Mulling over an idea

[Ted Ewert]

I was thinking about a coal forge and how the work is often buried in the coal to heat it up. It was the surrounding steel with hot material part that struck my interest.

Here's a different concept. A coal forge with a ribbon burner in the bottom and covered over with alumina, (or some type of refractory ceramic) balls. Think of a decorative fire pit on steroids. 

Refractory balls are often used in furnaces to retain heat. I was wondering if sticking a piece of steel into a pile of these heated balls would be an advantageous way to heat it up. 

Wadda you guys think?

[SinDoc]

What advantage would you have over simply using a traditional gas forge? Being that it wouldn't be enclosed, I feel like the fuel efficiency would be pretty bad as a large chunk of your heat would get lost. I am no expert in forge making or thermodynamics for that matter though 

[ThomasPowers]

You mean like the gas forges filled with mullite pieces that have been sold commercially for probably 80 years or so?

Plusses (fast heating of stock, less scaling if adjusted correctly), and minuses  (Like time it takes heating it up to working temp at the start.  Degradation of the media over time and use.  Cost.  etc.)  Generally you see them in industrial settings due to expense.

You might search on ceramic chip forge...

[Ted Ewert]

Thanks Thomas, I see it's been preinvented. Dang, I hate it when that happens. 

I guess this thread is a mute point then.

[ThomasPowers]

Another one wants to horn in on the puns!---Wake Frosty!  Tell John to inform the Maenadia!

[Mikey98118]

3 hours ago, Ted Ewert said:

I guess this thread is a mute point then.

Not so! In fact there is a manufacturer in England that has been building just this kind of equipment for use by schools; they have been at it for decades, and you can find out a lot more information on how to continue with your idea, and how many uses it has, by looking up there web site.

[Ted Ewert]

Thanks Mikey. I did do a quick search and saw those forges. I'd love to see how they're built. 

I don't think it would be difficult to build one of those. Has anyone here built one? 

The ceramic chips or balls might be difficult to find in small quantities.  You can find lots of that stuff online, but it's mostly sold in bulk with a 1 ton minimum. It all comes out of China. 

The rest of it is just a container lined with refractive material, a burner, a grate and lots of chips. They probably use a peizo sparker to light it. 

Might be a fun build.

[SinDoc]

Think of all the fun you could have with 1 ton of those!

Probably too hard for a ball pit though...

[Frazer]

I have an above ground pool I'm not using. You're more than welcome to use it for such antics.

[Ted Ewert]

A ball pit with this stuff would have about the same give as a brick patio.

[ThomasPowers]

Fluidize the bed with an air/gas mix.  That will make it have more "give" and a lot more WHOMPiness!

[JHCC]

3 hours ago, ThomasPowers said:

Tell John to inform the Maenadia!

I did. They are not a-mutes-d.

[ThomasPowers]

A Cross Victoria they are?

[Mikey98118]

55 minutes ago, Ted Ewert said:

The rest of it is just a container lined with refractive material, a burner, a grate and lots of chips.

One caution about the ceramic chips would be to make sure they have a high enough use rating to survive a really hot burner; like any of those we build on this site.

You would probably best served to cast your own chips from high alumina refractory. Since you will want that same refractory to line the forge with, you should be able to use a 55 lb. bag of cast refractory material. I suspect this will cost less money than buying refractory chips anyway.

As to moving the chips around easily enough; the present English chip forges are made for students to use. Sometimes, we look for problems where there isn't any

[Ted Ewert]

The stuff I was looking at is hard ceramic material. Much harder than anything you'd stick in it. 

Kast o lite is nowhere near hard enough IMHO, unless you're thinking of something else.

I'm still not sure if it would be worth it to build one. I'll have to do some more research. 

[Mikey98118]

I'm not talking about hardness. A lot of ceramic products can't take the heat that a gas forge with one of these burners will generate. Overheat ceramic products and they tend to partially melt into a solidified mess. Also hardness at room temperature has very little to do with mechanical toughness at elevated heat levels.

[Frosty]

Hardness isn't a factor Ted. The flammable mixture is distributed through the chips where complete combustion occurs. The grate and forge sides aren't subjected to as much heat as one would think. I was thinking of the things years ago but they don't work with NA burners and I lost interest. Largely because getting the "chips" the right shape and thermal characteristics is kind of tricky for a home build.

The shape of the chips really put the brakes on my plans. Spheres are too aerodynamic and the spaces are too large so the flame passes through and out before transferring enough energy. Sphere's also have the lowest surface to volume ratio so transferring energy in and out is generally lowest of all solid shapes.  Spheres are easy to slip projects in and out without damage so that's a plus. Maybe the only one.

More angular shapes like broken pieces have a high surface to volume ratio so absorb and shed energy well. Unfortunately they can "key" together blocking passage for the flame for a negative and keying together can make it nearly impossible to insert stock and once hot stock can be damaged removing. 

What I saw for commercial "chips" were cast multi sided convex pellets. I couldn't find out what they were made of but with the research and experimentation done by IFI members I think I could come up with something worth trying.

I still don't know how I'd cast the pellets AFTER I came up with a workable shape and size. The best I came up with back when was a 3 sided pyramid with round ends and bulging faces. Think of a clay D&D 4die made by a preschooler.  

I think I'd start experimenting with a ceramic made with: 3-4% Bentonite, a pinch of Vegum, 80-90% Zircopax and the remainder silica spherules. 

Maarten did some excellent experimentation with Bentone and Zircopax developing a though very high temperature ceramic kiln wash or flame face forge liner. I've played with a similar mix and it's stood up to anything my hottest T burner could put on it, even after rolling it in laundry borax hot. I finally took it out of it's corner of my forge as more than good enough.

Do I want to make the kind of press roll or mass tablet press necessary to make hundreds or thousands as a test? 

Even now the thought experiments fire right back up. I THINK I have a good starting point for a chip ceramic. What I lack is a good shape and way to make bunches in batches. Firing them is just a matter of lighting the forge for a given length of time or hiring space in a kiln.

Frosty The Lucky.

[Ted Ewert]

A good shape might be something like a charcoal briquette. A briquette shape is probably designed with many of the same considerations. 

I don't know, there are so many different flavors of ceramics available it's hard to tell which one would work best. 

Even with the right chips, an open top wastes a lot of heat. I would redesign the whole thing. 

The more I think about it, the less merit I find with the whole concept. The complexity doesn't really buy anything extra. 

Nevertheless, I think embedding ceramic balls in the floor of my forge would allow hot gasses to more easily pass under the work, heating it faster and more evenly. 

As it is now, I try and suspend my piece about 1/4" above the deck. Since the gas flow is circular, and hugging the contour of the sides, it hits the work from the left. Little balls would allow me to lay the piece down and still get some flow underneath. No big deal, but more convenient. 

[Frosty]

Maybe something like a briquette, maybe a triangular one. 

I was and maybe will, corrugate the floor of my next forge for much the same reasons. A regenerative forge primarily heats your work with IR radiation. Heating the liner by keeping the flame flowing is a big plus. However the radiance needs a clear line to the work, it won't go around corners and I strongly doubt pellets, spheres, etc. reflect IR in any usable way. 

Corrugations on the other hand are the flame face, the only thing between them and the far walls of the forge are the work.  The work would be well supported over all preventing sagging but be in minimal contact with the forge floor. It would be free to radiate to the work from it's greatly expanded surface area.

To keep it simple for purposes of discussion say the corrugations were circular with 1/8" radius. Being circular "grooves" up and down every inch across the grooves would = 3.1416" of "new" surface. The channels under the stock would be 1/2" deep and 1/2" from point of contact to point of contact to allow a free flow to the fame.

Now if a person were to make the floor a series of half spheres by say embedding them in the liner. (Not a bad idea IMNHO) I envision much the same thing happening but with a greater surface area. I'm not going to arithmetic it, it's YOUR idea after all but I like it.

Lets ALL say Hmmmmm. Maybe even ominously.

Frosty The Lucky.

[ThomasPowers]

Which direction would the corrugations go?  Parallel to the main axis or normal to it?  If the hot gas flow is "helical" then having the corrugations open to it might work better than being normal to it.

Hmm I have a "corrugated" cast iron pan for cooking bacon; I wonder if my wife would get upset if I inverted it over the gas range to test how heat is transferring...

[JHCC]

Just tell her that you're trying a new method for seasoning the pan.

[Frosty]

I'd planned on corrugating it in line with the flame flow. The idea is to make the flame path as free flow as possible. I like Ted's idea too though. 

I keep coming back to a trowel like used for hanging tile but I haven't seen a round one. Vs yes but I keep thinking the sharp tops would be really fragile especially at temp. 

Maybe draw the trowel in two directions to make a rounded knobldey surface?

Frosty The Lucky.

[Goods]

It would be pretty easy to make a custom trowel edge…

 

[Frosty]

Yessss? 

Frosty The Lucky.