Mikey98118

To the guy who asked for answers to his questions about his forge, today: I was busy replying to your questions when I lost your email to me. Please try again.

Frosty, Is it my imagination, or has the conversion been even slower this month than in January? Is everyone still trying to dig themselves out from under the snow?

You are welcome. Answers is what we are here for. Each one of you who speak out about a problem, is only one of many more around the world, who are also wrestling with similar issues. So, when we write back to one of you, all those others have the chance for an answer too. That you get particular answers to particular questions is your reward for speaking out

Most smiths prefer a reducing flame, to keep scaling minor; this is fine. However, this is one more example of "if some is good, isn't more better?" To which the answer is NO! A slightly reducing flame provides reasonable assurance that little super heated oxygen will impinge on the heating parts. Increasing the amount of fuel gas past this point adds nothing useful to this situation; it only lowers internal temperatures, and produces carbon monoxide gas into the exhaust. So, play with the flame, until you become familiar enough to see the point where the secondary flame envelope becomes minor, but is still present; that is the best balance of positive to negative factors. Four to five PSI fuel pressure is way to low for welding with this burner series. You need to understand that these tube burners are designed to produce high-speed flames; this is accomplished with smaller gas orifice diameters and higher gas pressures passing through them. Expect to run around fifteen PSI for welding. Lowering gas pressures is actually a losing proposition, since a successful forge operates as a radiant oven. A yellow-white forge enterior will heat the work far faster than an orange hot surface. So, increasing gas pressure saves more than it costs, so long as you aren't wasting gas with a flaming exhaust. Instead of adding bricks--even insulating bricks--to the forge, you are better off to add insulation over the floor, with Kast-O-lite 30 on top of it, so as to reshape the inside of the forge, closer to a "D" on its side shape. The reason is that you want the hot internal atmosphere of the forge to circulate without hindrance.

Scrap art is my favorite form of metal sculpture. Nice piece.

Once your burner can work properly, you will come up against another problem, for I see the cross angle, holding your brick doors is place, is already starting to overheat. You need to move those bricks about one-inch away from the edge of the forge opening, so that the exhaust gases can rise up between the brick doors and the edge of the exhaust opening. It is fine to leave the back doors where they are, because you want to encourage the exhuast to pour out the front opening; once it can without hindrance, it should stop pouring out past the back bricks. You would be wise to exchange the wood pieces near the back of your forge, for cement board...before they catch fire.

One of your problems shown in these photos is that your burner is severely choked down; open it up. The photo also shows blue flame coming out of front and rear openings; this is carbon monoxide being burned off, which should have been burned away in the burners flame; it was not, because the burner is being starved of air. At least open the choke enough to completely burn its fuel. Secondly, using extra bricks to eliminate space within the forge, creates all manner of problems. Such a 'cure' is worse than the illness. However, one of the photos also shows that, at least the end of the part is white hot. Are you sure that your welding problem is due to low forge heat? Finally, open the gas valve comletely; it is a ball valve, not a needle valve. A partially open ball valve creates cavitation; this will enterfere with the gas jet, which is your burner's engine.

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

Using an AC 110V to 220V adjustable voltage converter (4000-watts and $23 through Amazon.com, or eBay), will allow you to plug a 220V tool into a 110V power outlet, and provide speed control, without engaging the built-in speed control circuit on a power tool (which has no fuse to protect it from damage due to overheating; which these do).

A few months back 18V and 20V 3" angle grinders started appearing for sale, and since Makita and Dewalt had there own versions of them, they were to be taken seriously, despite there high prices. However, these are obviously designed strictly as cutoff saws; using them as grinders would be way too awkward. There are now 18V versions of the handy little 3” angle grinders, which were only available in 12V, previously; this fills the gap between under-powered 12V angle grinders and well powered but bulkier 3” 220V corded grinders. You can find them on AliExpress, But Harbor Freight Tools now sells their own brand of them. Of course, the nice thing about choosing the HFT model, is that you can take a lemon right back to their store. At present they are selling the Bauer brand batteries for the same price as the grinder; if you buy the battery during their sell, they have a list of tools for it you can get free. The 3" grinder is on that list.

Why Multiple burners? Heat management only begins with flame temperature. The reason burners are aimed on a tangent, is to cause their combustion gasses to swirl around equipment interiors; creating a longer distance from flame tip to exhaust opening. Obviously, a lengthened exhaust path increases the amount of its hang time. Thus, depositing more combustion energy on internal surfaces. What is not so clear is that the heat gained is not added by super-heated gases blowing an extra foot or two at high speed; it is due to their continuing drop in velocity over that added distance. Combustion gases begin to slow, as soon as they leave the flame envelope. The flames of two 1/2" burners will use the same amount of fuel to produce an equal amount of heat as a single 3/4” burner; but they will drop velocity much faster in a five-gallon forge or casting furnace; increasing efficiency, because their flames can burn faster/hotter without creating a wasteful tongue of fire out the equipment’s exhaust opening. Ditto for two 3/8” burners versus a single ½” burner in a two-gallon combination forge/furnace, or two ¼” versus a single 3/8” burner in a coffee-can forge or casting furnace. Because the parts and tubing these burners are built from cost less as their sizes reduce, it costs little more to make two smaller burners than a single larger burner. When heating small parts in a forge, further efficiency can be gained by placing a temporary partition in equipment interiors; separating them into twin spaces, and shutting down the rear burner. This is something that cannot be done with a single large burner, which is centrally located. Combination forge/furnaces require the forward burner to be shut down during casting operations, so that its flame is not wasted from being positioned too high up the crucible wall.

Sneaking up on Frosty, and getting him to start his own book?

Good for Glenn. This generation has seen the mechanics of authorship grow easy, while the passion and expertise needed to know something worth passing on, has become scarce. Perhaps, publishers will take a page from the military, and station recruiters in likely locations to sucker the unwary...for the good of the country

My best friend, Dan, has dyslexia. I have thought for years that he has a secret desire to author a book, and truth to tell, he has the two main requirements: A strong urge to write, and something valuable to say. At a recent breakfast, the subject came up again, and I could finally suggest something positive; chat bots. After all, A I can take care of the biggest problem, which also produces the least contribution to any topic; sentence structure, etc., leaving dyslexic brains to deal with what they are good at; real content. What-ya think?

If I where trying to figure out who the OEM is, the hunt would starts with turkey fryers and portable gas stove, etc.

Exactly so; its first problem is that the mixing ''cone'' (we can't really call it a tube), is way too short. On the other hand, its air funnel section looks fine. Bottom line is, that you would have to cut most of the mixing section away, and insert a pipe, with a ground taper into the air entrance to produce a proper burner. I am assuming that the burner is cast iron, so that the pipe would need to be glued into place, since even brazing cast iron is a troubling proposition. What to do? Make the guy a real burner; this one will never be worth the trouble. Or, buy a Mr. Volcano burner for him; mine cost a whole $25...

Make sure that the stand you buy includes its own guard; some of them do, and others do not.

Of course, there is always the choice between types of tools for the two main jobs in forge construction. Medium power die grinders are most useful in building larger linear burners, versus rotary tools, which are a better choice for building tube burners (with their internal cuts into tubing and pipe for air openings), or small linear burners; either tool is less helpful in building forge shells, and stands than an angle grinder. However, the main job of that angle grinder is surface cutting in sheet metal, angle iron, and pipe. So, once again, enough power (285-watts to 360-watts) from a corded angle grinder versus 35-watts to 50-watts from a 12V cordless angle grinder. Finally, we might think about grinder stands, which can turn an angle grinder into a chop saw. A 3" grinder can only cut about 1/2" into a surface; no good for plunge cutting. The reason for that is that the grinder's gear head takes up a lot of room. Too bad we can't mount a 4-1/2" blade on it, right? But, maybe we can. These 3" grinders turn at 12,000 RPM, which is the right speed for a 4-1/2" cutoff disc; not the 19,500 RPM of cordless 3" grinders. To mount such a blade on them would make them nearly as dangerous for surface cutting with a standard 4-1/2" angle grinder; but mount them in a grinder stand, and the objection becomes irrelevant. Naturally, any stand you buy would have to be adjusted to work with this smaller tool, but the work would be worthwhile.

Miniature angle grinders: A few years ago, 75mm (3”) angle grinders started being exported from China these were 285-watt 220V grinders, which were not only handy for light work (ex. auto mufflers and body work) but the ideal size, weight, and torque for safer surface cutting on sheet metal. Because they were 220 volts, they did not gain popularity, and stopped being offered after a few months. However, an improved version of them is making a comeback. These are still 220-volt models, but are a little more powerful (360-watts), and smaller than the original version. Some of the sellers also offer a box to plug them into, which changes 110V to 220V power, for about twenty bucks. You can find them listed on AliExpress by imputing “miniature grinder.” Up will pop the usual weak 12-vote cordless grinders, mixed with ads for these. Take your time reading through the ads; don't just jump on the lowest price, without looking at customer feedback. You will also notice that two of the ads include fittings that allow the grinder's spindle to be used as a die grinder...

I would only recommend it for insulation under a high alumina kiln shelf used as the floor. Otherwise, you are far better off to go with a floor made from one of the new insulating bricks, with Kastolite 30 over it, and if you wish, Plistix 900 over the Kast-O-lite. Do I think that the Kast-O-lite is better than Plistix? NO, NO, NO!!! But Plistix is just too expensive to use in a thick enough layer--even for mad scientist types I think the ceramic board is a fine choice for walls, ends, and ceiling parts, with at least a Plistix 900 covering, but better with a 1/4" thick layer of Kast-O-lite, and then covered over with Plistix. But then, anyone will tell you that am more into dragsters than family cars Simply think about why I suggest these things; then mix and match as you see fit. Over the last twenty years I have repeatedly suggested perfectionist answers to these kind of questions and have learned to expect and accept that others won't see eye to eye with my views; so long as you think things through first, suit yourself; it will be okay.

Doors: Maximum part clearance can be provided two different ways: One is with a hinged and latched forge door (stainless-steel toggle latches are your best choice); it should contain built-in interchangeable baffle plates (high alumina kiln shelves are perfect for this). A door makes building the refractory structures inside of equipment much easier, and permits larger parts to be heated than would pass through a narrowed exhaust opening. Best of all, it allows closely contoured movable internal baffles to be employed, which would not pass through a narrowed exhaust opening; this promotes the use of single burners for small pieces, saving money in tunnel, oval, and “D” forges, which are run by two or more burners; on these forge shapes, the door is a big step up from an exterior brick baffle wall; it should include a parts entrance that can be varied in size; for instance, with several round (or hexagonal) kiln shelves with different openings cut into them (for passing stock through); these can be exchanged, and held within a pocket structure on the door. These improvements do not all need to be seen to at once, so long as a hinged and latched door is included in the forge shell. On forge/furnaces, the door can be left as is, or can be attached to a singe pin hinge, and revolved out of the way. Sliding doors: Some people prefer vertical or horizontal sliding doors, instead of hinges. People usually employ the new insulating bricks as horizontal sliding doors. High alumina kiln shelves are seven times more insulating than clay fire brick, but not as insulating as the new semi-insulating fire brick now being used for pizza ovens and home fireplaces; but high-alumina kiln shelves are tougher at incandescent temperatures then the new bricks; this is a consideration for something you will end up shoving parts back and forth through. Exchangeable kiln shelves, with different part openings drilled and cut into them are fine, but building an elaborate system of moving kiln shelf parts to ape the ability of bricks to infinitely vary their openings comes under the heading of "gilding the Lilly." The additional energy savings it provides, probably is not worth the effort. Make up new openings in kiln shelves sparingly. Diamond coated and carbide coated rotary burrs (and diamond or carbide coated hole saws) are the preferred way to drill holes in kiln shelves. Friction cutoff blades (safest) and diamond coated blades (only of small diameter) are the best ways to cut out straight lines between those holes. A hinged and latched door, can also work on a box forge. Yet, movable bricks, trapped in an angle iron, or structural channel frame, will work out better than the hinged door. Furthermore, the channel frame works best, for sliding solid parts up and down on woven wire, and running through pulleys, and counter balanced. You want to coat the hot-face side of either kind of door with one of the re-emission coatings. You can use a formula of 95% zirconia silicate powder (crushed zircon) and 5% Veegum (or 5% bentonite as an alternate); this mixture makes a tough heat reflection coating for wear surfaces. The ingredients should be available in ceramic supply stores. Zirconium silicate can also be mixed with fumed silica to make a tuff and heat reflective coating on hard refractories, or on ceramic fiber products. There are other choices, Like Plistix 900F, but none of them are easily purchased in other countries. Zirconium silicate and bentonite clay should be readily available in pottery supply stores, in many places.

Exhaust openings One thing backyard casters and blacksmiths both worry over is how large to make the exhaust opening(s) on their equipment. Too small and you have high back pressure killing burner performance; too large and you cannot retain enough heat to do your work. Of course, the closer to the "right" opening size your equipment is the stronger the forge or furnace can be built. Just don't confuse the right size for a “perfect” size. As long as burner output can by varied (turn-down range), there cannot be any such thing as a perfect exhaust opening size. The right size is what is needed to accommodate the burner's highest output (the highest you are willing to take it to). Variable is the optimal opening size; all other dimensions can be outright wrong, but are seldom just right, with a burner flame that can be varied. This is one of the many reasons for controlling exhaust flow with an external baffle wall beyond a large exhaust opening; thus, allowing the least heat loss through radiation, while maintaining optimal atmospheric pressure in the forge. Note: Include a protruding ring of hard cast refractory around the exhaust opening, to divert hot exhaust gasses away from the shell, where it will super-heat the metal. If you decide on a movable brick baffle wall in front of the forge, keep the bricks at a small distance from the exhaust opening, to allow hot gases to move up and out, between the opening and brick, while bouncing most radiated heat off of a re-emission (heat reflective) coating on the near side of the bricks, and back into your forge. Keep the stock entrance only as large as is needed to move parts through. This arrangement helps to slow the flow of expended gas in the forge interior to what is needed, and no more; as it gets close to the exhaust opening, the gas speeds up and through the opening; another desirable trade off. So, you are gaining hang time for the heated gas in the forge, and recuperative savings from bounce-back of radiant energy; a win-win situation. A baffle wall also minimizes infrared and white light from impacting your eyes and skin, improving your health and comfort.

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.

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.

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.”