Hi all,

I'm going to keep this really brief as I know this subject has been covered to death 

I’m building a gas forge, the internal dims of the chamber will be 6” x 6” x 13.5” long.  Opening 4” x 4” 

It will be lined with insulating firebrick within a 4mm steel box  

I intend on using a single Amal burner fed in through the side of the forge 

 

Questions 

1.  Is there an ideal location for the burner ie towards front or back? 

2.  I have a load of ceramic wool left over from a job, as well as the 76mm thick IFB is it sensible to back this with a few inches of insulation?

3.  I have an option of 4 grades of brick from my supplier rated at 1260, 1430, 1530, 1650 degrees centigrade.  Obviously there a price difference so realistically what would be most sensible to use?

4. The internal volume in cubic inches comes out to around 486 so by both the calculations of Tim Gunn and Frosty this indicates a 1” burner would be a sensible choice if I have my calculation correct?

 

This forge is for occasional use as a tool that’s part of a larger varied workshop not for everyday forging.  Max bar to be heated around 40mm.  Do not require welding temps.

Quick heat up and efficiency are primary requirements 

 

Welcome aboard, glad to have you. These aren't a simple list of questions, the short answer would be, Depends. Some are just logic, for example positioning the burner in a 6" x 6" x 13" forge would be centered but I'd put it closer to the top to increase the circular motion of the flame rather than just hitting the far wall and spreading. Just spreading will direct more flame out the openings where a more tornadic flow will keep more in the chamber longer. It's not a lot better but it makes a difference.

AMAL burners are great burners a single 1" should be plenty. 

What heat rating fire brick to use depends entirely on how hot you're going to let it get, there are temp vs. color charts to determine that. The numbers you list mean nothing to me, living on the far side of the planet. Select firebrick rated higher than your target temperature.

Same story for the ceramic blanket, most aren't at all suitable in a blacksmith forge furnace. If you're going to use them as insulation on the outside of a firebrick chamber then it doesn't really matter, almost anything will work.

Same for IFB, if it's on the outside it doesn't matter, if it's going to be in flame contact then you'll need to see what's available to you, again the target temperature determines what to buy, pick one rated higher than the target temp to maximize longevity.

How long it takes to heat depends. If you mean the forge any hard firebrick forge will take a little time say between 5-10 minutes though partially blocking the openings will speed heat up considerably. IFB will come to heat much quicker, under 5 mins to welding heat has been my experience using home built burners.

I'm sure we can be of more help but your questions are kind of vague to give specific answers.

Frosty The Lucky.

Many thanks for the reply frosty, much appreciated 

I think you’ve answered everything to be honest 

burner position should be centred and towards the top of forge, got that 

1” burner is plenty, check

IFB, I’ve no idea of target temp having never run a gas forge before.  I’ll just run the highest grade therefore 

I should have specified I intended to put the ceramic wool outside the IFB as additional insulation not within the chamber.  The question only related to wether this extra insulation would be beneficial or have negligible effect considering the IFB is already 3” thick.

 

Hi Olly. 
By the choice of Amal burner, I'm assuming that you are UK-based.  If not, then I'd recommend updating your profile, as people from all over the world chat on here.

I use a 3/4" Amal burner with a multi-port flame head made out of an IFB. The multi-port designs are often referred to as Normally Aspirated Ribbon Burners, or NARBs for short.  I've used it in a home-made IFB forge and a home-made Ceramic Fibre forge with great success.

My observations from using the IFBs in a forge is that you don't want to encase them in a solid 4mm metal box. IFBs have a limited life when in direct flame contact, so you will want to be able to replace them from time to time. The most common IFB forges use angle-iron and threaded rod to assemble a frame that holds and pushes all the IFBs together. It makes it easy to replace a broken or worn IFB, and allows you to change the layout of the IFBs if you find you want a different size or layout.

Frosty has posted pictures of IFB-based forges with angle-iron frames many times in the past, and were what I based my first forge on.

My later Ceramic-fibre forge was more efficient, having an ovel cross-section, to allow for flame swirl.

Hope this helps.

Tink!

Many thanks for your advice tink

the NARBs look interesting and certainly make sense, I just won’t use this forge often enough to warrent investing too much time into researching the best forge so just keeping it simple for now 

I’ve seen the brick pile types forges and had considered it 

The forge I had in mind wouldn’t be entombed in the 4mm steel, the top section would unbolt allowing full access to replace the brickS etc 

Good to see your AVATAR again Tink, what have you been up to?

Speaking of my "no weld forge"

The IFBs I used are Morgan Thermal Ceramics, K-26. They're available all over the world under I don't know how many brand names. These are rated for a continuous 2,600f and are an alumina ceramic with is pretty much immune to borax based forge welding fluxes.

Their insulating rating is just worse than 8lb. Kaowool ceramic blanket refractory.

The burner is a 1/2" T burner which brings this forge to welding temp in about 3 minutes.

Not trying to sell you on any of this other than to say what I used, the K-26 bricks were much cheaper than the old type IFBs. The 3,000f split brick doors are self explanatory. As said above do NOT clamp fire brick together tightly, the space is provided by the wide angle iron at top and bottom.

At welding temperature you can touch the outside of the bricks briefly and they make a nice place to keep a cup of coffee, tea, etc. drinking warm.

Frosty The Lucky.