Burners 101

[Mikey98118]

58 minutes ago, KENR2600 said:

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

When I write to you, it is with all our "silent partners" in mind; so now it will be visa versa 

[Mikey98118]

Schedule #40 Pipe (standard water pipe) is generally cheaper and more accessible than steel tubing. If you use "seamless" grade pipe, one pipe will fit within another with some power sanding. If you want to cut down on sanding, choose zinc coated pipe, and burn it in a fire, or soak it overnight in vinegar to leach the coating away; the part will get thinner so that it should slide over a smaller pipe with little or no sanding.

Tubing must commonly be mail ordered, but comes in such a wide variety of wall thickness that power sanding can usually be avoided; once again, be sure to use "seamless" grade.

[Mikey98118]

Maximum Spin

I used to think that the primary concern with air openings was to make them large enough; that turns out to be ridiculously easy. Instead,  the primary thing about them is that they provide enough spin. Lately, I have warned people about holding the diameter of funnels at three times the inside diameter of a burner's mixing tube. But what about funnels on regular linear burners, without impeller fans mounted on them? Then three to one should be considered a minimum; not a maximum ratio; why? To create greater spin.

Jet-ejector burners also create spin through their side air opening or openings, which is why I now advise people to use three air openings on Mikey burners, rather than going for a greater number. Three openings will give the maximum spin. Maximum spin gives maximum mixing of the fuel gas and incoming air; and that has much to do with how good its flames are.

 

[Mikey98118]

So, why would a larger funnel create more spin than a smaller one? Becuase of the laws of vortical flow. The greater the difference between the large diameter of the funnel entrance and the small diameter of the funnel exit the greater the velocity of spin in the air/gas mixture.

[Mikey98118]

Axial DC fans

These burners are unusually forgiving about details like flame nozzle size, but one of the things you must try to 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 blade is an optimum size on a typical 3/4” burner, but good luck finding one at a decent price; so you’ll probably settle for a 70mm fan, which is an easy size to find; it equals 2.76" outside dimensions. The fan opening is 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 a little 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 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. If you can’t find a good match between fan and funnel, order as strong a fan in that size as you can find, to offset flow losses.

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 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. 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 ballbearing 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 on 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 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 usually 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 opening. 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:

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 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 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 watts) 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. 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.

W = V x A (watts equal volts times amps). 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 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.

[Mikey98118]

Wiring

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 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; 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.

[Mikey98118]

 

Employing fan mounting plates

Both axial motor and fuel gas tube must be mounted to the burner funnel—parallel and centered with its axis—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 the gas jet). Also, fan and funnel mouth sizes may not match up well enough to work on their own. Most funnels don’t have wide enough flanges to mount the fan directly to.

The best way around all of these problems is the employment of a fan mounting plate; you could also call it an adapter plate, as some do. Your fan can be screwed onto the back side of a 1/2” thick aluminum, brass, or mild steel plate, with its forward side attached to a funnel with screws that are threaded into it through larger holes in the flange, if the funnel’s flange is wide enough to accept screw holes; otherwise the screw’s heads can be used to trap funnels with narrow flanges in place.

The main points to using thinner mounting plates are ease of cutting for people using jeweler or jigsaws, and ease of acquisition for people buying the plate from scrapyards. If you have even a cheap drill press, and order aluminum flat bar online, thicker is always 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, you can 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.

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 temporarily 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.

Caution: 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 be silver brazed to the burner funnel, or attached to it with an exterior clamp, for safety; no exceptions.

[Mikey98118]

Installation and maintenance of the copper refrigeration tube and gas jet

Drilling: You are usually drilling a 3/16" diameter hole through the mounting plate's (or funnel’s wall) on burners up to 1/4” size; holes for refrigeration tube on burners up to 1” size, use 1/4” tube, and 516 on 1-1/4” to 1-1/2” burners. The side hole isn't very far from the plate's outside edge, to the edge of the center hole. If you have a drill press, with even a cheap machinist’s vice mounted on it, drilling this part accurately should not present any problem. If you are hand drilling (or employing a larger gas tube) you might want an extra thick plate. Extra thick plates are no draw-back; just more work to cut out.

But, what if you don’t have a drill press? The fan hole (AKA center hole) is no big problem; you can employ a slightly undersized hole saw in a hand operated variable drill motor; then enlarge it by power sanding (hand operated rotary tool) to finish your hole, and perfectly match up with the funnel opening/fan body opening interfaces. The larger the hole saw the larger the drill motor needed, because the larger the drill motor the slower its speed; also consider using a screw gun to reduce RPM. Extra-large holes can be made with a jigsaw, and power sanded back to a scribe line. If you don’t have a jigsaw, drill a row of holes inside the scribed circle, and power sand.

Caution: The larger and slower a drill motor is the more torque it has, and therefore the more serious injuries from kick-back can be, and so the better you should be braced against it.

A line can be scribed with a set of dividers, just a little smaller than the desired finish hole, with a starting hole for a jigsaw blade inside the scribed line, move the blade  diagonally forward and outward until it is near to the inner face of the scribed line, and then saw completely around the section to be removed. Afterward, the undersize hole is enlarged and finished by power sanding (with a rotary tool).  

Next, a scribe line is marked out to match up with the fan rib that you’ll run the gas tube parallel with. You need to clamp the plate to the edge of a horizontal work surface (if you don’t have a drill press), and drill the side hole reasonably level and properly aimed parallel to the scribed line on the plate’s upper face; this is done to reduce the airflow interference from the gas tube as much as possible.

So, how do you know that the drill bit is aimed level? Clamp a reasonably long rod (about one foot long) into the drill chuck, with a string level taped to it. Bring the drill up to level, and glue the string level onto the top of the drill motor’s plastic body (or if you mount it with screws, adjust the level until the bubble sits in the right position). You will find the mounted string level to be endlessly useful in future. You can also use a long enough drill bit to set a string level on; then keep the drill motor steady after removing the level: 

Centering rods: The best way to make sure your gas jet is positioned dead center and parallel to the mixing tube is to drill one end of a rod (brass, aluminum, mild steel, plastic, or wood) with a deep hole, into which the gas jet fits closely (but without forcing; use a “slip fit”). Turn down or sand the rod’s exterior until it slides easily into the burner’s coupling ring (or mixing tube on a small SST burner), or use electrical tape to build up a rod that is undersize; center and align the gas jet with it, and then permanently solder the gas tube in position within the mounting plate. Keep the rod on hand, for re-centering the jet as a part of future maintenance work.

LA-CO aluminum flux paste by Markal is used for surface preparation and as a protective flux during heating of aluminum alloys for soldering with tin/silver solders (94/6, 95/5, 96/4, etc.). The greatest advantage of this flux is that it’s designed for use with easily obtained non-lead plumbing solders, but this flux is also supposed to be good  for soldering copper, brass, chrome, and stainless steel, which means it should also be good to use for soldering stainless steel capillary tube gas jets into copper refrigeration tube; $13.89 and shipping online.  If your motor plate is brass or steel, regular flux will do fine.

LA-CO aluminum flux and filler alloy kits are available for $17 and shipping from Sears (also available through other online dealers); prices vary. The solder alloy as “#60”; their MSDS shows this to be a tin/zinc alloy, which isn’t the best choice for stainless steel.

    Have all your parts cleaned and ready to insert immediately after drilling a hole for the gas tube in an aluminum mounting plate (the oxide layer starts reforming immediately on this metal, so the longer you wait the harder your flux has to work). Use a stainless steel brush to clean the oxide layer from the hole’s edges before soldering the copper gas tube in.     

Note: Soft copper refrigeration tubing comes in coils; short sections of refrigeration tubing can be easily straightened by slowly twisting back and forth, while pushing it into a rigid tube that is a few thousandths larger than the copper tubing’s exterior; it is necessary to completely straighten the end of the gas refrigeration tube for a centering rod to work properly.  

The main reason your mounting plate is made from 1/2” thick material is to provide a generously thick cross section through which to drill a hole for the copper gas tube. Drill from the flat bar’s outer edge through to the fan hole (aimed to run parallel with one the motor case ribs that has electrical wires running under it)

If you don’t have thick plate, or don’t want to drill it the hard way, you can always mount a short bar of metal to build a thick area onto thin plate for the side hole, but you are exchanging extra work in drilling out the motor mounting plate for more work in mounting the bar, in order to do so; and then, you must grind an opening in the funnel wall for the refrigeration tube to penetrate; it is simply a matter of task preference—not a reduction in work load.

Measure the funnel’s depth and mark the refrigeration tube (with gas jet mounted) at 1/4” short of that figure. Bend the refrigeration tube at the mark up to a right angle. Shove the other end of the tube into the plate’s side hole until the gas jet is centered in the fan hole.  Employ the centering rod to trap the gas jet centered and perpendicular in the funnel’s small opening, and solder it in place.

[Mikey98118]

Seamless Copper Tube, Bright Annealed (ASTM B 68)

 Annealed copper refrigeration tube is designed to easily bend without collapsing; it comes in several sizes; a few standard examples are: 0.071" outside diameter, with 0.028" inside diameter refrigeration tube will fit within a 1/8” tube (with a little drilling), which will then fit within a 3/16” tube (for 1/2” burners). A number #49drill bit leaves a .073” hole that is perfect for silver soldering a short length of the tubing into. A number #50 drill bit leaves a .070” hole that only needs one-thousandth of an inch sanded away to make a perfect interference fit into a MIG contact tip, etc.

0.081" outside diameter, with 0.031" inside diameter0.093" outside diameter, with 0.040" inside diameter

0.125" (1/8”) outside diameter, with 0.064" inside diameter; this will fit perfectly within a 3/16” tube for brazing/soldering0.1875" (3/16”) outside diameter, with 0.127" inside diameter; will accommodate 1/8” tube inside it for brazing/soldering.

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

0.3125” (5/16”) outside diameter, with 0.252” inside diameter; this is large enough to contain a MIG contact tip gas jet for brazing. Larger diameter tips can be filed to size and inserted for brazing.

    The sizes listed above are just a few. And yes, if a small enough refrigeration tube fits into the gas tube you want, it can be used as the gas jet, or as a spacer (or spacers) between a larger tube and a smaller gas jet.

    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.

    Gas lines for burner sizes up to one-quarter inch equivalent can be made from 1/8” fully annealed thick wall (0.030”) copper refrigeration tubing; this is a convenient size for soldering 1/2” long gas jets (made from copper or brass capillary tubing) into. 1/8” refrigeration tubing can vary 0.002” to 0.003” over or under its nominal 1/8” outside diameter; it is approximately 1/16” inside diameter (typically 0.065” plus or minus 0.001”).

     Burners up to 1/2” can be fed from a 3/16” copper tube; burners up to 1” can be fed from a 1/4” copper tube; burners up to 1-1/2” can be fed from a 5/16” copper tube; burners up to 2” can be fed from 3/8” copper tube.

    You can purchase 1/8” 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 1/8” compression fitting, instead.

Note: 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 lauryl 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 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.

    Some funnels with narrow flanges (ex. cake decorating tips) 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.

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.

    If you’re limited by material choices or don’t feel competent to drill the side hole accurately, you can grind a recess in the funnel wall, through which the gas tube can exit, and then solder the copper gas tube unto the mounting plate’s underside. Be sure to power brush the mounting plate where the gas line touches it and sand or brush the refrigeration tube where it touches the mounting plate. Hold the gas line in position with your centering rod. Screw the plate onto the funnel (without the fan attached), and scribe lines on the gas line and mounting plate to indicate the area to be soldered. Remove the mounting plate for fluxing, and flux the copper tube while it’s off; then, remount the plate and solder the two parts together. Heat both the plate and the two protruding sides of the gas line; then apply solder.

   If you have the tools and thick enough aluminum flat bar to do so, employing a thick motor mounting plate is the simple path; which method you choose is a matter of personal convenience.

[KENR2600]

When you get to this stage - how can you not light it up and see what it does. Seems an issue loading the video portion. Hopefully the pics will be a start.  This holds flame from 3 - 30 dialing the regulator.

First fire of the twins...

 

First fire of the twins...this is the intended shell...

[KENR2600]

forge burner dual test1.avi       aha... Format matters!

test 1.avi   first fire burner1...

[Mikey98118]

What I'm seeing is an almost right set of burners; at present, the flames are not getting enough air, and so are burning rich. How about showing us the burner's other ends, and maybe we can help you.

BTW, your flame nozzles look a little too short, which isn't hurting performance yet, but may well do so once we up the burner's air induction.

Your forge shell looks okay.

Okay, I just looked at the video, which shows the whole burners. Double the length of your mixing tubes; they are way too short to allow sufficient mixing of the fuel gas and air.

[KENR2600]

.5x6.5.avi   .5x4.5.avi   ran both options through the same paces. Definitely a difference between the two.  

[KENR2600]

17 hours ago, Mikey98118 said:

Double the length of your mixing tubes; they are way too short to allow sufficient mixing of the fuel gas and air.

Using 1/2" pipe  , I went with 8xdia. +/- with a 4 1/2"tube.  It's supply is a .023 tip - cut back to 1/4" back from the 1/2" throat of the mixing tube. I had originally thought to put the tips closer to the tube - thinking the velocity at the entrance may increase the "siphon" effect drawing more air in around it. But most burners I've seen here needed tuning by backing off the fuel tip some... Frosty had mentioned, and a couple other places, backing that tip up,  or it will be too rich.  I've also seen  .023 and 1/2" just may not be the ideal mix... 

  It also occurs to me, my test may be somewhat flawed... If air in is an issue, laying one side flat on the table, may not be giving me the best picture of what it can do.......

  I'm VERY encouraged that my first shot is an "almost right" set.... I suppose the severity of the "almost" determines the ultimate wrongness however....

[Mikey98118]

You seem to be doing your homework and trying hard to think things through, so I will try to try as seriously to work with you.

The mixing tubes look too short, but there is nothing wrong with your math, so I'll look harder.

Your comments about how Frosty tunes his burners are spot on. Unfortunately, a ''T" burner has completely different flow dynamics with most NA burner designs, which is how he can make very hot soft flames with them; those soft flames are why I keep recommending his burners on box forges with top-down burner positioning--not their is of construction.  

So, move your MIG tip ends forward to find their sweet spots (between 1/4" and 3/8" between the end of the tips and the opening of the mixing tubes).

BTW, I use nine times the diameter on most of my burners. Once again it's a difference in flow dynamics. Most; not all? Yes, that's why we call it a rule of thumb. You can go as high as time diameters if you want to sacrifice some heat for a smoother flame when using a burner as a brazing torch. So far, I use fourteen diameters to tame the flames on Vortex burners, but plan to try internal vanes it an attempt to shorten their lengths.

That should read "...ease of construction."

[Mikey98118]

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Let's try this whole paragraph over again.

I use nine times the diameter on most of my burners. Once again it's a difference in flow dynamics between "T" burners and most others. Most; not all? Yes, that's why we call it a rule of thumb. You can go as high as ten diameters on a Mikey burner if you want to sacrifice some heat for a smoother flame when using a burner as a brazing torch. So far, I use fourteen diameters to tame the flames on Vortex burners but plan to try internal vanes in an attempt to shorten their lengths.

[Mikey98118]

Handling capillary tube gas jets

 Cutting gas tube parts from refrigeration tubing (and capillary tube for gas jets) is best done with a friction cutoff wheel mounted in a rotary tool (preferably diamond coated wheels, which can be run wet, but regular jewelers friction wheels will work); the preference for diamond is to reduce formation of internal burrs.

    When used as gas jets, cut ends on stainless steel, brass, or copper capillary tube can usually be cleared of burrs with a drop of water and a circular motion of the tube on #400 grit sandpaper; this can be done with less work if torch tip cleaners or piano wire that is 0.002” smaller diameter than the capillary tube’s orifice is used to poke out any debris from cutting and sanding away internal burrs.

    Once the wire pokes through the tube’s end, run its complete length through the gas jet, and then blow out any remaining debris, before going any further (wipe down the wire with a clean rag before reinserting it in the tube). For 0.016” and larger orifices, a set of torch tip cleaners can be used, instead of piano wire. You should make sure the tip set goes down to #28 gauge AWG, to clear 0.014”; some tip sets only go down to #26 gauge (0.016” diameter). Blowing frequently on the tube’s far end during cutting can help keep debris from scattering deep into the part and clogging it.

Note: Don’t try to buy your piano wire from a musical instruments store; look for it through one of the suppliers you use to buy heavy gauge stainless steel capillary tube; a few of them sell this wire for use interacting with the tube (so they list their diameters); you won’t find that in a musical instruments store.

    You are bound to leave some copper dust and other debris within the tube during sawing, filing, and sanding, or when drilling out the inner surface to better suit whatever brass or copper capillary tube you insert for a gas jet.  Grinding dust and drill debris must be thoroughly blown out of the tube before the gas jet is installed; otherwise, it will plug up the jet orifice repeatedly. If you don’t have a compressor, use canned air from an office supply store; such cleaning is best done by blowing air from the opposite end of the tubing and through the end on which work is being done, during and after each operation. Once work begins on the tube’s other end, repeat the process there too.      

Dispenser needles (AKA blunts) don’t have a point, unlike hypodermic needles (AKA sharps); they come with metal hubs (usually zinc or chrome plated brass), and with plastic hubs; the latter variety is known as “disposable”; either kind will work to cut sections from for gas jets. Dispenser needles come in all gauge sizes, and in lengths from 1/2” to 3”; occasionally even 4”. The larger gauge needles (0.030” and above) can accommodate longer lengths (up to 2”). Smaller gauge needles need shorter lengths to prevent friction from drastically reducing their effectiveness as gas jets. Note: Friction from continuous shear deformation, compression, and expansion of a “Newtonian fluid” (the fuel gas) within small tubes cannot be overcome with the smoothest tube wall.         

A #31 gauge has a 0.006” (nominal)  orifice; #30 gauge has a 0.007” (nominal)  orifice; #29 gauge has an 0.008” (nominal)  orifice; #28 gauge also has an 0.008” (nominal)  orifice; #27 gauge has a 0.009” (nominal)  orifice; #26 gauge has an 0.011” (nominal)  orifice; #25 gauge also has an 0.011” orifice; #24 gauge has a 0.014” (nominal)  orifice; #23 gauge has a 0.014” (nominal)  orifice; #22 gauge has a 0.017” (nominal)  orifice;  #21 gauge has a 0.021”  (nominal) orifice; #20 gauge has a 0.024” (nominal) orifice; #19 gauge has a 0.028” (nominal) orifice; #18 gauge has a 0.034” (nominal) orifice;  #17 gauge has a 0.043” (nominal) orifice; #16 gauge has a 0.048” (nominal)  orifice; #15 gauge has a 0.055” (nominal)  orifice; #14 gauge has a 0.065” (nominal)  orifice; #13 gauge has a 0.073” (nominal)  orifice; #12 gauge has an 0.087” (nominal)  orifice; #11 gauge has a 0.096” (nominal)  orifice; #10 gauge has a 0.108” (nominal)  orifice.

Note: #31 gauge is the smallest needle listed because 0.005” piano wire is usually the smallest size you can find, with which to clean out possible internal burrs after cutting the needle to a shorter length, and hand sanding its end; if you go smaller, buy packs of short disposable needles, because you won’t be able to clean them out with torch tip cleaners or piano wire. #18 gauge and larger needles are listed for those who don’t prefer to use MIG contact tips.

[Mikey98118]

Brazing S.S. Funnels to Couplers or Mixing Tubes

Aside from burners built from sausage stuffer tubes (and a  few other exceptions), a burner’s funnel section must be joined to its mixing tube by cutting back its small end, and adding a coupling tube, into which a mixing tube will rest, or by brazing the funnel directly onto the mixing tube, whichever you find most convenient.

    The main reason for employing coupling tubes is to provide a greater variety of available funnel sizes; it also gives easy access to the gas jet for centering during construction, and occasional re-centering after cleaning. On the other hand brazing a funnel directly onto the burner’s mixing tube eliminates any possibility of a gas leak in a joint between these two parts.

    Propane comes in widely varying quality from different sources, but even the best of it isn’t perfectly clean (we aren’t talking about triple refined lighter butane here). The waxes and tars that all commercial propane contains are capable of plugging small capillary tubes, or even the smaller MIG contact tips, thus ruining burner performance, while rapidly increasing pressures on a gas hose and gas fittings to full cylinder pressure, unless a proper regulator—not just a needle valve—is employed. Poor quality “bargain” propane can form plugging tar balls quite rapidly.

    It then becomes necessary to shut down and clean the burner by poking the tarball out of its gas jet with a set of torch tip cleaners (or piano wire for very small orifices), and blowing it back out through the larger diameter gas tube with air pressure; canned air canisters are fine for this, if you don’t own a compressor.

    You are being shown how available funnels can be attached to available tubing products as a convenience; nothing stops you from producing your own turned or spun funnels, should you have a lathe handy. Unfortunately, as with sausage stuffing tubes, working with what’s on the market restricts possible selections, and so the occasions when funnels can be directly screwed onto, or trapped within, mixing tubes are limited.

    Fortunately, “coupling tube” connectors can be generally employed to ease burner construction. A short section, made out of the same tubing used as a spacer ring between the burner’s flame nozzle and mixing tube, can be silver brazed directly onto the funnel after threaded holes are placed in its forward end, and its joint face is beveled to closely match the funnel’s angle (just as you would do if brazing the funnel directly to a mixing tube).

    This coupling tube replaces the original funnel stem (which is cut away before brazing, and any excess sheet metal protruding into the mixing tube is ground away after brazing). Subsequently, funnel and coupler are secured onto the mixing tube with socket head Allen screws (a kind of setscrew).

   So, how short is short enough? The portion of coupling tube that extends beyond the funnel should be at least twice as long as the mixing tube’s diameter on miniature burners, and one and a half times the diameter of 1” and larger burners. You need to keep the coupling tube short enough to easily reach well into the gas jet at the gas tube’s end with torch tip cleaners, for possible removal of tar balls. Standard torch tip cleaner sets are a full two inches long. There are also extra-long torch tip cleaner sets with more than twice that length. The gas tube assembly has to be removed to clean gas jets from funnels brazed directly unto mixing tubes.

    Not only does tubing come with plus/minus tolerances (between 0.002” and 0.005” on small tubing diameters), but it isn’t perfectly round, although it’s much more concentric than pipe. When you are power sanding parts to create a close fit, don’t forget to rotate them while frequently checking how well they slip together. Before securing the coupling tube on the mixing tube with setscrews, rotate both tubes to assure a tight fit; twist to loosen them before disassembly.

    Remember to completely remove internal burrs and chase the screw threads as many times as required to ensure a smooth fit between coupling ring and mixing tube; a round file wrapped in sandpaper can be a great help in removing the internal burrs and deformations made by a threading tap. Don’t forget to file or sand the ends of setscrews flat, before screwing them into the coupler tubes threaded holes; otherwise, they will scare the surface of the mixing tube, which will interfere in the fit-up afterward.

    Some funnel stems will fit closely enough on smaller tube sizes (up to 3/8” burners) to slip over the outside, or into the opening of D.O.M or stainless steel tubing. If outside, a separate tightening fixture is called for; a locking collar. After cutting a thin slot into the mixing tube or onto a funnel stem’s end (not quite as deep as the collar is wide), a simple inexpensive drill bit collar can be used to squeeze the slit tubing section tight around the funnel stem inside it. Stop collars are commonly found in sizes meant for 1/8”, 3/16”, 1/4”, 5/16”, 3/8”, 7/16”, and 1/2” diameter drill bits. But drill stops are also available in size differences given in sixty-fourths of an inch. Or the funnel and mixing tube can be permanently brazed together.

Note: Mandrel collars are very similar to drill stops, and the same part might be found under either category in a large hardware store.   

 

Two Allen screws can be added at one-third distance from the first screw, and from each other, to increase the tightening and centering effectiveness over that of a single screw. The collars are available in a variety of single piece sizes at most hardware stores and in cheap sets through amazon.com and eBay. By drilling threaded holes for three equally spaced Allen screws into at least 1/8” thick wall tube (thicker is better), you can create your own collar in a convenient length for any tube diameter. Drilled out round bar or hex stock can be even handier if your mixing tube’s outside diameter is a hard size to closely match. Worm screw hose clamps can only be used when the funnel is slipped inside of a mixing tube, and are not recommended in any case.

    When you choose to attach a reducer directly onto a mixing tube, it becomes important to ensure a perfect fit. Otherwise the inside of the joint must be power sanded into a smooth transition; this isn't only needed for good mixture flow. You must build and use a centering rod to ensure that the gas jet is soldered or brazed dead center in the middle of the mixing tube during construction. Afterward, the rod will be used to ensure the jet stays centered during maintenance. The rod must move smoothly past the joint, to work properly.

    Once you have the mixing tube and reducer fitting, buy a long enough length of threaded rod to extend comfortably beyond both reducer and mixing tube with room to spare for nuts, a large washer for the tube end, and a drilled plate or board for the reducer end. Then clamp all of the parts together for silver brazing. You will have to use at least 50% silver filler and flux meant for brazing on stainless steel.

As has been stated before, brazing on stainless steel parts requires: Sanding or wire scouring the stainless steel surfaces just before fluxing; the flux most be rated for stainless steel; the silver braze alloy must be at least 50% silver (higher is better).

[Mikey98118]

Internal vanes aren't the only way to slow down the very fast spin of Vortex burner flames. The exit tubes on stainless steel funnels can be pushed into mixing tubes, creating a 1-1/6" thick shoulder at the beginning of the mixing tube, which will slow the spin of its mixture flow. thin spacer rings can slow it even more; just take care not to overdo it. This would be easier to get right than internal vanes.

What would be the point of this? If it works, the mixing tube can be shortened.

[Mikey98118]

That should read "...a 1/16" thick shoulder ..."

[KENR2600]

On ‎3‎/‎11‎/‎2018 at 5:19 PM, Mikey98118 said:

What I'm seeing is an almost right set of burners; at present, the flames are not getting enough air, and so are burning rich. How about showing us the burner's other ends, and maybe we can help you.

BTW, your flame nozzles look a little too short, which isn't hurting performance yet, but may well do so once we up the burner's air induction.

  Air in seemed to be a major issue...assuming having PLENTY of air is an easy remedy - I went hog wild in some tweaks: -changed the throat to mix tube angle in, beveled the tops of the bells inward- sand smoothed and painted, while increasing the ID by 1/4" overall, and extended the tips closer to the throat of the mixing tube. Now, I've got more air than I can handle. Burner 2 won't even take a light without the choke cap tight, and whistles the air in as soon as I crack it.  And of course, my flame nozzles are looking to be just short of holding the flame on. BUT, I think I need to drag the jets back just a little more yet.  I've got a handful of them, and will be trying to hunt down that "sweet spot". I also have a mixing tube an inch longer than my current ones to try swapping in and out. Definitely some tweak tuning to do, but even now in decent pressures, I can adjust air and gas to go from greenish, to pale, to purple, while holding a decent flame. Open the air too much too quick, or hit the pressure to high, and it blows itself out right quick. Once I get the balance to what I figure is best, I'll notate and update accordingly. Thank You for the right pathway!

[Mikey98118]

4 hours ago, KENR2600 said:

I can adjust air and gas to go from greenish, to pale, to purple, while holding a decent flame.

You are describing burners with excellent balance. Probably, what you need now is simply to play with them until you become familiar with what it takes to balance them, which we call tuning, where you want them. I would love to see photos of them posted here with all three colors showing. You just described burners that can be changed from reducing (greenish); through neutral (light to medium blue); to heavily oxidizing.

Congratulations; you are a fast study in burner design  

[Mikey98118]

Light to medium blue? Yes; reducing, neutral, and oxidizing flames aren't points on a chart, but ranges of flame behavior:

Reducing flames range run from the faintest tinge of green in a blue flame to straight green flames that are pushing so much unburned fuel into your shop's atmosphere that you feel like gagging.

Neutral flames range range range from light to medium blue; they are neutral throughout this same for all practical purposes; what that means is, although their combustion chemistry is changing, we can't appreciate the difference without scientific instruments ($$$).

Oxidizing flames start just beyond medium blue, go through dark blue, and extend to purple.

Flame color isn't the only indication of how good the flame is. The amount of secondary flame is also an important indicator; the less secondary flame the better. There is such a thing as a perfect performance, which is no secondary flame. The perfect is usually the enemy of the practical. A wisp of secondary flame is actually better than no secondary flame at all; this is because burner flames fluctuate, so the "perfect" flame is likely to be slightly oxidizing part of the time. Since a wisp of secondary flame will burn up completely in the forge, it is better than added scaling on your work.

[Mikey98118]

Even with the best possible flame, that you can detect visually, there will be some separate superheated oxygen molecules that haven't had time to combine with fuel gas molecules; not enough that you can see the combustion going on, but any superheated oxygen that impinges on superheated metal, will joyfully combine to create scale. What this means is that a few inches between the visual end of the flame and your workpieces are highly valuable.

[Mikey98118]

6 hours ago, KENR2600 said:

Air in seemed to be a major issue...

I thought that enough air amount was the main issue for a long time, but air spin turns out to be what you want to maximize. With jet-ejector burners, spin amounts are determined by the design of the air opening. With linear burners, spin amount is determined by how large the funnel shape is; not just because larger funnels have larger entrance diameters to entrain more air, but because those larger openings allow the incoming air to be spun faster as it passes through the funnel from entrance to exit.