Burners 101

[colgate2004]

Hah! Well thank you, gents.

I've put my location in my profile (at least, *I think* I did that right)... it's funny, as you said, it's already turned out that there are more smiths nearby than I would have thought. I stumbled across a forge while just walking through town the other week and ended up chatting with a very nice gentleman who has apparently worked as a full-time commercial smith in the same location out of the same shop for 50 years. Very generous fellow, happy to take time out of his day to chat with me, even made me a little leaf to give my daughter right while I was standing there at his anvil. The kindness of many people really never ceases to amaze me.

[Mikey98118]

/

Swirl power

Craftsmen have constructed powered gas burners with squirrel cage fans for decades. Naturally aspirated burners have been around for centuries, but these two burner types could not be successfully merged. Powering air swirl, instead of push at a burner’s air entrance achieves this goal, by engaging vortical movement.

    Why have burner fans produced such limited performance? Because forcing air into the burner increases the gas/air mixture’s flow pressure; that additional pressure must be reduced in the flame retention nozzle, as the mixture exits; otherwise, the flame is blown off the burner’s end. That nozzle’s flame retentive ability is limited, so any strategy that increases flow speed by increasing flow pressure is self-defeating. Since a flame retention nozzle can only provide weak braking, limiting the burner’s gas/air mixture flow pressure at its source multiplies nozzle efficiency. Sadly, the idea of pushing input air is so entrenched that the other popular terms for fan burners are “forced-air” and “fan-blown.”

    There are numerous ways to swirl incoming air and fuel gas, but only when the mixture passes through a restriction (ex. pipe reducer or funnel) can vortical movement become a practical age to mixing. Any device that creates spin at the air entrance will increase vortical flow; this includes directly opposite openings on “T” plumbing fixtures, or blade structures in front of the opening of a reducer fitting, or slots on a Hybrid burner. But, forcing air directly into a funnel entrance increases vortical flow at the cost of increased flow pressure. Helping incoming air to start swirling does not.

    But didn't we start out by stating that fans can be effectively employed? Yes; most computer fans are designed to produce swirl-not push.

 

[Mikey98118]

So, if turbulence in the entrained air (incoming air) is the favored method of mixing, are their limits on what method you choose to mix it with air? Yes, and that limit is drag. Anything that helps mix the fuel gas and air will create drag on the mixture's flow; some methods more than others. Swirling incoming air around the axis of flow doesn't necessarily mix it with fuel gas better than other methods; it simply creates the least drag in exchange for that mixing.

[Frosty]

A vortex does more than limit friction, Mike. Because it is moving on a curved surface there is a low pressure boundary layer reducing friction significantly. The center of the vortex is at a significantly lower pressure increasing induction forces improving the effectiveness.

This isn't equal on all burners of course, a T burner doesn't generate a particularly strong vortex so realizes minimum effects.

I know you call this "swirl" but as it goes down the mixing tube of a burner swirl amplifies to a proper vortex. 

Frosty The Lucky. 

[Mikey98118]

Agreed, Frosty. I try not to use vortex all the time; it makes me sound like a broken record. And I didn't use the term friction. I was writing obout drag; not friction.

[Mikey98118]

So. moving on; vortical movement will cause swirl, along with other positive things, but swirl can happen without vortical flow. Air entrances in the sides of a tubular shape can create swirl without contributing other aspects of vortical flow. How? A gas stream shooting down the cylinder's center induces air in through the side openings, where the air currents are pushed a little sideways to avoid each other, creating swirl in the forward momentum. Mikey burners work this way, without any added vortical attributes. Similar air openings on a Hybrid burner create swirl in incoming air as it is pushed forward by the gas jet, but it then encounters a reducer, creating vortical flow, so the original swirl acts like a supercharger for the vortex, because  the air is already swirling before it enters the restricting shape.

[Mikey98118]

A fender washer can  cut into three separate openings between three separate ribs, then placed in the large end of a funnel shape, and provide swirl to the incoming air as it enters the funnel. Thus strengthening vortical flow, while providing a structure to hold the burner's  gas pipe.

[Mikey98118]

Air, when passing over a rim (surface edge) will create eddies (circular currents); this creates drag on air flow. Round edges create more drag than straight edges. Square or rectangular air entrances create less drag than round openings.

The greater the curve the greater the drag. One large hole creates less drag than several smaller holes.

A slot creates less drag than a hole.

[Mikey98118]

Dremel #420 Cut-off discs are 15/16 " (23.8 mm) diameter, by 0.040" (1.0 mm) thickness, and are rated to 35,000 RPM; they are sold in twenty discs kits for $4.97 through Amazon.com; they are not fiberglass reinforced, but are much more durable on steel than standard 0.025" (0.617 mm) thick jewelers’ discs, have the same added safety during kickback, and enhanced control when cutting next to corners. These discs are meant for slicing and cutting metals; do not use their sides for grinding. The smaller the air opening the handier these discs become.

[Mikey98118]

Cobalt drill bits

Cobalt drill bits are high speed steel with cobalt added, starting with M-35 (5% cobalt); the next higher grade is M-42 (8% cobalt); both grades have reasonable prices. The grades go up higher, but so do their prices. Also, M51 is tougher than the first two grades, but has no “red-hardness.” What matters to you is that M-35 and M-42 bits do have red hardness, which is very desirable when you are running bits at higher RPM than recommended, Cobalt bits are available through Amazon.com for the same money you would pay for regular high-speed steel bits at your local hardware store. Why are bits so much more expensive at a hardware store? Overhead.

    What does “red-hardness” mean? Most steel cutting tools, including drill bits, are hardened by quenching, to quickly reduce their temperature from around 900 F. The “glass hard” surface, is then tempered to the desired balance between hardness and toughness with various heating and cooling processes carried out at much lower temperatures. What is true for most steel is that heating it up beyond 400 F will further temper it into uselessness. Running a tool edge along a steel surface can rapidly produce such temperature ranges if no oil or water cooling is employed. Or if your tool RPM is too high.

    The exception to unwanted blue-hot tempering is red-hard steel, which will remain hard at much higher temperatures; in fact, you can heat it up to red incandescence, and it will remain hard, once it cools. So, friction heating produced (among other things) by high RPM doesn’t dull leading edges on cobalt bits anywhere near as fast as on high-speed steel bits. At proper speeds, cobalt drill bits last as long in stainless steel, as high-speed steel drill bits do in mild steel.

[Mikey98118]

Surface Cutting

When you run a chop saw, or plunge cut with a hand-held circular saw, the last thing you want to do is stop the saw during the cut; more often than not, doing so will cause kickback. The opposite is true when surface cutting through sheet metal products, like pipe and tubing.

    Those OEMs (like Dremel Tools) who bother with thorough safety tips in their rotary tool instruction manuals, all advise the operator to run the cutoff disc back and forth on the part surface, gradually deepening a groove at the cut line, until the disc begins to break through the groove, which is then called the “kerf.” Unlike chop sawing or plunge cutting through parts, the operator is supposed to bring the disc to a halt before exiting the kerf; it is dissimilar to other processes, because your disc isn’t deeply buried in the part. There is very little material for the disc to “walk up,” creating an opportunity for kickback, as the disc stops. Also, the numerous tiny grit edges don’t have anything like the tendency to grab unto stock that the teeth of circular blades do. Most kickback from resin bonded cutting discs come from the sides of their discs binding against the kerf. So, surface cutting creates a unique situation, where stopping the disc before removing it from the kerf is safer than removing the disc while it is still in motion.

    Die grinders are treated the same as rotary tools for surface cutting (my own description for the technique).

[Mikey98118]

Diamond coated cutoff discs, just like diamond coated burs, where originally designed to be used on glass, stone, and ceramic surfaces; not steel. But diamond coated burs and disks are quick and smooth acting on steel; most of them are also dirt-cheap imports; offsetting their short life expectancy, do to this “mistreatment”. The secret to quickly finding a large selection of these accessories is inputting the right word search; try “diamond rotary disc” on Amazon.com or eBay. Diamond coated discs are thin, rigid, and smooth acting; and therefore, are inclined to create an accurate groove for resin bonded discs to continue in, (instead of then “walking” around on a part’s surface, before taking a bite).      

    Some discs are plain, and others have air ventilation holes; holes help keep part temperature down, as does water spritzing the work during cutting (important to tool life on ceramic tiles, but irrelevant on sheet metal work).

    22mm discs (about 7/8”) can be especially useful; they are easiest to control in the cut, are perfect for grinding back to a scribed line (after finishing cuts beside it), and far less likely to suffer a kick-back at the beginning or end of a cut; they are also handy for sharpening small drill bits, and tungsten carbide tipped tools.

    Diamond coated discs have steel bodies, so they can’t fly apart like resin-based discs, but you must still keep them at or below their maximum speed rating, because they’re not balanced well enough to spin faster, and can vibrate enough to harm your rotary tool.

    High quality diamond coated steel cutting discs, meant for steel work, cost a lot more than the cheap imports, that are meant for cutting tile, but are well worth their prices.

    “More is better” is an especially false assumption with diamond coated steel discs. The larger the disc the more likely it is to create kickback, and the more powerful kickback forces will be. It should be mounted in a rotary tool; not a die grinder, and 1-1/2” discs should be the maximum. The smaller the disc the safer the choice. Overall, the cheap imported discs have limited utility, but at a much lower price. They work best when changed out back and for the with resin bonded grit cutoff discs. Use the diamond coated discs to begin and end cuts, for starting grooves, and for grinding the opening back to scribed cut lines.

[jlpservicesinc]

I have been using diamond cutting disks designed for steel and stainless steel for about 3 years now.. 

They have a far better life span than abrasives and do not shrink in size while being used.. 

Are reasonably priced compared to Carbide tipped blades and work a treat.. 

The carbide ones are much faster vs abrasive/diamond but for the money are worth the slower cutting.. 

I've been using ones from china and outlive abrasive disks 20 to 1 in the 5" and under sizes.. 

I have a 14" disk which I have not tried yet in the abrasive saw.. 

[Mikey98118]

 

thanks. Input from other users are very helpful for people who are making up their minds about doing something new

 

Layout Tools and Techniques Simplified

 

Air entrances should be three equally spaced openings on burner mixing tubes. Each opening has two longitudinal sides, so you will need six equally spaced lines for three air openings. Hex head bolts can be found down at your local hardware store, with the right size two match up with mixing tube diameters, and tape will allow them to be centered within the tube.

    ½” by ½” steel angle can be purchased from online metal providers, becoming perfect layout tools to extend ink points at hex points into perfect longitudinal lines. Sliding choke sleeves become layout tools for the circular lines at the forward and rear edges of the air entrances.

    While ink lines are sufficient for those who are practiced at cutting on tube and pipe, drilled holes just inside of each inside corner helps. Scribed lines are better than inked lines, and bluing improves the view on stainless steel surfaces. How much care you put into the layout is up to you.

[Mikey98118]

Wobble

Poorly finished mandrels can cause cutoff discs and grinding wheels to wobble. This is a common problem that is seldom correctly diagnosed, because customer complaints incorrectly blame the discs. But what is actually happening is that the mandrel’s forward edge is out of true right angles to the shank’s axial center. Or, one (or both) of the flat washers provided isn’t perfectly flat. Circular motion on find sandpaper can true up washer surfaces, and the mandrel can be spun in your rotary tool, while its forward face is quickly trued up with a silicon carbide stone, or diamond coated cutoff disc.

[Mikey98118]

MK MIG tips

MK MIG tips (and their MK style substitutes) are 1-1/2" by 1/4” diameter, but come with #12-24 threads. However some of their tips are 1-3/4" long, which can be an advantage with some burner configurations. The MK taper is short and blunt; it’s shape should be supplemented with further tapering, to at least conform to the longer Tweco taper, but can be used “as is.”

MK tips have smaller thread than Tweco style tips (12-24 thread), which can be an advantage when used in 3/8” and smaller burners, becuase you can use smaller gas pipes. The part numbers given below conform with those used by MK; the last set of numerals (25) indicate the number of parts to be ordered from the source listed in the resource section at the end of this chapter.

1-1/2” long MK contact tip for 0.023” wire (0.6mm) has an actual orifice diameter of 0.031”, and would run a burner made from 1/2” black wall (water) pipe, or similar tubing; part number 621-0057-25.

1-3/4” long MK contact tip for 0.023” wire (0.6mm) has an actual orifice diameter of 0.031”, and would run a burner made from 1/2” black (water) pipe, or similar tubing; part number 621-0328-25.

[Mikey98118]

Handy Micro Gas orifices

The smallest orifice diameter available on a MIG contact tip is thirty-one thousandths of an inch. In “Gas Burners for Forges, Furnaces, & Kilns” I recommended the use of welding torch tips as a simple way to acquire smaller orifice sizes; they were expensive then, and with one single exception (Hoke tips), are even more so now.

Also, while tapered tips pose little problem to laminar flow in burners down to half-inch, miniature burners have less internal area to allow for entrained air to flow past an obstruction.

A model maker might simply employ small number gauge drill bits in the US, or small metric drill bits in Europe, held in high speed chuck adapters, to both drill and clean accelerator bores down to size #80 (0.0135”), in order to create any desired orifice size.

But the longer the bore the more care must be taken to avoid snapping a tiny drill bit off in the hole. If you take this rout, be sure to use half-hard brass; not annealed brass, or even the softer copper. If the drilled hole is large enough (0.0135” or more) internal burrs can be smoothed out with torch tip cleaners used as tiny round files.

It is also possible to use numbered drill bits for enlarging small holes in copper and brass capillary tube a few thousandths at a time (any attempt to drill more than a few thousandths away only results in the drill bit getting caught in the soft alloy and snapping off).

However, if drilling is used, it still becomes necessary to file the orifice smooth again, because fluted drill bits leave spiral scoring in the hole, which prevents the formation of a smooth column of exit gas; and that interferes with the process of air entrainment, and mixture speed down the burner tube. Major problems sometimes grow from minor sloppiness.

Various capillary tube products can be utilized, as gas orifices. But let’s begin with the single exception to expensive torch tip gas jets:

Standard Hoke oxy-fuel torch tips: The Hoke jewelers torch (made by Grobet,) has been a mainstay of the trade for decades. Standard Hoke welding tips come in extra fine, fine, medium, and broad for all their different oxy-fuel torch models. The Jewelers Adapter Kit (also made by Grobet), but these are the standard Hoke torch tips that have been around for over seventy years. The tip’s importance to you is price and availability; they cost around $2.50 and can be found at any jewelers supply, local or online, that sells Hoke torches (see resource list). Unlike MIG contact tips, these tips are sold singly.

Hoke tips are 7/8” long, made from 1/4” hex stock, with 3/16” long flats, are bluntly tapered forward, and have 3/16-40 by 1/4” long male thread; they come in four different sizes:

Extra fine flame tips, stamped #04, have a 0.010” diameter orifice, and are fit for 1/8" burners.

Fine flame tips, stamped #03, have a 0.014” diameter orifice, and are fit for 1/4" burners.

Medium flame tips, stamped #02, have a 0.023” diameter orifice, fit for 3/8 burners.

Exhaustive list of Hoke welding tips at low prices at jewelerstoystore.com

[Mikey98118]

Them as have the parts name them

Many bright young hobbyists are learning to use machine shop equipment, but still don’t have a general shop background. I was surprised 17 years ago by complaints concerning Gas Burners for Forges, Furnaces, & Kilns “obscure technical language.” It turns out that terms like 1/4-28 thread presented otherwise well-educated people with a mystery. When you go shopping for parts and materials, you’re going to have to deal with technical terms.

When it comes to technical terms, whosoever has the power in any given situation gets to make the rules. In this case, manufacturers developed these terms to suit interaction between their own sales departments and mechanical engineers and contractor; they couldn’t care less if their old English teachers are appalled by the results.

If you want to play the game, you have to play by their rules, and resenting it won’t help you to choose parts from a sales catalog, or keep you from being treated like the village idiot by a clerk at the parts supply counter.

Even firms that are open to the general public don’t look forward to serving someone making a minor purchase; this kind of sale only profits a company like McDonalds burger chain. What you plan to spend may not even cover the cost of the paper work for the goods.

Therefore, the minimum wage sales clerk you’ll be dealing with just wants to see you gone one way or the other. If you appear ignorant, “I don’t think we carry that sir” is the quickest method of dealing with you; and his manager will stand right behind him without saying a word more often than not.

Know what you’re asking for, and keep up a pleasant front, if you wish to come away with the needed part.

[Frosty]

Might those same people who complain about obscure technical language be the same ones who wonder what's wrong with the tool? 

Frosty The Lucky.

[Mikey98118]

Obviously you have been cruising through customer complaints on Amazon.com, Frosty. I can understand the lack of desire to "learn a whole new language" just to do minor jobs around the house. However, those same people had no trouble learning computer terms, or legal terms, etc.," just to have a job." Yes, in fact I feel the same way about making my way around computer glitches, just to do a little writing

So saying, I confess my own shortsightedness...

[Frosty]

Nope, I've heard enough complaints in my life I don't need to cruise the complaint mills. You hear it all the time, "If I had one of those I could . . ." Learning to use one of those isn't necessary you know. 

One of the guys I used to work with took a machine shop extension course and could tell you all about the old lathe we had in the shop. Couldn't work it worth spit though and kept adjusting things because he couldn't.

The lathe just wasn't working right. He wanted to turn 1/32" off 40" of 1/2" round for some reason. He kept adjusting the angle and offset of the tail stock because every time he tried another piece it was narrow in the center. 

"It won't do that if you use the follower, Roscoe." (Not his real name) Oh boy, he knows what he's doing, there's something wrong with the lathe!

It took me about an hour to get everything trued back up. If there was a lock nut and adjustment screw he'd adjusted it. <sigh>

Oh, then there was one of the other guys who would use a hammer to start taps. "They call them TAPS for a reason!" No bull.

No I don't need to cruise Amazon, I have decades of real life examples to recall. 

Frosty The Lucky.

 

[pnut]

39 minutes ago, Frosty said:

"They call them TAPS for a reason!" No bull.

This is one of the funniest and saddest things I've heard. 

Pnut

[Frosty]

You should've had to work with the guy. No, you shouldn't have, I like you.

Frosty The Lucky.

[Mikey98118]

Hoke torch tip adapters, and separate tips can be purchased, along with complete adapter kits, Hoke torches, and regular Hoke tips from Shore International.

[Mikey98118]

Mounting a MIG tip in the Mensi needle valve.

Mensi needle valves are meant for use in some propane camping stoves; they have metric threads, which is no big deal. More importantly, they have the right internal diameter and thread type to be re threaded to mount a MIG contact tip into, and an external thread diameter on their outlet side to be screwed into the mixing tube of a 1/4" burner. The addition of a spacer ring will allow them to feed a 3/8" burner.

Pairs of Mensi valves only cost $9 through Amazon.com; that is one-third the price of the average needle valve. Equally important is the fact that they are set up to be hose mounted, and regulator fed from a refillable LPG cylinder.

    The original gas orifice is unscrewed from the Mensi needle valve; this is the valve’s outlet side, and its M1x1 male thread will be screwed into the new 1/4" pipel mixing tube. The original gas orifice will be replaced with a MIG contact tip, with a capillary tube gas orifice. The existing internal thread holding the original gas orifice is close enough to the MIG tip’s thread, that a ¼-27 plug tap easily re-threads the existing thread to accept a MIG tip, although some of the tip’s thread will protrude.

    Close the needle valve completely before re threading with the tap. Break off the internal burr by partially reversing the tap’s forward direction, every quarter turn, and tap the valve repeatedly to dislodge the brass fillings from the valve, before opening the valve, after re threading.