KenH Posted January 29, 2012 Share Posted January 29, 2012 Hello all, I'm in the process of building a 3/4" Side Arm Burner as designed by Larry Zoeller. I lit it yesterday and it burns ok - better inside the forge than in open air. In open air it needs the burner flare tip. Zoeller's flare calls for a 1 in 12 taper. That is .083" per 1" of length, OR .167" per 2" of length. Now, is that .167" per side? OR .167 total? i.e. assume a 1" pipe, is it 1.167" at flared end? OR is it twice that at 1.333" at flared end? Zoeller's burner flare is 3" long - does the taper extend the full 3"? OR only the last 2 " with a 1" section to fit on burner tube? I know I "should" know the answer, but for some reason it slips me. My plan is to turn a male form on the lathe, then heat a pipe to red, then hammer on form to shape. Now, just how important is that burner flare inside the forge? I read about using the insulation to act as flare, but that's hard to hold to exact taper. Thanks to all for any help and info, Ken H> Quote Link to comment Share on other sites More sharing options...
ironsmith Posted January 29, 2012 Share Posted January 29, 2012 my personal opinion, but i don't think they are necessary and don 't use them. as far as i know they do make them burn a little more efficiently, but if you are tuned up ok , what's the point? Quote Link to comment Share on other sites More sharing options...
MattBower Posted January 30, 2012 Share Posted January 30, 2012 Now, just how important is that burner flare inside the forge? I read about using the insulation to act as flare, but that's hard to hold to exact taper. Inside the forge it really isn't necessary. But if you're going to turn a male form, use that to mold your castable to shape to get the right taper inside the forge. Just to clarify, are you planning to use your male flare/mandrel to form the burner tube itself into a flare, or are you planning to use it to make separate flares that'll slide onto the outside of a burner tube? Quote Link to comment Share on other sites More sharing options...
KenH Posted January 30, 2012 Author Share Posted January 30, 2012 Well, my idea was to use the male mandrel to shape a separate piece of 1" pipe into a flare to slip over the 3/4" burner tube. BUT I do like the idea of using the male mandrel to shape the castable inside forge. Either way, I'll need the dimensions of flare to make the male mandrel. I read how critical the taper of the flare is for proper burning, and wonder how accurate the castable will hold the shape after a few times of heating? @ironsmith: I do not anywhere near the experience and knowledge to say how important the flare is, but I read the taper is critical for max efficiency.... but have never understood just how much improved "max" is over "normal". Thanks again to all for the help and info. Ken H> Quote Link to comment Share on other sites More sharing options...
MattBower Posted January 30, 2012 Share Posted January 30, 2012 I think you're overthinking this. The dimensions of the flare aren't that critical. And as far as I know the only purpose of the flare is to serve as a flame holder; I don't think it's an efficiency issue, at least not the typical blacksmith's burner flare. And good castable is a good bit more heat resistant than steel. The 1:12 taper applies to the diameter -- a 1" increase in diameter per 12" in length. So if the external diameter of your form is (for example) 1" at the narrow end, 2" further toward the big end it's 2.167". Quote Link to comment Share on other sites More sharing options...
KenH Posted January 30, 2012 Author Share Posted January 30, 2012 Thank you Matt - that's the info I was looking for - diameter at big end. I had not idea myself how critical the dimensions were, just what I read on Larry Zoeller's site. He things they are VERY critical. That is 1.167" at big end? Thank you again for all the help, Ken H> Quote Link to comment Share on other sites More sharing options...
John B Posted January 30, 2012 Share Posted January 30, 2012 I know this is engineering, not blacksmithing, but if you are going to turn a mandrel to use as a drift the angle would be more useful to work on than the sizes.Turn a witness on the end of the bar to the bore size of your tube, Then using the cross slide set it to the required angle, in this case 2 degrees 23 minutes 10 seconds to give the 1;12 taper, Leave a witness/guide and turn and blend the taper you can then make the flare any length you want, and you could just inscribe a line around the mandrel with a sharp point tool to indicate the depth to take it to when forging relevant data here; http://www.unionmillwright.com/2885.pdf Quote Link to comment Share on other sites More sharing options...
KenH Posted January 30, 2012 Author Share Posted January 30, 2012 John - you are correct of course, the angle is the important thing, but once I had the diameter on both ends, the angle is easy. They pdf file you linked has it all figured - easy as pie. Thank you for the help - I'm having to relearn my old meager lathe knowledge since it's been almost 40 yrs since I did any lathe work. 73 de Ken H> Quote Link to comment Share on other sites More sharing options...
MattBower Posted January 30, 2012 Share Posted January 30, 2012 Yes, of course 1.167". Sorry! Quote Link to comment Share on other sites More sharing options...
JamesBBrauer Posted February 8, 2012 Share Posted February 8, 2012 The last time I made flares, I'm pretty sure I turned a taper on the lathe. But I took some stainless sheet metal that was cut to fit a cardboard template, then heated it and wrapped around the form, and rammed the final piece into the refractory. I MIG welded the stainless taper, I think best practice is to TIG it, but I don't have one of those, and this has held together fine. The part about ramming it into the refrac helps shape the opening, so as the stainless burns away, you still have the shape pressed at the end of the burner tube to get a little slowing of the air/fuel mixture that helps keep a flame in place. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted February 9, 2012 Share Posted February 9, 2012 The forge is a flame holder, so NOT having a carefully shaped flare is not going to make a useless appliance. A proper flare can improve the low pressure stability and make the forge easier to use, and operate in a nicer manner when cold. A flare is not specifically necessary unless you want the burner to operate in free air. Since you are turning the male form, make it much longer than you need for this project (no point in not having a generally useful tool for later) Just use a piece of cold pipe to drive the heated part home with. Make sure you have some type of lubricant on the mandrel so you can get it off easily. Phil Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 10, 2012 Share Posted February 10, 2012 <SIGH> Flares have generated a lot of opinion and I don't know how to pull up the references I had when Ron and I were messing with the things. No, they're not flame holders though it is a partial effect. What they do is increase induction without inducing harmful turbulence. As a volume of gas traveling at a specific velocity enters a larger volume the pressure falls increasing the strength of induction, in other words the burner draws air more strongly and the flame is stronger and more stable. The ratio is 1:12. Meaning that the cross section of the tube gains that area every time it's length is 12X the dia. Why 1:12 is an important ratio is if you try increasing or decreasing the cross section of a tube more than that it induces random turbulence that inhibits flow so your inducer becomes less efficient. Ideally the whole burner tube should be tapered at no more than 1:12, a LITTLE less is okay but not as effecient. There are however expedients that will do reasonably well without having to make proper flares. For instance I just use thread protectors, they are similar to couplers but non-structural like a coupler, all they do is keep the threads on the end of pipe from getting buggered in shipping. The local plumbing/heating supply has boxes of them and seeing as they have to pay to ship them back give the things to me gratis. Of course being heating and cooling guys they're into fire so we chat and being a likeable bull . . . BSer they like me. If you're going to use induction burners outside the forge as a torch you must get them finely tuned meaning you'll need proper flares if you aren't going to taper the entire tube. I use an oxy propane torch so I leave mine in the forge. Frosty the Lucky. Quote Link to comment Share on other sites More sharing options...
MattBower Posted February 10, 2012 Share Posted February 10, 2012 Frosty, I don't think you were around when I asked about flaring the entire length of the burner tube about four months ago. That post is here: http://www.iforgeiron.com/topic/24229-venturi-burners/page__st__20 What you're saying jibes exactly with what I was guessing at in that post:better commercial burners seem to use a more traditional venturi shape -- large intake area followed by a short, necked-down section to reduce pressure and increase speed of the air/gas mix, then a long, gentle flare -- after which they finally straighten out again at a diameter close to that of the intake. . . . I'm wondering if the full venturi shape offers added efficiency over the straight pipe burners. Anyone have any firm ideas about this? However, I admit that I am having a hard time believing that if you stick a little tiny flare on the front end of 8" or 10" of otherwise straight pipe, it's going to have a significant effect on induction at the back end. Quote Link to comment Share on other sites More sharing options...
KenH Posted February 12, 2012 Author Share Posted February 12, 2012 Matt, Frosty, and all others - I've learned a bit about burners and flares from reading these threads. After getting a couple of homebrew burners working pretty good in the forge, I think I agree - the flare on the end isn't that big a deal. Just use the flare that is cast into the insulation. For burners outside of forge, the flare tip (flameholder?) is required. I'm not sure the flare on the tip will change all that much with rest of mixing tube (8" X 3/4") or (9" X 3/4") length doesn't seem to make a LOT of difference - both tend to burn pretty solid with a nice flame on end - inside of forge. Today I used a single burner on the dual burner Majestic forge I ordered - with firebrick closing off about 3/4" of rear opening and about 25% of front opening closed the single burner does a pretty good job. I'm built the side burner shown on Zoeller's site - except I made a jet by drilling an 1/8" plug to .042" rather than a mig tip. I've got a #35, #45, and #52 mig tips and they don't work as good as the pipe plug, even though the #35 is about .043" hole in end. Thanks to all again for the help. Ken H> Quote Link to comment Share on other sites More sharing options...
mudbugone Posted February 12, 2012 Share Posted February 12, 2012 Question ? The flares I've seen (online) have set screws to hold them onto the burner tube.... Is this to allow an air gap between the burner tube and the flare or only as a method of attaching the flare? Does the flare fit tightly with no air gap at the connection ? For the sake of discussion could a say 3/4" threaded flare be attached directly to a 3/4" burner tube if the flare was shaped or even turned to correct internal taper on a lathe ? From this conversation what I'm getting is that the flare would be better if it was the entire length of the burner tube instead of just the final 2 inches of the flare tip....??? If that's the case couldn't a 8-10" tapered tube be formed for use instead of a 3/4" pipe 8-10" long with a flare attached on the end ? I understand "making" that flared tube would be more involved than a piece of pipe with a flared tip,but I can't see it being that difficult if doing so would improve the function of the burner... I'm only asking because I really don't know, but wondered about how the flare was mounted while examining various burner threads and photos... I happen to know a guy that gets Titanium extrusion tubing scraps from a plant nearby that makes aircraft tubing... I use the larger tapered pieces as breaker bar extensions around the shop,but I see no reason I couldn't cut a short section of about the right diameter and length to use as the burner tube ...IF ... having a taper the length of the tube would be better than just a short flare on the tip... ??? I'm not sure what the internal taper on these pieces are,but I'm going to check. The taper seems very gradual in the small diameter pieces and I assume the end could be threaded for this use. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted February 12, 2012 Share Posted February 12, 2012 The screws are for fastening, there is a slight gap as a side effect but it is very small, about as thick as heavy paper. Phil Quote Link to comment Share on other sites More sharing options...
MattBower Posted February 12, 2012 Share Posted February 12, 2012 The machined flares that I have seen are fairly close fits to the tube, but flares seem to work reasonably well even with larger gaps. Threading the flare on can work, too. If you have the means to give the entire tube an internal taper -- or to get your hands on tapered tubing -- yes, I think that makes for a better performing burner. I don't entirely understand why, yet. But based on what Frosty said, and some other things I've read, and the way commercial venturi burners are made, I'm pretty sure there's an advantage to doing it that way:http://www.wardburne...uriburners.htmlhttp://www.axner.com...turiburner.aspx Quote Link to comment Share on other sites More sharing options...
mudbugone Posted February 12, 2012 Share Posted February 12, 2012 That's very interesting and not anything I had considered... (Thanks for those links BTW) Anyone that has ever handled commercial burners notices that the burner feed (usually cast iron) isn't straight,but bulged out indicating the interior of that assembly is flared (like the burner assemblies in your links) The few times I disassembled burners for cleaning I noticed the shape,but never thought much about the reason or shape. Sorta tosses a twist into the notion of just hooking up a piece of pipe and lighting it and expecting heat... There must have been a lot of thought that went into shaping the burner feed pipes considering they cast special shaped burner assemblies for a reason. I'll have to examine one much closer with more understanding that there was a reason it was done that way... Sometime things take on much more complicated design issues as you actually start examining them... assumptions of "how it's made" aren't always correct...and the facts can get complicated even on something that seems so straight forward on it's surface... I'm almost thinking the flare in commercial burner tubes are cast for a couple of reasons now. Strength and perhaps the rough interior casting causes a turbulance ? I doubt it'll matter much for building a forge,but a shaped tube would have been far easier than a casting that had to be machined not to mention the weight of them... I really am going to have to examine those tube extrusions closer now...Just for the heck of it. If nothing else I ought to be able to find one suitable to make a 3" long flare for a homemade burner tube. Seems the more you think you know the less you actually know. LOL Quote Link to comment Share on other sites More sharing options...
KenH Posted February 12, 2012 Author Share Posted February 12, 2012 Your question about a full length taper is a good one, and something I've been thinking about. If we consider an 8" tube, perhaps using 3/4" size tube for the first 2" for the straight section, then taper the other 6" in the 1:12 ratio would give 1-1/4" ID at large end. Hmmmm, that doesn't sound too hard to make. Take a 1-1/4" 1018 steel rod, cut a taper for the last 6" from full diameter of 1-1/4" to 3/4" at small end. Take a section of 3/4" pipe, heat hot and hammer down on the mandrell to form the last 6" - anyone tried that? edit: I wrote this post before reading the last 3 - good info. The venturi design is well know to increase flow - remember carburetors? Venturi is the basic carbuetor design to increase flow. Ken H> Quote Link to comment Share on other sites More sharing options...
dperk Posted February 12, 2012 Share Posted February 12, 2012 I'm not expert here, but I believe the flares on the commercial ones are made in stainless to be more durable and they are an attachment (set screw) because they are consumable item. I thought I read where over time they will burn up and need replaced. I know you can buy ones here if that helps: http://www.hightemptools.com/burners.html Quote Link to comment Share on other sites More sharing options...
MattBower Posted February 12, 2012 Share Posted February 12, 2012 @dperk: It's definitely a good idea to make flares replaceable, although the SS ones seem to last a good long time for some guys -- I assume keeping the flare tucked back into the insulation is a big part of it. But yes, they are more or less consumable. @mudbgone: That's pretty much my reasoning, too. Some of the commercial venturi kiln burners operate on very low pressure natural gas. ("Very low pressure" compared to the pressures most blacksmiths use with shop-built propane burners.) The fact that they're able to induce enough air flow to sustain good combustion and achieve high temperatures, at such low gas pressures, suggests to me that they must be very efficient. In fact, my natural gas furnace is fired by a row of little burners with the same basic shape. Obviously, if the commercial makers could achieve the same results using a piece of straight pipe, that'd cut their costs -- which would be a competitive advantage. There must be a good reason they don't go that route, and I can't help believe it's because they know they couldn't achieve the same results that way. So yeah, I'm pretty sure there's an advantage to a traditional venturi shape in making burners. @KenH: I've also given a little thought to how to make the internal taper. The mandrel idea is one I've considered (and have not rejected, although I haven't tried it). Another idea that I had was to take a piece of pipe and form the taper in just two dimensions -- in other words, use something like a guillotine fuller to make a constriction at the throat, then, forward of that constriction, forge a couple of flats opposite one another -- just two sides -- and let them gradually merge back to the original round shape. I have no idea how well this'd work, but it might be simpler than trying to form a round taper for most of the length of the tube. I also wonder if there's a real advantage to having the tube round. It might be easier to form the desired shape with square tubing, for those of us who don't have access to lathes. Quote Link to comment Share on other sites More sharing options...
mudbugone Posted February 12, 2012 Share Posted February 12, 2012 I would think a long taper might be accomplished using a cone mandrel (of correct taper) and a press or by shaping the taper and welding the seam... but the best method for durability would be turned on a lathe out of larger stock. I examined one of the tapered pieces of Titanium I use as a breaker bar cheater pipe and I really think I'll need to collect several pieces and cut them to length then measure both ends to see the taper involved...Just looking though I think they might actually work for this...The one I looked at sure might. The next time he picks up a load I'll experiment a bit with them... Quote Link to comment Share on other sites More sharing options...
KenH Posted February 13, 2012 Author Share Posted February 13, 2012 @Mudbugone: That Titanium sounds expensive!!! Even the scrape prices are pretty interesting. Back in '80s I purchased some Titanium tubing and tube fittings for installation in chemical plant - boy, those cost a pretty penny. Your using Titanium pipe as a breaker bar sounds like my Dad using some of Teak lumber as props around the farm. I explained to him the cost of Teak - Dad patiently explained to me that "No wood can be THAT expensive" - not sure I ever convinced him, I just hid my Teak. @Matt, not sure how the guillotine method would work - while a venturi doesn't have to be perfectly round (some of the carburetors are sorta oval), I'm not sure how a flat section would work - perhaps at reduced efficiency? Perhaps stretching 3/4" pipe out to 1.25" might be a bit much in an effort to get the flare, a person might take 1" pipe, spread the end a bit for flare, then cut a seam as you suggest to taper the small end? Good idea - maybe I'll try that. I've got the a 2" taper cut on a 12" peace of 1-1/4" rod...... maybe I could extend that taper for 1" from 3/4"?I've been working on the Railroad spike knife today and not fooled with burners any. I hope to get back to burners in a few days or so.Good discussion going here.Ken H> Quote Link to comment Share on other sites More sharing options...
mudbugone Posted February 13, 2012 Share Posted February 13, 2012 Now Titanium is VERY expensive but this old fart tosses it in the scrap bin with with regular scrap and sends it off in a dumpster....We've tried numerous times to explain it's worth ,but it's like talking to a stump. Some of the pieces are 2" in diameter and several FEET long ,but he will not listen. The plant gives it to him to haul it off so it's ALL scrap... Proves you can't fix stupid or DUMB. He's a likable old cuss just hardheaded. I find it hard to deal with him and I've known him 35 years,but my Uncle sucks up (no other way to put it) to him for "stuff" and gets hooked into helping him do things... I try to buy stuff and he always wants to work it out instead...which I'm not willing to do,but I might have to "suck up" to score some pieces of tubing. These tapered pieces are the end pieces that are fed into the tubing extruders. They start with a solid piece and then form it into smaller & smaller tubes which are mostly used for airplanes and aerospace applications. He had a large pile of very long 2" tubes that were rejected and sold them to some Mexicans for a couple hundred bucks..... I think scrap prices on it are around $10-12 a pound... He gave the entire pile to my Uncle several weeks earlier and he failed to go get it...Needless to say my Uncle was ticked off big time...LOL...You Snooze you Loose. He probably has 10-15 acres of an old junkyard around his house and I never fail to find something interesting when I look around it... Quote Link to comment Share on other sites More sharing options...
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