Burners 101

[Howling dog forge]

In regard to your vortex burner project :

I Have no dog in this fight but I feel like the kid who wanders into the middle of a movie.

The first question would have to be What is the object of this exercise?? Is there a base line that this improves on? How do you know when it has met your expectations? Yea I know , that is three questions, so here are a few more. Is the muffin fan for added air or are you trying to swirl the air to better mix the gas?

The aluminum block/ spacer in your illustration is for a transition from the fan to the SST??  I would offer that you may want to rethink the through bolt holding the three together, the aluminum is going to expand, a lot, and the weakest part of that sandwich is the fan, it is going to crack. 

 

This site seems a bit strange in that it keeps changing my font size and editing is a bit of a challenge. The space bar deletes letters? Hours and hours of entertainment.

 

[Mikey98118]

Funnel shapes for 3/4" Vortex burners

One of the most convenient ways to acquire parts for air openings on these burners is to use stainless steel reducer fittings, as they are high-quality castings, and cost no more than mild steel butt weld fittings; they are thick enough to provide good purchase for threaded holes, so that mixing tubes with beveled edges can be slid inside the fitting's small openings.

Aerating wine funnels are a good size (around 3”) for 3/4” burners, and a few of them are longer than average. The Metrokane 2-3/4” I.D. heavy wall stainless steel aerating wine funnel is a nicely convex cone shape. The inner part you see in photos simply lifts out; it is $20 and shipping from amazon.com, but can sometimes be had for less through their alternate sellers

ebay links removed

[DavidF]

I am anxiously awaiting the results of this. I will try a computer fan add on if the results look promising! 

[Mikey98118]

In regard to your vortex burner project :

I Have no dog in this fight but I feel like the kid who wanders into the middle of a movie.

For all your fellow movie watchers we will back up a little bit.

The first question would have to be What is the object of this exercise?? Is there a base line that this improves on?

It improves on the previous limit on how hard a flame could be kept from blowing right off a burner's flame nozzle; it also creates a more thorough mixing of fuel and air in the burner.

How do you know when it has met your expectations?

I know from long experience; you would know by heat output.

Is the muffin fan for added air or are you trying to swirl the air to better mix the gas?

Very good question; it is for the added swirl.

The aluminum block/ spacer in your illustration is for a transition from the fan to the SST??  I would offer that you may want to rethink the through bolt holding the three together, the aluminum is going to expand, a lot, and the weakest part of that sandwich is the fan, it is going to crack.

Incorrect; this end of the burner gets cold; the other end gets hot."

.

[Howling dog forge]

23 minutes ago, Mikey98118 said:

That should read "this end of the burner gets cold; the other end gets hot."

Now thats interesting, I guess I could see this as true. I have on occasion thought of checking temperature along the mixing tube and never quite got around to it.

Is the fan powered of just there to direct the air stream? free wheeling.

 

 

[Frosty]

The intake end of NA burners operates by a low pressure gradient, lowering pressure strips BTUs and so the intake end of NA burners are cooler than ambient. A good example of pressure reduction lowering temperature without going into how refrigerators work is a can of electronic device duster. Pull the trigger and the can gets COLD. 

Brownian movement is determined by temperature and psi within reason. Expand the volume occupied by a gas makes the molecules travel farther before bouncing off another molecule so they travel more slowly. Smoosh them into a smaller volume and they travel less distance but have the same energy going faster. More energy in a smaller space = HOT. less energy in a larger space = cooler.

Frosty The Lucky.

[Howling dog forge]

I was a commercial HVAC and refrigeration tech for 25 yearsI get the pressure drop thing but I would have thought the heat conducted by the mixing tube would have over powered the pressure drop on the other end. Guess not.

 

[Mikey98118]

No; the heat gain ends in about three inches. The back two-thirds of a 3/4" burner runs from cool to darn cold as it gets closer to the beginning of the mixing tube. Fortunately, there is enough flex in the fan housing to make the screws tight enough that the fan will not become loose from shrinking. This is the advantage that comes from listening to people who have dealt with these parts already Not that I know everything about every size and construction method possible when building Vortex burners, but I know quite a bit.

[Mikey98118]

Vortex burners are essentially linear burners. How easily older burners can be retrofitted with the right fan, I hadn't thought of before now. And with this let us turn to the fans and controllers that power them.

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

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

    You don’t get significant air spin from just any axial fan; its blades need to be curved and set at a significant 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 power provided by the fan running “all-out” can be combined with a second larger diameter flame nozzle; thereby allowing a great increase in turn-down range (flame output is still primarily varied by controlling gas input pressure, while varying blade speed gives fine tuning of incoming air to closely match fuel pressure). Or to put things another way, by building two different nozzle sizes instead of one, you get the output of two different burner sizes available from a single burner, with perfect flame performance attained throughout both of their increased ranges; that’s because this burner style permits flame varied diameter flame nozzles to work properly on the same diameter of mixing tube. 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.

    To recap; 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.

[Mikey98118]

Axial DC fans

 

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. 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 inside diameter anywhere from 7/8" to 1" because they come in a much greater variety of sizes. You need to order your fan in a size that matches with, or is just smaller than, a burner funnel’s large opening; it may 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 aluminum 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 repurposing 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 tube axial 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. A tube axial 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 heavily swirling output of a CPU axial fan is the most important 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 designs because their output is just like that of those fans; all push and no swirl—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 push of air; thus undoing all of the good accomplished by impeller style fan blades.

Finally, you usually 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 airstream 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

Many off site ebay links removed as per TOS

Speed controllers

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 turndown 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 fine 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.

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 is an excellent and economical method of changing input air to closely match variance in fuel flow. 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:

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 2 amp 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.

Computer fans (AKA CPU fans) swirl air 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 returns 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 wire 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 EXAMIN 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; so, 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.

[John in Oly, WA]

The wine funnel you posted a link to says "Currently unavailable". In the meantime, I went nuts this weekend and bought a schedule 10 - 2" to 3/4" stainless butt weld concentric reducer which has inside diameters of - large end 2.157" and small end .884". Then I bought 24" of 3/4" schedule 40 stainless pipe from Online Metals with an I.D. of .82" hoping to be able to blend the .884" reducer to the .82" pipe for a smooth transition AND I bought a LEM sausage stuffer tube - 2" base, part # 607B 1" O.D.  AND a piece of schedule 80 - 1.25" stainless steel pipe with an I.D. of 1.278" for nozzle material. Along with a couple of computer fans  that seemed to come closest to meeting the 3:1 ratio of funnel opening to mixing tube diameter. It's a little smaller than 3:1. Still need to find the aluminum spacer/inlet tube block and then get the specs on capillary tube diameter.

So, I thought I'd build two burners - one with the LEM SST and one with the SS concentric reducer.

And now seeing your last post, may have to buy 70mm fans.

[John in Oly, WA]

That was another thing I was wondering - does the fan run full blast, or do we need a variable speed control. Looks like speed control is a good idea.

[Frosty]

16 hours ago, Howling dog forge said:

I was a commercial HVAC and refrigeration tech for 25 yearsI get the pressure drop thing but I would have thought the heat conducted by the mixing tube would have over powered the pressure drop on the other end. Guess not.

 

I was surprised how cool most of the tube stays early on too but a hypothesis must yield to empirical fact so I started thinking about the things till they explained it to me. Well, I started listening actually. 

Steel is a poor conductor of heat and there's a LOT of cool air fuel flowing over the interior surface. I made a number of experimental burner designs trying to direct forge exhaust over the outside of the burner tube as a preheater. The Sandia forge is a recuperative design that works well but it depends on gun (blown) burners and I was into NA. 

I did get one recuperative burner to work but I had to make it from exhaust tubing to exchange heat efficiently enough to be worth the effort and even then it wasn't enough of an improvement to be worth the work.

The NARB on the other hand collects enough  heat in the burner block you have to keep the psi high enough to keep the burner cool enough it doesn't start burning in the plenum.

Frosty The Lucky.

[Mikey98118]

I suspect that "V" burners may do an even better job of cooling down the mixing tube, because the mixture flow will have a higher proportion of cold incoming fuel gas against the tube wall and less of it in the cross-section of the tube, which passes  into the burner nozzle without touching the heated wall.

48 minutes ago, John in Oly, WA said:

at was another thing I was wondering - does the fan run full blast, or do we need a variable speed control. Looks like speed control is a good idea.

Either way. The question is like asking how much better are specialty tires than what came on the car...it depends on the driver.

[Mikey98118]

John,

remember to wait till the reducer comes, and then mic it before looking for the fan. Since you aren't getting all the diameter allowed on the air intake, look for all the power you can find in the fan; no this isn't critical, but I  want to give you every possible break.

Aluminum flat bar is considerably cheaper than aluminum plate, at Onlinemetals.com. You will want at least 1/2" thick flat bar, which is one--inch wider than the outside diameter of the pipe reducer's large end and cut one-inch longer too. You don't need to wait for the fan before ordering the plate, because the plate needs to be considerably larger that the fan.

You can solder the aluminum fan plate onto the reducer with tin/silver solder and LA-CO aluminum flux past, or you can use soldered tabs and screws to do the trick; in that case pay to have a one-inch wide strip cut from the flat bar at the same time you order the fan plate, and cut and sand it into four tabs to receive the fan screws.

That should read "... flux paste,..."

[Mikey98118]

This flux is needed to solder the refrigeration tube you will employ as a gas line into place into the side of the aluminum fan plate, and the gas coupling and gas jet onto the copper tube.

[Mikey98118]

Soldering copper, brass, & stainless steel

 

Soldering uses the lowest temperatures of all thermal joining procedures, but soldered joints are weaker than those that are brazed; they are also less able to withstand elevated temperatures. Therefore, soldering is only used here as a method for affixing capillary tubes to other parts in micro gas jets, and for trapping copper tube within aluminum mounting plates. Even in these areas, some may prefer silver brazing of heavy wall S.S. capillary tubes to soldering of dispensing needle tubes, because brazed joints will withstand higher temperatures, which carelessly handled miniature burners, can be exposed to.

Furthermore, silver bearing soft solders (essentially tin/silver solders) aren’t much less expensive than silver brazing, once you pay the premium prices charged for effective stainless steel rated solder flux (resin based fluxes aren’t sufficient; powerful acid based fluxes must be used), and purchase a full one-pound roll; the better solder alloys (ex. Stay-Brite) are also comparatively even more expensive.

You could purchase four or five feet of (56% silver) brazing wire and flux through eBay, or down at your local jewelers supply for less money than a one-pound roll of the better tin/silver solders (ex. Stay-Brite is 94/6 instead of the more typical 95/5), but is the difference really worth the expense? When used for the plumbing problems, probably not; for general use in gas assemblies for burners, yes.

But, it would also depend on your opinion of your personal abilities. If you want everything going for you when doing this work, the possible extra expense of brazing on stainless steel is nothing. If you’re an old hand at stainless steel soldering and already have the solder on hand, the savings can be more significant.

La-Co aluminum flux can be successfully employed in soldering on S.S.; since you need it and the (and tin/silver filler alloy) for the copper gas line to aluminum fan mount joint anyway, soldering a heavy wall S.S. capillary tube in place might be the way to go, for most.

Tin/silver (Sn/Ag) solders adhere better, are about five times stronger, and have a much greater ability to elongate than tin/lead fillers; qualities that are critical for successfully joining dissimilar alloys with different rates of expansion.

A higher silver percentage will wet joint surfaces better than a lower one. Try to find five percent silver (95/5) rather than one of the cheaper two or three percent silver filler alloys(be sure to acid etch or sand the S.S. parts first). Silver/tin solders don’t max out at five or six percent silver content. Johnson Matthey Metals Ltd. manufactures JM MP5; a 10% silver/tin/copper solder (flow range of 417º to 527º F (214º to 275º C); they also make JMM, a 25% silver/tin solder (flow range of 430º to 437º F (221º to 225º C).

The potential for galvanic corrosion between soldered (or brazed) S.S. and copper or brass parts is quite low.

Lower working temperatures aren’t the only advantage to be found in use of tin/silver solders ; these fillers tend to fall in the “capping filler” category; meaning they tend to form “weld” beads at the lower end of their liquidus range, and can bridge much larger gaps than brazing fillers used for sweating work. What advantage is that for you? A capping alloy is far less likely to end up plugging the capillary tube during construction of micro gas jet assemblies because you can drill a tight fitting hole at the base of the tubing cavity, and enlarge the section above it that is to be filled with solder.

Note: Lead is still commonly found in imported plumbing fittings, and 2 to 3.7% lead content is commonly found in every form of brass rod (round, hex, and square). When joining S.S. parts to brass fittings (of unknown alloys), the joint area of the brass should be prepared with an appropriate etchant to remove possible traces of lead, before fluxing. This will improve wetting. Wut, any lead content in the join will eventually be converted to lead carbonate by left over acids from the flux, weakening the joint.

Stainless steel oxides can be abraded from part surfaces. Roughened surfaces also improve capillary flow during wetting. A certain amount of roughening (ex, with sandpaper), where part thickness permits, is helpful.

It is especially important to remove the chromium oxides formed on stainless steel before soldering or brazing; otherwise your flux has to work much harder, and if you are soldering thin walled parts (ex, dispensing needles), the last thing you want to do is use an over aggressive flux. Stainless steel, like gold, can have a completely oxidized surface that is also quite lustrous. Oxidation of other nonferrous metals is obvious, as it dulls and discolors them. Carbon steel oxidation forms rust that is obvious to see.

Copper and its alloys can simply be wire brushed to remove oxides and provide a roughened surface.  Inner surfaces can be considered clean if they have just been drilled. Copper alloys bond well with most fillers, even pure lead. However, high temperature fillers can promote problematic formation of oxides within capillary tube; therefore low temperature, fast flow fillers are recommended for brass or copper capillary tubes and gas jet parts.

Even 95/5 zinc-tin filler alloys will work for this job, but the two fillers below can help you to avoid drawing the filler into the capillary tube via its bottom face (inside end) during joining.

Stay-Brite 8 is a tin/silver solder (94/6) used in refrigeration and air-conditioning (HVAC) work, produced by Harris Products; it can be used with low enough heat to avoid weakening the metal tubing being joined (also producing less internal oxide buildup); it bonds with most ferrous and nonferrous alloys, including stainless steels, copper based alloys, and aluminum; it has excellent toughness in dissimilar metal joins, is highly resistant to vibration damage, and is a good capping alloy (it is especially effective in filling loosely fitted couplings); its flow range is 430 °F to 535 °F (221 °C to 279 °C) Stay-Brite 8 is available from Harris Products online; it is also sold through some hardware stores; Avoid exposing            any soldered gas jet to overheating from chimney effects.

Off site sales links removed again

Phosphorus-copper filler alloys are self-fluxing on copper to copper joints, and can be used on copper to brass joints with common borax flux. However, their melting range is more than high enough to produce unacceptable amounts of oxide in gas jet parts; avoid their use for this purpose. Do not use phosphorus based fillers on any of the ferrous metals, including S.S. (they will crack).

[Mikey98118]

Mounting the fan. The fan shall be mounted on a thick aluminum mounting plate (minimum of  1/2”), which is affixed with four screws; these are to be screwed through the drilled flange plate that you just silver brazed onto the funnel or reducer fitting. You deburr whichever end of the flat bar end is closest to square, and then finish squaring it. Next, you should layout a cut line as far from the first edge as the flat bar is wide, deburring the second edge, and scribing two crossing lines between the four corners. You should center-punch the lines where they cross each other.

Note: You need flat bar that is at least 1” wider than the outside diameter of the funnel or pipe reducer you use; larger is okay but smaller could lead to weak areas in the fan plate. You want that plate rigid to resist warping.

Employ a set of dividers to scribe a line matching the funnel opening’s inside and outside diameters. After the fan arrives check its opening against the scribed circle; if the fan opening doesn’t match the funnel opening, scribe another circle, which matches the fan opening, on the plate’s other face. Cut and power sand up to the inner side of the smallest circle line, once it is used for a soldering jig part is done; then power sand the hole’s edge at an angle to touch the inside of the funnel or reducer wall, and the plate’s other face to just under the fan line. This method allows you to be sure that the hole you’ll cut and power sand will end up centered with both the funnel and fan. The fan hole in this part must not exceed the opening diameter in your fan body. You need to do your sawing well inside the scribed line and power sand up to it carefully, to avoid going outside that line.

Unless you have a large lathe or drill press meant for metal work, it is unlikely you can lower cutting speed far enough to comfortably turn the part, or spin a hole saw large enough to cut the hole. Therefore you will likely need to use the “line of holes” method to drill it out, and then power sand back to a little inside scribed the scribe line of smallest diameter.

Drilling in line: Lay out the finish hole as mentioned above, and then lay out another line one-half the drill diameter plus 3/32” inside of the inner line; layout and punch mark each hole to be made in the line, so that the drilled holes will end up near to each other or just barely touching; then drill a line of holes. You are best off using a split point drill bit; these are specifically designed to self-center and stay where you start them. If you decide to use the cobalt bit, originally purchased for drilling the stainless steel parts, center-drill them first, because even #6061 series aluminum tends to gum up drill bits, and can dull their cutting edges if you don’t continually clean them with a brass bristled “tooth” brush. Use a cheap foam paintbrush to clean off the drill press after drilling each hole, and let the part float; don’t clamp it in place.

Note: It is better not to use a standard chisel point drill bit to drill the finish holes; they are notorious for their tendency to wander off center as the hole is started; if you don’t have a split point bit, enlarge the prick punch marks with a larger center punch, and drill oversize pilot holes with a drill bit smaller than the enlarged punch mark; next, enlarge these holes past the width of the point on the finish drill bit size, to keep the larger bit from wandering. And then drill out the finish holes.

Should you “mess up” the mounting plate’s fan hole, it isn’t necessary to live with your mistake; simply apply aluminum putty (make sure to clean the plate with acetone first, and use tape on the fan body) and re-sand.

Hopefully, you can use the same thread size for the machine screws through the flange plate as you use for socket head Allen screws on the flame nozzle; this will save in drill bit and tap costs.

MAKE NO ATTEMPT TO CUT OUT THE ALUMINUM MOUNTING PLATE'S FAN HOLE OPENING BEFORE THE FAN ARRIVES.

Caution: The fan hole, which the fan blows air through, can be a little on the small side (not smaller than the fan blade); but in no case can it be larger than the plastic rim that the fan blade is surrounded by. If you mess up the fit between these two parts, you will be reduced to fixing the poor fit with aluminum putty, or adding plastic (ex. hot glue) to seal the mounting plate to prevent some back-wash from the fan blade exiting the funnel area instead of being forced through it. You can’t ignore this situation, because that back-wash is not the minor problem it seems to be; in fact it will utterly ruin burner performance, sby leading to back firing. Vortex burners are pretty forgiving about most construction details, but the connections between fan and funnel are critical.

[Mikey98118]

 

Mounting the gas line and gas jet

You will be ordering about one foot of 1/4" fully annealed refrigeration tube, which has an inside diameter of 0.190”. You’ll probably use only four or five inches of it, but hardware stores simply aren’t interested in cutting it off the roll in less than one-foot lengths. The section of 1/4" refrigeration tube is going to hold a long tapered Tweco or MK style MIG contact tip for .030” welding wire for a gas jet at one of its end and, a 1/4” threaded gas-tight fitting (or barbed hose fitting) on the other end.

Note: 1/4” refrigeration tube has an I.D. of 0.190”. MK brand MIG contact tips have 12-28 thread, which has a minor diameter of 0.1722” and a major diameter of   0.216”  and a length of 1-1/2”. Praxair carries them, and they can be ordered online from mkproducts.com. You would probably want to silver solder an inch long section of 3/16” refrigeration tube inside to help to form thread, rather than soldering the tip directly into the refrigeration tube.

Or, you can use a Tweco 14T-030 MIG contact tip for the gas jet; they are available online and at most welding supply stores. You may want to silver solder a section of 5/16” refrigeration tube outside to help thicken the tube to offset losses from forming the thread and screw the contact tip into the refrigeration tube. Or, you can spin one Tweco brand tip size in a hand drill, and file its threaded end down to fit within the 1/4” refrigeration tube. The contact tip is then silver soldered or brazed into the end of the tube. You can also silver braze a longer tube section onto the refrigeration tube and run 1/4-28 thread inside it, so that the tip screws into position (recommended), and the tube ends up stiffer.

The refrigeration tube should be inserted through a side hole, by being drilled edge-on into the mounting plate's center hole, and then forcing the tube from within the center hole to several inches beyond the plate edge. This side hole should be drilled to run parallel to one of the fan's supporting ribs; the rib that the fan wiring runs under. So, you can't drill the side hole without having the fan for comparison.

Support ribs on most fans bridge the gap between edge and center at an acute angle, rather than at ninety degrees. It will become obvious to you that the gas tube will have to be bent in two places for the tube to end up in the center area immediately below the fan motor. You can’t easily adjust the gas tube’s centering after those bends are made.

Keep two things in mind before allowing yourself to become discouraged by this task: In the first place, you can use a fan rib to lay out the gas tube on for visual comparison, before insertion; secondly, annealed copper tube is easily bent and re-bent so as to adjust the tube’s position perfectly; use of the centering rod (needed for silver soldering the tube in position in the next step) to help provide assurance that you can eventually stumble over the victory line, no matter how clumsy your efforts may seem at this point.

The first bend is made after mounting the MIG tip. Ideally, you want the tip to end up between 1/4” and 3/8” short of the mixing tube entrance at the funnel’s small end. However, linear burners are very forgiving about whether or not your tip is placed in the “sweet spot” for distance from the mixing tube entrance.

After the gas jet is installed in the 1/4" refrigeration tube, the tube gets pushed and pulled through the side hole. Then it is kept centered and aligned while the tube is being hard soldered into permanent position within the mounting plate by use of a centering rod, which you need to find or sand to the right diameter for a slip fit within the funnel’s mounting collar. Drill a 1/4" hole in the end of a wood, plastic, or metal rod used to trap the gas jet's refrigeration tube centered and aligned parallel with the mixing tube’s axis.

Note: The centering rod only needs to be a few inches in length (3” to 4” is fine). Afterward, you pull it out of the collar. Be sure to keep the centering rod for checking alignment during maintenance work, later on.

La-Co aluminum flux and one of the tin/silver solders (ex. 95/5) is suggested for permanently affixing the refrigeration tube into place within the mounting plate. All other connections are best silver brazed, although they can be silver soldered if you’re careful.

You must prep, bend, and fit the refrigeration tube, and then solder it into position as soon after drilling the side hole through the aluminum plate as possible; this means that you'll want the MIG tip mounted and the refrigeration tube’s first bend made before you even begin drilling the side hole. The reason for all this haste is that aluminum immediately begins forming a new oxide layer after drilling; the longer between drilling and soldering the more work your flux has to do to overcome that layer.

Once the gas tube is fitted into position within the mounting plate, but before soldering it, the other end of the refrigeration tube gets a threaded fuel hose fitting, or a 1/4" hose barb silver brazed on, and you may want to cut the length of tube down to where you only have a couple inches of tubing protruding beyond the fan mounting plate's edge; this is done to keep flow resistance in the gas tube from increasing overmuch. Braze the hose connection in place (compression fittings aren’t recommended; they don’t need brazing, but have their own complications).

Now you can solder the refrigeration tube permanently in position within the aluminum mounting plate. You will have access and a good view through the large center hole in the mounting plate, because the plastic fan is removed for this operation. If you’re new to soldering and brazing, pack wet paper or cloth around the MIG tip and gas connection, to keep those joins from overheating, before soldering the copper tube into your mounting plate.

Also, if you are smart there is now ether an internal or external doubler tube soldered into or onto the last 1-1/2” of your refrigeration tube, between the MIG tip and the area that has been bent at right angles to center within the reducer fitting or funnel. This leads the bent area as a weak spot, which can bend too easily, so while soldering the copper tube into the aluminum plate, allow the solder to cover the protruding bent section of tube and down past the beginning of the section of doubler; this will greatly stiffen the copper tubing, preventing its previous flexibility from becoming a problem after it is no longer needed or desirable.

Use the play left in the straight section of tubing to flux the side hole and copper tube as best you can, before trapping the MIG tip with the centering rod. With the wet packing in place around both ends, and the MIG tip held centered within the funnel or reducer by your centering rod, lean the whole assembly in a vertical position, while heating the aluminum plate just enough to liquefy the flux. Next, back off you torch or other burner, while keeping that plate hot enough to run solder into the hole until it starts running out the bottom of the plate. Lay the mounting plate flat and try to get a little more solder to suck into each end, and let the whole assembly cool. Remove the centering rod and packing. Next, bolt the fan back into position on the mounting plate.

Note: Keep the torch flame small; aluminum melts easily. If you don’t feel competent to do this soldering, then, sand the copper tube clean, and use permanent thread locker to do the job.

[Mikey98118]

By the way, the Metrokane thick wall wine funnel and the Rabbit Wine Aerator Shower Funnel are one and the same thing;: it has an inside diameter of 2-3/4” at its large opening, and ends up at 2-3/8” long when cut back for the coupling tube and fan mounting plate, which adds a farther 1/2”; because of its greater length then any suitable  SST, and a moderately convex shape, so backpressure is created further from the fan than with a straight wall kitchen funnel ($20 and possibly free shipping through Amazon.com):

[John in Oly, WA]

I will look into the wine funnel. The SS concentric reducer arrived yesterday. The inside will need a bit of machining to make a smooth transition from large end to small. It has an odd ridge in it around the diameter, aside from the linear seam weld. The SS pipe for the mixing tubes and nozzles also arrived. I have  plenty of 1/4" copper refrigeration tube and MIG tips. The 1/2" aluminum bar and the SST is on the way. Need to pick up some solder and flux.

[Mikey98118]

Once the fan, fan plate, and funnel, SST, or pipe reducer have been successfully joined into a working assembly it becomes time to deal with the flame nozzle or to place the burner into your forge. Why the hurry? because you need to be sure that no more work needs to be done on this assembly before sealing the joints between these parts with non-hardening thread locker, or some other suitable form of gasket sealant. 

[Mikey98118]

Flame nozzle diameter sizes on these burners are not anywhere near as limited as they are with other burner styles. I would love to say that I know exactly how that works. The fact is I don't. Previously, I have found a progression of schedule #40 pipes, or their equivalent diameters in a tube, to work well; this has held true whether the nozzle was tapered or stepped. I prefer stepped nozzles because they are easiest for novices to buy parts for,  assemble, and get right. That doesn't mean they are superior to tapered nozzles; either kind can be varied more on these burners; this doesn't mean you have nothing to go by anymore; it does mean that after you play by these standards for your first nozzle, you can  successfully play with thicker spacer rings on secondary nozzles, or with greater tapers on them.

The length of the flame nozzle's overhang beyond the end of the burner's mixing tube has so far ended up just a little longer than the inside diameter of the mixing tube--so far. But flame nozzle length also depends on how long the spacer ring is. I have found an extra 1/4" beyond the size of the mixing tube's inside diameter to allow all the leeway needed to tune a burner, add to that a minimum of 3/4" for the spacer ring, and you have a good minimum length for most flame nozzles. That said, additional length on the flame nozzle's spacer tube will help ensure that the nozzle can be brought into line with the axis of the mixing tube, by a simple rotation of the two tubes on each other. The smaller the burner size the more important alignment is, and the less the extra tube length costs.

[John in Oly, WA]

The solder and flux is a bit confusing. Not to mention spendy. There's a Harris SBSKPOP Stay-Brite Silver Bearing Solder kit (96%-4%) says works with stainless and copper (the HDepot description says not for aluminum). Another description I found said the Stay-Brite 8 is not for aluminum. Another said good for all ferrous/non-ferrous alloys.

[Mikey98118]

Any silver bearing solder works on stainless steel. I would not be surprised to find that some nonsilver bearing solders do as well. It is the kind of flux used that is critical. Stay Brite solder is expensive because of its physical characteristics; it is a product famous for solving difficult plumbing problems; its high price has little to do with its silver content. I would use it simply for its ability to create beads, as though the work had been welded if I was feeling flush; overwise, I would look for another product. You can also go with glue to save money. There are aluminum solders as well, although I would stick with my recommended flux unless the aluminum solder comes with flux that is rated for stainless.