Forges 101

[stevomiller]

Interesting side note relayed to me on hot faces when used with one company’s high emissivity type coating for industrial settings:

The mfg told me that my castolite 30 liner wasn’t ideal for THEIR product, and something less insulative worked better. They didn’t go into much detail but it was inferred that the idea was to heat the liner (with insulative layer behind it) so tha this thermal mass would then reradiate said heat back into to the working chamber. Anyways none of us will probably use this makers product as you can’t purchase it direct especially in small quantities,  they only sell through contractors that specialize in industrial forge/foundry building and repairs. 

Most hobbiests want heat, and fast vs industrial shops wanting very consistent heats once at temp. I do know that Tim Zowadas older forges used to use a less insulative very high alumina liner with ceramic wool outer layer, I don’t know if he still does it this way, that was over 20 years agp.

 

[Mikey98118]

I think there are always several ways to deal with a problem like flux build up on forge floors. But thinking ahead is going to give us more latitude when dealing with this mess.

High alumina kiln shelves--when they are installed in a way that is easy to remove--can be taken out and cleaned of flux; then returned to the forge. When making a tunnel forge I like to trap kiln shelves in recessed notches in the forge shell; afterward they just slide in and out. Hot flux makes a sticky mess, but cold flux can be power sanded right off of a kiln shelf. The shelf itself is very hard, and will not lose much surface too the process. Someone else might simply lay the kiln shelf on the forge floor.

One forge manufacturer uses refractory dishes for forge bottoms; such shape could hold kitty litter to absorb flux. I think that a thick layer of kiln wash could allow cold flux to pop off a forge floor with a little help from a spatula. Just as Frosty developed a kiln wash to protect refractory surfaces from heat and flux he might come up with one is easily removed from beneath cold flux...maybe something that includes plaster in the formula 

The point is to plan ahead; if you do, getting rid of flux doesn't have to be a big deal.

[Frosty]

Borax based fluxes are water soluble so if you can remove the forge floor you can dissolve the flux in water. The trick is getting it thoroughly dry BEFORE replacing it and lighting the forge!  Something thin like kiln shelf would only require maybe an hour at 230 f. brick, etc. will take a couple hours per inch. 

Your best bet it to keep it off your forge.

A while back a topic was how to prevent flux bleeding from welds. Traditional methods include vigorous brushing, etc. I found dropping it in water when it's still a few hundred f. cleans it right out. 

Frosty The Lucky.

[Mikey98118]

On ‎8‎/‎18‎/‎2018 at 10:07 PM, Frosty said:

One of the guys in our club has been experimenting with bentonite and zircopax. Not to the extent that one of our IFI members in the Netherlands I believe was. However in my playing around I found that sticking it in a HOT forge about tooth paste consistency made ceramic foam. Looks more like bread than whipped cream but it was IIRC about 80% zircopax and doesn't care about flux. 

And that's my more recent experimenting to think on.

Well, yes; I be thinking about that. You may have come up with a real good new high temperature insulation!

[MonkeyForge]

Being that member from the Netherlands: I have no conclusive results as of yet. I managed to get a  shape from my clay/grog/zirconium silicate mixture (including paper fiber for molding and dry strength) But it has not been put to the test under heat yet. I have a lot going on at the moment, still read the threads here almost daily.  I am mainly interested, at the moment, to see if we can take the zirconium silicate/molochite/bentonite mixture and have it double as both refractory and ir reflective  coating. Refractory it is as I had it baked as a porcelain in a potters kiln at 1300/ 1350 centigrade . Apologies for not having anything conclusive but I thought it made sense to report the experiment is not dead, just stalled.

[Mikey98118]

I don't discuss your refractory experiments much, but I avidly read everything you write about it. Mostly what I read keeps me so busy thinking that I forget to reach any conclusions outside of the desire to read more 

[Mikey98118]

So we've had burner size to forge volume recommendations for around two decades for tube burners. Have anyone got any size to volume figures for ribbon burners yet?

[Another FrankenBurner]

It seems like the burner block itself would determine the minimum and maximum through put of the air/fuel volume and the rest would be adjusted to be within that range.  In the case of Frosty's NARB, he had to design the burner block to match the available air/fuel volume at the low pressures.  Where as the blown version that Wayne Coe has on his site has a bit more nozzellette area but the blower and fuel can be increased to match it.

A lot of the ribbon burner builds I see, don't use a fuel gas jet but a needle valve.  With no way to quantify fuel input, the ability to pump in air and increase fuel, different input plumbing, different blowers, and different burner blocks with different quantities and sizes of nozzellettes (Frosty's term), wouldn't that make the ribbon burner output too variable per burner to make a general suggestion?  

This post is meant to be a question for those who know more then I do.  None of this post should be read as fact.  

[Buzzkill]

You may be right about it being too variable for good definition for blown ribbon burners.  However, for NARBs, the amount of fuel and air that can be supplied is dependent on the jet and mixing tube (and pressure of course), while the number and diameter of holes has to be balanced with this input in order for it to function.  In other words, the operating parameters of NARBs are narrower and are therefore we can probably make some reasonable generalizations as to the maximum volume of a well-constructed forge that can be heated with one of these.  From what I've seen so far it probably matches fairly closely with the single port NA burner recommendations for mixing tube diameter and forge volume. However, my impression is that my NARB is a bit more fuel efficient and provides a more even forge chamber temperature than a single port NA burner with the same size mixing tube.  The stable operating range is also wider.  Even after running my forge at high temperature around 20 psi for a while I can still turn it down to about 1 psi without backfires, and I don't have any issue with the flame blowing itself out at moderate to high pressure even when first lighting the forge.  So far for me the biggest drawback has been difficulty getting close to complete combustion in the primary flames from the nozzellettes.  I'm not sure whether this is an inability to draw enough air, incomplete mixing in the plenum, length/shape of nozzellette holes, or some other factor.

[Another FrankenBurner]

I had not thought of that, with the NARBs.  They are an orifice of a given size at a given pressure.  Do you feel that the NARB you are using is equivalent to what would be the matching tube burner?  At least in terms of heating the same volume of forge to similar temperatures. Do you suspect a 3/4 inch NARB would follow the 300-350 cu. in. general suggestion?

[Buzzkill]

I'm actually using the same T, mig tip, and same length of 1/2" tube for my NARB that I had previously used for my single port burner.  Originally that was in a freon tank forge.  When I built the NARB I cut a hole in the forge so I could use it.  With both burners I was able to forge weld in it.  However, I really messed up my Kastolite layer when making the opening for the NARB, so I built another forge designed to accommodate the NARB.  At this point I do think mixing tube to volume recommendations are fairly close for both, but I haven't used a 3/4" NARB in a larger forge yet, so someone else may need to answer that for you.

[Mikey98118]

So far we have two indications that mixing tub diameter is a good indication, at least for NARBs. And for fan-blown?

[Mikey98118]

What exactly constitutes "dragon's breath"? Are we just talking about hot exhaust gases, or does it also require flame content in that exhaust?

[Buzzkill]

When I use the term I refer to visible flame in low or no ambient light.

[Frosty]

I've been operating on the home made NA burner rule of thumb for burner to forge volume ratio. 

The bright orange of excess dragon's breath in my NARB Lives post has diminished to a little blue flame since the calcite in the kastolite refractory has finally burned off the surface. Calcium burns with a vivid orange flame. 

I believe the term "Dragon's Breath" is most commonly used for any flame exiting the doors or exhaust port of a forge or melter. It's condition is an indicator of combustion in the forge.

Multiple outlet burners can be virtually any shape, check out some of the glass blower sites. You can buy the things, of course you won't get in on the fun of tinkering. 

Frosty The Lucky.

[ThomasPowers]

I use that term to refer to hot exhaust, visible or invisible, that a learning smith needs to watch out for as they can be invisible in daylight.

I usually demonstrate it by running my arm through it and showing them the burned hair on it.

[HojPoj]

On 3/27/2018 at 7:37 PM, Mikey98118 said:

there is no mention of clamshell forges in this thread. Do any of you want them included?

I know this is more than a few months late,  but I'm interested if nothing more than to learn about something else. 

 

[Frosty]

I'm sure Mike will be along shortly but I'll get it rolling. What do you want to know about them?

Frosty The Lucky.

[Mikey98118]

What frosty said for sure! Ask away 

I will even start the ball rolling by saying that clamshell forges can be dedicated (special forge shape) or an optional forge head on a hot equipment base; that is the way (optional head) that I built mine, but as a dedicated forge, clamshell's can be a lot smaller.

[HojPoj]

I guess the fundamental question is "What is the use case for that type of design?"

When you say 'dedicated', does that mean the inner chamber dimensions would be specifically sized/shaped for repeat/production work?

And when you talk of interchangeable heads, does that imply you might have a flat base,  and just the upper sections have special geometry?

[Frosty]

I think in general the "clamshell forge" is one of those things that sound better than they actually are. There are folk who use them regularly, maybe they'll chime in. In general I believe they're used for large or awkward pieces that won't fit through a forge door. Say you wanted to tweak a spot on a gate. A garden gate isn't going to fit in your forge so you get out the rosebud tip on your torch. OR heat up the clamshell forge, open the lid, insert the section of the gate you want to heat and close the lid.

If you had a production run you could make one to fit or be more effective for a given product or type of product. 

Interchangeable heads? (what I've been calling lids) Sounds like a good idea to me. 

When you start talking about having a forge head sitting on a refractory table you're starting to get into my shop forge area. I call it a "Variable Geometry" forge. The lid has 4, 3/4" T burners mounted and plumbed in from a manifold with individual valves. The lid is 20" square, the deck is 24" square. The lid is on a jack so I can lift it and rearrange the partition bricks. I usually run a single chamber of approx 350 cu/in under a single burner. The second most used is  a chamber 18" long under 2 burners. 

The #1 down check for clamshell forges is what you experience when you open it. If it hinges open like a clam you'll be standing within a few feet of a large surface radiating temps in excess of 2,000 f. You don't need that hair do you? The smell of toasting clothe can be quite memorable. No synthetics! Or you'll be shrink wrapped in the BAD way. 

Frosty The Lucky.

[SLAG]

Frosty said,

"  shrink wrapped in a bad way..."  or worse,  napalmed big time.  And end up a little like  Saint Joan of Arc.

I like your red-colored note.

How did you do that ?

SLAG.

[Mikey98118]

I enjoyed both the question, which was dead on the money, and Frost's answer which was also dead on. I will only add that these forges can also be quite small. The smaller the forge the less the heat when the lid is raised; also flat work such as  horse shoes, quatrefoils ,or crosses do not need the lid to be open very far. But such a forge tends to be of more use for repeat work, such as sub assemblies for gate work. The limited uses of such forges are offset by changeable lids in brick pile forges or on fired work benches.

[HojPoj]

Mikey, et tal, thanks for the responses- that clears it up.

After noodling it over I could see where oddball pieces still wouldn't work with a brick pile forge if some of the dimensions were oversize.  Beyond the use in specialized repeat/production work, perhaps a good way to spin the description would be that it's a forge you could 'clamp on' to a piece, rather than having to move the piece into a forge? (and thereby are free of the limitations of the forge opening size)

 

 

[Frosty]

On 8/30/2018 at 2:26 PM, SLAG said:

I like your red-colored note. How did you do that ?

Slag: In the bar on top of the reply text window there's a capitol A   next to the Size button. The A is the text color on mine. I bolded and redded it after typing it or sometimes I have troubles shutting the special effects off and it can look goofy.

A version of the clamshell I considered on occasion I wanted to do a lot of twisting was based on a couple pair of long jaw vise grips welded to a length of thin walled pipe split lengthways. The idea was to make a tunnel(?) forge to heat long length evenly. Had it worked well a person could pass full sticks through it slowly and texture it as it came out for things like guardrails and such.

The main problem I ran into for the experiments was pipe size. I made extensive use of semi exhaust pipe from the heavy duty shop's scrap dumpster but 4" was the largest and that left just too little for adequate Kaowool in the liner and I wasn't about to have some rolled up for me, nor to I have a brake. So it's a back burnered idea.

Always thinking, sometimes it's even worth the time and 1,000 yd. stare.

Frosty The Lucky.