forge burner blues...

[rynegold]

Sorry, my bad. I posted this first over'ta the solid fuel forge area and couldn't find "where/how" to delete or edit that post so... here it is in the "right place":

 

 So I've built, redone several forges but in resurrecting this one, I find that the burners don't burn evenly. I've tried/looked at any possibility here and can't see what I'm missing. Here's a little vid of a test firing and of course, without back pressure it's hard to see how they will work in the forge but I didn't have time this morning. everything is the same on both sides, and the pipe fittings/migs tips free from any restrictions. Still they don't burn/fire evenly! And, I'm wondering if I can get weld heat from these two or, if I'll need to go back to a three burner setup?

https://www.youtube.com/watch?v=ISS2...ature=youtu.be

 Lastly, it's come to my attention that a "blown forge" (I guess that means an electrically powered squirrel cage blower design?) is the best/hottest forge design for welding up billets for Damascus knives. So any thoughts on that too. If that/the squirrel cage blown forge is the hottest I can make, then does anyone know of a site w/plans for such?

 I guess I should add that I'm an ABS journeyman bladesmith and have considerable ability to make my own forges, just need a direction here. 


tia, mitch

[ThomasPowers]

Do you mind if the hottest forge design costs more than a new car?  And BTW the fellow who wrote the book on it, "The Pattern Welded Blade", used aspirated burner forges when he lived in Nevada to make billets for a living.  So your attention may be deficit or disordered.

Blown burners are easier to build as they are less picky in construction. I don't know if I would call any burner "BEST" without providing the use case details.

[78sharpshooter]

Ribbon burner is without a doubt the best way to go. My experience is that it is much hotter than venturi and you can use the forge in wind that would otherwise cause venturi burners to not operate correctly. The ribbon burner is easier to adjust the heat to the desired level and heats a larger area so you don't have hot spots. 

[Charlotte]

Essentially the gas burner Is a question of BTU in per unit volume - BTU out.  Venturi   burners are restricted by the back pressure of the gas in the forge.  One of reasons that we like insulating brick and Inswool for line our forges is we keep more of the heat.   An engineer for a refectory manufacturer showed me the calculation for several  different forge construction.  (I was buying hard brick and inswool and a bunch of stuff at the time)  What he demonstrated to me was that hard brick is essentially transparent to heat input.

The point here is that blown burners of what ever variety are able to over come the heat losses by packing more BTU in the same volume because they can overwhelm the heat lost more easily by shear force.   The second advantage is blown gas can be adjusted to neutral or reducing without affecting the temperature to the same effect of a Venturi system.

Were I going to built a billet welding furnace I would build ribbon burners  and use 2600 degree insulating materials.  I'd make the volume no bigger than necessary for the largest billet I wanted to weld. 

On the other hand since I only occasionally weld and that is mild steel and mostly with a charcoal/coke mixture  or cable in my venturi  those are sufficient for me.

 

[ThomasPowers]

I got to use a large forge running off a ribbon burner at 7000' altitude.  It ran at welding heat as another smith accidentally welded a piece of 3/4" rod to my piece of 2.5" x 36" by sliding it along my piece in the forge---had to use a sledge to remove it!  (so good atmosphere too as there was no flux involved.)  It was a professional smiths set up and time was more expensive than fuel for him.

[Mikey98118]

On 11/11/2015, 7:08:31, rynegold said:

 

 

 

tia, mitch

Dear Mitch,

Your video is quite revealing. In the first place the burner with the smaller flame definitely is partially clogged. At one point it starts to go out as it passes something through the flame; this is what causes the temporary yellowing of that flame. The only question remaining is whether the obstruction was coming out of the mixing tube or through the gas accelerator. You should have look at the MIG tip. take it out, hold it up to a light source, and look for a partial obstruction; such as tar build up. The common cure for tar balls in the gas accelerator is to poke them back out the tip's rear face using a set of torch tip cleaners (about $3 online or from your local welding supplies store). If the tip is clean, look for such an obstruction in the fuel line where it hooks up to the burner or at any point where the feed suddenly narrows.

Unfortunately, this isn't your only problem. Due to design flaws your burners are putting out weak reducing flames, which is the reason they are followed by those large purple secondary flames. In order to burn those secondary flames you will need to leave the burner ports unsealed, which will pull in more secondary air than your burners need-- in effect, super-cooling the forge interior--which is very wasteful, and will likely prevent you from reaching billet welding temperatures with those weak flames.

The quickest solution for your weak flames is to change out the reducer fittings for the type that are used on so called modified side-arm burners. The kind of side-arm burners you show are the original design, which I first tried in 1999, after seeing them featured on Ron Riel's burner pages; they never worked worth spit. A Southern blacksmith (Kentucky?) first used a better shaped fitting for air induction and came up with a pretty nice flame on his burner designs.

To give fair warning you should know that I'm kind of the hot-rod maniac about burners. So, while I don't personally recommend his burners , it is only because I want to scream down the street with fire shooting out of my rod's tail pipes. If you just want a burner to ride back and forth to work and take your family out for summer drives...his burners are fine and dandy.

Forced air forges are not the hottest/best forge designs; "there ain't no such animal"!!! The best forge design for the task(s) you want to complete is whatever it turns out to be, just as there is no such thing as the very best burner design, or the ultimate forge hammer. Forced air versus naturally aspirated burners was a debate that was raging when I first started building forges sixteen years ago, and it's still nothing more than a "my dog's better than your dog" debate today. People get used to working with a certain tool, and if that tool does a good job for them, they tend to personalize their view of it.

But, the truth is that a forge designed to get the job done, while meeting your other goals (such as fuel thriftiness, or quick heating times; compactness, and/or portability versus hardiness); overcoming some back pressure or working outside in winds; even heated interior, or spot heating for best efficiency on small areas; in other words prodycubg tge best results for your needs. The other man may have very different priorities. Love your dog, but don't kickdhls his pooch around.

There is another trap to avoid in tool design; when a tool serves well, we may get blinded by that and refuse to move on, once we outgrow it.

I started out building naturally aspirated propane burners because I had recently worked in a very large and drafty building that was  warmed up quite effectively by one five-gallon size fan-blown gas forge. Thinking about what it would be like living with this (in effect) monster shop heater in my little garage in the summer was the stuff of nightmares! So, I learned to make very compact efficient flames in very compact efficient heating equipment, and "lived happily ever after" for about twelve years. But, there were signs of trouble in paradise...my lovely burners would melt down the heating chambers of chip forges, and would melt the stainless steel flame nozzles right off the ends of burners if not placed just right in heating equipment. Obviously, very hot compact flames were Jim Dandy for most stuff, but not for everything. So, I decided to play nice and pet the other guy's Fido. Thus started burner book two, on fan-blown burner systems, which got interrupted by burner book three on Vortex burners; this all seems pretty rambling, but the point is, I had to abandon my own prejudices to discover Vortex burners, and furthermore, the book on ordinary fan-blown burners still needs to be written, because fan-blown burners do some tasks better than any other kind.