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About D.Rotblatt

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  1. D.Rotblatt

    Forge top glowing after re-lining

    If that top of the forge is steel that is red hot, it is a serious problem. It appears you have flame between the top of the brick and the forge shell. How far are the burners extending into the brick? They should extend about an inch into the brick, which means you will need a 1" hole in the brick, assuming those are 3/4" burners. The red hot shell will quickly warp, the metal will oxidize and soon become brittle and fall apart. A 3 burner will go through a lot of gas. You only need a 1 burner to work on up to 8" knives. You can put ball valves on the back two burners (if you got the economy model) and turn them off, but be sure to stuff ceramic blanket in the top of the burners to prevent chimineying and them getting too hot. That way you can use 1, 2 or 3 burners. You will use 1/3 of the gas. That's fine. Others will give more insight, I'm sure.
  2. D.Rotblatt

    Forges 101

    Adbond II only comes in 5 gallon amounts from Remet company - it's a colloidal silica used for ceramic shell molds. Pottery supplies have it for rigidizing, but I'm not sure that's the same stuff (since the adbond melted ceramic fiber in my tests). i'm looking into finding small amounts. I'll let you know if I find them.
  3. D.Rotblatt

    Naturally Aspirated Ribbon Burner. Photo heavy.

    Update on my 1/8" 123 hole NARB. I welded a billet of Damascus with it today, basically same pressure as I would use my Reil burner for welding, but I could get 9" of steel up to heat without moving it rather then 5". Once the forge was hot, (after about 1.5 hours welding and drawing the billet) I tested temperatures at different pressures. It went from 2400F at 12.5 lbs down to 1560 at so low a pressure that the burner didn't pull enough oxygen and the flame went to yellow reducing flames, I'd guess 1/4 lb or so. At the pressure just before the flames went yellow/reducing (maybe 1/2 lb), I was at 1630 F and the flame cones where about 1/8 or less long. No backfiring except when I turned it off. None. Perfect performance I got a bit of yellow dragons breath out of the forge at high pressures, but it did produce a small amount of scale on the metal in the forge. Must still be reducing, cause I welded the billet without flux at about 2350 F with the damper on the burner wide open (full air). 13 layers, 15n20 and 1095. Pic below. The organ tone is loud at startup, but if I make gate off the burner intake and make it a bit reducing it goes away. Based on the quench distance theory, and the other article listed, a reducing flame is more prone to quenching, so that supports the theory that these burner holes are at just over that edge. That also supports the fact that they do not backfire easily.
  4. D.Rotblatt

    Naturally Aspirated Ribbon Burner. Photo heavy.

    Wait....this is nerdy?
  5. D.Rotblatt

    First Forge Build Plans

    I have another thought regarding the backfiring. You have cast nozzles, and it is that variable that is different from other 'T' burners. What are the sizes and shapes of them? What PSI are you running? The backfiring is happening when the forge gets hot, and sounds similar to what happens in my ribbon burner is the pressure is too low - it's fine until the burner head gets too hot, then it backfires and I have to turn the pressure up. Dan R
  6. D.Rotblatt

    Double burner issue

    Mikey is the flame king, he'll have the best take. What pressure are you at in the video? I can say two things for sure; 1) they will act completely different inside the forge, do you have a video of them inside the forge? 2) The reducers you are using for the nozzles are not ideal. Those are Reil burners with the mig tip mod. As I recall, when you use mig tips he specifies a larger reducing coupling to allow for more air. I tried a few like that and never found them as good as the original Reil burner with the Bordeaux mod. I've used those for years. I can hear them huffing when you give them more oxygen in the end of the video. I think the flame is starting to backfire a bit. The nozzles might be the problem. You can get a piece of stainless tube from speedy metals dot com. 1" OD x .120 wall thickness. Sometimes takes a little filing to make it fit on 3/4 pipe. 12" of tube is only $12 plus shipping. In regards to the burners burning different, try cleaning the tip on the one not doing as well, make sure there is no obstruction (like a bit of teflon tape) in the orifice. It should behave the same if it's built the same. But I defer to Mikey in all of this.
  7. D.Rotblatt

    3D printed plastic burner experiments (photo heavy)

    As a general rule, if possible you want all parts with a similar thickness. Barring that, you sprue into the thickest (if possible) and put the thinnest furthest away. Metal crystalizes as it solidifies, and the crystals are denser than the liquid (it shrinks), so needs to draw liquid metal from somewhere else. Thinner sections cool quicker than thicker sections. If an area doesn't have a place to draw metal from, you get porosity which is space between the crystals (though it can also come from dirt, trapped gas, or pieces of investment that have broken off). Ideally, you want to control the cooling of the metal to start furthest away from the button and to end closest to the button. The last place you want the metal molten is the button (or cup) where you pour the metal in, so it should be of large cross section. Sometimes you have to sprue into two places to get this to happen, or put a feeder next to a thick section of your casting. Remember, with aluminum you can remelt the sprue and button, so make the sprue short (though long enough to cut off easily) and the button large.
  8. D.Rotblatt

    3D printed plastic burner experiments (photo heavy)

    Possibly sprue size or too small a button. also looking at your casting, I'm betting you are sprueing into the end. The spiral "fins" may be freezing off before the downstream portion is solid causing porosity if the downstream section. I'm more familiar with bronze casting then aluminum though. Do you have closer pics showing the porosity problems and a description of how you sprue it? Maybe I can help. Dan R
  9. D.Rotblatt

    Naturally Aspirated Ribbon Burner. Photo heavy.

    I added too much water purposely to try to get it to flow better. As you said, I wasn't worried about structural issues. I have some Kaolin clay, and some bentonite and a bag of zircopax....hmmmmm. I'll try some mixes. I did a bit of a internet search and found this in the eBook: Modeling of Combustion Systems: A Practical Approach. It is talking about Hydrogen rather then propane, but I bet the principle is the same. "One important consideration is the 'quench distance' - a characteristic length for a given orifice geometry through which a flame cannot propagate. For small-diameter orifices, the edges will abstract sufficient heat from a propagating flame to extinguish it. The quench distance varies with the orifice diameter - small orifices are more effective than larger ones." Theres an appendix that shows orifice size...but I'd have to pay $45 to see it. This also makes me think that that may be the answer to my Singing Forge sound! The flame is backfiring into the orifice, but looses heat and extinguishes, then starts burning back again setting up a vibration. Once the edges of the orifices heat up to ignition temps, the flame catches and doesn't burn back.
  10. D.Rotblatt

    Naturally Aspirated Ribbon Burner. Photo heavy.

    It was a pain, and it took a bit of time, but it ended up with a good solid face. I did a lot of vibrating to try to get the bubbles out and it worked. One thing I'm noticing is that the area with the nozzles is staying pretty cool, but I ran out of gas and haven't run it very long. I'm hoping this might be a cure for the low pressure backfire issues of multi-burners. Zircopax is a powder (or my zircon is) and I don't think it will perform the same function as an aggregate, though it might work as a filler. On the other hand, it seems the muddy liquid that bleeds out of the refractory when vibrated still sets up hard so I'm going to try just sifting the Mizzou through a screen and see if that works. If it does, I can try adding zircon to see if it extends it. I might also try a paste of zircon and colloidal silica binder. We'll see if I have the time to really play with this. I also saw a post here of a person using a mix of 95% calcined alumina and bentonite to make a burner nozzle. He seemed to just fire in a forge after baking it at 400 till dry. I'm trying to figure out what those white ceramic burner heads are made of - I think that would work well. The spacing of the burner tubes could even be closer. This is the only thing I've found online. Dan R
  11. My bad. I misremembered some of the results from my eggshell experiments. What I said works works, and what didn't didn't, but it was a little different from what I remembered. First, the Colloidal Silica (Adbond II) used alone without zircon flour melted the ceramic blanket rather then acting as a rigidizer, so use fused silica as a rigidizer. This may not apply to what you bought, since the colloidal silica's I'm seeing sold at pottery supply houses are for rigidizing ceramic blankets for glass slumping and such. You'll have to try yours on a piece of scrap ceramic blanket. Second, the fused silica/zircon mix didn't melt the blanket, it just didn't bond and form a shell, but rather flaked right off. The colloidal silica (addend II)/zircon mix forms a hard shell as previously stated. My original description is on Page 35 of the Forges 101 thread.
  12. D.Rotblatt

    Naturally Aspirated Ribbon Burner. Photo heavy.

    Since the burner is working so well, I thought I'd post some pics of the build. I used an ancient box of Kerr sprue wax, the rods measured 1/8" x 4" long. Can't find that brand anymore, the closest I see on amazon is 8 gauge which is 3.25mm or .128". I cut the 4" rods in half. 123 holes = 64 pieces cut in half. It came to 1.55 oz of wax. The wax on amazon is $25 for 8 oz. That's enough for 5 burners the size mine was, so purchased new it comes to about $5 of wax for the one burner. The main problem I had was that the aggregate in the Mizzou was too large to fit between the sprues. I had to use a thin knife blade to push the refractory between the rods in little bits. Took quite awhile and the Mizzou started to set up around the edges...then I had to dig up a groove to put the Plenum into...basically it was a bit of a cluster ****. But I got it together (no pics of that part of the build). I believe that Frosty has mentioned running the refractory through a strainer to remove the aggregate. I'll try that if I do this again (and I might for my longer forced air ribbon burner). I made a plate with matched holes thinking the wax would bend, but the 2" pieces kept pretty straight and I didn't use it.
  13. D.Rotblatt

    Naturally Aspirated Ribbon Burner. Photo heavy.

    Well I'm home from my trip, had an hour to play with the new burner! The sound: I found when I change the mix to reducing the whistle goes away. As the mix moves towards neutral the whistle comes back. I can make it get louder and softer by putting my hand over the intake on the Venturi (I'm using a standard Reil Bourdeaux modification). When I do this I can actually see the flames vibrating and then stop vibrating when I put my hand on the intake. After about 2 minutes the burner head heats up enough and the whistling dies down and goes away - takes about 10 seconds. The heat: Once warmed up I turned it down below what the gauge could read and the flame was stable. I then continued to turn it down so low it wasn't pulling any air and turned into straight propane flames - no backfire at all. But the burner head wasn't really hot yet, so we'll have to see once it's been running a bit longer. I then turned it up to 7.5 lbs and the forge stabilized at 2130-50 F. Before I modified this forge for the ribbon burner I used to forge at 5-7.5 lbs with this same Reil burner (haven't changed insulation or anything). It has a more even and wider heat area than with the single burner and 1" nozzle. I then turned it up to 10 lbs and the temp increase was slowing down at 2220, but then.... ...I ran out of gas. This may have also effected the 7.5 lb test, so I'll do it again once I fill my tanks. Next: I'll run it at 10 lbs, 12.5 and 15 lbs (12-15 was my welding temp with the single burner), and let it run for an hour til the burner is hot (probably weld up a billet). Then I'll see what kind of stability it has at low pressures of 1/2-1 lbs. and see if it will be stable at tempering temperatures. It's looking like it might be...but we'll see! Dan R
  14. D.Rotblatt

    Ribbon burner forge design, Yes? No?

    Check out the table forge build at Flemmingknives dot com, look at his shop build, click on second pic for his tabletop forge. It's a good example. Haven't used one, but seems nice versatile forge for doing blacksmith work or smaller knives. Allows for different shells to be put on.
  15. D.Rotblatt

    3D printed plastic burner experiments (photo heavy)

    I was thinking about this this morning. I think you would have to print two halves with keys on each half. Think of taking the cylinder and splitting it lengthwise, put two or more short posts (or 1/3 spheres or really any irregularity) on the edge of one side and matching holes on the other. When you pull the wax halves, the posts/holes would key the two halves together so they match and you fuse them together with a hot knife in a few places. Clean up the joints and spray with shellac. It's a little wax work, but I know how long it takes to print 3D. Don't know which is more efficient for you, since you don't have to be around when the 3D prints. I was taught to paint my waxes with shellac as a way to fill pinholes and allow for a surface that the investment will stick to (helping to prevent bubbles). No difference between shellac or no shellac except less bubbles. In short, it burns out fine. Sounds good. I'd just paint with shellac to make sure. That one may have no pinholes in it, but another one might. If investment gets inside the model...well, the casting will be full of bits of investment which will probably break off inside the mold during pouring leaving pits etc. You'll probably see a lot of bubbling from the model when you vacuum the investment if there is a pinhole to the inside cavity. Dan R