This is a drawing of a propane forge I am designing. I'm looking for feedback on the concept. The opening on each side is 10" x 2-1/2" with a single burner in the center. The burner has an adjustable choke to allow control of the lean/rich flame mixture.

Your feedback is appreciated.

As background, I use a Whisper Momma in the truck (front vent) and a Whisper Lowboy (two end vents) in the shop (and when I used to play at contesting). I love them both. Your design looks ok but I would have questions regarding the lack of doors. The doors seem to give me a faster and better heat (the whisper momma used to be a Whisper Delux with the flap door) and keeps the heat contained. What are your design considerations for this area?

I like the convenience of the corner opening (at least on paper). Are you planning one one of the more efficient burner designs to help with gaining a welding heat in an open forge?

Ok, let me do it. Who the ***** needs a truck forge that allows welding?

I can beat anyone with my little arc welder. Faster, cheaper, better.


Ronald Aalders

Ronald Aalders wrote:
Hi all,

I think about this subject lots and Ron you are right and you know a forge for heating shoes and for drawing clips that would work great could be made out of a $20 tiger torch and and a chunk of 8" asbestos or ceramic sewer pipe.

Looking at Toms forge design I would say that you wouldn't be able to weld and you will have a steady blast of flame out of the front.

I'm contimplating building a new killer 2 burner forge and I'm thinking the burners need to be moved forward of center and tipped backward slight so I get less blast from the door. My current forge has a provision to adjust burner depth for changeing gas pressure caused by frosting. I'm also thinking of a way to point both burners to the same spot thinking this will make welding quicker better. I'm also convinced that a forge needs doors front and back.

Kevin

jseyffer wrote:
The burner I am using is a true tapered venturi burner, not just a straight pipe with a flange and an orifice at the end. The BTU output capability of one of these burners exceeds the 3 burner NC . . . assuming I would use the largest gas orifice that will still achieve a neutral flame. A tapered venturi can use a lot larger gas orifice than a straight tupe without problems with back pressure. The burner I am using will run a #56 orifice from 0.5-PSI up to 60-PSI without "huffing."

The reason that a door makes a hotter forge is because there is additional surface area to reflect IR and UV heat back into the chamber. It isn't about heat containment so much as surface reflectivity. The inside dimensions of my forge design provide large reflective surfaces above, below, and on the back sides of the center burner "hot spot."

I don't believe reaching welding heat is going to be an issue in this design. Keeping the top to bottom distance inside the forge close enough so that the primary flame (the blue bulge) from the burner is touching the floor is one of the considerations of this design. In the taller forges like the NC Whisper Daddy, the primary flame from the burner is already expended long before it reaches the chamber floor. Any time you have a forge that is taller than 3", you will have this problem. You can weld in a taller forge, but you have to depend on the entire inside of the forge reaching welding temperature (bright yellow) - it takes a long time and a lot of gass.

In a forge with a lower ceiling, the primary flame strikes the bottom of the forge and bounces off - which increases the surface area of the primary flame. Once the combustion chamber surfaces reach IR UV temperatures, they reflect that heat back into the flame - in this case the primary flame which is now bouncing off the bottom and reflecting back toward the top. Bottom line, it makes a hotter hot spot.

Hi all,

Budget forge.

My little wire feed welder in the truck does a lousy job on aluminum and the welding store says the little mig welders also do a mediocre job on aluminum.

Tom,
That being the case (depth of box), would the welding brick used to protect the bottom liner of, say, an NC forge, help to increase the interior temperature of the chamber? And, would using flip up doors on the end ports also increase temperature or do I have to worry about air flow? Or, to put it another way, would covering the end ports "choke off' the fire.
Thanks,
Mike

jseyffer wrote: A tig welder is the best way to weld aluminum.

Gary

Hoofangler wrote:
No. No, you have to allow the hot gasses to escape from the chamber. The air is drawn into the chamber by the gas stream being injected through through the burner tube. Once the gas is burning it expands and any backpressure will force the expanding gas back out of the burner tube.

Ronald Aalders wrote: Since I got a Henrob 2000 torch I can weld aluminum, steel, cast iron, stainless steel, and cut steel and aluminum . . .

Welding in a gas forge is the best way to mess up a good forge liner.

cowboy_bc wrote:
While you're thinking, go read:

Gas Burners for Forges, Furnaces & Kilns by Michael Porter
ISBN: 1879535203 ~ paperback ~ 216 pages
111 illustrations by the author

The burner can weld in open air if you push enough gas through it.

This will be my fourth forge. I've already been there and done that. No matter where you point the burners, the hot gas is going to come out of the door eventually . . . and since heat rises, and since your burner intakes will wind up directly over top of the door, then your burners will be sucking the hot gasses into the intake. With a straight tube burner, you are already severely limited by any kind of backpressure. The gas jet stream is what is suplying the force which draws air into the burner tube. The force is a very weak vacuum.

So if you're gonna do that design (that was my first forge) you need to plumb your burner intakes away from the door. Every time you put an elbow or a bend in the tube, you are restricting the gas flow through the tube. If you really want to use that kind of design, the best way to do it is to use an electric blower to feed air into the tube with the gas.

You can eliminate the frosting by using a larger propane tank. That book also explains this issue and how to deal with it.

The taller the opening the more benefit you will get from having doors. The welding potential is determined by how many BTUs per cubic inch you can put into the chamber - 500BTUs per cubic inch is a good minimum rule of thumb if you want to weld. The number of burners you point at the hot spot is not as important as how much gas you can mix with the apropriate volume of air and direct toward the hot spot.

More reading . . .
http://ronreil.abana.org/SiteMap.html