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Forges 101


Mikey98118

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Rigidizer usually consists of fumed silica suspended in water; thus forming colloidal silica, which coats the surfaced of ceramic wool, and is then bonded to it by being melted at much lower temperatures then the ceramic fibers melt at. As to whether it will also bond to other surfaces; the answer is yes; no; maybe; somewhat.

Yes; no; maybe; it depends.

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Well, the propane tank forge is moving forward.  Snapped a quick picture of the insulation.  Im not done with all the layers, i'm waiting on some more that should be here tomorrow or the next day.  Entry hole and pass through cut out along with the burner hole have been put in.  I got all the paint removed.  Picked up my welder from my father-inlaws so Im all ready to go.  Nice thing was along with my welder I had a bunch of scrap steal from building my smoker.  Planning on using it to make a free standing 3 leg forge stand.

I will get some more detailed pictures. but here is one I have available.

 

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Just want to say sorry for the picture heavy post.  I got my insulation in today.  I have have 2 inches total insulation in the entire forge except for the floor.  As was suggested by I believe Frosty I added an additional piece to the floor.  I trimed the edges so that it feathered into the sides of the forge.  I have applied the remaining rigidizer I have on hand.  There again Frosty turned me onto a local supplier that carries fumed silica.  Hopefully I can get down there in the next day or two.  My burner will hit the first 3rd of the floor which should cause it to swirl around the forge.  I have roughly calculated the internal volume right now without the Kastolite or plistix to be at approx 350 cu inches.  I plan on making a sacrifical floor tile/brick by making my own that contours the floor out of Kastolite.  Not planning on forge welding but you never know.  Critic is always welcome. Currently the forge front is held on with tape.  I will be tack welding here maybe tomorrow.

Here in the first picture you can see the two tier entry for the burner holder and burner.  It shold put the burner flare approx. 1 inch inside the insulation. The second picture is looking through the front of the forge and you can see the pass-through in the back.  Third picture is the pass-through door.  The last picture is me attempting to possison the burner holder in the correct place.

 

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Farrier forges should be lightweight and physically hardy. Since farriers usually travel to job sites, their forges must withstand frequent shocks; this must be taken into account in everything from your choice of refractory, to the construction of legs.

Starting from the hot-face side of its refractory material, high alumina kiln shelf is obviously the best choice, because it is a physically tough (in both cold and hot states), can can stand up to flame. Kast-O-lite 30 makes a good hot-face alternative in shop forges, but as a structural part, when traveling over bumpy roads.

    Primary insulation is the first layer outside of the hot-face material. I would recommend 2” thick Morgan K26 bricks; they are highly insulating, lightweight, and rigid enough to do well, so long as they are supported by tough exterior walls and tough kiln shelf interiors. A second choice would be Kast-O-lite 30, separately cast and laid in place as floor, walls, and ceiling. Furthermore, about one-third Perlite should be included in the refractory mix before casting, to increase insulation and decrease weight.

    A box shape serves best in a farrier’s forge; angle iron and sheet metal, held together with machine screws, will serve best for its shell. Spring surfaces should be built into whatever stand, legs, or carriage the forge is mounted on.

Why not use ceramic fiber insulation? Ceramic wool blanket is springy when newly compressed; it would seem to be an ideal material to cradle hard refractories from shocks. Unfortunately, thermal cycling causes the fibers to stiffen, and the material "takes a set," and begins breaking down; repeated shocks will accelerate that process. Rigidizing ceramic fibers will also cause repeated shocks and vibration to accelerate fiber breakdown.

     Ceramic fiber board should hold up better than blankets, but at their steep prices, I would not want to take a chance on it. Newer tougher ceramic board products may change the ground rules, but again, without information on how resistance they are to shocks...

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    Perlite can be used as secondary insulation, to fill gaps between flat insulating boards, or bricks, and round or irregular surfaces; it is only good to 1900 F, but will not break down like ceramic fibers do, from thermal cycling. Perlite is very lightweight, and can be purchased cheaply where garden products are sold.

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Well the forge has been lined with Kastolite ( ended up using 7 lbs) then after curing coated with plistix 900.  Below is a picture just after lighting.  Running 8 psi.  The first video is the forge running at 10 psi for about 4-5 min.  Looks like the flame is really swilling.  The second video is running at 15 psi.  I put a piece of 1/8 x 3/4 angle iron in and it heated rather quickly.  Just a couple minutes.  Lots of dragons breath.  Let me know what you think.

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Forge running for a couple minutes: 8 psi

 

Forge running at 15 PSI

 

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So if I move the mig tip away from the throat of the mixing tube I should be able to introduce more oxygen correct. I noticed that after warming up a short bit it was orange.  Wasn't sure if that was coming from the burner, the kastolite and or plistx.

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It isn't coming from the burner; it's coming from an excellent job of forge construction. Tune the burner right, ahd that forge should get to yellow heat.

27 minutes ago, Fishgod said:

So if I move the mig tip away from the throat of the mixing tube I should be able to introduce more oxygen correct.

Prbably; without more photos we have no way of knowing if the MIG contact tip is properly centered; another major building goof with these burners.

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Mike,

Thanks for the comment on the forge build.  That is thanks to this site (Forges 101). Its a Z Burner from Larry Zoeller.  There is a set screw that allows the propane injector to be moved in and out.  Was the rich burning coming evidence comming from the dragon breath? Just trying to figure out what clued you into oxygen starvation for future reference.

Edited by Mod30
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The orange dragon's breath is the calcites in the refractory oxidizing, it'll diminish but not completely go away. Looking good. 

Backing the propane jet (injector) back from the mixing tube will increase combustion air induction. Move it a LITTLE bit at a time and test between adjustments.

Unless it got manhandled in transit Larry's jets are centered.

Frosty The Lucky.

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Thanks everyone for so much help.  I really appreciate all the help.  

How do I tell if I'm going the right direction.  What indicator do I use.?

4 minutes ago, Buzzkill said:

For me it was the blue-green tint to the flame that was the main indicator of burning rich.

Ahhh,  I saw that as well.  So I will have to tune it while the forge is relativly cold because it all disappears once it gets hot and I cant see it.

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Rich flames have a blue-green tint to them.   Neutral flames are a good medium blue.  Lean flames tend towards having a deeper blue to purplish hue to them.  And yes, you do have to check that before the forge starts glowing too much to see the flame color clearly.

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Well, I worked on adjusting the position of the jet last night.  I moved it back a little at a time.  It seems to have made it better but I feel like the flame still has a green hue.  I realize now when typing this that without pictures/video there isnt much  help that can be given.  I have the air intake pointed straight up.  I could feel the forge exhaust near the opening.  Could the intake of exhaust be compounding the rich flame?  I am going to try the theory this evening when it gets dark.  I am going to rotate the burner intake down and away from the front of the forge.

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Above is the photo of a coffee-can casting furnace, employing a friend's version of a 1/4" Mikey burner; such furnaces started out twenty some years back, employing two three lb. coffee cans. Why so large? aluminum melting only takes about 1200 F crucible temperatures, to be ready to pour. So, a larger furnace could be quickly heated to such a low temperature with a minimum loss of time and fuel, as shown from the 16 oz. disposable propane cylinder, which feeds gas through a needle valve and gas hose that was scavenged from an air/fuel torch; this assembly is connected to the homemade burner through a 1/4" hose barb to 1/4" pipe thread fitting, on the burner's near end.

    I wouldn't recommend refractory cement in equipment running at forging temperatures, but a really hot burner (near total combustion in a singe flame envelope) could run a 1/4" burner running hard, or a 3/8" (much simpler to build) run at low PSI, quite easily heat a forge built from a single coffee-can, one-gallon paint can, or #10 soup can. when lined with a 1-1/2" layer of Kast-O-lite 30, it will reach yellow heat in a few minutes.

Isn't it better to have a layer of ceramic wool blanket included" Sure, but before you assume you can't make a good forge without it, remember to include the economies of scale. What is only common sense on a larger forge, which must be fed from a much larger burner, might be considered as "gilding the Lilly" in a tiny model. What I'm saying here is that circumstances alters cases. What is "written in stone" at one equipment size, may become a matter of preferences at another.

    The same goes for how much insulation is preferable. In this small a forge, a little insulation takes away a whole lot of internal diameter; such loss is a positive in a larger space, but may be a negative in an already small one.

 

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So we talk a lot about rigidizing and coating and treating ceramic blanket.  
 

When it comes to box forges insulated with Ceramic board, should this material be coated as well?  Even if it is not needed for safety, is satanite or similar still a good idea for efficiency and protection?

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Engineering is constantly concerned with the law of diminishing returns. Where it comes in here is that one giant factor in forges is size; the smaller the more fuel efficient. This advantage effects material cost versus fuel costs, on a far different scale than in larger forges. All things being equal, I'm still a fan of fuel minimization; all things frequently aren't, though. How long the ceramics will last, and how cheap and easy a first forge is to construct, become larger concerns in a mini-forge. Where to start drawing the line? Paint-can and coffee-can forges is that point for me.

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