Frosty "multi port" forge build

[Donniev]

I'm starting to gather everything necessary for a frosty multi port burner (NARB...he said it's not so much a NARB as it is a multi port so...) I think I have everything figured out for the most part but I do have a few questions.

I'm going with a box shape forge 8"*5"*12" unless I'm way out of line at 480 cu inches. I know it's best to have 1 t burner per 350 cubic inches in the forge, but if I remember correctly that was if forge welding temps were desired. My main needs this forge needs to meet is the ability to get a 10-12" long piece heated for bending/ scrolling, and I want to leave 3-4 pieces in the forge at once, I don't want to reach forge welding temps- I'll always have the coal forge for that.

As for the door on the forge, should I intentionally make a fairly loose fitting door to allow for warping, or would leftover high alumina kiln shelf be more appropriate?

If there was only say a 2*2" hole in the back of the forge for a pass through is that something a firebrick could be ok to use to cover it or just don't use firebrick anywhere ever on a forge because of their heat sinking?

I'll have more questions down the road, just trying to get everything somewhat close to cemented in my head so I can start rounding up everything. Daughters having another open heart surgery later this week, so I'll have plenty of time to order stuff online and run down the 6 blocks to the harbor freight and supply house and grab things. 

[Frosty]

You're asking two different but related questions here. The multi port burner can be shaped to whatever you need within reason, maybe even more than one lobe. This is a big maybe here, don't quote me. say two, 9 outlet lobes. MAYBE. I'm pretty sure you can stretch the 19 outlet 3/4" t multi port to more than 6" easily, 8" probably but they've surprised me every time so maybe all the way to 12" or beyond.

Will it heat 480cu/in even to decent forging temps? Probably but a 12" long one? I don't know. Unless you're using benders and jigs you want to have steel pretty hot if you want consistent bends without spending a lot of time hammering to fine form it.

The forge I built for the first NARBs is warping all over the place. I'm going to make sure there's a couple inches of insulated liner between the fire and the shell. This means the door and opening will look like bread dough raised over the edge of the pan. I think I need to come up with something better than a porch to set fire brick baffles on.

The baffles do their job by containing and re radiating IR back into the forge but the exhaust is rolling right over the top of the forge shell and warping it like crispy bacon. I think I"m going to have to wrap the insulated liner right over the top so there isn't a linear exhaust flow.

I'll put the doors on double swing arms so it raises up without swinging out of vertical. This will keep the door facing back towards the forge and won't point IR at me. The portion of the door that remains in front of the opening will continue to act as the IR baffle reflecting IR back into the forge where it belongs. The liner extending above the forge shell will shade it from the door's IR, at least partially.

The IR spilling over the top of the forge with the doors opened is still going to warp the shell so I'm thinking of using polished stainless steel. It's a better IR reflector, has a lower COE (and thermal warpage) and is less thermally conductive than steel.

The present experimental forge running a pair of NARBs is a number of lessons learned so I'm not calling it a failure, it even works not unwell as a forge I've welded with it. It's just not satisfactory. It's too large even after all these years I still do that. <sigh> So I have to build something else for the next one and I'm still brainstorming a design.

The above is a glimpse of my current skyballing.

The NARB is so new to me I can't give you even close to a solid answer. I just don't know. When I put one in a brick pile forge it looked like it was in the one 3/4" to 350 cu/in forge ball park. This forge broke too many of the norms to yield good results on what the 3/4" T NARBs working range is. I made too many experiments in one package. Ayup, I broke the one change one test rule. 

If you build that forge, please keep careful notes, pictures and keep me in the loop, it's dark country to me.

Frosty The Lucky.

[stressless]

On 8/8/2017 at 2:00 AM, Donniev said:

If there was only say a 2*2" hole in the back of the forge for a pass through is that something a firebrick could be ok to use to cover it or just don't use firebrick anywhere ever on a forge because of their heat sinking?

I know this is a older post but I thought I would mention that there is firebrick and there is firebrick. if you get the WHITE low density ones (extremely light to the feel) they have over a 99% IR refraction rate. They just don't suck up heat in my experience. IDK if it is a good brick for the bottom of forges but for doors and walls and ceiling used in combination with 3000° mortar for fireplaces and all that over kaowool I get almost no warpage. (burner heat transference only)

The reason I am saying not to use on the bottom is because IDK if the FLUX will eat it or not and it is pretty fragile stuff. you can easily cut it with a wood hand saw to the thickness and shape you desire in seconds. If you drop it it can crumble or shatter very easily.

Here each 4.25"x8.25" @ 4.25"thick brick is about $8USD but the refraction of the heat and IR being what it is has allowed my forge to get to extreme heats. So you may want to keep this in mind as well as you don't decarbonize your steel.

for my doors I welded on some angle steel and placed smaller pieces on sides to hold up the bigger piece and also to narrow the hole from the sides and I have different side pieces for different holes but plan a better version on my next try.

 

[Mikey98118]

I think most gas have some problem with building a little too large on their ribbon burner, and then have a backfire problem when they try to turn the heat down as much as they would otherwise be able to. Adding that to your desire not to run the forge heat up as much as possible, I don't think its cubic inches will bother you.

[Frosty]

What kind of IFB (Insulating Fire Brick) are you using? The typical old IFB is rated to 2,200f. and reacts to hot flux like a sugar cube in hot water. Morgan K 26 IFB, as far as I've heard, don't care diddly about flux, typical forge temps or fast thermal cycling.

Refraction rate? I think you're mixing up your terms but if not, please clarify for us. 

I don't understand how you're putting this stuff together. Putting Kaowool AND IFB together in a forge is an odd use, I don't know of anybody else doing it. Nor do I know what kind of IFB you're using, full brick is usually 2.25" x 4.5" x 9". Split brick is 1.125" thick. 

Fireplace mortar? 

If your forge is indeed 2" of Kaowool INSIDE? 4.5" of IFB then it's small wonder it gets plenty hot, that's a LOT of overkill. Short lived though.

Frosty The Lucky.

[JHCC]

18 minutes ago, Frosty said:

2" of Kaowool INSIDE? 4.5" of IFB

stressless said:

1 hour ago, stressless said:

all that over kaowool

So if I'm reading correctly, it's IFB inside kaowool, not the other way round.

[stressless]

kaowool inside covered in IFB. don't let kaowool deteriorate and don't breath kaowool. The mortar should hold everything together if you do it right.

36 minutes ago, Frosty said:

What kind of IFB (Insulating Fire Brick)

"KT Refractories offers a complete range of insulating firebrick (IFB) that offer excellent performance and value for a wide variety of industries and applications. Different grades of insulating firebrick are manufactured according to international standards, and are suitable to operate in various temperatures and atmospheres up to 3000ºF. Excellent Features of Insulating Firebrick are listed at the lower right side of this page." Quoted text from website avaliable upon request.

if you want the link message me and i'll give it to you.

but it is a soft firebrick that is made with ceramic fibers. it feels like caulk when you hold it. and probably would almost draw like it as well.

Also I have them cut down to 1/4" and am not using the whole brick. I coat the kaowool in mortar and place the brick on it and add more for joints. has lasted me over a year now. the bottom is just normal clay type IFB 3000° rated 1.25" thick on the same mortar over kaowool.

try and get just one soft IFB from someone and try it for the door. It does work rly well surprisingly so.

[Frosty]

While I think you're putting way more work into your forge than necessary for equal results it should work okay. When you're describing the IFB you sound like a salesman, we can search KT Refractories and see what we need. Looks like a heck of a company. 

Frosty The Lucky.