Latticino

Personally I would fab up an inner ring of say 1/4" square stock, and weld it on the inside edge of the top of the lid. Then I'd put the cut board section, dampened, into the upside down lid and press it into place. I'd make a outer form around the upside down lid with sheet vinyl flooring material taped into a cylinder with duct tape. Then I'd cast the refractory insulation into the top section with it projecting out of the top at least 2". The refractory will hold the board in place since the fabricated ring will make a shelf to hold the refractory, and the slight overlap will protect the steel can. Remember the insulation of the forge interior will hold up the lid, and you should have ports in the side and not remove the lid unless relining the forge interior or replacing the kitty litter. Guess you could also use it for a casting forge, but I'd be careful with that.

Sounds like the OP has already made a couple of knives, so I certainly don't see why he shouldn't try for a forge welded patterned blade. Takes some boldness, but others have succeeded with forging up a successful billet the first time. Keeping clean surfaces, forge temperature and atmosphere control, and careful tacking before any major deformation is the key in my book. I know some don't use flux, but for a first billet I would recommend using it. Weld from the center section of the billet to the outside though to try to push the flux out and avoid inclusions. Before you go for a large billet it might be prudent to test your materials on a smaller one, with relatively low layering, just to see how hard they are to weld together and whether the stack hardens successfully. I would expect decent saws-all blades to be high carbon steel, but avoid any that have imbedded carbide teeth. In fact you might want to grind the teeth off altogether. For patterning you may want to include something with a bit of nickel in it as well as the saw blades, to get contrast. I think folks who are trying pattern welding on a budget often mix saw blades with pallet strapping material and truck leaf spring to get some nice contrast. Good luck

Don't have time right now for a full response, but here are a few notes: electronic control valves for piping certainly exist. Pneumatic to electric conversion is not essential, and even a bit out of date, though reaction times may be faster. Modulating control valves rated for gas service may be expensive though. I am more familiar with those for hydronics. Usually they use a 4-20 MA signal or a 0-10 VDC signal for control. Control authority is necessary to approximate the linear response you are looking for in the action to valve feedback loop. This linear response is not critical (see below), but it does make things easier. Typically this is done by reducing the valve diameter one pipe size relative to the supply line (i.e. if you are supplying at 3/4" your control valve is 1/2"). For gas it may be easier to have an "idle" circuit with a low level bleed serving your burner (manual valve and needle valve) and a "power" circuit with a high level bleed. Both go into your single burner and the controller modulates between high and low fire rates based on feedback. Actually I would recommend use of a proportional "zero pressure" regulator that keeps the gas and air mixture in the same proportion regardless of combined flow rate (within reasonable ranges). Then you modulate the air to low and high flow rates and the gas follows suit. Modulating air valves are much easier to acquire (and safer to use). If you are only using a linear response feedback loop from a PID controller you have it configured incorrectly. Do some reading on Proportional/Integral/Derivative feedback control. Sounds to me like you have your constants set incorrectly and are experiencing overshoot. Setting constants up correctly is something of an art, but newer controllers have autotune capabilities that may make this easier. Unless you are trying to reinvent the wheel programming your own controller sounds like a waste of time to me. Programmable PID controllers for temperature control with ramp and soak functions are pretty available and cheap these days. Thermal mass in the object to be controlled will make the response slower and more stable. Generally speaking you need to have the heat source well sized for the volume and mass being heated to permit accurate and converging control strategies.

As another data point, and not to minimize the importance of Frosty's testing in any way, Ransome style NA burners have been used with multi port burner heads for many years . Please see Dudley Gibberson's site for more detail.

This sounds like a medical issue, and I'm not going to touch that with a 10' pole. However there is a chance that you may have irritated your throat when relining the forge if proper PPE was not worn during the operation. Also, as far as I know ITC does not act as a fiber sealant, you should have used rigidizer first. If your forge is getting hotter, there may be more friable glass fibers in the air, these should be avoided. Get a CO monitor before doing any more forging!

Speculation as well, but how about painting...Could have just been painted below the waist.

No idea on brand, sorry, but that sure is a big one in what appears to be excellent condition. The cast stand is particularly nice as well. Good luck

Bubble alumina is expensive per unit volume in my opinion. As previously stated, many times, there are a number of ways to line a forge, compromises with each. My current favorite, for a conventional hobby forge, is : 2" 2600 deg blanket, skim coat of rigidizer, 1/2" - 3/4" of high alumina refractory insulation (kastolite 3000 or equal), loose casting of high alumina refractory (or Mizzou) in the major flux areas and for flame impingement (or split high alumina brick or high alumina kiln shelf. The bubble alumina can be used for the last coating indicated. Then if desired a final coating of some kind of IR reflecting material (not completely sure of the utility of the IR material, but folks I respect swear by it). As regards the non-toxic thing; must be a matter of fine definition. I certainly would wear a respirator and gloves when installing and up till full rigidizer coating. I have lung damage from not taking these precautions with high temperature blanket and urge everyone else to avoid this at all costs.

I may be totally off base, as I haven't seen the video, but from the photos I'm seeing a couple of questionable things: Looks like your flame is detaching from the front of your burner. As I understand it that means the gas/air mixture is moving too fast for the size of your burner outlet. If the mixture has the correct proportion, and I can't tell that from the photo, then you need less of each. If not enough air is being induced and mixed with the gas then you most likely need to increase the gas velocity with a smaller diameter orifice and position it properly. I'mnot that familiar with the burner design you are using. Perhaps you should contact the designer for advice? It takes a lot of time and experimentation to get a well tuned NA burner to work well. If this is your own design, be prepared to put in the work to get it right. How thick and what insulation have you used for your forge? Looks thin to me, but hard to tell I sure hope you removed the doors to show us the flame. Otherwise you are fighting a losing battle with those huge openings

Unless you plan on spending a fortune in fuel you need insulation in any case. You have a lot of options, all have their benefits and drawbacks. I'm certainly not going to catalog them all for you. A kiln shelf forge without additional insulation would be arguably worse than a hard brick forge. You would be better off with a torch.

Kiln shelf is pretty useless as an insulator. I'm also uncertain whether silicon carbide shelves will stand up to Flux. High alumina shelves are the recommendation. In any case if you use that much Flux I would cast a Mizzou inner floor liner and fill it with cheap kitty litter. Then make a second opening, could be the removable top, and clean it out periodically.

For those who are interested in learning more about sophisticated blown burner design there is a great free resource I just found: http://www.eclipsenet.com/products/eclipse_engineering_guide/ Eclipse does lean towards nozzle mix burners (which we typically don't use, they are efficient, but extremely loud) with all kinds of safety equipment, but there is still a wealth of info on everthing from controls to material selection for forge liners. Enjoy.

First, Don't be disappointed about a blown burner, they certainly aren't that hard to construct or use. I wouldn't write off your NA burner just yet either. The vertical forges I've seen have the openings at the approximate 2/3 point in the height of the forge. Really they didn't seem all that different from a horizontal forge, just with a deep well below the opening. Not 100 sure on the logic behind a preference for a forge like that, though I do remember reading something about it on the Don Fogg site back before I lost the connection there (as an aside, is there still some way of accessing that info, there was some great knifemaking info on the site). Anyway, I would certainly try your NA burner placed low, like Mikey has suggested, before switching to a blown burner. With a pass thru door at the 2/3 height, and a lid without a door in it (think in terms of a crown construction for that if possible), I don't see why the door openings would be that different from a conventional horizontal forge. Admittedly virtually all of the vertical forges I've seen use blown burners, but that doesn't mean you can't be the first to get a NA to work. Here is a picture of a particularly nice one (not mine): As regards the variable height baffle plate. I think that Mikey is considering someone using a casting melter , not a vertical forge, though I may be wrong. In any case, there is no way that threaded rod will hold up to the temperatures inside a forge (unless you are just using it for heat treating) if it is directly supporting the kiln shelf. If you have to have a variable height baffle, and I still don't understand the reason for that, I would support it from below with ceramic kiln stands. These can be stacked to make more or less height and will withstand the temperatures involved.

No I mean that the blower is connected to the steel pipe in an inefficient fashion. It should be rotated 180 degrees about the axis of the pipe at the connection point for best effect. I have posted an earlier photo of my forge, while it was still in development. Am in process of setting up a new one and will post when done. Probably won't help you through as I use industrial burner parts.

I have heard his theory before regarding the 1 inch thickness being better, but respectfully disagree. The portion of the lining that would reflect the heat is the inner surface. If the forge reaches say welding temperature, the inner surface of either a 1 inch or 2 inch thickness will be essentially the same temperature. The only difference is that the 1 inch thickness will lose more of that heat through the skin. Logically if the inner thickness reflects any of the heat, the more of that thickness you have the more heat reflected. Oh and his blower is 180 degrees rotated out of position. Set that way he loses close to 25 percent of capacity. A perfect example of "breaking the back" of the blower.

I prefer a regulator to control gas, with additional 1/4 turn ball valve for isolation. From what ive read, Ed seems to know his stuff, but don't know where he gets the 1 inch of blanket insulation is superior to two inches of thickness. That runs counter to my understanding of thermodynamic heat transfer and my interpretation of the manufacturer's published material specifications. Burner outlet design is critical to good stable performance. Please consider a ribbon burner. I can hook you up with a guy who sells them for around 70 bucks. If you don't know what or where to weld the gas connection, then you shouldn't be building a burner. Look at the link to the Fogg burner. It should be obvious from that. Note that your weld must be gas tight!

Wrote a long involved response to this which unfortunately go lost to the posting gremlin. Don't have time or energy to repeat myself, sorry. Gist was that for a blown burner the mixing tube diameter is more a function of the blower selection than the forge size. The burner outlet is another case, as the diameter, or number of ports, or flame retention style nozzle needs to be able to operate at the correct velocity for the quantity of fuel/gas mixture you need to produce the heat. Bottom line, my recommendation is to take a good look at the simple Don Fogg design, use few long sweep elbows, add a normally closed solenoid valve if you ever plan on walking out of the room and leaving your forge on, use a multi-port (ribbon) burner head or some form of enlarged flame retention nozzle and the 1-1/2" or 2" mixing tube should be fine.

Alan, Honestly I've never fire cured my rigidizer, so can't comment on that. Since I only used one layer, the air cure worked fine for making it solid enough to support the inner liner of refractory. Then when I fired the refractory slowly I assumed that both layers got fired together. I expect that you could fire the first layer of rigidizer inside your shell with your burner. The underlying blanket does not need to be babied as far as heating rate goes (one of the big advantages of blanket).

Sounds to me like you are on a good path (provided you mean two 1" layers of refractory blanket). If you are concerned about longevity and cost tradeoffs I would certainly see if you can get the inner layer of blanket at 2600 degree rating and the outer layer at 2300 degree rating. It really only depends on what the inner face will be exposed to. The direct flame impact zone will be hottest (directly in front of the flame) and that could be up to 3000 deg, so I usually err on the side of caution and use the higher temp blanket for an inner layer. I also like to use some form of castable refractory as an inner liner; after the rigidizer and before the IR reflective kiln wash. I have used a number of different materials including MIzzou, high alumina refractory (like Greencast 97), and multiple layers of high temperature furnace cement. The first two do add more thermal mass to your forge, which is a mixed blessing (longer to heat, but holds heat better when the door gets opened or masses of metal get put in - kind of like a heat battery). I've never done two layers of blanket with rigidizer in between each layer. Not saying it is a bad idea, but not completely sure why it is a good one. As I understand it, the intent of the rigidizer is to capture the blanket fibers after they heat and become more friable as well as maintain the overall thickness of the blanket (from crushing) and the general shape of the forge chamber. Not sure how an intermediate layer helps there, but guess it could contribute to structure if nothing else. Hard brick splits are not the worst thing to use for a forge floor, provided that you put the same layer of insulation under them as you have in the forge walls. It is when you use them as a floor without any backing that they draw the heat right out of your forge. They won't have the same kind of resistance to flux damage that a high alumina kiln shelf does (check with a local potter, they may have broken shelves that are just the right size for you. Shelves can be cut with wet diamond wheel tile saws), but they are very cheap and can be replaced as a consumable. You can even give them a coating of Wayne's bubble alumina and they will last pretty well. I've had pretty good success with a loose casting of Mizzou for a floor that is pretty resistant to flux damage as well. Your forge shape as an oval sounds good to me. If you have concerns about odd shape forging you might want to consider designing a side door that will open to allow shapes like that to be heated. Good door design is tricky though and something I still struggle with. Just remember to put something directly opposite the burner outlet that can take the extreme heat of the flame.

My concern isn't just with turning the air on before the gas (which, of course is the correct policy, as is turning the gas off before the air). Even if you turn the air on first, if you happen to have a blower that is out of alignment, or has an arcing electric motor for some reason (say loose brushes) if the gas is introduced into the blower that spark might cause ignition inside the blower. Unlikely I agree, but I didn't expect the top to melt off my propane grille regulator either...

I'm planning on doing this with my updated gas forge as well. A couple of suggestions from my experience with using these thermocouples and covers in glass furnaces: Thermal expansion can be a problem. The metal will expand and shrink at a different rate than the ceramic sheath. Suggest you wrap the exterior of the sheath with refractory blanket and leave a reasonable gap between it and the metal tube holder. I'm not sure how well the sheath will respond to rapid thermal cycling. My glass furnace ran continuously and used to warm and cool over a period of days. Keep an eye on it and look out for cracks. Type K thermocouples aren't really rated for the high temperatures you will see in a forge used for forge welding (type R or S are better, but quite expensive). I'm not sure if mine degraded quickly due to the temperatures, but they certainly don't last long term. The thicker the thermocouple wire of the thermocouple itself the better. The tips start to look glassy when they are failing. You probably know this already, but you can't just wire it to the pyrometer with regular copper wire. It needs to be wired up with special thermocouple wire, as used for type K units. An inch or two inside the inner wall should work fine. You won't get a highly accurate reading, but you should get relative data that will be helpful (i.e. when the thermocouple reads 1500 deg. F the knife blank has just hit the transition zone, the blank might actually be at 1450, but it is all relative anyway) Good luck, post photos when you finish.

Frosty, If you are being conservative regarding safety, please don't suggest that the blower interior be used as a mixing chamber unless it is a piece of equipment specifically selected for this purpose (i.e. spark-proof construction and special motor). The typical Dayton squirrel cage blowers that many folks use certainly aren't, and I'm sure you would hate to hear about someone having their blower explode. I'm not saying that it is likely to happen, and the gas air mixing via the impeller is certainly an attractive option, just prefer to err on the side of caution. In my experience, with a multi port burner outlet (ribbon burner or the like) and a couple of pipe diameters for the mixing tube, there is more than adequate premix for these burners without having to resort to mixing in the blower.

Good one. Someday I'll have to write something up for forge blown burners specifically. Unfortunately the burner assemblies I have the most direct experience constructing and tuning were made with industrial components and might be a little prohibitive cost wise for the casual hobbyist. I was lucky enough to be onsite for a "dumpster dive" when a local university was upgrading their glass studio and got a lot of commercial grade equipment before it ended up being scrapped. Free is good! I reconfigured these components to build my own low pressure natural gas/ forced air burners, which included some that were PID controlled for full ramp and soak temperatures, with zero pressure regulators (for single point control of mixing range), high and low pressure gas safety valves, pilot burners and UV flame safety sensors. My current forge is a little less complicated, but the Eclipse components I'm using are still kind of pricey. I have also been responsible for upgrade and maintenance on a number of "home built" systems, but they weren't specifically my designs. These latter were the more conventional "Alfred" burners that utilized simple Tee fitting mixers with drilled orifices and squirrel cage blowers. There are great sketches of their construction in Dudley Giberson's glass facility design guide as well as Henry Halem's books (which I believe shows an enhanced design with things like zero pressure regulators and an idle circuit). I could scan and post them, but I'm not sure about the whole copyright issue involved and would prefer to err on the side of caution. I do have my own thoughts about things like blower selection and use as well as the relative ease in building and tuning a blown system. Hopefully I'll get a chance to share them with the group sometime in the future.

There are two conventional types of natural gas fired Makeup air units: direct fired and indirect fired. The former has the combustion operating right inside the breathable airstream while the latter has a heat exchanger where the essentially sealed combustion occurs outside the airstream and the heat gets transferred in through the metal walls of said exchanger. Needless to say the indirect unit is less efficient as well as being more costly and prone to failure. Because of this, many industrial facilities use a direct fired makeup air unit, but that is not the case in all locations. There are some drawbacks to the direct fired units, including adding the combustion products to the ventilation air as well as the associated water vapor (believe it or not some companies are more concerned with condensation on the walls of their insufficiently insulated buildings then their employee's potential breathing of combustion byproducts). Be that as it may, you are correct that the vast quantity of air being introduced by the direct fired makeup air unit far overshadows the relatively minor amount of combustion byproducts added to the space. You also have (or should have) additional general exhaust in your facility as well as specific vehicle exhaust (that connects right up to the vehicle exhaust pipe). As a reference the current International Mechanical Code requires a ventilation system that exhausts and makes up enough air so that the open side of a paint spray booth has a capture velocity of 100 ft/min. This means if the open side of your booth is 12' x 10' Hi you need 12,000 CFM of exhaust and makeup air during operation. If it is 0 degrees outside and the makeup air needs to enter the building at a minimum of 65 deg. F for comfort, this means the direct fired unit needs to add 842.4 MBH to the air. That sounds pretty substantial, but if you consider that an indirect system is likely only 80% efficient, that system will need an input of 1,053 MBH to deliver the same amount of heated air (with the associated ongoing cost). I'm not going to do the combustion calculations regarding the CO byproducts of burning 842 MBH of natural gas, but have been assured by manufacturers that the dilution factor takes care of it. Needless to say it is different if you have a (3) burner forge in a 20 x 20 shop with each burner outputting 70 MBH (like a T-rex at 30 psi say) and limited ventilation... Probably wish you hadn't asked this question now

No idea as yet what made it let go. Have to take a close look at it, but the whole top cap disappeared and there was a good 6" of flame shooting out of the top of it, roasting the interior of the grille compartment (of course the flame was around 50% yellow in color, so Mikey wouldn't rate it as an efficient burner at all . Fortunately I was nearby when it started and noticed the change in sound, or it could have been catastrophic. Still a lesson for propane forge builders to use a good quality regulator, not the garbage that is sold with a propane grille.