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[GreenTwin]

Furnace #2:

 

[GreenTwin]

Furnace #2:

 

[GreenTwin]

Furnace #2:

 

[GreenTwin]

Furnace #2:

 

[GreenTwin]

Furnace #2:
I would never build another furnace without using some plastic refractory, especially for the domed lid.

Two layers of 1" ceramic blanket go over the insulating fire bricks, and then the stainless shell on the exterior.

 

[dazz]

Hi
Furnace 2 looks like the product of a lot of learning and experience. Nice.

If you did use your design below, you should extend out the end of the spiral slightly, so as to start to turn the air before it strikes the flat wall on the left, otherwise you could disrupt the combustion air flow.

Hi
I had considered this because I think the spinning air flow could collide with, and distort the combustion zone.
So I thought that rather than mold a flat base, I could mold in a spiral ramp that raises the hot gas to just above the turere. It is likely that the hot gas will spiral upwards anyway. so maybe not an issue.

I could start with a flat base, then try just placing molded wedge shaped bricks on the base to form a spiral ramp. Easy to try.

One of the advantages of using close fitting morterless bricks made with 3D printed molds that I posted much earlier, is that I can produce bricks in any shape quite easily. If I do things right, it should be easy to dismantle/assemble the hot liner bricks for maintenance or replacement. More importantly, I could make changes to the furnace shape by just changing the affected bricks. Ideal for experimentation.

Dazz

 

[GreenTwin]

It is likely that the hot gas will spiral upwards anyway. so maybe not an issue.

I think you are right about that.

I could start with a flat base, then try just placing molded wedge shaped bricks on the base to form a spiral ramp. Easy to try.

Another good idea I think.

One of the advantages of using close fitting morterless bricks made with 3D printed molds that I posted much earlier, is that I can produce bricks in any shape quite easily. If I do things right, it should be easy to dismantle/assemble the hot liner bricks for maintenance or replacement. More importantly, I could make changes to the furnace shape by just changing the affected bricks. Ideal for experimentation.

A LEGO furnace !
Yes not a bad idea at all, and there are commercial furnaces that are made in a similar modular way, which does allow for easy brick replacement.
If you have access to plastic refractory, you may not need to replace bricks, but you never know.

I think I linked this previously, and added the parts that I don't agree with that are stated in the MIFCO manual.
See page 34 for a B-301 furnace.
A B-301 is about the same as my furnace build #2.
Note that the B-301 is a dual-burner furnace, with two tuyeres at 180 degree spacing.

https://mifco.com/wp-content/uploads/2019/12/B-C-furnace-manual-revised-12-19.pdf
.

 

[Foketry]

Furnace #2:

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exceptional work !!!
what material did you use for (120 lbs of cast refractory) ?
how thick is it ?

 

[GreenTwin]

The hot face is 1" thick Mizzou.
The 120 lbs includes the refractory for the lid, which is also Mizzou.

 

[Ed T]

When you say "fuel oil gun burner", I assume you are talking about a packaged burner unit like the Beckett unit below?
View attachment 127437

I have seen one person use a packaged burner system with their furnace for a while, and then they changed to a more traditional burner tube / nozzle arrangement with remote mounted gear pump.

Packaged Burner Assemblies:

There are several problems I see with using packaged burner with a foundry furnace, as follows (I have not used a packaged burner):

1. A packaged burner is a rather bulky assembly, and that would make getting the burner tube in exactly the right place at exactly the right elevation would be far more difficult than just a burner tube.

2. The output tube appears to be about 4" diameter, which is really too large for many/most furnaces used for hobby work.
I guess the output tube could be changed to a 2.5" diameter tube?

3. All furnaces sooner or later will leak hot gasses past the burner tube at the tuyere (the tuyere being the entrance low in the furnace).
When the tuyere leaks, and generally before you notice that it is leaking, anything that can be ruined/melted in the vicinity of the tuyere is melted/ruined, such as a packaged burner unit.

4. When a furnace is open, and the crucible is pulled out and set on the ground, the radiant heat is very intense (this is especially true for an iron furnace).
The radiant heat will melt plastic 10 feet away, so I tend to think that over time it would ruin a packaged burner unit.

5. My general rule is that anything in the furnace area (say a 20 foot radius around the furnace) should not be plastic; this includes wheels, and anything else.
There are a lot of furnace photos out there with melted plastic wheels, and melted plastic burner parts/gauges, etc.
The only thing that is plastic/rubber in the furnace vicinity is the fuel line, and that is somewhat at risk.
I intend to slide a piece of flexible metal conduit over my fuel line, to give it mechanical protection, and also to give it heat protection from spilled metal/slag.

Comments on hot-tube burner designs:

The burner tube should remain cool to the touch along most of its length, except perhaps right at the furnace end, which may get a little warmer, but not really hot. There is a school of thought that the burner tube should be operated red hot, and a type of burner that uses a flame impingement out of the side of the furnace and onto the burner tube, I guess with a drip-style burner, to assist with atomization of dripped fuel.
I think that for a typical backyard foundry application, there is no need to run a hot-burner-tube design, and many many reasons why you should not run a hot-burner-tube design.

The main reasons that a hot-burner-tube design is not desirable is that it tends to cook whatever is inside the burner tube, and build up varnish on the hot surfaces, and the burner tube steel will degrade over time, even if it is stainless steel.
But the #1 reason why I don't use a hot-tube-burner design is that it does not work any better than a cold burner design, and I have seen some folks have a lot of problems with their hot-tube burners.
Why introduce new "features" to a burner that are known to cause problems? (Short answer: Because you can get millions of views and likes on ytube featuring all sorts of Rube Goldberg burner deigns).

There are folks out there who make burners and such seemingly only for the purpose of proving that they can make a better (new and improved better mouse trap) burner, and so there are droves of burner styles that actually will melt metal well, and they are almost universally of a bad design from the standpoint of providing a maintenance-free burner that operates consistently every melt without the need for adjustment during the melt.

There are folks out there who embark on multi-year Don Quixote type quests to design and build the ultimate foundry burner.
The problem is their quest never seems to lead to a functional new burner type, or if the burner does function, it functions in a highly unreliable way that often will not melt iron.
There are numerous burner folks out there in videoland, and many/most never cast anything, or anything of any value other than a lump of metal.
For the professional burner builders, its not about foundry work and casting usable parts; it is about endless burner experiments, and maximizing ytube views.

I have done my share of burner experiments, and have done enough to have a good feel for what works for an oil burner.
When it comes to oil burners, I can say that a cool burner tube and proper atomization of the fuel are what is important to good burner operation.
Beyond that is just a matter of how you want to assemble the parts.

I have never gotten a drip-style oil burner to operate or control correctly, or burn cleanly at all output levels, and so I don't use that style.
A siphon nozzle burner will burn cleanly and control precisely at any fuel flow level within its designed operating range, which is a very wide range of outputs.
A siphon nozzle burner will operate without combustion air (it will naturally aspirate if the combustion air tube is left open), for smaller melts, and most folks are not aware of this function.

Summary:

My siphon and pressure nozzle burners weigh perhaps 5 lbs, and their critical components are located far away from the furnace, out of heat range and spilled metal danger.
It is easy to support my burner tube at the tuyere, and easy to adjust the height of my burner tube to work with multiple furnaces (I have more than one furnace, and the tuyere heights are not the same).

Everyone has their favorite burner and melting methods.
I can't say what works best for others, but I can say what has proven to work well for me.
To each their own, but in my mind the real proof is in the quality of the castings created.
"Show me the castings" as they say, and then we talk about burners.

Edit:
I do know of folks who make very good castings, and use very problematic burners.
They use the fact that they can make very good castings to justify using their problematic burner style.
I make quality castings, and my burner is maintenance-free, and does not require adjustment every.
I see no justification for using equipment that is problematic. Would you drive a car that breaks down constantly? Some do; I am not sure why.

.

Thanks for taking the time to reply and for the experience based insight.

 

[dazz]

A LEGO furnace !

Yes that's it.

Nice job on your hot liner.

The thing that is delaying my attempt at furnace building is a queue of unfinished projects. If I started building a furnace, that would only add to the list of unfinished projects. In the mean time I am looking and learning.

You have made repeated references to the amount of radiant heat from the crucible after removal from the furnace.
I see a piece of sheet metal if often fitted to the lifting handle to shield the hands.
Has anyone considered using a light polished stainless steel shield around the crucible to reflect the heat back to the crucible??
Obviously the shield would need cutouts to avoid interfering with the pour, but even if the shield could wrap half way around, the radiated heat loss would be a lot less.

The melt should stay hotter for longer.

 

[GreenTwin]

The think that is delaying my attempt at furnace building is a queue of unfinished projects. If I started building a furnace, that would only add to the list of unfinished projects. In the mean time I am looking and learning.

I know the feeling well.

Has anyone considered using a light polished stainless steel shield around the crucible to reflect the heat back to the crucible??
Obviously the shield would need cutouts to avoid interfering with the pour, but even if the shield could wrap half way around, the radiated heat loss would be a lot less.

A shield around the crucible would most likely get in the way of pouring.
The trick with keeping the metal in the crucible at pour temperature is to do most of the skimming in the furnace.
I do the initial skim with the furnace/burner running, and use a long handled skimmer (I will be adding a heat shield to this skimmer), reaching through the opening in the lid.

I do another skim with the lid open, sometimes with the burner running, and sometimes not.
Often this skim is the last one I do, and unless I spot something floating, I don't skim the melt outside the furnace.

And I add ferrosilicon and stir it in while the crucible is in the furnace.

I like to do the lift out and pour within 60 seconds maximum, with iron, to keep the pour temperature as high as possible.
I have not measured the time-to-pour after I pull the crucible, but I will do that.
30 seconds would be even better.

Iron cools down very quickly after you pull the crucible out of the furnace, and you have to work fast, else you will get a partial mold fill.
With an induction furnace, or a cupola, it seems you can get some superheat with iron, and get an elevated pour temperature above what an oil furnace would produce, so you have a bit more time after pulling the crucible.

The art-iron folks use a synthetic ladle, which is quite light; I am not sure what the material is, and it is insulating, so the have a lot of time after tapping the cupola.

The art-iron folks often use old radiators, which have phosphorus in the iron, and so between that, the ferrosilicon, and the insulating ladle, and the cupola superheat, they seem to mill around for ages with the iron in the ladle before they pour.
You can't do that with a crucible with iron. It basically has to be poured almost immediately after pulling the crucible.

 

[dazz]

View attachment 127060

Hi
Are you willing to post a CAD file of this drawing?
I want to change the dimensions to metric and blatantly plagiarize it.

Dazz

 

[dazz]

VelvaCoat from ASK Chemicals LP
495 Metro Place South
Suite 250 Dublin, OH 43017
Phone: +1 800 848 7485
Fax: +1 614 761 1741
[email protected]
www.ask-chemicals.com

Download their PDF catalog which includes water-based products;
https://www.ask-chemicals.com/filea...oundry_products_brochures/US/Coatings_USA.pdf

Good luck,
Larry

Has anyone purchased from this company and used their product for iron casting?
Do they sell their products pre-mixed or as a dry powder?

Dazz

 

[GreenTwin]

Has anyone purchased from this company and used their product for iron casting?
Do they sell their products pre-mixed or as a dry powder?

You generally have to go through a distributor in your area.

.

 

[GreenTwin]

Are you willing to post a CAD file of this drawing?
I want to change the dimensions to metric and blatantly plagiarize it.

PM sent.
.

 

[dazz]

You generally have to go through a distributor in your area.

That guarantees it is unobtanium for me. I doubt there is a distributor within a few thousand miles.

 

[dazz]

What is the recommended face shield??

The "proper" protection is gold coated but these are expensive. More so for me because I have to pay $$$$$ for shipping.

This video Casting explosion and the importance of face shields shows people wearing a variety. Clear and tinted plastic. The metal mesh type, normally used by forestry workers.

I am thinking that the tinted plastic will likely melt as it absorbs/blocks the infra-red. The mesh type look like a good option, combined with welding/safety goggles underneath.

 

[dazz]

And I read a post today about making thin parts in machinable gray iron.
I have read in several books that iron with high phosphorus should not be used to make engines.

So this guy who made a mini-V8 in gray iron said "I had to use old radiator scrap, which is high in phosphorus, due to its high fluidity".

LOL, so much for never using high-phosphorus iron for engine parts.

.

I can't see how radiator scrap could make good iron for engine parts.
My plan is to use cast iron engine blocks because the metal properties and quality of the iron would be optimised for long engine life.

 

[dazz]

It has been about 20 years since John Campbell published his first book on casting, yet I rarely see examples of his guidance being applied.
Here is an example of casting the John Campbell way. Only worth watching the first half.