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Hello, little question.

 

Assuming I have this burner 300 mmX90  mm and input is 2"  (I have 380V blower with 2" pipes)  this is 28 holes.  28   10 mm holes has more area than 2" pipe on input of the burner  by about 3 holes. 9 mm holes is about 2 holes short.   Should I strive for perfect equilibrium in this?

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Like this.  I remeasured my profile I can use for the burner, its 80 mm.  33 holes around 8,7 mm will give me equilibrium to 2"  (50 mm) tube.  Why I am doing this

 

 

My current forge is just too angry with venturi burners.

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I'm not sure but I don't think it will matter. The air and gas mixture is under pressure and a difference in area will give you a difference in pressure, you will be adjusting the mixture anyway.

 

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Like Mr. Kehler said it wont make a huge difference at that level of imbalance if you had a 2" inlet but 4 10mm outlets it would be an issue. You want as close to same area as possible but its not machinists levels of precision. A good example I can give where this matters if you have to much output vs input you wont pressurize the furthest ports enough to keep the heated atmo from reentering the manifold. The opposite direction is a bit harder to give an example but is problematic in a couple ways. Going slightly over/under wont be enough of a problem to cause burner failure from your current posted design.

 

When you say your current forge is angry with the ventures could you elaborate? Do you mean the amount of dragons breath coming out is way to much or is it something else i'm not seeing in the video?

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24 minutes ago, Sean Blum said:

Like Mr. Kehler said it wont make a huge difference at that level of imbalance if you had a 2" inlet but 4 10mm outlets it would be an issue. You want as close to same area as possible but its not machinists levels of precision. A good example I can give where this matters if you have to much output vs input you wont pressurize the furthest ports enough to keep the heated atmo from reentering the manifold. The opposite direction is a bit harder to give an example but is problematic in a couple ways. Going slightly over/under wont be enough of a problem to cause burner failure from your current posted design.

 

When you say your current forge is angry with the ventures could you elaborate? Do you mean the amount of dragons breath coming out is way to much or is it something else i'm not seeing in the video?

 

Thanks for that insight Sean.  So I need to put a valve to the air duct to be able to tune and needle valve for the gas to get the correct mixture.  What you ask - Yeah its lots of dragon breath.  You cannot see it here because I m blocking the port, but I think I m burning too much fuel for nothing. It will weld, but just about. Also I have used hard brick inside. Its indestructible, but I think it would be better to have the wool insulation, just with refractory. So when at it, I can easy build this type of burner in my shop and I have finaly found refractory that holds up to 1700 C  for the burner and the inside, if I build a new one and this one sell to some who just wants to start quickly.

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What size are the gas jets in your "Venturi" burners? Can you change them fairly readily?

 

If you are using mig tips as gas jets, try a smaller size.  It may seem counter-intuitive at first, but there is a very high probability it will increase your temperature and dramatically reduce the Dragons Breath. I would aim for about half the area at first; 0.707 times the diameter and see where you need to go from there.

 

Ideally, you want to get to, or just above, the maximum (welding) temperature you'll ever want with the choke slides fully open. Then you can reduce airflow with the chokes to get cooler, more reducing, temperatures for forging. 

 

Note that mig tips are sized by the wire diameter they are intended for welding with and the hole is typically about .006" or .015mm bigger than the nominal size. 

 

 

I'd certainly spend a couple of hours playing with the burners you have before embarking on a ribbon burner build. Even if you don't get them working to your satisfaction, you'll become familiar with the effect that varying the mixture has on the flame temperature.

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40 minutes ago, timgunn said:

What size are the gas jets in your "Venturi" burners? Can you change them fairly readily?

 

If you are using mig tips as gas jets, try a smaller size.  It may seem counter-intuitive at first, but there is a very high probability it will increase your temperature and dramatically reduce the Dragons Breath. I would aim for about half the area at first; 0.707 times the diameter and see where you need to go from there.

 

Ideally, you want to get to, or just above, the maximum (welding) temperature you'll ever want with the choke slides fully open. Then you can reduce airflow with the chokes to get cooler, more reducing, temperatures for forging. 

 

Note that mig tips are sized by the wire diameter they are intended for welding with and the hole is typically about .006" or .015mm bigger than the nominal size. 

 

 

I'd certainly spend a couple of hours playing with the burners you have before embarking on a ribbon burner build. Even if you don't get them working to your satisfaction, you'll become familiar with the effect that varying the mixture has on the flame temperature.

I will definitely point you in the same direction as you may have perfectly operational forge that needs some tweaking to get working correctly. 

 

1 hour ago, Jaro Petrina said:

 

Thanks for that insight Sean.  So I need to put a valve to the air duct to be able to tune and needle valve for the gas to get the correct mixture.  What you ask - Yeah its lots of dragon breath.  You cannot see it here because I m blocking the port, but I think I m burning too much fuel for nothing. It will weld, but just about. Also I have used hard brick inside. Its indestructible, but I think it would be better to have the wool insulation, just with refractory. So when at it, I can easy build this type of burner in my shop and I have finaly found refractory that holds up to 1700 C  for the burner and the inside, if I build a new one and this one sell to some who just wants to start quickly.

So from the sounds of it and the little I see from the video is your current setup has maybe two big problems though its hard to tell from a video that doesn't give perspective like in person. The first one is definitely the construction of the interior hard FB is tough but sucks at all the important parts of being a forge lining after that. Its a huge heat sink and has comparatively no insulation. This might explain why it seems to have a huge dragons breath but still running "cold". I would recommend a layer of 2" blanket and then hard facing the blanket with refractory to save your heath and prevent damage to the blanket. The second problem is if those venturis are similar to the ones I think they are then you might have to much burner for the size of forge its in. The burners are outputting more than the volume of the forge can efficiently take so you have a surplus of fuel and not enough O2 to burn causing the large DB. 

 

It might be that solving problem 1 will allow you to not use the second burner meaning its not wasting fuel just to fight the heat loss of poor insulation. If it is the case of the forge being too small for the amount of burners you have putting on the ribbon might cause more problems as right now from what it sounds you are brute forcing your way through the heat loss/sinks of hard FB and the ribbon will do that but it will still be just as wasteful. Plus if you have a smaller than the minimum for the size of ribbon you have it means to run it with enough air to keep it cool with make it always be oxidizing but if you lower it to make it neutral it will overheat and backburn in the manifold which is bad. I made this mistake with my current forge as its just slightly too small so overheats the manifold if you aren't paying attention to it.

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This forge is 10X10X50 cm that is like 490 cubic inches. It has insulation behind the brick. But I m still gonna build a new one.

Edited by Jaro Petrina
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Wayne I have found and read the instructions, I know your page, thanks.  I m far away, and as you remember our customs are pain in the arse - I bought some IR paint stuff from you, while ago, that works well actually, but it was difficult to explain to our official knobheads what it is and why I want it. :D :D :D   Our propane tanks are different size, but a friend of mine is gonna roll me thick walled tube.  Ill go further like this, the burner is 12X3"  (in your units)  the metal shell is about 14" diameter and 20" long. The inner space is gonna be 7" in diameter.  The fiber insulation is not drawn here, only the hard lining.   My blower is 1,1 HP and according the sticker it should do about 1800 m3/h which should be 105 cfm. 

 

sestava.jpg

Edited by Jaro Petrina
just clarification
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The hardest part was to find refractory for lining. I have something called MSG-1  which is for working temperatures around 1400 C, but it has heat resistancy up to 1700 C and it can be improved by adding further compounds. I think if I mix around 10 kilos I can add some sandblasting AL2O3. Normally it has about 35% of it, but the instruction say, you can add whatever fillers up to some ammount.

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  • 2 weeks later...

This is the current one I have it used a 11gal harbor freight air tank for the body, 2in kaowool, then I hardfaced the bottom with Mizzou refractory and the top with kast o'lite 30.

 

So im terrible at eyeball estimating dimensions but it looks like it should work just fine to have a large interior but still run fine.

p_20210123_164109.jpg

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On 1/27/2021 at 2:21 AM, Sean Blum said:

This is the current one I have it used a 11gal harbor freight air tank for the body, 2in kaowool, then I hardfaced the bottom with Mizzou refractory and the top with kast o'lite 30.

 

So im terrible at eyeball estimating dimensions but it looks like it should work just fine to have a large interior but still run fine.

p_20210123_164109.jpg

 

 

I can questimate from yours somehow, many thanks Sean.   The tank I have is almost twice the size - its 80 liters.  Its 65 cm diameter so plenty of space. I am beginning to think to have the burner simply on the top and make the inside shaped so it would take ocassional axe.   What are dimensions of your burner and blower?  My blower has about 105 cfm in your units.  I have made the manifold from 12"X3" square tube.   

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My burner is made through the Wayne Coe's method with a 12"x3"x3" manifold. Unfortunately I don't have specs on the blower as it was an old one we had lying around. the 11 gal tank was something like 12" diameter and 22" long so the interior is about 6" diameter of forging space about 16"+ long.

 

With ribbon burners having the burner offset is still a good idea but is less of a hot spot issue like venturis but most people dont worry about that anyways it seems like. I would recommend not hard fitting your blower until you've run the forge a couple times as I don't remember the ratio of cfm to burner size and mine is way over powered so the gate is at most a quarter open at any given time.

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45 minutes ago, Sean Blum said:

My burner is made through the Wayne Coe's method with a 12"x3"x3" manifold. Unfortunately I don't have specs on the blower as it was an old one we had lying around. the 11 gal tank was something like 12" diameter and 22" long so the interior is about 6" diameter of forging space about 16"+ long.

 

With ribbon burners having the burner offset is still a good idea but is less of a hot spot issue like venturis but most people dont worry about that anyways it seems like. I would recommend not hard fitting your blower until you've run the forge a couple times as I don't remember the ratio of cfm to burner size and mine is way over powered so the gate is at most a quarter open at any given time.

 

What if I go for inner shape like this, its about 25 litre (that would be about 0.88 cf)  of inner space but it will fit largest viking axe, should I try to forge one.  Any canting of the burner will do the hotspot anyway, unless I would place it completelly on the tangent of the upper arc. That would require some clever casting. 80 mm square tube is pretty close to 3" you have.

výhen nová konfigurace.jpg

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Just to add some complexity to the mix, what if you angled the outlets in your ribbon burner so that they swept the walls rather than pointing straight down.  That might lesson the hot spot and give you some swirl.

Just to be clear, I have not built a ribbon burner, so this is pure blue sky.  I use that term advisedly, I live in the Pacific North West (or Wet) and have never seen blue sky.  Next year in Jerusalem, eh?

 

Geoff

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Like I said you will have hot spots always you usually just try to put them where they are out of the way for most of your work. With ribbons the hot spot is not a series of spaced circles like venturi's can do but an almost copy of the ribbon burner on the opposite surface so its more spread out and not interrupted hot spots.

 

For chamber sizing that should be fine as long as you are able to restrict the front and back openings down to smaller sizes which I assume you will with doors or brick piles.

 

Yours will be more appropriately sized for the 12" burner where as I now know I should have made a smaller burner since its interior volume is only 11.4 liters and is more finicky due to not appropriately sized interior to burner.

Edited by Sean Blum
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With my Ribbon Burner, when I watch the flame (pointing straight down) when the flame hits the floor I then see the flame swirl, 1/2 to the right and 1/2 to the left.  I get a much more even heat with a Ribbon Burner.

 

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There surelly will be doors.     Wayne, that is what I thought, that it will swirl anyway to the left and right.     I honestly kind of want a hotspot under the burner as that is the place where I put the packet to be welded.  

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Cast the burner on the manifold, cut and cleaned the inside of the old expansion tank. It has now legs, so it stands.  My old forge, which I sold to friend.  I have enough isolation for something like 3"  of fiber and then about 1" of hard cast.   I will weld reinforcement around the hole for burner and also round ones at each end, so I can draw the cast over and have no contact of metal with fire.

 

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