Mikey98118

Forges 101

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Mikey, I have a question regarding re-emission.  In the course of your research on all this did you ever look at different forge shapes in the context of focusing the IR re-emissions?  I'm thinking of something like the effect of a satellite dish or a focusing mirror.  I'm not even sure it would be desirable to have a tight focus, but I am curious to know if you ever went down that rabbit trail and what you found out if you did.

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Yes, concave surfaces will focus the radiant energy on a chosen target; this is handier with crucibles than metal parts. You have to do some math to avoid over focusing on the target area, but the effect isn't minor.

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On 9/10/2017 at 2:45 PM, Mikey98118 said:

 

I have noticed that you "lean toward" the D or mailbox shape and the half muffler shaped forge.  Is there any correlation between those shapes and the above statement?  Would the math be akin to laying out a truncated cone pattern? (As in laying out a pattern for a flare.) Just curious!

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On 9/10/2017 at 8:50 PM, RandyScott said:

 

Hi RandyScott, 

i heard through the grapevine that Mikey has been having some computer issues and is unable to respond until he gets his password straightened out, lest you think he is ignoring you.  

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Sorry for the delay, Randy.

ede;  thank you for covering for me.

I would have hated to miss this one. You are right in thinking I push people to consider D"" and oval forges, but not because I personally prefer them; they are both useful forges, having room for a wider floor in a smaller forge. So, I push them to keep the idea solidly in the public mind. I featured a clam shell forge in my book for the same reason back in 2004. My personal preference is a "knife maker" forge  from a free non-refillable Freon or helium cylinder. It is natural for you to look to your intended use for a forge, when deciding what to build, or buy. I look at forges from an educator's view.

Shaping a forge to focus some of its radiant re-emission is only a clever idea if you have a small target area all of the time. If you mostly heat the same item, such as a crucible, over and over; otherwise, you could learn a brand new meaning for "hot spots," as a negative :rolleyes:

 

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Yeah, that darned life thing, it keeps getting in the way of my plans. <sigh>

Gas forges are known as "reverberatory furnaces" in that the fire heats the furnace and the furnace heats the work via IR. It's not directly a flame heater.

Using the flame face as a lens has always been a factor, what kind s the issue. For example, a box forge's liner radiates straight out from the walls, the IR is directed at the far wall which re-radiates it straight back. radiation only goes in a straight line after it's radiated still it will take the path of least resistance meaning it isn't going to radiate strongly towards the super heated refractory it's next to in the wall. 

In a pipe forge the IR is more or less focused in the center of the cylinder. In a vault (D) shaped forge the radiation tends to focus on the flat floor, more or less in the center. The radiation from the floor is directed more or less at a lens aimed back at it.

I like the D, (I've been calling the shape a Vault, it's an ancient term for the shape of a mail box in architecture.) 

My next will be a NARB fired vault.

Frosty The Lucky.

 

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Forge/furnaces

Multi-task tooling is always a trade off; the more tasks done the less any task is done well. It is best for for a full time tool to do one thing only. For hobby heating equipment, two tasks give the most gain for the least drop in efficiency; this falls off sharply with every additional task done. In addition,, you need to decide which of any two tasks is most important, and try to push all the efficiency trade offs on the other.

A well known example of a multi task tool is the the brick pile forge, which exchanges much of its efficiency for the flexibility to heat a variety of odd shapes, well enough for occasional use.

The main difference between a tunnel forge and a casting furnace, is the forge's horizontal versus the casting furnace vertical position; so a a half cage, or axle arrangement needs to replace four legs, so that the forge/furnace can be placed in the horizontal and vertical positions, at will. The trade offs come in the  equipment details; A single burner in a forge is positioned in its center; in furnace it is placed about 2" above the floor. Obviously, two burners can be placed with the back burner 2" above the floor, and the forward burner one-third of the way in from the exhaust opening, if casting is done more than forging. Or the two burner can be divided at the one-third and two-third positions if forging is the main work to be done.

If casting is done, the exhaust opening needs to be left as large as possible, and an external swinging baffle door intalled. A box shaped forge also needs a swinging door to deal with a crucible.

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So what is the deal with Veegum and or bentonite clay?  Is it being looked at for a kiln was, a hot face, refractory material, or all of the above?

thank you,

jeff

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It is the zirconium silicate that provides all of the refractory and heat reflective qualities; this is why it comprises between 95 and 96.5% of the formula. Veegum, bentonite, or bentone is used as binder (cement) and plasticizer. The formula with 5% is good as a coating, but nothing else, because it is sticky. The formula with 3.5% makes a refractory with excellent thermal properties. 

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It's an interesting topic and have started reading up on it.  Came across a person throwing crucibles on a potters wheel out zircopax and 3-4% Veegum T.  

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Add to that the ability for the 5% formula to act as the perfect glue for  refractory parts made with 3.5% Veegum, and many interesting things can be made at home. Things like multi hole burner nozzles, to replace ribbon burner heads for very small NA burners.

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Just take in to account that this particular mixture has a long drying time. After mixing (for me) it was sticky between 3 and 5 % Bentone. Adding more water will just make it a slurry or cause the Bentone/bentonite to gel after mixing. When I made my test tiles (96% Zirconium silicate to 4 % Bentone)  the consistency would be as follows:

- Sticky, good enough to plaster or press
- After forming and drying for  day or 2 (depending on water content) it would be more like clay and plastic
-  When dry it will act like dried clay, it will hold together but don't try to bend it.

Note that above does not have the water in the equation of the mix, I added it until I had a workable consistency. When the mix gets sticky I could trowel or press it into the form I wanted. 

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Did you find that you required a mold release on your form, or did it naturally release from the tile mold as the material dewatered?

Thank you,

Jeff

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Maarten, (MonkeyForge,) is the one who's been doing the most direct experimentation so far. Mike has been doing a lot of research and I've been keeping track. I have some experience with bentonite as drilling mud and watched it used plugging the tap in an cupola iron melter.

I'm not going to encourage someone else to make experiments I think will work but from what I've seen almost drippy bentonite mud will dry then bisque fire in just a few minutes. The casters plug the tap hole by shoving a gob of bentonite mud directly in contact with a 2,400f hole that was dripping molten iron and slag and it dries, hardens and fires into a soft rock in a couple minutes.

I need to get hold of some bentonite so I can start experimenting with just how fast it can be forced to dry. Left on it's own it takes days to dry from plastic to hard but pliable. Mixing it with 95% zirconium silicate should almost make it dry and fire, maybe even vitrify from soft plastic to ceramic tile directly. Bentonite is some funny stuff, lots of weird characteristics. 

Frosty The Lucky.

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Keep us posted please and notes, please take notes. Getting a good home made recipe with this stuff may be a matter of tiny details.

Frosty The Lucky.

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Maarten,

I have followed your posts about making thermal tiles with great interest. At first I had concluded that the author of the Digitalfire articles preferred Veegum because it was somehow a higher quality material to its alternate choices, and that it was therefore the reason this refractory is practically immune to thermal shock; apparently that isn't so.

But the author could work the 3.5% formula on a potters wheel; this wouldn't be possible if it were sticky. Could this be why he prefers Veegum over bentonite and bentone?

My point? Nothing more then an attempt to squeeze as much data possible from what is being posted :D

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Mike, I have not tried drying my mixture on plaster first, I rather processed it right after mixing the powder and adding water, as far as I read on digital fire Veegum has this same property. After about a day the tile will be more like clay and can be bent. After several days it is hard. What The guy at Digital fire does is mix his Veegum and Zirconium silicate, dry on plaster until it is plastic and no longer sticky so he can throw it on the wheel. I imagine that I can do the same with Bentone.

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I am presently interested in shaped forms like crucibles and flame retention nozzles, but believe that thermal tiles ( both flat and curved) will be the refractory's most important purpose.

Thank you for further practical insight on the particulars of working with these refractories.

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Thought this needed posted here  my rigidizer recipe 

don't forget the few drops of food coloring for tracer

 

"Jasen said  "...used a cup of silica in a pint of water. Idk if it's proper amount but it worked very well on my forge."

Incidental,  is the most useful kind of information on this group. Thank you for posting; this will help loads of people

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Ive got some bentonite now, along with zircon, so in about 2 weeks when i go home next, Ill be able to put together my forge, and will be testing this mixture, using it to coat the forge, and im going to try and make some burners out of it.

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