impeller type blades, which are designed to create air swirl, rather than push, so that they power up the vortical flow somewhat even without being spun.

It is all but impossible to establish a stable flame on your burner without swirling the air and fuel gas into a somewhat homogenous mixture, as they travel through the burner’s mixing tube.  Any burner providing a stream of gaseous fuel before the entrance to a cylindrical opening (the mixing tube) will induce air entrainment (via Bernoulli’s principle), a funnel behind the gas stream will also provide swirl to the air entering the mixing tube. All linear burners, unlike jet-ejector designs, need some type of constricting form mounted at the air entrance, to create air swirl for sufficient mingling of air and fuel gas.

Blowing air into a burner’s funnel entrance with a fan is hardly a new idea, yet doing so hasn’t done much to increase flame power in the past, because along with the increased gas/air mixture flow came an increase in mixture pressure. It is the partial vacuum (low pressure area) that allows ambient (surrounding) air pressure to push a flame back onto or even into a flame nozzle against the force of combustion, because increasing mixture pressure greatly   reduces how well a flame can sustain itself at the nozzle. In the past, air swirl’s importance to gas/air mixing was recognized, but the other principles of vortical flow were ignored.

Even when operating only in naturally aspirated mode (fan motor off), miniature vortex burner sizes put out powerful flames; this shouldn’t be a surprise as miniature burners (smaller than 3/8") of nearly all types tend to have an excess of potential, which usually must be tamed a bit. What is surprising is that hese miniature burners are also incredibly stable; even when pushed far beyond the limits of other types.

Note: 1/2" or larger vortex burners won’t surpass the heat range of high speed tube burners, until the fan is engaged.

So, if miniature burners already run quite hot, why power them in this way? The answer is, to increase total output, while increasing flame stability, because no burner’s input fuel and oxidizer can’t be used pass the absolute limit of what the difference in mixture pressure is to ambient air pressure.

Even when an impeller blade isn’t running, intake air passing by it will begin the swirling of air before it enters a funnel shape, which then increases air spin all the way down its length, resulting in a surprising escalation in flame stability.

With the fan running, mixture spin becomes so strong that an increase of the usual mixing tube length is needed, to sufficiently tame out swirl in the flame. The so called “nine diameters” rule of thumb for mixing tube diameter to length becomes the “fourteen diameters” rule on vortex burners.

While a flat blade tends to force air forward with some spin, an impeller blade tends to sling the air  outward against the funnel wall. You don’t get significant air spin from just any axial fan; its blades need to be highly curved and set at a steep angle, similar to impeller blades, rather than barely curved or flat blades set at a low angle, like box fan blades (the newer computer fans favor the impeller style blades; old models don’t, so buy new). 

You will normally run a Vortex burner’s fan at about half speed, but the excess flow provided by running the fan “all-out” can be combined with a second larger diameter flame nozzle; thereby allowing a greater increase in turn-down range. Total flame output is still primarily varied by controlling gas input pressure, while blade speed gives fine tuning of incoming air to match fuel pressure. Or to put things another way, by building two different nozzle sizes instead of one, you get the turn-down range of two different burner sizes available from a single burner, with perfect flame performance attained throughout both of their increased turn-down ranges; that’s because this burner style permits flame nozzle variance to work. With previous designs, nozzle diameter was strictly a function of the mixing tube’s diameter, and not to be varied by even a tenth of an inch.

People have previously found two different burner sizes to be a handy addition to casting furnaces and tube forges; 1/4” and 3/8” burners for equipment based on one-gallon steel shells; 3/8” and 1/2” burners on two-gallon shells; 1/2” and 3/4” burners for five-gallon shells, etc. Coffee-can casting furnaces and bean can forges did okay with 1/4” burners; this equipment size is too small to benefit much from two different burner sizes, but the much greater turn-down range of a 1/4” Vortex burner will more than cover any burner input desired in a coffee-can furnace or bean can forge, without two different flame nozzles. 

Note: The flame output of this burner series has nothing in common with old style forced-air burner systems previously used to build heating equipment; for all practical purposes; such systems can be described as employing the equipment’s interior to combust secondary flames, which usually amounts to far less efficient flame use; there are exceptions, such as chip forges, brazing stations, and pottery kilns, where colder dispersed flames can provide advantages over compact super-hot flames, but they are better served with ribbon burners.

To repeat; given correct gas and air inflow, flame nozzle diameter determines the limit of a burner’s maximum output, because a flame cannot be maintained at the nozzle beyond the limits of its ability to be anchored there by the nozzle’s low pressure area. The tendency of a flame to blow completely off its nozzle is balanced by the countering push provided by ambient air pressure (equally from all directions except the area of reduced pressure inside the nozzle opening; behind the flame); this forms a delicate balance; increasing any flame beyond the low pressure area’s ability to hold it on (or partially within) the flame nozzle will lead to complete destabilization.

Thus, greatly lowering mixture pressure into the flame nozzle becomes a vital factor, which allows vortex burners to put out more flame volume from the same nozzle diameters than all previous home-built burner designs. Superior mixing and a great increase in high speed/low pressure fuel/air feed also enables choices in nozzle diameters; something that other burners (including my own high speed tube burners) could never provide.

It is a well-established fact that burners without any nozzle at all can operate well enough if properly positioned (swirl effect) in forges and furnaces of a compatible size (too small an interior and the furnace or forge becomes a flame thrower; too large and a stable flame cannot be maintained). While this may seem to contradict previous statements, it is merely a case of “apples and oranges” because, sans nozzle, the furnace or forge interior becomes  the flame nozzle,                                                                                                                                                                                                                                            So, why bother with a flame nozzle’s balancing act when you can just stuff the burner’s mixing tube directly into most heating equipment? Well, some people do not bother. Let’s try a different question: Why drive a Ferrari when you can purchase a beat up old farm truck pretty cheap? A complete burner, flame nozzle included, gives you full flame control, so that the heating equipment it’s placed in only refines the flame still further.

The smaller your equipment the more important flame control becomes (keeping the flame burning inside the forge or furnace instead of overheating your work space). But, the larger your equipment the more full flame control saves in fuel costs, because complete combustion within a few inches of the flame’s entrance port means better heat transfer before its spent gases exit through the equipment’s exhaust opening.

Heat savings are dependent on your ability to seal burner entrances against infiltration of ambient air, which were only ever needed to combust the large secondary flames of outdated burner designs. But why should even such a secondary air source on old burner be allowed to continue to blow excess air into the equipment? Unintentional induction of ambient air via the turbulence that forms behind a high speed flame is a well-documented source of excess air entrainment. The whole heating system becomes more efficient; about 20% hotter than with an unsealed burner port.

So, do we finally have the perfect burner? NO; there is no such thing. These burners are going to be quite superior in casting furnaces, vertical knife forges, brazing stations, and smaller kilns where “chimney effects” help cool them, but can’t be safely employed in standard horizontal gas forges, where burners face downward, so that chimney effects could rapidly destroy their fans after shutdown; they should therefore only be installed in casting furnaces and redesigned horizontal forges (with burners angled upward against a solid refractory hot-face section, and in oval forges where the area of impingement is further from incoming flame).

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 displacement by thot air by incoming cool air,; overheating any burner that can’t be sealed. Even if the burner could be sealed, delicate fan parts would get too hot to survive.

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Burner Funnels

(excerpts)

Why recommend thin sheet metal funnels? The first LPG hobby burners employed bell shaped concentric steel (butt-weld) pipe reducer fittings as air scoops on the end of black water pipe mixing tubes; these gave fairly good flow dynamics and were easy to mount for people who could weld, but they’ve become expensive since the nineties.

As linear burners gained popularity in the nineties , threaded bell reducers became prevalent with hobbyists who didn’t weld, and didn’t want to spend much money; unfortunately they don’t share the superior flow characteristics of butt-weld reducer fittings, and available choices of their in-stock sizes are constantly being reduced, as steel water pipe continues to be marginalized by copper and plastic pipe; worst of all are imported parts with thread that leave parts utterly misaligned, so that they really can be “as crooked as a dog’s hind leg.” Thus, the funnel choices employed on this burner series; but this isn’t meant to preclude reducer use. You will be given generous construction choices throughout this book.

The easiest way to build a Vortex burner is to employ a stainless steel sausage stuffing tube (SST) as your basic construction unit, and then mechanically affix all the other burner’s parts to it.

Photo here

Stuffing tubes come already provided with flanges on their own bell housings or  funnel  shapes; this eliminates any need for fit-up and silver brazing of funnels to fans and mixing tubes. Canning jar funnels and schedule #10 stainless steel pipe reducers can also be affixed with screws to mixing tubes, but aren’t so easy to fasten a fan mounting plate to.

The extra wide (1/4” to 1/2”) rims at the open ends of SST bell, short. And long funnels are called flanges; these are normally used to help trap the SST effectively on sausage grinding machines. For your purposes, flanges promote easy mounting of both an axial fan’s to an aluminum mounting plate (with an internal  gas tube) onto the funnel base’s mouth (large open end); eliminating the need to construct a clamping ring to provide a base on which to attach a fan mounting plate, and allowing attachment of a gas tube that doesn’t penetrate the funnel wall. The SST also provides easy attachment to the burner's mixing tube.

The most efficient and safest base shape is a long cone; short funnels and shallow bell  shapes are less efficient, and given to greater problems from creating back pressure near the fan.

Fan width compared to mixing tube diameter is another central consideration; it is best to avoid a fan more than three times the mixing tube’s inside diameter, although thick motor mounting plates can help bridge the gap between an ideal design and available parts.

inside dimensions for some tubes are given, but there can still be variance (these aren’t precision parts, after all). Waiting for your SST to arrive, and measuring it with a cheap digital caliper before ordering other parts can save a lot of fit-up problems later on: http://www.vxb.com/page/bearings/PROD/Kit7426

Also available from Harbor Freight Tools: http://www.harborfreight.com/catalogsearch/result?q=digital+calipers+Search+Keywords+or+Item+%23   

Flange diameter widths for SSTs vary according to the sausage grinder they mount on. You must keep in mind that given sizes are for the outside diameter (at the flange edges; the size of the funnel opening), which will be between 1/4” and a 1/2” larger in accordance with flange width: knowing this helps you to match up base opening sizes more closely to mixing tube diameters on the burners when they are given in product sales literature. Fortunately going under a 3:1 fan blade to mixing tube ratio will cause no problems. You don’t have to use a caliper to check your parts, but it is the easy way.

 

If you can’t find cone shaped sausage stuffing tubes from other on-line dealers, you can order most of them direct from LEM Products.com. They keep their full line of TIG welded (stronger than silver brazed) cone based stuffing tubes in stock: http://www.lemproducts.com/category/333

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Axial DC fans and speed controllers

These burners are unusually forgiving about details like flame nozzle size, but one of the things you must consider "written in stone" is that fan blade diameter is not to exceed a three to one ratio with the inside diameter to the mixing tube, for safety’s sake. So, you have to match up dimensions of the parts you can buy with this limit in mind. In example, a 75mm fan is the optimum size on a typical 3/4” burner, but good luck finding one at a decent price; so you’ll settle for a 70mm fan, which is an easy size to find; it equals 2.76" outside dimensions. The fan opening is a few thousandths smaller, and the blade is smaller still. The inside dimensions of 3/4" pipe are actually 7/8". You can use a mixing tube with an I.D. anywhere from 7/8" to 1". You need to order your fan in a size that matches with, or is just smaller than, a burner funnel’s large opening; it must not be larger. Most of the swirling action from these fans is generated near their blade tips, so having the blade oversize to the funnel opening is self-defeating; worse, it will cause major back pressure. So you will lose power in two different ways, one of which trades lost power for increased risk. Therefore, wait until the funnel arrives and measure its opening before ordering the fan, then wait till the fan arrives and measure it before creating the center hole in the fan’s mounting plate.

The amount of space between the fan blades and the fan body’s opening varies. All you can do is order the fan size as near to the funnel opening, without exceeding it, as you can, and may well end up with actual fan blade diameter as much as 1/4” smaller than the funnel opening.

Note: Most of these fans are exactly the size they are advertised as, but not all of them are. You are re-purposing parts that were originally manufactured for different tasks. Equipment manufacturers aren’t thinking about your expectations, but those of the computer owners they normally sell to. So, do nothing with the mounting plate until your fan arrives, and its opening can be measured exactly.

The fans for this burner series are axial DC computer cooling fans (technically known as tubeaxial fans); they can be run off small batteries in the field, or from standard low cost wall-warts in the studio (AC to DC converters that plug into 120V AC electrical outlets and are preset to limit voltage/amperage output); the fans recommended in each burner construction chapter provide more than sufficient air to run those burners. You don’t have to match the outlet exactly to the fan rating, so long as the electrical source is greater than the rated fan draw, but not ridiculously larger; two or three times the rated draw is about as overpowered a power source as is prudent.

A tubeaxial CPU fan moves air parallel to the axis of rotation; such fans are better suited for high flow applications, with low air resistance.

All types of centrifugal fans (including squirrel cage) move air perpendicular (at a right angle) to their axis of rotation. Squirrel cage fans—all other factors being equal—should be better suited than axial fans for mounting on burner funnels, which automatically produce considerable resistance to airflow.

But, all other factors are far from equal, because these particular axial fans produce heavy swirling of their output air before it even starts its journey down a funnel, contributing significantly toward forming a strong vortex, which results in greatly increased flame output and stability. At the same time, they only produce enough air pressure to overcome resistance from the funnel’s constriction; not enough to raise mixture pressure in the mixing tube, where, ideally, you want fast flow and low pressure.

Axial fans also offer the simplest solutions for mounting on funnels. A squirrel cage fan must be specially mounted on the burner funnel (with considerable added difficulty) to produce any swirl effect in its air output, and that still won’t be done with the evenness of an axial fan’s output.

Sleeve bearing fans sell for less than ball bearing fans, but ball bearing fans last about 30% longer, can take more heat, and be mounted in any position. Sleeve bearing fans must be oriented vertically; meaning that your burner should only be mounted in a horizontal position; otherwise, their lubricating oil leaks out over time, leaving bearing surfaces dry.

Blade design of the fan is critical. New computer fans feature impeller style blades, which produce a lot of air swirl; old blade designs (regular box fan blades) don’t. The swirl of a CPU axial fan’s output is the most important performance factor in these burners, because everything magical about their performance springs from it.

Avoid double thick axial fans. You will find some axial fans that appear as though two fans were glued and wired together; such fans are precisely that, but their double set of blades run in opposite directions. If you look at their high wattage and CFM ratings, it’s obvious that these fans are designed as blowers. Remember what you read earlier about squirrel cage fans being exactly wrong for these burners? These fans might as well be squirrel cage, because their output is just like that of squirrel cage fans—near to useless for a vortex burner.

At times you’ll be looking at a single fan with a double thick body; the purpose of that body is to house support ribs in the shape of a second, and opposite facing set of blades, which turn an impeller’s swirling output into a straight force of air; thus undoing all of the swirling goodness accomplished by impeller style fan blades.

Finally, you don’t want high CFM output in the first place; you want low added force and high swirl at the funnel entrance, to avoid high mixing tube pressure. So, you should avoid extra high CFM rated fans in any case.

Note: the single exception to avoiding high-output axial fans would be when you mount a smaller fan on a larger funnel in order to preserve a 3:1 (or less) fan to mixing tube diameter ratio; at that point extra fan power may be needed to overcome too much weakening of the air stream as it spreads into an oversize funnel area. If the disproportion isn’t too great, full fan speed may take care of the problem; otherwise a stronger fan must be employed.

Low priced metal grills are available for all axial fan sizes. If you live someplace with a lot of bugs, a grill and even a pre-filter is preferable to bug parts being flung into your burner’s flame. Usually, eBay has the most reasonable prices on axial fans, grills, and screens, along with the best shipping rates; you should check there before buying from some other online source:

Axial DC fans and speed controllers

These burners are unusually forgiving about details like flame nozzle size, but one of the things you must consider "written in stone" is that fan blade diameter is not to exceed a three to one ratio with the inside diameter to the mixing tube, for safety’s sake. So, you have to match up dimensions of the parts you can buy with this limit in mind. In example, a 75mm fan is the optimum size on a typical 3/4” burner, but good luck finding one at a decent price; so you’ll settle for a 70mm fan, which is an easy size to find; it equals 2.76" outside dimensions. The fan opening is a few thousandths smaller, and the blade is smaller still. The inside dimensions of 3/4" pipe are actually 7/8". You can use a mixing tube with an I.D. anywhere from 7/8" to 1". You need to order your fan in a size that matches with, or is just smaller than, a burner funnel’s large opening; it must not be larger. Most of the swirling action from these fans is generated near their blade tips, so having the blade oversize to the funnel opening is self-defeating; worse, it will cause major back pressure. So you will lose power in two different ways, one of which trades lost power for increased risk. Therefore, wait until the funnel arrives and measure its opening before ordering the fan, then wait till the fan arrives and measure it before creating the center hole in the fan’s mounting plate.

The amount of space between the fan blades and the fan body’s opening varies. All you can do is order the fan size as near to the funnel opening, without exceeding it, as you can, and may well end up with actual fan blade diameter as much as 1/4” smaller than the funnel opening.

Note: Most of these fans are exactly the size they are advertised as, but not all of them are. You are re-purposing parts that were originally manufactured for different tasks. Equipment manufacturers aren’t thinking about your expectations, but those of the computer owners they normally sell to. So, do nothing with the mounting plate until your fan arrives, and its opening can be measured exactly.

The fans for this burner series are axial DC computer cooling fans (technically known as tubeaxial fans); they can be run off small batteries in the field, or from standard low cost wall-warts in the studio (AC to DC converters that plug into 120V AC electrical outlets and are preset to limit voltage/amperage output); the fans recommended in each burner construction chapter provide more than sufficient air to run those burners. You don’t have to match the outlet exactly to the fan rating, so long as the electrical source is greater than the rated fan draw, but not ridiculously larger; two or three times the rated draw is about as overpowered a power source as is prudent.

A tubeaxial CPU fan moves air parallel to the axis of rotation; such fans are better suited for high flow applications, with low air resistance.

All types of centrifugal fans (including squirrel cage) move air perpendicular (at a right angle) to their axis of rotation. Squirrel cage fans—all other factors being equal—should be better suited than axial fans for mounting on burner funnels, which automatically produce considerable resistance to airflow.

But, all other factors are far from equal, because these particular axial fans produce heavy swirling of their output air before it even starts its journey down a funnel, contributing significantly toward forming a strong vortex, which results in greatly increased flame output and stability. At the same time, they only produce enough air pressure to overcome resistance from the funnel’s constriction; not enough to raise mixture pressure in the mixing tube, where, ideally, you want fast flow and low pressure.

Axial fans also offer the simplest solutions for mounting on funnels. A squirrel cage fan must be specially mounted on the burner funnel (with considerable added difficulty) to produce any swirl effect in its air output, and that still won’t be done with the evenness of an axial fan’s output.

Sleeve bearing fans sell for less than ball bearing fans, but ball bearing fans last about 30% longer, can take more heat, and be mounted in any position. Sleeve bearing fans must be oriented vertically; meaning that your burner should only be mounted in a horizontal position; otherwise, their lubricating oil leaks out over time, leaving bearing surfaces dry.

Blade design of the fan is critical. New computer fans feature impeller style blades, which produce a lot of air swirl; old blade designs (regular box fan blades) don’t. The swirl of a CPU axial fan’s output is the most important performance factor in these burners, because everything magical about their perfomance springs from it.

Avoid double thick axial fans. You will find some axial fans that appear as though two fans were glued and wired together; such fans are precisely that, but their double set of blades run in opposite directions. If you look at their high wattage and CFM ratings, it’s obvious that these fans are designed as blowers. Remember what you read earlier about squirrel cage fans being exactly wrong for these burners? These fans might as well be squirrel cage, because their output is just like that of squirrel cage fans—near to useless.

At times you’ll be looking at a single fan with a double thick body; the purpose of that body is to house support ribs in the shape of a second, and opposite facing set of blades, which turn an impeller’s swirling output into a straight force of air; thus undoing all of the good accomplished by impeller style fan blades.

Finally, you don’t want high CFM output in the first place; you want low added force and high swirl at the funnel entrance, to avoid high mixing tube pressure. So, you should avoid extra high CFM rated fans in any case.

Note: the single exception to avoiding high-output axial fans would be when you mount a smaller fan on a larger funnel in order to preserve a 3:1 (or less) fan to mixing tube diameter ratio; at that point extra fan power may be needed to overcome too much weakening of the air stream as it spreads into an oversize funnel area. If the disproportion isn’t too great, full fan speed may take care of the problem; otherwise a stronger fan must be employed.

Low priced metal grills are available for all axial fan sizes. If you live someplace with a lot of bugs, a grill and even a pre-filter is preferable to bug parts being flung into your burner’s flame. Usually, eBay has the most reasonable prices on axial fans, grills, and screens, along with the best shipping rates; you should check there before buying from some other online source:

eBay 12V DC axial fans: http://www.ebay.com/sch/i.html?_odkw=DC+axial+fans&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.X12V+axial+fans&_nkw=12V+axial+fans&_sacat=0  

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When I started R&D on Vortex burners, I used 12V DC axial fans, run off of 9V batteries with great success. Sometimes, easy success can get in the way of progress. After a while, I ordered a six watt controller, and found out that it gave a much better control of fan speed than I'd ever have believed possible. When you have tight control of fan speed, you can fine tune the intake air to precisely match up with the burner flame's turn down range, which the gas regulator and needle valve control.

To sum up; do you need a speed controller? Heck no. But, do you want a speed controller? Oh yes; very much. These are linear burners; without air chokes like jet-ejector burners; nor can they be baffled, like squirrel cage blowers. Your only control of intake air is by fan speed. These are PWM controls; they work by pulse width modulation; not by creating resistance, so they create a lot less waste heat, and use very little energy.

Note: The higher a fan’s top rated voltage the more speed variance it can provide. Thus a 12V fan has a much longer range of speed variance than a 3V or 5V fan. On the other hand, a 24V fan has far greater speed variance than a 12V fan. Generally, 12V fans and speed controllers are less expensive than 24V systems; there is also a much greater selection among 12V than 24V fans.

Note: Fans are pretty much self-cooling, but speed controllers are not. It is better not to place a speed controller in a case, unless it needs physical protection. I usually leave the controller exposed to ambient air, and ideally, mounted to an aluminum plate for better heat dissipation.

6W (six watt) 5 to 12 volt speed controllers connected between axial fans and incoming power are an excellent and economical method of changing input air to closely match variance in fuel flow. 

Note: Obviously, the closer a fan’s rated output is to an ideal amount for any given burner size, the less stress need be applied to its motor through electronic speed control.

Wattage equals voltage times amperage. Six watts on a twelve volt device permits up to a half amp draw, which should be enough for most DC axial computer fans.

Eight watts on a twelve volt device can handle up to a 0.67amp draw, which should be more than enough for any 12V DC axial fan you’re likely to employ:

Universal AC to DC adapter switching power supply 1.7amp draw: http://www.parts-express.com/universal-ac-to-dc-adapter-switching-power-supply-1700ma--120-150  

Since lower voltage permits greater amperage within your wattage limits, 3V or 5V fans might seem to have an advantage over 12V fans, but it just isn’t so. 12V fans have greater speed variance than fans with lower voltages; so only buy 3V and 5V models when you can’t find the small size fan you want in 12V.

Caution: Be sure to get the wiring polarity right on incoming power, or you may "cook" the controller. Reversing polarity on the fan motor simply doesn't permit it to run (but doesn't hurt it), so, temporarily hook the fan up to the wall wart or battery, WITHOUT THE CONTROLLER IN THE CIRCUIT, to make sure you understand which wire is positive and which is negative, before including the controller in the circuit.

If you run the fan from a portable battery, it is a good idea to include a fuse in the circuit to protect your motor and controller from exposure to too much amperage. If you live in an area with power surges, it is a good idea to protect the motor and controller with a fuse, even if you’re using a wall wart.

Universal DC Adapter Power Supply for 3, 5, and 9V fans: http://www.parts-express.com/velleman-compact-universal-dc-adapter-power-supply--320-140?utm_source=google&utm_medium=cpc&utm_campaign=A_Cats_BP&utm_group=ac-dc-power-adapters_1463_BP

12 VDC 500ma wall transformer: http://www.parts-express.com/12-vdc-500ma-ac-adapter--120-045

You can find low cost fan speed controllers on Amazon.com, and sometimes, on eBay: This is my favorite speed controller: http://www.amazon.com/Unique-Goods-Controller-1803BK-Adjustable/dp/B00QGMESHM/ref=pd_sim_sbs_23_4?ie=UTF8&refRID=1N5MKZ953JC5BDCCABEQ

This is a more expensive but still acceptable speed controller: http://www.amazon.com/VicTec-Motor-Speed-Control-Controller/dp/B00K4W4FQO/ref=sr_1_1?ie=UTF8&qid=1438360662&sr=8-1&keywords=12v+dc+speed+controller  

http://www.xoxide.com/fanmate.html This source has good pricing and reasonable shipping charges; the device is excellent.

Fan Mate speed controller: http://www.amazon.com/Zalman-Fan-Speed-Controller-FANMATE-2/dp/B000292DO0/ref=sr_1_1?s=electronics&ie=UTF8&qid=1438369768&sr=1-1&keywords=fan+mate+2

Fan Mate in the UK: http://www.amazon.co.uk/Zalman-Controller-Adjusting-Speed-Single/dp/B000292DO0/ref=pd_bxgy_ce_img_y  

An alternative 8 watt UK choice: http://www.amazon.co.uk/Computer-CPU-Cooling-Speed-Controller/dp/B007PODS0I

AC adapters for UK voltage (230V): http://www.amazon.co.uk/Power-Supplies-AC-Adapter-Components/s?ie=UTF8&page=1&rh=n%3A430514031%2Cp_n_feature_keywords_browse-bin%3A1033175031    

Computer fans (AKA CPU fans) blow one way; that is typically toward the face with the ribs connecting the motor and fan blades to the fan body.

Fans come with a minimum of two wires, and up to four wires. The black wire is power input (negative -); in this case 12V, 24V, 5V, etc. The red wire is ground (positive +), because DC power runs from the negative connection, through the controls and fan, to the ground, or return to power source. Test to make sure you have the wires connected to a power source (battery or wall wart) correctly before making permanent connections by touching the power source wires or battery poles and fan wires together. If your connections are backward the fan simply won’t run; reverse those wires and the fan will run.

BUT, be sure to get the wiring polarity right, or you may "cook" the controller. Reversing wires polarity on the fan motor simply doesn't permit it to run (but doesn't hurt it), so, temporarily hook the fan up to the wall wart or a battery, WITHOUT THE CONTROLLER IN THE CIRCUIT, to make sure you understand which wire is positive and which is negative, before including the controller into the circuit.

Three pin (AKA three wire) fans carry the current through the red and black wires, and the third (usually yellow or white) wire is meant to connect to a tachometer through a computer motherboard. Isolate (block), or cut off the third wire; you have no use for it.

The boxy looking plastic cases that most fan wires come connected to are called Molex connectors. There are three pin to two and pin connectors that effectively reduce the amount of wiring you must deal with, by simply blocking off the third (tachometer) wire from any activity.

Four pin (AKA four wire) fans carry the current through the red and black wires, have a white or yellow tachometer wire, and the fourth (usually blue or green) wire is meant to connect to the motherboard to provide speed control on command from the computer software.

 NEVER CUT OFF THE MOLEX CONNECTOR BEFORE YOU EXAMINE IT TO MAKE SURE WHAT WIRES GO WHERE!!!

Color coding of fan wires doesn’t change, but occasionally the manufacturer messes up the wiring colors; to make sure the colors are correct, look at the key side of their connector (opposite side to where the wires are connected) with this empty side of the connector facing you, the far left opening (pin) is negative power supply; the second to left is the positive ground; and the third from left is the tachometer connection.

The Fourth pin from the left in a four wire fan is pulse width modulation (PWM), or speed control, and the incoming wire should be blue. You are not connecting the fan to a computer motherboard, so a four pin fan will always run at maximum, no matter what you try to do with it; don’t buy a four wire fan.

Speed controllers typically have four places to insert wiring; two places beside each other marked negative (black lead) and positive (red lead) power (for wires running from the power source), and two places beside each other marked negative and positive motor (for wires running to the fan).  There is no place on them for third and fourth fan wires; those are useless without a motherboard. The third (tachometer) wire is meant to feed information to the motherboard, and so can be isolated (blocked off) without harm. But, the fourth wire comes off an internal transistor, and so, without a motherboard to feed it information to it, will keep the fan running at full speed, despite the fan being hooked up to a speed controller.

Employing fan mounting plates

Both axial motor and fuel gas tube must be mounted to the burner funnel—parallel and centered—one way or another. While the gas tube could be connected through the funnel wall, it is best mounted to a part that can be unscrewed with little bother (for occasional cleaning and re-alignment of its gas jet). Also, fan and funnel mouth sizes may not match up well enough to work on their own.

The best way around all of these problems is employment of a fan mounting plate; you could also call it an adapter plate, as some do. Your fan can be screwed onto the forward side of a 1/4” to 3/8” thick aluminum, brass, or mild steel plate, which is attached to the funnel with screws that are threaded into it through larger holes, if the flange is wide enough to accept screw holes.

Note: Aluminum plate is expensive, but aluminum flat bar (even cut to length) is not: http://www.onlinemetals.com/merchant.cfm?id=997&step=2&top_cat=60

The main points to using thinner mounting plate are ease of cutting for people using jeweler or jig saws, and ease of acquisition for people buying from scrapyards. If you have machine shop equipment and order aluminum flat bar online, thicker is better. If you use thicker plate, you can also use larger refrigeration tube, with more choices in just how to create your gas jet, etc.; not to mention that beveling of the fan hole (to help adjust for sizing problems) becomes easier.

A square instead of round mounting plate is also simply a matter of convenience, most axial fans have square bodies. If your fan has a round body, go right ahead and use a round mounting plate; or, if there is sufficient room to mount a square fan on a round plate, you can use a lathe to turn both inner and outer plate edges; it’s just a matter of personal preference.

Photo here

The mounting plate can be trapped against a narrow funnel rim with a mounting ring, or fitted within the funnel mouth and secured with screws penetrating into it through the funnel wall.

If you mount the plate within your funnel, first screw it to a larger wooden plate, to prevent it from moving away from true right angles to the funnel opening during drilling threading and screwing.

Note: metal mounting plates are recommended in case of a burner fire. After all, you don’t want the gas tube falling away from the burner and further spreading flame in places it does not belong. Of course, plywood or plastic sheet would call for much less expense, and work to make a fan and gas tube mounting plate from; if you do so, the gas tube m-u-s-t also be silver brazed to the burner funnel, or attached to it with an exterior clamp, for safety; no exceptions.

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Seamless Copper Tube, Bright Annealed (ASTM B 68)

AKA annealed copper refrigeration tube is designed to easily bend without collapsing; it comes in several sizes.

0.250” (1/4”) outside diameter, with 0.190" inside diameter; this is large enough to contain a MIG tip gas jet, once the thread is filed off

Refrigeration tubing in sizes from 1/8” to 5/16” are common enough to be found in most large hardware stores, along with compression fittings to match them. But the smaller of those sizes listed above (below 1/8”) are only found through HVAC supply dealers, locally or online: http://www.ebay.com/itm/071-081-093-125-1-8-Diameter-Copper-Capillary-Tube-Tubing-10-/390484140451?pt=LH_DefaultDomain_0&var=&hash=item99b0bac8b5  

You can purchase refrigeration tubing at most hardware stores by the foot, cut it down to 4”, and solder or braze a hose barb on its other end for insertion in small diameter fuel hose. There is nothing to stop you from silver brazing the tubing into a 1/8” brass (plug) pipe fitting or hose barb. You may choose to employ a brass compression fitting, instead.

Your local safety codes may call for either compression or flared fittings on fuel gas lines; if they favor flared fittings, I’d suggest silver brazing a hose barb or pipe thread fitting on, instead.

Flared fittings are, theoretically, stronger than compression fittings; for certified plumbers with industrial quality flaring tools, this generally holds true. For hobbyists with cheap imported flaring tools and total ignorance of how to properly form and lap (polish) flare fittings, attempting to produce a joint, which will remain gas tight is a poor gamble. In many municipalities, local building codes only permit flared fittings (water or gas) to be done by a licensed and certified plumber, for this very reason.

Compression fittings can also leak, if over or under tightened. Use the nut to snug the brass ferrule against the refrigeration tubing until it crushes the copper tightly around the heavy wall S.S. capillary tube (gas jet) forming a seal, all the while pressure testing for leaks, and only tightening until leakage ends (a shampoo containing laurel sulfate, mixed in water and brushed over gas joints, will produce bubbles from gas leaks).

Caution: Afterward, compression fittings can work loose and start leaking if subjected to sufficient physical stress, so if you choose to use them, handle your burner gently.

Mount the fan centered over the mounting plate’s center hole (which matches the motor’s blade diameter) with four screws. Make very sure that the mount’s hole doesn’t exceed the fan housing’s inside diameter.

Funnels with narrow flanges don’t provide sufficient space to screw a motor mounting plate directly to the funnel; in such case, use four screws placed through a flat “mounting ring” trapped on the funnel rim’s forward side (facing the funnel to mixing tube joint), to trap the rim of your chosen funnel against the mounting plate; another four screws slide through four holes in the plastic axial fan’s body; affixing it to the mounting plate.

Photos here

Note: the fan must be reasonably sealed against the fan mounting plate; otherwise escaping air from around the fan body will cause such strong turbulence as to disrupt forward vortical flow.

In order to stop air from being blown back around the outside walls of a slightly oversized center hole in the mounting plate (instead of being forced down the inside of your funnel and into the mixing tube), use aluminum putty to build up the failed surface and sand it down again.

Photo of motor mounting plate, gas tube, and drilled centering rod here

Installing a copper gas tube into the mounting plate, or onto its underside (facing away from the motor) provides a convenient opportunity to avoid silver brazing copper tube onto a stainless steel funnel; if the funnel can also be mechanically pinned onto the mixing tube (or screwed onto an SST’s rim), 56% silver filler alloy and S.S. rated flux doesn’t need to be purchased at all.

In addition, a plate mounted gas tube also promotes brazing of the funnel directly to the mixing tube or a coupling collar, when so desired, because only one joint needs to be dealt with. Brazing more than one place on a given part can be a tricky process for novices.

Copper, mild steel, and brass can all easily be silver brazed together without employing the more expensive 56% silver content filler alloys and S.S. rated flux needed for stainless steel brazing. Use of wood or plastic for the mounting plate should be avoided for safety’s sake.

Attaching the gas tube this way also permits employment of a simple drilled rod (see further on) to aid in centering the gas jet; no small advantage in itself. The gas tube should be run directly under the motor strut which has the the wire harness, so as to reduce interference with the fan’s output to a minimum.

Before installation of a thin plate and gas tube, a trough must be ground through the funnel rim, and a recess must be ground into the funnel wall below it to provide access for the gas tube; still another reason to expend effort in order to employ the thicker plate recommended for a motor mount.

Photo of opening here

 

The proper MIG contact tip for 3/4" vortex burners is .030"; that is by MIG wire size; not orifice size.

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Safe use of accessories

It is only forethought that prevents incidents from becoming accidents, or accidents from turning into disasters.

While using cutoff wheels, the direction of tool travel should be opposite to the rotation of the wheel, whenever possible (this is counter to the direction that friction is trying to push it along the material surface); doing so greatly reduces the chance that your wheel will bind in the work piece, creating dangerous kickback and/or shattering the wheel. During those rare occasions that you must ignore this advice, switch to a smaller wheel and reduce speed, to diminish the force of kickback.

Warning: Never position your eyes directly in line with a cutoff blade, grinding wheel, or rotary brush. Keep your eyes, face, and neck out of the path of shattered blades and flung parts, regardless of safety glasses, goggles, face shields, or other protection that you may employ to stop normal debris; otherwise, acquiring such a bad habit will eventually bring you grief.

Line-of-site with your work is always to be above “the plane of spin.” Any cut-off blade, grinding accessory, or rotary brush should be aimed in line with your chest; never in line with your face or neck. Several people have been killed by grinders kicking back into the neck; don’t think a shattered blade section from a cutoff wheel won’t cut into an artery just as easily; is this likely? Fortunately the answer is no, but it does happen.

 With the part clamped so that your cut line is horizontal, position the blade just below the line; this gives an excellent view, while keeping debris trajectories well below your neck. Rotate and re-clamp the part whenever needed to keep the cut line in plain sight above the wheel.

Photo showing exactly how to safely cut beside air opening lines with a guarded rotary tool, aimed in line with your chest—no higher.

Think about what you’re going to be doing before running a power tool. Spend a moment picturing what reaction you’ll need to make in case of kickback, for instance. You won’t have time to decide during an incident.

Always assume a safe work posture. There are three ways to grip a rotary tool:

(1)  As you would a pen, for fine detail work like engraving (only employed with pendant hand-pieces or with very weak rotary tools (ex. engravers).

(2)  As you would a knife (only used on out of position work (where you have no other choice).

(3)  Two handed, as you would a golf club or baseball bat; this is the safest position. Always use the two handed grip during bench work.

Keep your fingers well away from accessories; especially cutoff wheels.

Set your footing for best balance before operating the tool; sitting down with feet spread is safest.

Whenever you have the chance, brace your body, one of your arms, or one of your wrists against some solid surface, which is out of harm’s way. Try to keep one or both elbows close to your side when possible.

If following these instructions seems too demanding, practice each recommendation, while you have someone push sideways a few times against your hands (with an unplugged tool in them). Kickback can push you out of position with equal force, and far too quickly to react in time—unless you’re already braced for it; if you are braced, a possible accident is reduced to just another incident.

Never overextend your reach; especially during out of position work (ex. on ladders); doing so is an invitation to disaster.

Tie back long hair, and don’t wear jewelry, a wristwatch, or loose fitting clothing.

Be sure to secure the part being worked in a vice, or other properly constructed holding device.

Wear respiratory protection; a two string dust mask at the very least. Earplugs are also highly recommended.

Use common sense; don’t employ a large wheel on a small job, or use a more powerful tool than the work requires (ex. rotary tool versus 2” die grinder; 3/4” wheel versus 1-1/2” wheel; full speed versus reduced speed).

All power tools should be “blown out” with an air compressor after each use (just lung pressure applied through a rubber tube can be effective for this purpose), and then stored in a dry place (or in a sealed plastic bag), for long life.

 

Drilling and threading stainless steel

While “keyless” chucks were supposedly made popular by their ability to rapidly change tools, it was probably more due to a problem with gear ring chucks (AKA keyed chucks); the real failing of these chucks is found in the profound ignorance of their operators. A keyed chuck is meant to be tightened gradually, employing all three keyhole insets in progressive order; so doing insures a tight grip on the bit, without effort. Pounding on a chuck key with a hammer produces lopsided tightening, rapidly followed by severe damage to the chuck. Thereafter, the chuck must be rebuilt, replaced, or pounding the chuck key becomes necessary for the rest of its very short life.

Three-hundred series stainless tends to compress during drilling and/or threading, thus compacting its surface; this is a form of work hardening. What actually happens is the compressed surface becomes denser than the metal underneath; this condensed layer begins to act like a bearing surface; cutting edges tend to ride on it ineffectually, instead of penetrating it, thus causing rapid heating of the cutting tool, which is why only very sharp drill bits should be used to drill stainless.

Note: The softer stainless alloys tend to gum up tool edges, which then rapidly become dull. Dulled drill bits have a tendency to ride on the surface of stainless steel, instead of cutting into it. Stainless steel work hardens easily if a dull drill bit is used, if too little feed pressure is applied, or if drilling fluid coolant isn’t used (tapping oil is perfect for this, and can be purchased in amounts smaller than a pint).

It only takes seconds to overheat a dull or dry bit in stainless, which rapidly results in melting temperatures on a drill bit’s leading edges, followed by transference of some of the bit’s high speed steel material to the stainless part’s surface; thereafter, no further drilling is possible, although the resulting mess can be removed with diamond coated burrs and a lot of patience. High speed steel lathe tools can suffer the same fate as drill bits. In a similar manner, the leading edges of carbide tools can “gum up” with deposits of partially melted stainless, and then shatter from overheating.

When a drill bit is about to exit the far side of a hole, feed pressure on the bit can cause its flutes to suddenly catch in thinned metal, and bind; small drill bits usually snap off at this point. To avoid breakage, ease up on feed pressure when you feel the bit “breaking through” the far side of a hole; this is true for any malleable metal--not just stainless steel.

It is generally a good idea to employ the drill bit recommended for a given tap in a given metal. However, the drill bit sizes listed in threading charts are normally meant for use on soft metals like aluminum or brass; they produce a 75% thread engagement.

Only 50% thread engagement is recommended for most stainless alloys, but the relatively few threads produced in most tubing/pipe products are under more than moderate stress at times; this makes the additional pressure on your tap, which comes along with the additional 25% thread engagement, a recommended burden, when using set screws in thin tubing. Threading through the thicker tubing or pipe used in stainless steel burner nozzles is done with the recommended 50% thread engagement.

Plain “high speed steel” drill bits are the earliest form of tool steel; if you’re careful you might get as many as eight holes in stainless before they start to dull. “Cobalt” bits are actually high speed steel with a percentage of cobalt added for further hardening and toughness. When you can find cobalt bits with 118° points (standard angle for drilling ferrous metals) in the size you need, they are well worth their higher prices (they are usually only available in fractional sizes). Look up any decent drill bit chart to understand the differences between fractional (fractions of an inch), wire (adhering to wire gauge), and letter drill sizes. The harder the alloy the more brittle it is; therefore, treat cobalt drill bits more gently than plain tool steel bits, and tungsten carbide bits more gently still; use light feed pressure on cobalt and carbide drill bits: http://en.wikipedia.org/wiki/Drill_bit_sizes  

135° split point cobalt drill bits work well for drilling stainless steel; these bits come in a greater variety of sizes, including number and letter drill sizes than chisel points. They work well enough on tubing and pipes, and are worthwhile at their lower prices and greater toughness (as compared with solid carbide); because they are made for drilling hardened and stainless steels, hard bronze alloys, and titanium—all tough jobs, their webs are thicker and clearances smaller than standard bits, which means you’ll have to work a little more diligently at chip removal. One of the advantages of split point bits is that they don’t tend to “walk” (move around on the part surface before penetration) like chisel points do. Buy American made M42 (8% cobalt) bits; most of the imports are only M35 (5% cobalt), and some are only cobalt coated: http://www.panamericantool.com/cobalt-drills/cobalt-aircraft-drills-wire-gauge-number-sizes.html  

Start threading with your tap as close to right angles as possible, and only turn the tap until you can feel resistance suddenly increase (the “quarter- turn and reverse tool to break burr” rule of thumb isn’t adequate for stainless or high carbon steels); instead, you must back off the tap as soon as you feel a sudden increase in resistance to movement. It doesn’t matter how little progress you make before breaking the burr away from the thread end, and starting another twist; have the patience to follow this advice. You are using small and therefore easily broken taps.

Be liberal with your tapping oil, and back the tap out completely (in order to clean out collected metal chips) every couple of full turns; a broken tap can be removed with diamond burrs, but it's even less fun than removing high speed steel layers left from partially melted drill bits.

There are three kinds of thread taps: "Bottoming," "plug," and "starting” (AKA “taper”) It should be obvious that stubbornly insisting on a starting tap (even if you have to special order it), will return big dividends once you start threading in S.S. Learn the difference between starting and plug taps, so as to defend yourself against ignorant or lazy sales clerks. It is better to pay a premium and wait days for a special order starting tap then to try forcing a plug tap to work in a stainless hole.

Should you break a tap off in the hole, gently rap on the protruding point within the tube with a hammer driven rod, flat bar, or flat blade screw driver, to loosen the tool point, and then try to back it out of the thread with needle nose pliers. Otherwise, you must drill the piece of high speed steel out with a diamond coated drill bit.

Once the hole is cleared try to thread the hole with a new tap; most likely this will work out well enough to accept a screw, but if there isn’t enough thread left to properly engage the screw, you must use a larger screw.

Any malleable metal will form a raised area on the starting and ending surfaces of the part, during tapping; #300 series stainless steel much more so than other ferrous alloys. The inside face of threaded holes in the burner nozzle and other close fitting parts must be filed or sanded in order to keep proper fit. After sanding, the tap must be run through the threads again to “chase” them (to help clean out debris and get rid of burrs and/or malformed thread ends). Chasing and sanding the inner face of tubes must be repeated until you end up with a satisfactory result.

Soldering copper to aluminum

Copper refrigeration tube is soldered into aluminum fan mounting plates on nearly all Vortex burners. There are two types of filler alloys used on aluminum. Abrading fillers (AKA “hard” fillers) depend on the sharp zinc crystals in their alloys to break up hard aluminum oxides on heated part surfaces, so that the filler can flow under them. If you’re soldering large exposed joints together, abrading solders are cheapest to employ.

There are also various soft solder filler alloys that depend on the right flux and surface wetting to promote capillary flow, in order to solder inside of joints (often called “sweating”); obviously, the second process is what you need for this task.

Good aluminum sweating solders come in two kinds: Tin-zinc alloys wet to both aluminum and copper, but are not commonly found at your local hardware store; the other likely candidate for this task is tin-silver solder, which is easier to find and does a better job of wetting, so that is what I’m recommending. Any 5% silver or better alloy is fine.

The surest bet for flux with tin/silver alloys is La-Co Aluminum flux; http://www.bettymills.com/shop/product/view/Markal/MAR434-22404.html

Aluminum begins reforming its hard oxide layer immediately after removal by abrading or drilling; this leaves you with two choices for best results when soldering the copper gas line into your fan mounting plate. Either you prep the side hole with flux after drilling it, or prepare your gas line and gas jet in advance of drilling your hole; and then solder the copper tube in place without wasting a moment. If you choose to buy time by fluxing the side hole in advance, then you need to either collapse the end of your gas line or else plug it with a wad of paper, or cloth, to keep the flux out of the copper tube’s interior.

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There will now be a short pause while I finish the 3/4" burner notes, since the present burner doesn't employ an SST for its funnel, but a more complicated part, which would force me to get into a discussion of silver brazing of stainless; just to much extra work for this thread.
 

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Hey Mikey, for the summer I've been using a particular Bernzomatic torch to fire my forge(TS4000), and I've found it to work quite well. If you have the time, I would like to know what you think with regards to its design. I know you have mentioned that you build burners from torches, but my limited knowledge tells me that this one is pretty darn close by itself. Any thoughts?

The first photo is rather blurry, but it shows the general set up. I couldn't get a picture of the jet itself, but you can see the fuel supply line. As you can see a little in the second photo, there are four 1/4" holes behind where the fuel jet is. Out side the forge this torch puts out a lot more heat then you standard run of the mill torch. I don't know if you are familiar with this model, but I thought it was something that might be somewhat relevant. It is definitely a more expensive option than a burner build. I guess I'm just curious what you think.

 


Torch (1).JPGTorch (3).JPG

 

 

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