Firebrick Forge Questions...

[WY_Not]

Over the last few months I've been gathering the pieces to assemble a firebrick forge as seen on Zoeller Forge website. The bricks I have are not as thick though; 9" x 4-1/2" x 1-1/4" as opposed to 9" x 4-1/2" x 2-1/2". So, the chamber is a little larger at 263-1/4 cubic inches. I've got either Castable Refractory Cement or Outdoor Fireplace Firebrick Mortar to paint the interior of the chamber and possibly between the bricks. Sorry, don't remember which one I have and not at home at the moment to check. Final piece was two of the Atlas Knife 30k burners; last week. This will be my first forge but definitely not the last. Just looking to get my feet wet as it were and get something built with materials on hand that will heat metal so I can pound on it at home rather than driving in to town for the club's open forge night each week. Won't be doing any forge welding at this time so not worried about flux eating the bricks,

Will the cement or mortar help hold the heat and/or protect the bricks? Or is it just for joining bricks?

If anyone has experience with the 30k burners will one of them be sufficient?

Does the 30k burner need any kind of flare on the end? Was also thinking about threading the end of the burner and attaching a short piece of pipe that could be changed if it gets damaged. Good idea? Bad idea?

Any input or suggestions will be much appreciated. In the meantime I'll continue reading through the posts on this site.

Thanks, WY_Not

aka Joseph

 

Mod note: links removed
 

[WY_Not]

Sweet.41 views and not even a cranky RTFM. 

Anyway, finally got out to the garage to check and it is the refractory cement that I have. So, it will be used to "paint" the interior of the chamber.

[Glenn]

Photos would be very helpful.

[timgunn1962]

To be fair to the guys who have viewed the thread, for most, there's probably not really much information that can usefully be imparted given the contents of the Original Post.

You are describing a build that is some way from any of the "usual" designs and you are using a proprietary burner (or two) in it. There are a lot of unspecified variables in there and it's a pretty safe bet that nobody else on here has direct experience of a setup similar to yours.

There is perhaps some very general information that could be given, but that's already on the forum and you have presumably either read it and chosen to ignore it or not read it. In either event, adding to the amount of information you are going to ignore is not a particularly constructive use of anyone's time.

Being as how I'm a sad, lonely old git with a lousy cold that's keeping me out of the workshop, I've actually got nothing better to do and may as well give it a go. However, it's probably going to mostly be a cranky RTFM.

The exact type of brick makes a huge difference. Some are very prone to breaking up with temperature cycling, others less so. If you have one that is prone to cracking up, the thinner bricks will see steeper temperature gradients and this is likely to exacerbate the problem. 

Whether or not the furnace cement will help much is quite likely to depend on the type of bricks. 

The Original Post included links to specifications for 2 very different materials, each with what appear to be pretty good descriptions of their intended applications. The details for the castable cement seem to refer to "large voids or cracks" and mention a slab 1 1/4" thick. This would seem to suggest that it is not intended as a thin paint-on coating. It may work really well, but most folk probably use something developed for the purpose.

As far as I can tell, the Atlas 30k burners are designed to run the Atlas forge, which seems to have a 2.5" diameter, 11" long chamber. I make that about 54 cu.in. You are looking to run a forge with nearly 5 times that volume on one, or maybe 2, of these burners. 

There is an oft-quoted rule-of-thumb that welding temperature needs 450 Btu/hr per cubic inch of chamber. For your 263 cu in chamber, that would suggest 118k Btu/hr is needed; about 4 of the 30K burners?

Though I'm not personally convinced by the 450 BTU/cu.in figure, it may well be pretty close for general blacksmithing. 

There are a number of variables to consider, not least the material to be welded. For bladesmithing, I've built forges that easily achieve welding temperature at something under 300 BTU/cu.in. For bladesmithing though, with around 0.8-1% Carbon steel, the temperature needed is likely to be significantly lower than for mild/wrought and the workpiece access opening for bladesmithing can be smaller than for scrollwork or similar.

You've said you won't be welding, so the lower temperature will reduce the BTU requirement considerably. 

I think my inclination, in your position, would be to try to keep the internal dimensions of the firebrick structure pretty close to the Zoellerforge dimensions and maybe try to back up the bricks with additional loose insulation if possible: something cheap and readily available like Perlite or Vermiculite. I'd certainly give it a try without any cement first, since it keeps it easy to modify if you just have the bricks. Once you've got it working to some degree, you'll have a better feel for what needs to be done to make it work better/well enough.

Pictures will help a lot, as Glenn says. Don't forget the wide shot(s). All too often there's a tight shot of a forge chamber that's not performing as it should with nothing to show how the burners are set up.

 

 

 

 

[Frosty]

Well said Tim, your first two paragraphs were right on target.

Joseph: Your question has been addressed in depth and detail many MANY times in the "gas forge" section of Iforge. I recommend you pull up a comfy chair, bring a beverage, snacks and do some reading.

In short though, as proposed your forge is a deal breaker on several counts, as explained in the gas forge section. Sorry but you'll have to do some reading to even find the subsection in which your questions are answered in specific.

Frosty The Lucky.

[StumpingIron]

I have made a huge firebrick forge 80cm by23.5 by 23.5 inside diameter but my bricks are made for industrial forges and can't be bought unless you own an industrial buisness need for them. But it works great

[lanternnate]

Hey Joseph,

I don't know that I'm of great help because I bought rather than built a forge, but mine might have some comparisons that are helpful. I have the Graham Forge made by Atlas Knife Co. It comes with their 100k BTU burner rather than the 30k BTU burner. The chamber volume is about 245 cu in. I would say the 100k BTU burner is "just right" for this size chamber, so I'm not sure your 30k units will be proper for the size you are talking. If you haven't cemented the fire bricks together yet, you might try making a smaller forge to start. The Atlas mini forge the 30k was made for is I believe just the fire bricks cut in half to make squares with a 2.5 in hole saw cut through the middle of each. They are then stacked together to make a tube chamber. Atlas uses a welded metal box to hold them together, but some metal bars with threaded rods to sandwich the bricks is something I've seen in diy pics as a simple method to hold it together.

As for flaring or modifying the burner, I wouldn't suggest doing that. It looks super basic and simple compared to some other burners I've seen, but it just works and works well. If it ain't broke don't fix it is my opinion.

[WY_Not]

The firebricks are a Vogelzan brand brick. They were picked up somewhere along the line (probably on sale) and are meant to be used to replace bricks inside a fireplace and have a rating up to 2200 degrees.

I've been reading. Finding specific info is not going well though. Lots of different opinions and frankly contradictory information. Not asking to be spoon fed the info, was simply presenting the info and materials I had gathered so far and looking for some feedback. I've been reading from many sources and trying to piece together the info needed. But gas forges are a completely new creature for me. Everything I've done in the last year so so has been on a coal forge.

I'm not ignoring anything. There have been good suggestions in this thread. I was focused on copying the Zoeller design with the bricks I have, the suggestion by timgunn1962 to back them with additional insulation was helpful. it got me to step back and take another look. This led to the idea of doubling up the sides to bring the interior dimensions back down and possibly doubling the top and bottom to get the equivalent thickness on those walls as well.

Thanks, lanternate. Still trying to figure out why some burners have a flare and some don't.

 

[lanternnate]

Are those hard or soft bricks? The hard ones usually meant for fireplaces etc. are not very good insulators. They're more meant to be tough. The soft ones made for kilns do a better job in a forge application (they are weaker because they are less dense, but that also makes them preferable for insulation). If they are the hard ones you might not get the performance out of your forge/burner that you are hoping for.

[WY_Not]

Hard brick.

[Latticino]

Hard brick will have lots of thermal mass and limited insulating value.  It can be used for a forge design, but will be quite wasteful as regards energy.  My preference is for a relatively thin inner layer of refractory or hard brick and a thick outer layer of insulating material (soft firebrick or refractory blanket).  The Zoeller brick forge is made of soft (insulating) brick.  If you are going to follow it I would use soft brick rated for 2600 deg. F as is clearly spelled out in the design sheet.

[Mikey98118]

I would use the bricks for the top surface of a hot-work table, and build a tunnel, oval, or "D" forge.  If you do go for a brick forge, the advice you got about using thread stock to hold it together was golden. I would add that some flat washers and springs on one side of the thread stock will only improve it. Look to Frosty's method of holding the burners in place in the brick openings for your guide. Use a emissive coating on the inside of the forge; it will help a lot. You don't have to pay out a lot of money; some of the guys here make there own with good success. 

I have read good things about this burner design; just because it makes no sense to me doesn't mean they're no good. It is encouraging that they are moderately priced. In any case you can upgrade the burners later on if you want more heat.

Latticino is right in choosing 2600 bricks; they have reasonable insulating value and make a good choice for endurance as well. A heat reflection coating should bring them up to snuff for holding up to flame impingement.