Cast iron gypsy video.

This video is all about using a crucible furnace to melt iron for the art shows she goes to. These shows always use a cupola to melt iron so it is unusual to see a crucible furnace being used.

The furnace and burners are discussed in this article.

https://www.colescastings.com/a-sustainable-melt-furnace-for-school-and-small-foundry-applications/


And some info here:

https://www.colescastings.com/sustainable-oil-furnace-at-asu-phoenix-arizona/

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A few notes about oil-fired furnaces and burners:

As 100model and I both know, the statement Coles makes (these folks are not related to the Coles model engine company in the USA) about gas (such as natural gas or propane) not getting hot enough to melt iron is false.
Not sure why they make that statement.

The Coles guy does mention that you can have all sorts of problems when using used vegetable oil, such has having large amounts of solids in the oil, water contamination, etc.
Someone else I know who has used a lot of vegetable oil to run his foundry burner said that vegetable oil causes a lot of corrosion and blockage issues as the oil sits in the burner and tubing between melts. He uses vegetable oil because it is free.
He also has a lot of clogging issues due to solids being in the oil.
And in the USA, they have started locking up all the used vegetable oil containers outside of the fry places, and you can't even access it unless you know someone.

There are many good reasons to not use vegetable oil in a foundry furnace, but if you want to make a feel-good statement about the environment, then you can do that with vegetable oil.
It takes a lot of energy to refine the vegetable oil, and hydrogenate it, so if you are using commercial cooking oil, it took a lot of energy to make that, and it is a falacy to think you are getting something that did not pollute when it was made.
The intent of the Coles guy is good, ie: trying to use a sustainable fuel, but not very practical/trouble-free in actual use from what I have heard from those who use it.
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If you want consistent iron melts, use automotive or non-automotive grade diesel.
If you have access to non-contaminated waste engine oil, you can use that, but it is often contaminated with radiator fluid, water, etc., and it also contains heavy metals, which is why I don't use it.

Diesel solves the problems of having all the solids in the fuel (I still use an inline automotive filter just in case, but they have never clogged when using diesel). And diesel can sit in the fuel tank and fuel lines/burner for a long time without sludging up or corroding things.

The Coles guy in the video uses a drip-style oil burner, as does 100model.
I could never get consistent results with a drip-style burner, so I use a siphon nozzle burner.

I did make a dual siphon-nozzle burner setup, but unfortunately that was early on in my foundry journey, and so I did not know how to tune it correctly, and went back to a single burner.

Many of the commercial furnaces like the one he converted in the video above used dual natural gas burners, and so he probably had the dual tuyeres at 180 degrees already.
I think the dual burners will melt faster, and if I get time, I will probably go back to using a dual burner system.

And the Coles guy is correct, the burners must be tuned for a reducing flame (rich), so that you don't oxidize the iron.

The Coles guy does not mention using ferrosilicon to prevent hard spots (called chills) in the iron, so I am not sure if he is aware of that product or not.
It is very difficult to make model engine parts without ferrosilicon, if you want parts that are machinable.
Thin gray iron parts that are cast without ferrrosilicon can be the hardness of tool steel.

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I did a demonstration iron pour for "cast iron gypsy" (the person who made the video), and the local art-iron group, locally in 2019.
I thought that many of the art-iron folks would convert over to oil-fired furnaces after seeing how I did it.

As it turns out, the art-iron groups around the country hold festivals, where many of the artists travel long distances, and they fire up one or more coke-fired cupolas/cupolets.
It is a big, messy, hot, sometimes dangerous, very involved, very labor-intensive affair, and they work like ants in unison to make it all happen.
It is like a religious ceremony that goes on for several days; often a day of mold making, a day of pouring, and a day of shake out/cleanup, and often many group learning workshops.
They have no desire to melt and pour iron efficiently.

It is all about the comradery of working together in a ceremonial fashion, for a common goal (to make artwork in gray iron), and the coke-fired cupola/cupolets are the centeral part of that.
The cupolas/cupolets beltch out fire, smoke, and pour out and spill impressive streams of molten iron for the crowd to witness, and so it is show business as much as it is creating artwork.

I am convinced that art-iron folks will never use oil-fired crucible furnaces.
It would ruin their display/show.
Doing things the hard way/old-school way is an integral part of what they do to create art.

And the art-iron folks have access to coke (coal heated in the absence of oxygen) for a fuel, but for a normal hobby person like myself, small quantities of coke have been basically impossible to find for sale.

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And one final note, if you are pouring model engine parts in gray iron, I highly recommend that you do not use the very tall waterfall pour that they are using in the video above, since that entrains air, slag, sand, etc. into the melt.

If you watch 100model's videos, he gets the lip of the crucible almost touching or even touching the top of the sprue, to eliminate the waterfall effect.

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GreenTwin said:

highly recommend that you do not use the very tall waterfall pour that they are using in the video above, since that entrains air, slag, sand, etc. into the melt.

Click to expand...

I could never understand why they do that because there is one advantage to pouring close to the sprue, you do not spill metal like they do. In a hobby setting where small amounts are melted spilling metal means that it is going to be short pour.

GreenTwin said:

about gas (such as natural gas or propane) not getting hot enough to melt iron is false.

Click to expand...

When a silly statement like that gets onto the internet it becomes a fact and is repeated over and over which means it is a fact. I used propane gas to melt iron for ten years until I realized it was costing me too much and started to experiment with waste motor oil.

"until I realized it was costing me too much" I can second that statement, I swapped from using diesel to propane mainly because of the smoke when firing up , the smell and the mess.
I buy my propane in 47kg cylinders which is the cheapest way for me but it is far more expensive per melt than red diesel.
Although many do so , it is illegal to burn waste mineral oil in the UK without a license issued by local authorities.
Dan.

Isn't the waterfall partly due to the full large crucible they are using and the distance from edge of flask to where they are pouring. As they work their way through the flasks the waterfall height reduces as they can tilt the crucible more and therefore lower.

Some of those art-iron molds are huge, and so that can make for a tall mold, and require a large ladle, or in the case of the video above, a large crucible.
Art-iron pours can be rather wild affairs, although they spend a great deal of time and effort to make sure they are safe.

The art pieces are not structural, and so it does not really matter if they have porosity, slag, inclusions, etc.
If you use spin traps at the end of the runners, you can overcome a lot of bad pouring style, assuming you keep the sprue full once you start pouring.

I would agree, they are filling the crucible very full, and that makes for a difficult pour without spilling everywhere.
They are also mixing molds of all different types, with sprues located in sub-optimal locations.
Sort of a hit and miss affair, but they do make some impressive artwork, such as attached alligator.
They bring in coke by the ton.

abby said:

mainly because of the smoke when firing up , the smell and the mess.

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If you are getting smoke and mess using diesel, then you are not doing something correctly.
I don't have smoke or mess.
I use a siphon-nozzle burner.
The drip style burners can make smoke, and puddle fuel in the bottom of the furnace, etc., which I why I don't use them.

As far as smell, I can't smell diesel, but my wife can, so I guess my sense of smell is gone.
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This photo is right after the compressed air and diesel have been turned on, but before adding combustion air.
There are flames, but they are blue/yellow, and so not really very visible.
No smoke though.





This photo is a few seconds later when the combusion air blower is turned on.
Large yellow flames for a few seconds, and then the flames settle into the furnace.
Again, no smoke.
The large flames are the cardboard under the crucible burning, along with the paper towels that are in the bottom of the furace as a fire starter.
The cardboard prevents the crucible from sticking to the plinth.
I don't do any sort of incremental ramping up of the blower; it is full power all at once, and as soon as you close the lid, you can begin the melting process.




This is the furnace about 60 seconds after starting, and it is operating at about 2.7 gal/hr diesel.
You can only see the slightest hint of flame inside the furnace.
I am in the process of swinging the lid closed.





And here is the furnace operating, melting gray iron.
There is no smoke before, during, or after operation of the furnace.
Diesel burns very cleanly.
The infrared heat coming out of an open furnace when it is at maximum temperature is most impressive.
The video makes it look rather tame.
I hold up a refrigerator shelf as a shield, so that my faceshield does not melt when I bend over to look into the lid opening.




Edit:
The only way my next door neighbor can tell I am running the furnace is due to the low frequency roar/rumble.
I have since added rubber pads under the wheels, to stop transmission of the rumble.
I am planning on locating the blower remotely inside the shop, so that will further reduce the noise.

I am aware of one individual who added a noise reduction stack, about 8 feet tall, lined with ceramic insulation, and that worked very well with reducing the roar. His neighbor was complaining. He also installed his blower in a box.
His furnace is extremly quiet now, and far less noisy than a lawnmower.

Here is a random diesel-fired foundry furnace.
Probably a siphon-nozzle style.
Very clean operation.

abby said:

it is illegal to burn waste mineral oil in the UK without a license issued by local authorities.

Click to expand...

In Australia they are not so petty making it mandatory to have a license to burn waste oil.

Jasonb said:

Isn't the waterfall partly due to the full large crucible they are using and the distance from edge of flask to where they are pouring.

Click to expand...

This is why I never put a pouring sprue in the middle of a box, always on the edge and make sure that the box is above ground level so it is easier to pour a full crucible.

So which is the better option, position the sprue to best feed the work, or position to give the best pouring position?

Opinions vary on all things foundry, but the bottom line is that you should be able to repeatedly create defect-free castings with the methods and materials that you use.

I locate the sprue either in the corner of the flask, or centered at one side, and generally have runners (shaped like a horse shoe) and gates on both sides of the cavity.
If the runners are not the same length, then one side of the cavity will fill before the other, which may or may not be a good thing (probably not a good thing).

If you don't have spin traps on the ends of the runner(s), and if your gates are not at the top of the runners, then you will not sweep/clean the sprue/runner system prior to the mold beginning to fill, and you will not sweep out the initial aspirated air that is mixed into the melt when you first begin pouring, and you will have defects in at least some of your castings.

I use the gates for velocity control, so that the sprue can remain full at all times.
There are other ways to do velocity control, but this way works well.

And the bottom of the sprue should transition smoothly into the runner(s).

For hand pours, I may go up to a #16 crucible, but above that things get pretty heavy, and so I have a pouring cart for crucibles above #16.
100model also uses a pouring cart with great skill.
I know of a guy in the pacific north west who also uses a pouring cart with good success.

It is more a matter of having sufficient space around the molds to manuver the cart and/or pouring shank.
You can generally always get the lip of the crucible very close to the top of the spure, with either a pouring cart or pouring shank.

So my answer is that the spure should be located to best feed the mold cavity, but generally that is at the corner or side of the mold.
Putting the sprue in an odd place almost guarantees that some of the castings will have defects in them.

Nothing worse than machining an engine casting, and finding a big hole concealed in the center.
Holes in castings can be directly attributed to sprue/runner/lack of spin trap/and gating issues.
Sometimes the sand mold fails in spots, and causes a sand inclusion, but I don't have that issue with bound sand.

And if you watch 100model's pouring technique, it is one of the best I have ever seen.
Crucible lip very close to the sprue opening, no pour basin, fill the sprue very quickly, and keep the sprue full during the entire mold fill.
So many people start a pour, then wander all over around the sprue opening, not keeping the spure full and causing an interrupted pour, and that entrains air into the melt.

I have copied a lot of what 100model does, mainly because he repeatedly makes high quality iron castings.
I use a modified John Campell/Bob Puhakka method for the spure/runners/gates/spin basins.
Bob Puhakka has modified his methods over time, and I think is now using some gravity fills, but I use one of his early methods, and it works very well, so I stick with that method.

Art iron pours are a good example of how not to pour iron for engine parts.

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Here is 100model's pouring cart video.
My cart is similar, except I use larger wheels so I can roll in the grass if desired, and so I have more height.
I removed the rubber from my tires, since sooner or later you will probably melt the rubber.

Here is the guy from the Pacific North West, who uses the silencer on his furnace, due to noise complaints.
He has since changes his tires to cast metal (no rubber).

If you use his lift mechanism, be sure you have large enough outriggers, since it is very easly to flip over the entire furnace with this sort of swiveling mechanism.

This guy gets some pretty good results with gray iron, especially with long narrow mold cavities, but I don't really consider him in the same league as 100model as far as overall breadth and width/time/knowledge base, of gray iron casting work.
This guy does listen and learn, and so he is constantly improving his techniques, and getting better with time.

Jasonb said:

So which is the better option, position the sprue to best feed the work, or position to give the best pouring position?

Click to expand...

Using a sprue to feed a casting is not a good idea, risers should be located close to thick sections so they can feed them. I used to pour down risers located in the center of a box but it makes it hard to pour and can draw in air, dross etc. So if that is your only option to pour in the center of your box do it when the crucible is only half full.