Burners 101

[Greg in Maryland]

Any input on "flame aim"?  I recall reading in your book that centerish (if that is a word) on the kiln shelving is best.  Do you agree that position C or slightly right of it is what I am looking for?r?

[Mikey98118]

Yes, I remember making that drawing. However, at that time, I preferred to aim the burner at the near edge of the floor from a position of two o'clock. Only after years of watching others aim the flame toward the far edge, have I come to agree with the way you propose to aim it. But which line? between "B" and "C"

And why the change? Many people prefer to merely seal coat the forge wall, while others use up to a 1/2" thick coat of Kast-O-lite 30. The first gets the forge hot faster; the second heats more than fast enough, and the insulation lasts a whole lot longer. The more substantial flame face doesn't need the extra distance before flame impingement against the side wall.

My first inclination is always to accomodate choice. Over time, I will reluctantly change that preferreance, for the sake of what's practical; that is the "long" of it

Why then, be so particular that flame impingement be on the floor? Either the floor will have a high alumina kiln shelf as its flame face, or a thicker layer of hard refractory than the side wall; either way, the floor will be better protection against stress in the insulation than the flame face on the side wall.

So, why not aim the flame even further from that wall? Becuase, you don't ever want it to impinge on the work that you are heating in the forge. Aimed where you plane for, the flame will make a complete circuit of the forge before it can impinge on work pieces.

[Greg in Maryland]

I have (2) 3200 degree insulated firebricks.  Are you in agreement to use one on the floor and one on the wall where the flame will hit?  If I go with placement between b and c the flame will be centered on the joint formed by the wall and floor.  Correct?

Also - what “reflective” coating do you recommend for the interior?

Lastly, I am thinking an oval or d-shaped forge for the build but will defer to you after we nail down what I want to accomplish.  I will gather my thoughts on the “wants” and advise.

Regards

[Mikey98118]

51 minutes ago, Greg in Maryland said:

I go with placement between b and c the flame will be centered on the joint formed by the wall and floor.  Correct?

Some of the periphery of most flames would. However, Hybrid burners to a better job of narrowing with distance than any other air/fuel burner flames I am familiar with. Even a Mikey burner showed narrow enough to mess the corner, once the forge is fully heated. Before you ask; no, I don't know why Hybrid burner flames are narrower than other burner flames, nor why they narrow so much over longer distances, nor even why burner flames narrow in heated forges

What I know, I know; what I don't, I don't

3200 degree insulating firebricks? How much did they cost?

1 hour ago, Greg in Maryland said:

Also - what “reflective” coating do you recommend for the interior?

Okay; that question has gotten a little complicated of late, because ITC-100 has changed their formula; the new formula is a lot hardier than it was when I last used it. Also, Mister Volcano forge now sells this product for $15. These facts edge out other products at this time. That doesn't mean this is the very best product you could use, but it is probably good enough. So, for now it would be my choice, as the most practical product.

[Greg in Maryland]

I ordered the ITC.

 I got those bricks from a refractory dealer going out of business.  I can’t remember exactly what I paid but is was less than $5 per brick.  They are Thermal Ceramics SR-99.

 

[Mikey98118]

Sometimes I know darn well better than to ask a question, and go right ahead and ask for it anyway

[Greg in Maryland]

I’ll try not to rub it in the future 

[Mikey98118]

Oh, I sincerely hope you're not going to go and get all nice and gentlemanly; where's the fun in that?

[Greg in Maryland]

Your request is perfectly timed.  My sensitivity training class at work has just been cancelled.  We can let the fun begin.

[Mikey98118]

Excellent! Most of us old farts here on IFI are waaaaaaaaaaaay too technical (born geeks). Ribbing and childish behavior may be our most redeeming quality

It's a little like grade school, where they insist that you learn this, and you learn that, on account of they say so. Then, they break out the crayons, and say "this is going to be great fun." I still like various colored inks for writing letters. You can say "your mother's on the roof and we can't get her down..."; it will look so much better in orange, right?

So, coffee breaks over. Lets get back on our hands.

Have you thought about what size forge? Remember efficiency only goes so far; smaller is cheaper to run; a small gas forge can also be  put away under the bench, after use.

Do you think you might want to do some casting too?

Though I am very fond of oval forges; there is a lot to be said for "D" shapes. For small  "D" forge shells, consider mail boxes.

Eventually, I think you will recycle those bricks in your box forge, into a brick pile forge. Historically, the point of box forges was to protect their dilicate interiors from the occasional gorilla that hadn't been fired fast enough. However, you can't afford to have such people around hot work at all...

Once, we stop trying to protect the forge from gorillas, brick forges can become any size or shape needed for special projects

It's way too early to ask for conclusions, but what beginning thoughts are stirring in your brain?               

 

[Mikey98118]

21 hours ago, Greg in Maryland said:

have (2) 3200 degree insulated firebricks.  Are you in agreement to use one on the floor and one on the wall where the flame will hit?  

I looked up those bricks. They are very high alumina and low silica content. I would guess that they are equivalent to high alumina kiln shelves in insulating efficiency; that is nowhere near as efficient as their insulating firebricks. However, I consider them moderately insulating, and therefore good enough, if backed up with ceramic wool blankets.

Moderately insulating? What the heck does that mean!?! Regular clay firebricks are about forty percent silica. which is a poor insulator. High alumina kiln shelves, for instance, are seven times more insulating than clay bricks. Furthermore, your bricks are much thicker than kiln shelves, so yes, they will provide pretty good insulation...But not compared to Morgans latest insulating firebricks, which are full of little air voids.

[Mikey98118]

So, what's so hot about Morgan brand insulating firebricks? For a long time, insulating firebricks where made of clay, with a foaming agent added, to create insulating voids; they were great at insulating, but structurally weak, with low use ratings (2000 F, and 2300 F). Such bricks start falling apart in the box, and only last for a few months.

Morgan started using steam to create insulating voids in their refractory bricks; they are far stronger, and better lasting, but just as insulating; they are available in higher use ratings. Used with care, they last just fine.

[Greg in Maryland]

4 hours ago, Mikey98118 said:

 

It's way too early to ask for conclusions, but what beginning thoughts are stirring in your brain?               

 

I plan to keep the forge stationary so portability is not a major concern.  With that said - maybe an appropriate sized D-shaped forge setup for welding?

•  Need: Knife/sword shaped objects.  Damascus billets.
• Would be nice:  Flexibility to handle a softball sized object.

Hopefully that should get us started.

[Mikey98118]

It does make a nice start. So, lets begin by thinking about the forge's floor. This kind of forge usually gets set up on a table, etc. Because there is no curve on its lower half, like tunnel forges, and oval forges, it is wise to make the forge bottom pretty deep below the forge floor. Why? Most insulation is expensive. However, If you use your fire brick as the floor, with a removable kiln shelf on top of the brick, you can slide it out to power sand the sticky mess from welding off of it, once the forge cools down. Below the brick, you can sandwich a layer of Kaowool between the brick and 3" or 4" layer of Perlite from the garden department of a large hardware store; it is highly insulating, cheap, and light as a feather. Your thoughts?

[Greg in Maryland]

I am open to finding the balance between performance and cost of assembly.  If performance will suffer by trying to make materials on hand work - I will spend the dollars on the proper materials.  My wife may not approve but I think there is something to say about “pay me now or pay me later.”

 I honestly will be leaning towards your advice as I lack the experience in building high performance forges.  We can have fun ruminating over the options

[Mikey98118]

28 minutes ago, Greg in Maryland said:

I think there is something to say about “pay me now or pay me later.”

There is a happy medium; its called sweat equity

So, what kinda sheet metal can you lay hands on for cheap, which can be cold bent over a five-gallon propane bottle, to form a "U" shape?

Or cut an old cylinder in half, lengthwise. You can pick up free cylinders, from a propane supplier; they always have old cylinders laying around that they're happy to get rid of; just make sure they now that you don't intend to ever try filling it. Then sheet metal can be welded unto it to create the straight lower side of its walls, and bottom. You only have to bend the ends around the cylinder, whi;e tack welding it in place, that way. Thoughts?

 

[Greg in Maryland]

I would prefer shaping some sheet metal rather then cutting a cylinder in half.

 I can scrounge something up.  I assume the proposed forge length will be same as a propane cylinder?

Can you send a sketch, with dimensions, of what you are thinking so I get enough material for the u-shape and bottom?

[Mikey98118]

That would not work out very well, as the dimensions of propane cylinders differ somewhat between manufacturers. So, you need to measure the circumference of the cylinder you are using, divided by half. To this length, you add the distance from its center to a table top, times the two lower sides it will form.

    Cut a separate piece as wide as the diameter of the cylinder. The length of this bottom piece, depends on how long you want your forge to end up. You asked if it should equal the full length of the cylinder; that is strictly up to you. On the one hand, the cylinder's rounded ends are too short a distance to create a problem when bending the sheet metal. On the other hand, lots of guys think that  their forge ends up longer than it needs to be, using full cylinder length. I feel that is because they want to heat the forge from a single 3/4" burner, rather than a pair of 1/2" burners; I recommend two burners so that, with the aid of of a removable inner baffle wall, one of those burners can be shut down, when the whole area inside the forge isn't needed. Thus the longer forge becomes more fuel efficient than a shorter version

You also need two rectangular end pieces cut and installed. This brings us to how you plan to stick all of these parts together. Do you have a welding machine? Oxy-fuel torch for brazing? Will you  pop rivet, or sheet metal screw the parts together (employing small angles for the corners)?

Let me know what isn't  clear, or what you prefer, but foresee problems doing. Everything is simple, once it's broken down into step by step instructions.

[Greg in Maryland]

Is this what we are going for?

I have a mig welder or can employ whatever assembly method makes sense.  I also have a small sheet metal brake.  My friends have whatever tools I don’t.

 I am assuming the sheet metal formed around the propane cylinder will form the outside shell.  I have a  cylinder with a 39” circumference to use for the form.

 39/2 =19.5. The radius of a 39 inch circle is 6.2.  Am I correct that the side walls will be 6.2 inches tall?

[Greg in Maryland]

Results from jet change.

First picture:  Schedule 40 nipple with .035.  15psi.

Second picture:  Schedule 80 nipple with .030.  15psi.

[Mikey98118]

9 hours ago, Greg in Maryland said:

Am I correct that the side walls will be 6.2 inches tall?

Yes.

 

9 hours ago, Greg in Maryland said:

My friends have whatever tools I don’t.

Good friends to have

You're flame is getting closer and closer. Go for 025 MIG tips next; that should do it.

As to burner placement in the "D" shaped forge in the photo: Two burners are usually placed by making three equal spaces, which shows where to space out the two burners. A lot of people fudge and leave the middle space longer; this always puts both burners too close to any exhaust openings in the forge ends.

Next, you will want the two burners placed on one side wall or the other. How low, is to be as low as you can make them, while still keeping them above the forge floor, and  and pointed at as steep an upward angle as the burner body will allow; ideally more upward than inward. It becomes obvious when looking at this photo that they would have done better with the addition of 6.2" side plates, like you are planning to use.

getting back to the earlier point about using Perlite beneath the wool blanket for cheap additional insulation. I forgot to mention that the Perlite handles compressive loads nicely. Also, you would be wise to include an "X" pattern of stiffening struts in the bottom metal sheet; say about 1" wide sheet metal strips?

[Greg in Maryland]

Am I close?

[Another FrankenBurner]

Your lowest measurement of 19.5 width is incorrect. 
 

It will be 12.4 wide because of the curve.  Radius x 2 or diameter. 

[Mikey98118]

1 hour ago, Greg in Maryland said:

Am I close?

No; you have added way to much side wall. Your original 6.2" added height for the side wall was minimal, but good enough. If you increased that to 8", that should be the maximum. Forge dimensions are also a question of balance; not to0 little, but not too much.

Picture how you will maintain the "D" shape in the forge's interior; not just its outside; this is your goal. Easy and economical construction is just a happy side effect.

[Another FrankenBurner]

This is my interpretation so far:

If two inches of blanket and a half inch of kast-o-lite are lining the forge.  The volume of the forge would be half the area of 7.4" diameter circle multiplied by the length.

Click the image to enlarge.

Hope it helps.