Burners 101

[Mikey98118]

One of the problems that remain with all this equipment is the delicacy of their speed control circuits; if you do not want them to burn out, do not run the motor slower than half speed. Aft this circuit dies, because you ignored this warning, you can bring the dead tool back to life, by cutting out the speed circuit, and replacing it with a length of wire. Your tool will only run at full speed thereafter, but that beats a dead tool.

[Mikey98118]

Flame retention nozzles

Details of burner construction depend on how fast and how low pressure the flow of fuel gas and air down the mixing tube is into the flame chamber made by the nozzle; and these factors hang on the overall design of a gas burner.

    There are two functions of flame nozzles; the lesser (but still important) of them is to provide a low-pressure area barrier before the mixing tube; thus, providing a safety factor by reducing the ability of flame to burn-back down the tube into the burner.

    The greater function is, by reducing pressure in the nozzle it helps "glue" the flame in place. Expanding gases from combustion creates forward pressure, which can blow the flame away from the end of the burner, blowing it out: all there is to stop that is the counter pressure of ambient air beyond the flame envelope (AKA pressure front). What air pressure? Only the difference between surrounding air and the lowered pressure of a partial vacuum formed by the drop in mixture pressure, which is made by the increased internal diameter in the nozzle area; this is assisted by the partial vacuum formed by a vortex in newer burner designs.

    There is an additional factor gained by flame nozzles; the ability to partially "suck" the flame back into the nozzle area, super-heating the nozzle into incandescent temperature; creating a large second ignition surface to add to the flame front that ignition usually tends to burn back toward the flame retention nozzle from.

    Finally, there is a synergistic motor affect created through the ability of flame nozzles to allow combustion rates to be greatly increased. Just as we are aware that the gas stream at the burners other end entrains air into the mixing tube by induction (Bernoulli's Principle), the flame itself can become, in effect, a second induction motor, speeding up mixture flow even more within the burner.

    But the flame also becomes a powerful induction motor on the outside of the burner, causing a lot of secondary air flow passed an entrance way, which should therefore be partially or fully closed (depending on burner design), to stop or slow secondary air, as needed.

Intense burners require slide-over stepped flame retention nozzles (AKA flame retention cups); the simplest of these consist of a spacer ring, and outer tube, held in place by one to six socket set screws. The main job of the spacer ring is to keep the nozzle’s outer tube centered and parallel to the mixing tube. But, why stepped instead of tapered nozzles? Unless you have a metal spinning lathe, changes in taper angles, which are needed for changes in mixture flow is going to somewhat arduous to manage correctly; therefor, they will not be. The pitiful examples of tapered nozzles on commercial burners, prove this point. Exchanging wall thicknesses on pipe and tubing a few thousandths of an inch, to accommodate flow changes in burner designs is much esier.

    Cutting a longitudinal slit in the pipe or tubing being employed as a spacer tube, allows its diameter to shrink or expand as needed, within the flame retention nozzle’s outer tube, which increases the choices of suitable pipe and tube; it also allows the spacer ring to be contracted around thin wall mixing tubes, which would otherwise be dimpled by direct contact with set screws; this increases choice in usable parts, as most sausage stuffing tubes have thin wall tubing.

Note: It has been repeatedly proven that an air gap between the outer tube and the spacer ring, or between the ring and the burner’s mixing tube (of up to 1/16”) does no harm, if you are willing and able to use six set screws to center the outer tube, and keep it parallel to the mixing tube.

    Due to the ridiculously high cost of small orders in stainless-steel pipe and tubing, as their sizes increase beyond 3/4”, mild steel pipe nipples, should be substituted for stainless-steel to make mixing tubes and spacer rings in the larger burner sizes. Schedule #40 pipe nipples of various lengths are available in hardware stores, and longer length pipe nipples are available in plumbing supply stores.

    Because cutting fees make 1” long parts used as as spacer rings, and approximately 2” to 4” long parts used for the flame retention nozzle’s outer tube nearly as expensive as 12” lengths), they should be cut from male pipe nipples (mild steel for spacer rings, and stainless-steel for outer tubes) to become far less expensive versions of flame retention nozzles; this can drastically reduce the costs to build your burner. This choice will produce slide-over step nozzles, which work every bit as well as nozzles that are built from lengths of tube and pipe, but which will not last quite as long, because the nozzle’s outer tube can only be made of #304 stainless, instead of #316.

Note: These nozzles are kept in position with stainless steel socket-head screws. Do not use mild steel screws; they will freeze in place after a few heats. It takes months to wear out a flame retention nozzle, but they are disposable parts, and frozen screws must be drilled out.

    The outer tube should overhang the mixing tube by 0.125” longer than its inside diameter. The spacer ring should be 1” long, so that additional inch is added to the length of the outer tube. The nozzle is kept in position on the burner’s mixing tube with as little as a single screw, or as many as six screws, depending on how well it fits up to the mixing tube.

Caution: Stainless steel flame retention nozzles on a good burner design, will get to yellow heat in ambient air, if you burn propylene, and will quickly melt down in a forge. The same nozzle will get to orange heat in ambient air, burning propane, and will melt down in a forge, if they are not recessed at least one-inch into the burner portal; do not position them close to the forge’s swirling super-heated atmosphere!

[Mikey98118]

On 12/21/2023 at 5:33 PM, Mikey98118 said:

From mini 12V angle grinders to rotary tools

 

Going on with this discussion, I got a Phalanx 12V rotary tool for Christmas; its motor has lots of torque, and you can get replacement batteries for it for $20. All of these manufacturers insure that their tools will not accept a different OEM's battery, worse luck. But, at least they are available for this brand.

[Mikey98118]

                                                                                     Burner sizes

The first thing you must decide about your burner is what size it is going to be. Home-built burner sizes are given according to schedule #40 pipe sizes (or its equivalent inside diameters in round tubing) that is used as the burner’s mixing tube. These burners were built from fractional pipe for many years (and most still are). So, it is handy to know what actual inside diameters these nominal pipe sizes have, since it is the inside diameter, you are trying to match in a gas orifice diameter, and to whatever you use for a conical air entrance.

    Actual Imperial (fractional) pipe diameters are larger than their nominal pipe sizes, both outside and inside. If you choose tubing instead, it will seldom be an exact match with pipe, so choose a little larger inside diameter, when possible (rather than a little smaller), for your burner’s mixing tube, or the flame retention nozzle’s spacer ring, and outer tube. Imported stainless-steel tube can be a handy alternative to fractional tube in the smaller sizes, and is more likely to match up well with most stainless-steel funnel shapes. Imported cast stainless steel pipe, while being advertised in inches on Amazon.com, are nearly all  made to metric dimensions.

       Schedule #40 pipe dimensions:                    Metric

(A) 1/8” pipe is 0.405” O.D. x 0.270” I.D.      10x8mm (0.390” O.D. x 0.312” I.D.) tube. The burner’s nozzle size is 0.493” I.D; this is sufficient to heat 22 cubic inches on naturally aspirated burners.                                                  

(B) 1/4” pipe is 0.540” O.D. x 0.364” I.D.      12x10mm (0.468” O.D. x 0.390” I.D.) tube. The 1/4” burner’s nozzle is 0.622” I.D.; this is sufficient to heat 44 cubic inches on naturally aspirated burners.

(C) 3/8” pipe is 0.675” O.D. x 0.493” I.D.       14x12mm (0.546” O.D. x 0.468” I.D. tube. The 3/8” burner’s nozzle is 0.824” I.D.; this is sufficient to heat 88 cubic inches on naturally aspirated burners.

(D) 1/2” pipe is 0.840” O.D. x 0.622” I.D.     18x16mm 0.702” O.D. x 0.624”) I.D.) tube. The 1/2” burner’s nozzle is 1.049” I.D.; this is sufficient to heat 175 cubic inches on naturally aspirated burners.

(E) 3/4” pipe is 1.050” O.D. x 0.824” I.D.      20mm pipe nipples sand couplers are 0.78” The 3/4” burner’s nozzle is 1.315” I.D.; this is sufficient to heat 350 cubic inches on naturally aspirated burners.                     

(F) 1” pipe is 1.315” O.D. x 1.049” I.D.          25mm pipe nipples and couplers are 0.975” The 1” burner’s nozzle is 1.61” I.D.; this is sufficient to heat 700 cubic inches on naturally aspirated burners.

Be advised that imported cast stainless steel pipe fittings are very likely to be metric; not fractional (Imperial), no matter what their online advertisements state.

[Mikey98118]

Note: “Sufficient to heat” means that it can raise a properly built forge interior of those cubic inches to welding heat, or pour in an equal size casting furnace. Are these figures legitimate? In fact, they are under stated; not over reaching. What about the optional second (larger) flame retention nozzles on fan-induced (impeller blades) burners? Whatever inside diameter is used with one of them, with the gas pressure turned up to match the fan running at full speed, can be considered as producing a flame equal to that nozzle size in a naturally aspirated burner. You can more than match the maximum output on the next larger size naturally aspirated burner.

    The number of cubic inches that can be brought to welding temperature in a properly built forge, or the number of cubic inches in a casting furnace that can b bronze casting temperatures (from a burner with a neutral flame), depends on the inside diameter of its flame retention nozzle; this is limited by the diameter of a burner’s mixing tube, in naturally aspirated burners, but nozzle diameters on fan-induced burners must be larger, when the fan is running at full power, and the fuel gas is increased to match its increased air induction, so the amount of cubic inches a fan-induced burner will sufficiently heat depends on the internal diameter of its flame retention nozzle; not on its mixing tube diameter.

[Mikey98118]

Note: “Sufficient to heat” means that it can raise a properly built forge interior of those cubic inches to welding heat, or pour in an equal size casting furnace. Are these figures legitimate? In fact, they are under stated; not over reaching. What about the optional second (larger) flame retention nozzles on fan-induced (impeller blades) burners? Whatever inside diameter is used with one of them, with the gas pressure turned up to match the fan running at full speed, can be considered as producing a flame equal to that nozzle size in a naturally aspirated burner. You can more than match the maximum output on the next larger size naturally aspirated burner.

    The number of cubic inches that can be brought to welding temperature in a properly built forge, or the number of cubic inches in a casting furnace that can b bronze casting temperatures (from a burner with a neutral flame), depends on the inside diameter of its flame retention nozzle; this is limited by the diameter of a burner’s mixing tube, in naturally aspirated burners, but nozzle diameters on fan-induced burners must be larger, when the fan is running at full power, and the fuel gas is increased to match its increased air induction, so the amount of cubic inches a fan-induced burner will sufficiently heat depends on the internal diameter of its flame retention nozzle; not on its mixing tube diameter.

Small stainless steel tube is the simplest choice to work with for any tubing part (although schedule #40 stainless steel pipe nipples purchased online might be cheaper); and stainless steel is the choice that is demanded for at least the outer tube of a burner’s slide-over stepped flame retention nozzle. Online prices are set by the desire for profit, and regulated only by competition from other profiteers. Therefore, you might as well end up with stainless steel parts, because you will a premium price, whether you choose a premium part or not.

    Thicker stainless steel millimeter tubing (2mm or more), needed for flame retention nozzle outer tubes, become pricy in 14mm sizes and up. So, you will find it cheaper to switch to stainless steel fractional tubing or pipe for such parts. When changing from millimeter to fractional tubing, you will be unlikely to match up a fractional outer tube with the nozzle’s spacer ring, and then the ring with the mixing tube for a sliding fit. So, it is good to know that up to a 1/8” gap between outer tube and spacer ring, is easily tolerated by the burner.  You can make the parts fit by slitting the spacer ring, and only drilling the outer tube for socket set screws. Under sized rings can be sprung open, and over sized rings can be compressed to fit into the outer tube.

Mixing tube lengths of naturally aspirated high-speed burners should be nine times the inside diameter of the tube. Mixing tube lengths of fan-induced burners should be fourteen times the inside diameter of the tube, unless internal fins are placed within the mixing tube’s end, to stop mixture swirl. These lengths are rules-of-thumb, for best overall performance; they can be adjusted to suite performance in particular circumstances. If a burner of either kind is primarily used as a hand torch, lengthening the mixing tube will provide a smoother flame for silver brazing. Shortening the tube will make harder shorter flames to help use up oxygen before the flame can impinge on parts that are being heated in a forge. Lengthen a mixing tube no more than twenty percent, and slowly cut it back, while observing the flame, for best results. Shorten mixing tubes less than ten percent of length, and shorten further while watching the flame, for best results.

[Mikey98118]

Conical air entrances (funnels, pipe reducers, etc.): Why recommend thin sheet metal funnels for air entrances on linear burners? Back in the eighties, Australians started making homebuilt LPG burners (this is a mixture of liquid petroleum gases; primarily propane and butane); they mounted mild steel (butt-weld) pipe reducer fittings, on the end of pipes that they used as mixing tubes; these gave very good flow dynamics and were easy to assemble for people who could weld. Americans seem to have followed suit, as best I could determine from searching the Net during the late nineties.

    As homemade linear burners gained in popularity, threaded bell reducers became popular with people who could not weld, or did not want to spend the money for thick walled butt-weld pipe reducers (meant for use in hydraulic lines). Unfortunately, threaded reducer fittings do not quite share the superior flow characteristics of butt-weld reducer fittings. Available choices of in-stock threaded reducer sizes are constantly being diminished at hardware stores (as steel water pipe continues to be marginalized by plastic pipe). Worst of all, are cheap imported pipe fittings with misaligned thread, which often end up out of axial alignment with the burner’s mixing tube; when using them, take a few minutes to screw the parts together and have a look before choosing parts.

    Thus, we come to the use of stainless steel kitchen funnels; but this is not meant to preclude other tapered shapes being used as air openings. There is a generous variety of part choices available; from butt-weld thin-walled stainless-steel pipe reducers, to sausage stuffing tubes, to kitchen funnels, icing tips, French-fry cones, etc.

    The easiest way to build a superior linear burner, is to employ a stainless-steel sausage stuffing tube (SST) as its body; then, mechanically affix a gas assembly onto its funnel flange, and a flame retention nozzle over its tube portion. With the present high prices for stainless-steel tube and pipe, this will greatly reduce your costs (along with your work load), compared to what is needed for a high-speed tube burner. Another advantage of SSTs over other part choices are that they are constructed with perfect axial alignment between funnel section and mixing tube, and with generous flanges already affixed to true right angles, to screw gas assemblies to.

    Some sausage stuffing tubes have long funnel shapes eliminate any need for fit-up and silver brazing of funnels to mixing tubes, and greatly reduce the work needed to employ them on others. Kitchen funnels, canning jar funnels and schedule #10 stainless-steel pipe reducers can also be affixed to mixing tubes with screws, but are not as easy to fasten a gas assembly’s mounting plate to. If your burner is ½” or smaller size, you will not find an easier or cheaper way to build it.

    The extra wide (1/4” to 3/8”) rims at the large openings of SSTs are called flanges; these are normally used to securely trap an SST on a sausage grinding machine. For your purpose, flanges enable easy mounting of a fender washer (or sheet metal) mounting plate, and gas tube assembly onto the funnel’s mouth (large opening), via screws, silver brazing, or silver soldering.

    Sausage stuffing tubes are long enough to make 1/4”and 3/8” pipe diameter equivalent burners, needing only a flame retention nozzle added on. Cutting back the SST tube section to between one- or two-inch lengths, and inserting it into a mixing tube, is recommended for larger burners in most cases; at other times, a smaller diameter mixing tube can be inserted within the SST instead, to create a convenient burner size. The mixing tube is placed into, or over, the SST in accordance with which position will provide the closest match with a 3:1 ratio between funnel opening and a mixing tube’s internal diameter.

Note: When a mixing tube is fitted inside the SST, you must remember to internally bevel its rear edge, to streamline mixture flow. You must also ensure a gas tight fit between the two parts, if the SST is fitted over the mixing tube; hardening thread-locker, gasket sealant, or an interference-fit can all see to this.

    Sausage stuffing tubes come in a limited number of sizes, but they can be used to construct 1/8”, 1/4”, 3/8”, 1/2”, 3/4”, and 1” burners, but not always providing the very best parts for the job in the larger burner sizes, or always at a modest price for a particular SST.

[Mikey98118]

Inline gas tubes have two advantages over cross pipes, whether those pipes only have drilled holes for gas orifices; even if they have MIG contact tips or 3D printer nozzles in threaded holes in the pipe, they still lack those two adantages, which are:

(1) the added length of the gas tube helps accelerate the fuel gas that exits through the gas orifice; the strength of this gas jet is the motor that energizes air induction into the burner's mixing tube.

(2) The ability to move the end of the gas orifice back and forth, to find its sweet spot, where it will induce the most air into the burner per pound of gas pressure, or which can be moved to a further distance from the mixing tube's entrance, to soften the flame, when desired.

Cannot a flame be softened by moving the flame retention nozzle's end a little further from the end of the mixing tube? Yup; but it is very difficult to find tune that softening with the flame retention nozzle, compared to just moving the gas orifice. Also, using the gas orifice does not require taking the burner out of the forge.

[Mikey98118]

                                                                          Square mixing tubes?

so there was a discussion going on in another thread over the merits of a forge that featured a square tube as part of its burner; this is not the first time burners with square mixing tubes have come up. I have never seen such a burner in action, and am not inclined to prejudge its performance. But two questions popped into my head about its choice. In the first place, why use a square tube, rather than pipe or round tube? The answer came just as fast; it was all someone had. Anyone who ever spent time working ornamental iron will not find that surprising.

The second question is what would I have none, if I was working in such a shop, knowing what I do about burner design? And again the answer was just as quick; twist the mixing tube.

Some of you might have fun with the idea.

[Mikey98118]

                                                                                Cleaning gas orifices

Propane comes in widely varying quality from different sources, but even the best of it is not perfectly clean (we aren’t talking about triple refined butane lighter fuel here). The waxes and tars that all commercial propane contains, can plug small orifices on MIG contact tips, and the even the smaller orifices of 3D printer nozzles; ruining burner performance, while rapidly increasing pressures on 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 tar balls quite rapidly.

    It then becomes necessary to shut down and clean the burner by poking the tar ball 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 is fine for this if you do not own a compressor.

How likely is this problem to happen? The answer has more to do with gas orifice diameter than propane quality. I only know of one instance of low quality propane plunging a MIG tip orifice (with an a 0.031" through hole. On the other hand, small commercial propane torch-heads, which depends on tiny gas orifices to work, are commonly plugged shut with two or three 16 oz. canisters of propane.

[Another FrankenBurner]

I have cleaned the orifice in the main forge twice in 3 years because of this.

[Mikey98118]

Its times like this that makes us glade to have gas orifices that can be unscrewed

[Mikey98118]

    Newly constructed burners must have their gas systems thoroughly cleaned from all construction debris, dust, etc. Otherwise, it will inevitably end up plugging the gas orifice. Once, propane has been run through gas hoses, and regulators, they should be kept on the heating equipment, or have their ends should be capped. Insects and spiders are attracted by mercaptan that is added to propane, and are likely to crawl into any opening; finally ending up plugging the gas tube, or the orifice.

[Mikey98118]

    Newly constructed burners must have their gas systems thoroughly cleaned from all construction debris, dust, etc. Otherwise, it will inevitably end up plugging the gas orifice. Once, propane has been run through gas hoses, and regulators, they should be kept on the heating equipment, or their ends should be capped. Insects and spiders are attracted by the mercaptan that is added to propane, and are likely to crawl into any opening; eventually ending up plugging the gas tube, or the orifice.

[Mikey98118]

                                                                       Forced-flow Burners

As the vanes (blades) of a closed face impeller (ex. squirrel cage fan) rotates, the air around it is forced to rotate with it, creating centrifugal force, which pushes it out outward toward the impeller’s periphery, and against the fan housing. An opening in the housing allows air to exit through it forcefully, while a low-pressure area is created by the centrifugally displaced air, sucking in ambient air.

    An open face impeller has the same kind of vanes, but lacks a back plate; its housing is closed, so the slung air is forced around the housing and out into the area beyond the vanes. Such an impeller placed at a funnel opening will swirl incoming air around the funnel wall, but will create a partial vacuum across must of the opening; this perfectly offsets the pressure increase near the funnel’s wall, creating a forced-flow vortex, at the funnel opening. The funnel’s constriction completes the factors needed to create a miniature tornado. So, how is it pushing a gas/air mixture through the burner’s mixing tube, rather than acting like a little vacuum cleaner? In the middle of the burner’s funnel entrance is a gas tube, ending in an orifice, which spurts out a jet of fuel gas. So, the burner has a little positive pressure. The point of both funnel and fan is to mix fuel gas thoroughly into a high-speed gas stream, without adding any positive air pressure to the mixture.

Note: This high-pressure area at the periphery of the funnel/fan interface, is why you should seal the joint between them with thread-locker or gasket sealant, to force the air to swirl down the funnel, rather than creating an air leak through any gap between them. Such a leak at this point will suck fuel gas into the gap, and then back into the fan.

    Gas burners have been constructed with squirrel cage fans from their beginning. Naturally aspirated venturi burners have been around just as long, but the best aspects of these two burner types could not be successfully merged. Powering air swirl, instead pushing air at a burner’s air entrance achieves this goal, by inducing vortex motion.

    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. A flame retention nozzle’s retentive ability is limited, so any strategy that increases flow speed by increasing flow pressure is largely self-defeating. Since a flame retention nozzle can only provide limited braking, reducing the burner’s 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 powered burners are “forced-air” and “fan-blown.” what is needed is fan-induced.

    Squirrel-cage fan burners still have their place; notably in feeding multi-flame nozzles, where the increased flow pressure—into a plenum chamber—helps prevent backfires into the burner’s mixing tube, because the much greater area of a plenum chamber can drop excess pressure far better than any flame retention nozzle; but they are an awkward fit on compact heating equipment. Last century’s “bigger is better” worldview is totally out of step with soaring fuel prices and high rent rates. “Compact and light weight” should be the watchwords for modern tools and equipment.

    During vortex flow, the incoming air’s forward velocity and spin rates are constantly increasing, all the way through the burner’s funnel section, without increasing its flow pressure. This high-speed air flow, joins with the gas jet, to swirl through the mixing tube; when it expands into the burner’s flame retention nozzle; an enhanced low-pressure area is produced, behind the flame, trapping it in place.

    If you look up "flame" on the Net," chances are that you will see a photograph of a candle flame, along with an explanation of how it operates to produce a flame envelope. However, even the simplest fuel gas flame, springs from an orifice (ex. Whether a gas stove’s flame holes, or a gas tube’s end (ex. Gas tube on a Bunsen burner); both of these examples are merely laminar flames, if you're looking for intense heat, laminar flames are so far back in your rear-view mirror that they're less than a dot in the distance. Your starting point is turbulent flames.

    A turbulent gas flame’s envelope creates outward force. But the push of a gas flame is not equal in all directions. The gas/air mixture is being flung forward from the mixing tube’s end, so that is the one direction in which the flame envelope doesn’t occur; thus, it is less shoved away from the mixing tube’s orifice, than in any other direction, so long as the gas/air mixture pressure is kept low. The harder the flame is tuned the faster the gas/air mixture will rush forward.  At some point, the out-flung gases will force the flame far enough from the ignition source to extinguish it.

    Atmospheric pressure is a constant force all around the flame envelope.  But, create a low-pressure area at the burner’s exit (by use of a flame retention nozzle), and atmospheric pressure will press the flame harder back against that nozzle, than in all other directions; the difference is enough to allow much faster gas flames to be maintained, so long as the kinetic force of out rushing air and gas molecules is kept minimal.      

    But, doesn’t the gas jet produce positive pressure in the burner? Yes; of course. Some positive pressure in the mixing tube is needed; otherwise, the burner flame would back-fire into it. The trick is to increase the mixture’s feed rate without a matching pressure build up, by increasing the rate of incoming air speed, without an equal increase in air pressure. In summary, excessive positive pressure in the burner’s gas/air mixture flow severely restricts the potential for flame intensity, with single flame burners. Inducing vortex flow, instead of pushing air forward, permits stronger flames than are possible in forced-air burners. Every part of a fan-induced burner is designed to either enhance, or profit from, the principles of vortical flow; so, the term vortex-burner is completely relevant—not just “happy talk.”

 

[Mikey98118]

                                              Needle valves versus needle valves

Most propane torch-heads have needle valves; as do other propane equipment. Needle valves are great for adjusting gas flow, but they are not well designed as shutoff valves; some of them leak even when new; most of the rest will start leaking eventually. How do you tell if your valve is gas tight? If the valve doesn’t leak, it will hold a small amount of compressed gas after closing; you can hear it escaping when you unscrew the torch-head from a gas cylinder. And if you hear nothing? Then your valve has a slow leak, which is not surprising. A needle valve that never starts to bleed off is the exception. Yes, there are such needle valves; they are produced by name brand oxy-fuel torch manufacturers, at the high prices that you would expect, and are purchased from welding supply stores, or online from name brand oxy-fuel equipment suppliers. What this means is; don’t depend on low-priced needle valves found on propane equipment to stop a gas cylinder from leaking during storage.

[Mikey98118]

There are three kinds of gas valves that matter to you; needle valves ball valves, and variable pressure regulators. Ball valves are meant to start and stop flow. In a burner system, they’re mainly used for emergency cutoff in case of fire; they are also used to rapidly divert flow from one pipe system to another. They can be used to control flow, but not in a satisfactory way. While the most dependable kind of gas valve, if the are cheaply made, expect them to leak, too. To find dependable ball valves, choose gas rated ball valves from the plumbing department of your local hardware store.

    Needle valves are best used to quickly fine tune flow in a gas system that has a variable pressure regulator. A good quality valve, which is new, can be used to stop flow completely, but most will begin to leak flow, eventually; with oxy-fuel equipment, eventually while mean decades. What about air-propane cylinder mount torches; they only have a needle valve, right? Expect them to have or develop small leaks.

    Variable pressure regulators limit the amount of pressure in a burner system to a little higher than the desired range you want to use; this allows rapid fine tuning of the burner with a needle valve, while protecting the hose and pipe connections from possible damage, from constant exposure to full cylinder pressure. Yes, it is possible to use the regulator to fine tune your burner, but if you have very much hose in your burner system, every change will be just a little slow; they are less likely to leak than needle valves, but once again, cheap regulators are not dependable, and are likely to leak.

 

[Mikey98118]

Previously, gas burner design was driven by fuel cost and availability, so venturi (AKA wasp-waist) fan-blown burners were developed to do well with natural gas,  which is pumped at low pressures.

Propane has been around since 1910, but became more widely used in the nineteen forties; probably do to tanker car distribution by rail. That made naturally aspirated burners practical at a time when portable gas forges came to have a market with farriers. So, small manufacturers started designing forges with naturally aspirated burners.

Back in the nineteen eighties, Australians started making home-built LPG burners (this is a mixture of liquid petroleum gases; primarily propane, or propane/butane mixtures); they mounted mild steel (butt-weld) pipe reducer fittings, on the end of pipes that they used as mixing tubes; these gave very good flow dynamics and were easy to assemble for people who could weld. Americans seem to have followed suit, as best I could determine from searching the Net during the late nineties. Threaded pipe reducers speeded up these burner's popularity.

Since 2000, there has been a design explosion in burners...compared to the past. However, design, whether manufactured or hobbyist, seams to be driven at least as much by convenience, or even whim (guilty as charged), as by engineering factors.

For instance, I started playing with tube burner design, simply because I did not care for large pipe reducers on the end of 3/4" and larger size burners. I had already figured out that that smaller than three to one air entrances hurt burner performance, so I was not willing to settle for smaller pipe reducers for the sake of appearance. Thus, came twenty years worth of tube burners. 

The desire for smaller burners, make the original objection irrelevant, and the need to press on to more intense flames, using vortex flow, brings linear burners back into the game; circumstances alter cases now, just like it did back in the forties.

There are other very good burner types, I'm not discussing; but only because they aren't down my rabbit hole

 

[Mikey98118]

On 12/21/2023 at 5:33 PM, Mikey98118 said:

From mini 12V angle grinders to rotary tools

About three years back, Milwaukee came out with a 3" battery powered angle grinder, which they had built in China; it was a ridiculously overpriced and glitch filled design--since then the design as been improved, and it is only seriously overpriced. In the meantime, other China OEMs redesigned  their own versions of that tool, which are marketed for around $50. Their tools feature 12V interchangeable batteries and high torque brushless motors. The main point of these tools isn't grinding, but surface cutting.

I have wondered every since then, when the Chinese would make the obvious move, and come out with the same combination in a rotary tool, so that a battery powered rotary would finally be practical. There are now such rotary tools advertised on Amazon.com, by three different manufacturers; none of them feature a brushless motor, yet. But this upgrade is only a question of time; in the meantime swapping out the motor is just an additional twenty bucks and some wiring work

So the 220V 3" angle grinder arrived from China through Alyexpress.com (a few days early). The first thing I noticed was that its cast aluminum gear housing was clean and sharp; no flaws or inclusions. The motor and gears are fairly quiet. 

Even though it is meant to run on 220 volts, you can plug it into a 110 volt outlet, with its speed control turned up  full (6), and it runs just fine; doing this is the equivalent of running the grinder speed control at half speed (3) from a 220 vold outlet. So, you can use this tool while you wait for a 110 to 220 voltage converter (which you can also order from China, or buy through Amazon.com) to arrive.

The only disappoint I have so far, is that the The mandrel's collet only allows 1/8" rotary tool accessories to be mounted (this grinders threaded spindle is hollow, so that it can allso be used as an angle head rotary tool). There is plenty of room in the angle grinder's spindle to mount a 1/4" collet, if you can find one that fits.

The motor is mounted in a plastic case, which I find easy to wrap my long fingers around. Most people would probably prefer using both hands, and at full power that would be the only safe position to use.

So far, I am delighted with this product, which costs no more than one of the cheaper rotary tools on Amazon.com. However, you must be prepared to put up with some hassle when buying the tool. None of these sites were developed buy people who knew what they were doing. Also, there is a wide range of pricing for what at first appears to be the same tool; don't believe that for a minute, and become "penny wise and pound foolish." If you want to see how cheaply you can come by a second tool, fine; you can always use it for parts.

[Mikey98118]

update: It took some time to find an up/down 110V to 220V transformer I was comfortable with purchasing. Finally found a Japanese model for $110. It arrived today, so I could finally check out the grinder on full power; there was pretty good power for such a small grinder, but the speed control circuit did not work at all. I don't personally mind that, since I plan to run speed control through a separate circuit, but others would probably feel ticked off by that. All in all, am still happy with the purchase.

[Frosty]

No picture Mike? You know how we are about believing wild claims without photographic evidence don't you? Hmmmmm?

Frosty The Lucky.

[Mikey98118]

Coming tomorrow. I will need Kathy's help with the technical stuff

[Mikey98118]

[Mikey98118]

[Mikey98118]

 

Sorry about the huge photos. We tried to remove the first two, but couldn't. So, we put up a third photo that had been downsized, but it came up full sized too. The moderators are welcome to get rid of all three photos; we could not do anything with them on this site. In the meantime, the cutoff disc in the photos are 3" diameter, which should give folks a fair idea of how small these grinders are.

A rotary tool mandrel, which accepts 1/8 shafts, can be mounted in the grinder's hollow spindle, so that this tool, which sells for less money than a good quality rotary tool can be used to cut, grind, and shape burner parts, along with the heating equipment they are mounted in.