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Forges 101


Mikey98118

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What do you think of putting the exhaust behind a concave shaped movable back wall made from a castable refractory coated with an IR coating with a gap around the circumference for the gases to pass through or would a convex shape be better . My thought was to mount the wall to a threaded rod of some material that I have thats similar to iconel.

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Yes I read an article about  a forge built based on that design a while ago . The article mentioned that the intake temperature could excede the ignition point of propane so it was nessasary to have more control of the propane injection . It briefly mentioned the problem had been dealt with be using injectors from a diesel engine as I recall.

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1 hour ago, Jlou said:

What do you think of putting the exhaust behind a concave shaped movable back wall made from a castable refractory coated with an IR coating with a gap around the circumference for the gases to pass through or would a convex shape be better . My thought was to mount the wall to a threaded rod of some material that I have thats similar to iconel.

I think it is fine; you should use a concave shape for best results.

 

1 hour ago, ThomasPowers said:

I rather like using the workpiece opening as the exhaust as it means that heat is being pushed that away .

Have you looked at the Sandia Forge Design that uses the exhaust to preheat the incoming gasses?  AKA as a recuperative forge. 

The Sandia forge I read about way back in the beginning, was estimated to raise forge bemperature 1000 F more than non-recuperative forges. But at that time the stainless steel tubing had to be replaced too frequently, due to premature ignition in the tube. Glad to hear that they sorted the problem out.

Jiou,

BTW, they are called baffle walls. You will get more utility out of it, if you mount it on threaded threaded hinges, so that it can be pulled nearer or farther from the exhaust opening, and a simple latch on the baffle wall's other side, to move larger peices, and crucibles, in and out of.

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I saw a Sandia recupertaive forge come up on auction awhile back.  I ended up bidding on it, but didn't win.  I took plenty of pictures of it.  The gas manifold was expertyly tig welded together.  

Mikey, thanks for the pic of your vortex burner! 

Ede

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IMO,hat the Sandia forge design boils down to, is a question of benefit versus cost, not the cost of parts and trouble, but the cost engineering wise. If there were no other way to recuperate some of the energy flooding out of the exhaust, than this forge, would be a sound investment. However radiant recuperation of some of that energy, is cheap and easy via re-emission. That being available, how much of a forge's design do we want to be dictated to recuperating some of the exhaust gas's energy this way? 

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On 8/12/2017 at 1:21 PM, Mikey98118 said:

After decades of failed attempts at making a good homemade refractory, zirconium silicate/Veegum, which can be found at many large pottery supply stores, is able to meet this need; back up a couple of pages, and read about it.

Would this be what I would use as the refractory coating over the ceramic fiber, and is this something I can trowel on or will I need to make a form

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20 minutes ago, ThomasPowers said:

Well it was originally designed to deal with altitude problems people were having; you do test at 9000' as well as sea level right?

It was also invented back when a Reil burner was the best deign available; we are a long way past that.

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4 minutes ago, kander54 said:

Would this be what I would use as the refractory coating over the ceramic fiber, and is this something I can trowel on or will I need to make a form

With 5% Veegum or bentonite, zirconium silicate should work well as  troweled-on coating. 3.5% Veegum or bentinite in a zirconium silicate refractory can be molded like clay to make an armored hot face; it can probably be successfully used as a castable refractory, if it is vibrated during casting.

Either way, you would want to rigidize the ceramic blanket layer its cast in, molded molded onto, or coated on. I would be inclined to  coat the insulation first, and follow that up by molding a plastic layer in place, wants the coating was fired.

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Thomas,

Please note that I don't intend to denigrate the Sandia forge design; it was a very successful  forge in its day, and a well worthwhile forge to buy at auction in this day; I only mean to point out that anyone building a forge with today's burners have better choices available now.

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No problem; I've done some altitude testing for a burner maker before and still need to get a day free to go up to the 10000 feet level and try it out. (Parking lot of the Magdalena Ridge Observatory---if I can wrangle permission..."The Magdalena Ridge Observatory (MRO) is located on 1,000 acres at 10,600 feet in the Magdalena Mountains of the Cibola National Forest in Socorro County, New Mexico (NM). This multi-use research and educational observatory is built and operated by the New Mexico Institute of Mining and Technology (NMT) with offices located on the NMT campus in Socorro, NM.")

My previous job involved visiting a radio telescope at 16400' (about 5000 meters) in Chile---but I don't expect burners to work at that level; I had trouble just walking there.

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I don't foresee a lot of call for them, or much of anything else (other than observatory equipment) at such a high altitude :P

The Denver  area has a large enough population that high altitude naturally aspirated burners matter there. I would suppose, that burners for ridiculously high altitude could be covered with fan- blown models; the problem of lower heat output could be overcome with polypropylene fuel?

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The best way to become savvy enough to tune an air-fuel burner, or an oxy-fuel torch is to look at as many flames as you  can, and study them until you understand what you are seeing

Start by discounting any sales ad for a burner that doesn't include a picture of its flame in action. It is becoming commonplace for burners to be shown running, in order to produce some proof that their burners are worth buying. Call anyone claiming to have a good burner to "show you the beef." Either they will change the oversight, or they really have nothing worth showing.

Nearly all butane blue flame lighters, and air-fuel torches have perfect flames. Ignore their needle flame shape, which is due to a much lower fuel pressure than propane torches. Concentrate on the total fuel combustion in a primary flame envelope, and on their shade of blue; never blue-green, which means a reducing flame; and never dark blue, which means an oxidizing flame; they are always a light to medium blue, which is in the ballpark of neutral flames.

You will find faked up photographs of imported blue flame torches, but they shortly become easy to identify as the frauds they are.

 

 

Finally note their lack of secondary flames throughout half of the range, and very small secondary flames, even when turned up to wide open.

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Charles R. Stevens wrote the following on another thread:

"As you already have tools and skills using them I would advocate building a forge. Not only is the cost in your favor, so is future maintenance. Mike and Jerry have a wealth of knowledge on gas forge and burner construction and are happy to share. Wayne has a nice side gig sourcing non industrial amounts of refractory materials. 

Guys with "gassers" find out fast that one size dose not fit all, and wile 90% of smiths will do 90% of their work in a 8" deep forge.  But then their are the other 10% who either need a bigger forge all the time, or the 100% who need a bigger forge some times. Having the confidence to build allows you the opportunity to own 2 or 3 forges for the same money. You may have a soul can forge for small work, a 10x8" for general work and a 10x12 for longer twists, scrolls and knife heat treating. 

This will really help with fuel efficiency."

This advice is too well put, and too valuable, not to save for more than the usual month.

Drain holes

These days, I recommend drilling a small hole (1/8") in the bottom of the forge shell. The point is to provide a sufficient exit for steam, water vapor, and liquid water, no matter how well sealed the hot face surfaces of the forge ends up.

From the beginning I designed all my equipment to be built without need of a welding machine, or anything more than hand tools. Nevertheless,  hot water could be seen running out of some forges, after long periods without use. Because wire feed welders are being used in ever more home shops, forge shells are also becoming more water and steam tight, so the time has become ripe for water drain holes :P

What do you want to build first, when constructing your forge?

Whatever part of it that can also be used as a tool; the burner, of course! You will find lots of forge parts that are made of steel. Heat them up, and GENTLY hammer them into shape, and you can reduce your work load, during construction.

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I was thinking today, while scrounging the scrap yard looking for stainless steel pipe.  If I had a forge I could shape some nice flares for the burners I want to make.  But wait, I need to make a tool to flare the burners with.  So many plans, I've got to get to work building that forge.

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Forging a flare is easy, you don't need or want to try driving it over a cone mandrel type thing. Do as Mike says, a cross pein does the first draw, remember the MORE you work an area the farther it draws. Meaning hit the "wide" end more than you hit the "narrow" end. Yes?

Pein it for a revolution then plannish it with the face of the hammer to smooth the cone. Pein between the first set of marks to even the draw and plannish. Repeat till you have the cone you wish.

Check out sheet metal forming as in "Creasing" and "Stretching." It's the same technique you'd use to make a funnel or chalice or similar cone shape without joining a seam. 

Frosty The Lucky.

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I didn't talk about this much for a long time; knowing that most guys would completely blow the 12:1 taper, by working way too hard with the hammer blows. But the results that guys are getting these days--by doing just that--has eased my second thoughts on the matter.

Mini-forges

  We advise would-be knife makers to look into non-refillable Freon and helium cylinders for making forge shells all the time; these forges are the same size as as Ron Reil's mini-forge (listed on his burner pages; there appears a blow by blow account of how to turn one of those cylinders into a typical knife maker's forge. Duh; talk about missing the obvious!

Like they're going to make the connection :P

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Easy burner ports

Every since that evil heartless Larry Zoeller (villain, fiend, and cad) started using conduit locking rings to hold short pipe nipples in place on forge shells, I have been unable to convince most people to do things the hard way--er...I mean the right way-- and go through the minor trouble to:

(1) Grind each burner opening in the shell into an oval shape, so that each burner port (pipe nipple) could be positioned at the proper angle for the burner flame to impinge at just the right spot on the forge floor.

(2) Mark and cut one end of each burner port (still a pipe nipple) at just the right angle to match the forge shell's oval openings, cut them into castellated shapes;  bend the end tabs at right angles, and drill them, so that pop rivets could affix them to the forge shell.

(3) Drill and thread two sets of holes for thumb screws (not those low brow bolts) to keep the burners trapped at their desired angles.

All this, just to make your work easier. Poor old Frankenburner is so disappointed (double hiss)! Therefore, I am not about to mention that a hole drilled off center through a pipe cap could bring your easy way up to par with the RIGHT WAY. No, no; in a just world, it is better that all you lazy people just suffer...besides, it would allow you to aim just as well with only one set of aiming screws, and that would just be wrong.

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