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MCalvert

Multi-port Forge

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I am new to the forum, and I am thankful that my Google searches led me here as I have learned much in a few short hours of reading (including TOS and read this first, thank you). The expert knowledge is appreciated. I am planning to build a multi-port gun burner. I have flipflopped between a couple different chamber ideas, and I am starting to settle on a 'D' (flat face down) with relaxed 90s at floor corners. D's seem like they are common, and from other threads, ovals direct the flame path well. This is why I am thinking about making a relaxed oval with a flat floor. I have access to a large amount of scrap metal, including sandblasting tanks and 20lb propane tanks. I was wanting to use a sandblasting tank sectioned down to 12 inches (not including domes), but with a diameter of 13 inches I feel like the volume may be too large (possibly 8 inches wide). Ideally I would like the chamber to be 6 inches wide, and 10-12 inches long. I will have to keep looking through our metal to see if I can find something closer to my end goal for the size. 

For the design of the forge, I'm not designing squat. I'm just following the recommendations here. 1 inch 2700 degree blanket soaked in water/colloidal silica (two layers), heat cycle, bubble alumina refractory, matrikote, heat cycle. I plan to orientate the burner in the same manner one would with a Frosty T burner, 2 inches off center with a tangent 25ish degree angle. 

The part I am not as settled with is the runners in the burner's refractory. I had an idea that I thought might be fun to try. I wondered if putting a slight curve in the runners (but not to parallel, still striking the floor) would increase the speed of the flame travel across the floor, which may strengthen the swirl of the flame. Sure, this is min-maxing, but it's fun. For a 10 inch long chamber I would aim for a 6 inch long burner. I read how many ports would be appropriate but I have forgotten, so I will have to find it again. I even considered making the runners square as apposed to circular after reading a comment from Frosty that this can mitigate a specific type of turbulence (edy current). The bottle to burner will be standard regarding the various valves in the plumbing. I am going to fabricate the burner's plenum differently, which really only amounts to giving the airflow a smooth transition from pipe to plenum. I want to do this to reduce the mass of turbulence from the air going from a round pipe/orifice to a block. On the other hand, the turbulence may be the primary AF mixing element? Anyway, I don't feel that this forge will be any different than the other forges that follow the recommended design/parameters. I'm sure it will forge weld ok, provided I don't muk anything up (it happens). The only elements I lack are the right size steel tube, matrikote, and colloidal silica. Feel free to suggest/correct.

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Welcome aboard, glad to have you. For a start I think we need to start speaking the same jargon. When you say "D shaped chamber" I assume you mean the forge chamber. Yes?

16 hours ago, MCalvert said:

The part I am not as settled with is the runners(?) in the burner's refractory.

You lost me there. 

I don't think your target forge volume is too out of line, a bit large maybe but you're building a gun burner so it's in range. If it turns out to be too much volume it's easy to make the floor thicker and reduce the volume. making a 8" x 12" floor 1" thicker takes 96 cu/in off the volume. Yes?

Adjust the length of the ribbon to fit the forge, I wouldn't go less than 6" in a forge 12"L. Be better in 10"

A gun isn't so sensitive to how many ports you have in the block, you can adjust the blower and gas to match what you have and what you want it to do in a session. It's one of the nice things about gun burners. If you're going to er, more outlets is better than too few. 

I don't recall worrying about making the transition from the inlet to the plenum and the plenum smooth, especially low turbulence. You need turbulence in the plenum on two counts: First is to more evenly distribute the flow to all the outlets. and second, YES to make sure the fuel air is mixed as completely as reasonably possible.

No good reason to try and accelerate the speed of the flame from the orifices. Gun burners are notorious for crazy high velocity flames as can be seen by dragon's breath shooting 3' - 4' out of the forge openings. That's fuel burning outside the forge, wasted money and dangerously B A D air. 

You want as low velocity flame as you can generate without it burning back. The slower the fire is moving the longer it stays IN the forge and does more work for you. Yes?

Frosty The Lucky.

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Frosty, you are correct. I apologize for my terminology. I come from an automotive fabrication background, so my word association is not very good. By runner I meant the individual passageways inside the molded refractory part of the burner. This is really irrelevant though, because I reread the thread where you were teaching someone about edy currents and I grossly misunderstood what was being taught. After going over it again I understand better, and realize that it does not apply to what I thought it did. My ideal of the internal volume of the forge coming out to 10in L by 6in W by 5in tall sounds like it will be workable after reading your reply. By 'D' I was meaning the shape of a ladybug, but with rounded corners. So maybe saying an oval with a flat bottom side (floor) makes more sense? Apologies if I am still butchering it.

I believe my mistake with my plenum idea was in thinking that if a strong enough vortex could be achieved inside the "ladybug," that the rotation would keep more combustion inside due to being caught in the swirl. I realize the flaw in my thinking, so thank you for that. It makes a lot more sense that the more heat that ends up outside the work area, the more wasted energy. I will follow the plans linked on Wayne Coe's website exactly then. Also, it sounds like a 6in burner paired with an 8in long internal volume would be a better idea? Thank you for the information.

Oh and burner angle/orientation stays the same? Thank you.

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Don't apologize, everybody has to learn the jargon, I'd be in the same shoes were I the new guy where you work. 

What you called runners we call outlets and the block they're cast in is the burner block. We've worked through a few terms before someone who actually uses commercial multiple outlet burners clued us in on terminology. He hasn't corrected "burner block" so I guess it's okay.

I don't so much "teach" as pass on what I learned when I can. I learn as much or more in the process. I'm just a guy with excellent reading comprehension and good memory for the written word. Just a guy on the internet who likes to talk. Relax and just talk. Okay?

I took your D shaped chamber to mean the shape of the cross section. Yes? We just need to be on the same page. Flattened oval gets used and I've about given up trying to get folks to use the architectural term, "vault." However if you do start butchering ladybugs shoot some video and post the Youtube link please. :rolleyes:

6"w x 10"l x 5" h should make a fine sized forge. They're nice proportions, close to what I use.  Rounding the corners where the floor meets walls is a good idea it'll help keep the vortex flowing smoothly. 

Yeah, what you missed is how much burning fuel air is pushed into the forge and how much it expands going from ambient temperature to near 3,000f. It doesn't stay in the chamber long on a good day. Pumping it in at high velocity pushes it through faster. Mikey articulated that little bit a while ago it was a real DOH moment for me. 

About the ribbon burner plans on Wayne's site. Those are by John Emerling, he published them in either the "Anvil's Ring" or "Hammer's Blow", the ABANA magazines. Those plans are what made me winkle out the NARB. The gun as designed requires a blower with a high static pressure to operate which means very high flame velocity.

Looking over the plans the FAM (Fuel Air Mix) inlet pipe is in line with the outlet holes so the flames directly in front  are much longer or just blow out. So John put a deflector in front of the FAM inlet to even the flow to all the outlets. Unfortunately I believe he put the deflector too close to the inlet so the design requires a blower with a pretty high static pressure to work. 

What I did at first was move the deflector half way across the plenum and make it larger. This meant the T inducer wasn't fighting against a small gap so it flowed more easily but the deflector prevented the flow from blowing straight onto the outlets in the center. It worked pretty darned well.

Then on the next test plenum I welded the inlet to the side so the flow wasn't directly down the outlets and left the deflector out entirely. BINGO! Stable flame stop to stop on my 0 - 20 lb. regulator. SWEET! The T burner doesn't like breezes or back pressure but hooked to the NARB it stopped caring.

I'm not trying to convince you to go Naturally Aspirated, I don't care. My point is you don't need such a restrictive deflector nor a high static pressure blower. A less restrictive deflector should lower the flame velocity significantly. 

Oh, sorry for the side track. I think your proposed burner angle sounds good but we should get Mikey involved he has a better handle on burner angles than I.

Frosty The Lucky.

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Not really :)

Ribbon burners pretty much eliminate the need for care in flame positioning; still another advantage in choosing them over single flame burners. The only reason I haven't jumped down that rabbit hole is what I've been saying from the beginning: No one shoe fits all, and no one burner design is best all the time.

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Thank you for the replies. I will use a vault design with an 8in burner. I would like to copy your NARB design regarding the plenum's fuel/air inlet orientating from the side. If I need to include a baffle, it stands to reason that it could be much smaller using the NARB design.

My thoughts are a 2in by 2in by 8in plenum with a 2in thick refractory section protruding 1in out of the assembly. This would make the metal section 2in by 3in by 8in. I will probably keep the same location and angle as previously proposed because it sounds more fun to build than a 90° angle. Does this sound workable?

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I found a tank that I was happy with. I am getting it sectioned currently. Progress is a bit slow right now as I have many irons in the fire, but it's progress none the less.

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Another progress update - The door and exhaust guides are on, nuts to hold the ribbon burner are on, and the ribbon burner is cast. I let the burner sit in a bag for 24 hours, then in open atmosphere for five days. I cast it a little different. I cast the refractory a little long, made a guide setup on some dowels, preset the voids for the crayons with a tapered rod of less angle than the crayons, then set the crayons tapered end down. This worked fairly well, but when setting the burner plenum in, a couple of crayons settled a little lower than the rest. The crayons were tapered, and when the bottom 3/4 of an inch was cut off, the smaller holes were exposed. The crayons were then melted out. I am hoping to slightly increase the air fuel mix velocity exiting the outlets. If it works, I came up with a precise way to do it next time so that the outlets will be very uniform.

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11 minutes ago, MCalvert said:

Another progress update -

You are having almost too good a time building this aren't you? :)

Looking good I'm just waiting to see it all glowy yellow inside. 

Frosty The Lucky.

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Frosty I'm having a blast. I traded my hot rod gig in a few years ago for a police job, so this is my regular mental health recharge. Everybody needs an outlet.

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Ooooh, a hot rodder goes over to the dark blue side and you're talking about a mental health recharge? DRATS it's tough not having a reset button isn't it? Yeah, decompression is a good thing, cops have high stress jobs, even if you aren't in the field. I can't imagine being a dispatcher and sending people I know into danger over and over let alone a patrol officer. Thanks for doing what you do, you're one of the things that hold civilization together. 

We have a number of vets suffering with PTSD and a cop in the club, smithing is great therapy for everybody, very meditative.  

Frosty The Lucky.

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I couldn't agree more, though I sometimes wonder about civilization. The patrol life is honestly a good one, but you NEED a support structure and avenue to decompress! In my case a wife/kiddos and lots of metal.

(This comment intended for anyone by chance considering law enforcement as a career.)

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Progress has been slow till tonight. I got my shell finished (I think). I did run into some trouble though.. Two of the bolts warped in their nuts while welding. I have had good success with the method to hold the nuts while welding, but in the past I had used a TIG. I think the MIG had way too much heat transfer. I should have switched but didn't think about it at the time. Everything turned out ok though. I'm pretty happy with the shell, and if the next four days go well at work, I will be cutting and rigidizing refractory blanket. If the setting of the guts goes as planned, the forge volume will be somewhere between 302 and 318 cubic inches.

As a side note, you may see these pictures and observe popping/high wire speed on the shell's welds/beads. This was due to an issue with the spool, and I had to turn her speed up to make it work.

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Overdue update: Except for casting of some refractory doors, the forge is finished. I am on to working out the burner. The interior is 1/2 in. bubble alumina for the floor and 1/2 in. COL30 for the walls.. light coat of matricoat90. I wish it was about an inch wider, but overall I am happy so far.

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I got my forge doors cast finally. Being that the doors are consumable items, I made a mold that I can zip together to cast more as needed, and leave in a corner in the mean time. These particular doors are cast-o-lite with soft brick cores. The soft brick had passages drilled and packed with cast-o-lite to tie the faces together and increase strength. I am impressed with cast-o-lite as it is very strong after it is cured. My hope is to have doors with reasonable toughness that will aid in insulating the forge to a degree.

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Long overdue. The burner creates some level of heat, at least. When I get my table built this weekend (Monday-ish), I will fire it in the forge.

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Edited by Mod30
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Your build looks great!  

Some suggestions on your setup.  The pressure between the jet and the needle valve may be unreadable on the gauge depending on the size of your jets.  I would put the gauge before the needle valve (actually before the ball valve shutoff) so you can see/set the maximum line pressure, and then adjust with the needle valve and air to fine tune.

You have a very rich flame, and the regulator is showing nearly 0.  Given the type of blower you have (Ive got one like that too), you should have excessive air.  I'm guessing it's gated down in the pics.  If not, I noticed the pipe after the jet is a much smaller diameter and may restrict the air flow.  An HVAC guy one told me about the importance of larger vents...I carried that onto my build.  I used one the same size as the exit on the blower.... 2.5" I think.  Either way, looking really good, it will work completely differently in the forge anyway, and all this might be moot!  

And thanks for your service!

DanR

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Thank you sir. I'm going to do as you suggest with the pressure gauge. I was actually showing my dad the difference between rich and lean flames, and I had the blower gated almost all the way down.. the thing puts out gobs of air. I'm looking forward to finishing my work bench, I need more workable area in a bad way!

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I got my new work bench on its own legs. I will probably add a bottom shelf tomorrow to sit a tank on. I'm torn on what to do with the other side of the bench.. mount a vise and bench grinder, install a coal forge, or leave it open with a square/ruler etched into it for whatever comes up.... or all three in a modular fashion :blink:. I  could even 'Y' the blower to also work for the coal forge so I'm not using hair dryers anymore. I plan to get it on casters so that it's super mobile like by belt-grinder and accessory table. Any curmudgeonly suggestions are welcome. Also to the mods, I am not trying to annoy you with my big pictures, I just cant find the option on my phone to reformat them into a smaller configuration.. or whatever the term is ( not so up to speed with my smart phone, still learning). Apologies. 

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I wouldn't try to find something to put on the whole table, having room is a good thing around an engine of demonic heat. Yeah, at least get spreaders on those legs, the heat from the forge will cause it to warp and it may not come back to flat when it cools. 

Looking pretty good, I'll be watching for pics of it HOT.

Frosty The Lucky.

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