The Metal Artist Forum

First off Hi, this is my first post.
I'm just I'm just getting started in blacksmithing. Putting together my first forge (propane). The design is off Larry Zoeller's website. I'm starting out with a single burner, but designing/building as a dual burner so that I can add a second burner (down the road) to ensure forge welding temps.

I'm going to copy and paste my post from another forum cause it's rather long. Thought I'd ask here too to cover all my basses.

So I'm getting ready to cut the holes for 2 burners (one will be plugged until I get a 2nd burner), I was going to put them evenly off center. To explain I found the center of the interior of the forge (front to back) then split the distance front and for each burner hole. When i made the markings the front burner seemed kinda close to the front of the forge. So I started looking at pics of dual burner forges. Some of them appear to bias the burners toward the center. Each burner is still equal distance from the center (front to back) of the forge, but not splitting the distance between center and front/back rather slightly closer to center than front or back. Is this making any sense??

Example:
Back wall to front wall is 10 in.
Center of the forge is 5 in. from either wall.
So if everything was equal center of each burner would be 2.5 in off center.
With me so far (not sure I am)

This just seems like the front burner is too close to the front to me.

So some pics look like the burners are biased towards center.
Example:
Same forge as above but put burners at 2 in off center. This of course would mean they are at 3 in. from the front and back walls.
Would this be a better design?

Clear as mud??

If you made it through all this and can make sense of my ramblings, I would much appreciate your advice and opinions.

Thanks,
LouieIV

to the forum
As to your question, I think it would or will depend on personal preference. As you can see in this thread dealing with a 2 burner Zoller type forge along with others. most are designed so that you can add or remove burners as needed to work you are doing.
question on covering the burner hole or one hot potato, or two!.
I'm sure that you will receive some more answers in a day or two.

(06-13-2010 06:06 PM)PTsideshow Wrote: [ -> ] to the forum
As to your question, I think it would or will depend on personal preference. As you can see in this thread dealing with a 2 burner Zoller type forge along with others. most are designed so that you can add or remove burners as needed to work you are doing.
question on covering the burner hole or one hot potato, or two!.
I'm sure that you will receive some more answers in a day or two.

Thanks, I did see that thread.

Right now I'm concerned about placement. For now I only have one burner until I can afford to add a 2nd one.

-LouieIV

---

I feel like I should mention that eventually I want to try my hand at forging knives, so if that affects burner placement please explain.


Thanks,
LouieIV

Hey Guys,
I'm also concerned about the angle of the burner(s) because I want to try to avoid hot spots as much as possible. I don't have a welder, so I'm using locknuts to attach the burner holder. If I angle the burner as much as possible in the holder this is what I get. Let me know what you think.

Thanks,
LouieIV[attachment=14446]

You will find the people tend to go with what they learned on or built themselves. Like NASCAR drivers,brands of beer,or type of women or men one cares for everybody has their favorite!
Take a read about what Larry said about the slight angle of the pipes.
As with the angle of the burners on his top side forges, it is for getting the gas line, and assorted burner parts out of any heat that manages to get up and out around the burner holding fittings. When they are straight down from the top side soon the builders find that they need some form of heat/flame shield above the mounting fittings, even when they are filled with fiber insulation.

If you look at any of Larry's units, whether he has the torch version, the coffee can version,(First time I seen that size and kind was in a reprint of a 1930's hobby magazine and it was based on a white lead can that was used for priming surfaces to be painted at the time.

The brick stack forges for knifers and small occasional forgers generally have the burner(torch) horizontal into the heat area, for easy of mounting and keeping it in place.

Some of his other ones are angled from the side, Now the offset from the back of the forge can is to adjust the placement of the burners. Because of the 2" thick insulation that is in the back of the can. If it was 3" of insulation the offset would be 3" etc.

In a two burner rig, the burners would be spaced equal distance, from the insulation offset and the front of the can.
Front of forge/space/burner/space/burner/space/back insulation. Then the back of the forge can.

There are as many theories on producing swirl's inside of a forge as there are patterns that the boiler companies have used with deflectors,baffles, and what ever fancy names they call them.

Don't know if this is what you are looking for, or if it will help. You want the insulation if of the fiber kind to have the extra insulating spray liquid mix on the fiber so it will last longer. As the original purpose wasn't direct impingement of the high temperature flame on it constantly.

Sorry for the slow reply Louie:

Burner placement can be pretty critical for sure. Some of us actually WANT a hot spot in the chamber, this helps keep some rigidity in the overall piece while getting the spot you need to work to a good working temp. This keeps the dreaded "floppy part" syndrom from occuring.

Okay, placing burners in a cylindrical chamber to provide the most uniform temperature is easiest with a tangenital arrangement at even spacing. A lot of guys will place the burner(s) horizontally at the top of the chamber so the flame impacts the liner at a tangent and then circulates in a strong vortex.

If you're going to use multiple burners the rule of thumb to remember is 1 ea. 3/4" (diameter burner tube) per 300-350 cu/in volume. Just figure the overall volume of the forge from end to end and divide by 300 for a linear or 350 for an ejector type burner. This'll tell you how many burners you'll need, round UP if a fraction occurs.

Okay, so now figure placement so each burner is heating the same volume and reinforcing the vortex. The burners at the end can be aimed slightly towards the center of the overall chamber to help keep the fire in the chamber as long as possible. This isn't critical but might be a good thing, it falls into the "can't hurt, might help" catagory of things.

One last thing, there's no problem putting burners on opposite SIDES of the chamber if opposing burners are either at the top or bottom so the flame reinforces the vortex. Just remember burners aimed on a tangent with the bottom of the forge chamber WILL make a HOT zone so seeing as you want uniform heat this isn't a good burner arrangement for you.

Well, that's all I can think of right now but I'll try to keep an eye on the thread if you have any questions or you can just shoot me an e-mail.

Frosty the Lucky.