Home foundry blunder

[creast]

Today I was testing my new home built diesel fuel burner for the furnace which itself is working a treat.
I melted half an A2 crucible of brass scrap in just 5 minutes which pleased me no end and duly poured it into a muffin tray as normal as two nice ingots.
Then I decided to melt some copper pipe scrap which took a little longer and poured the muffin ingots.
That was a big mistake!
Unlike Aluminium and Brass muffins which just fall out when cool the copper ingots bonded to the tray itself and I had to chisel them out complete with steel skin bottoms!
Doh!!

 

[GreenTwin]

A properly designed and tuned diesel foundry burner is a marvel.
I call a diesel burner "a poor man's induction furnace".

Here are typical heat values you can get out of a diesel burner, assuming you tune it correctly with the right amount of combustion air (tuning is critical):

1 gal/hr = 138,500 Btu/hr (40.59 kW)
2 gal/hr = 277,000 Btu/hr (81.18 kW)
3 gal/hr = 415,500 Btu/hr (121.77 kW)
4 gal/hr = 554,000 Btu/hr (162.36 kW)

There is no way I could get 122 kW out of my home electrical panelboard.
That would be 508 amps at 240 volts single phase.

When melting aluminum, one has to be very careful not to overheat it with a diesel burner.
I can have an A10 full of aluminum (about 20 lbs) to pour temperature (1,350 F) in 12 minutes with my diesel burner.

I don't use muffin tins for ingot making, but I do have some steel molds made from angle iron.
The ends of the mold are sloped to allow ingot removal.
And I let my ingot molds get rusty, and don't clean them, which pretty much assures release of the ingots.

I made the mistake of not preheating my ingot molds hot enough, and one of them poppped the molten iron out onto my jacket, and some ran into my gloves.
Ingot molds have to be preheated pretty hot, say in the 500-600 F range or perhaps a bit more, else the residual surface moisture can toss the molten metal right back in your face.

I have not tried to melt copper, but I do have a recipe for lead-free bearing bronze that I want to try.

I welded handles on my ingot molds so I could hold them over the furnace exhaust stream to preheat them.
The ends of the mold slope about 3 degrees.

 

[creast]

My setup is on a much smaller scale about 1/2 gal / hr but so far seems to do the job well and is much faster than my propane burner but the gas is definitely cheaper to run. Diesel over here is about £1.80 per litre!
If I could source some heating oil/Kero then the savings would be much improved.
My previous oil burner was a siphon nozzle and I got sick of my compressor cutting in all the time so this design uses a gear pump which I designed and built and uses a blower with variable speed controls on both.
It runs very quiet, much quieter than the propane Reil burner.

 

[GreenTwin]

I am using a siphon nozzle burner, but am building a pressure nozzle burner with gearpump.
The gearpump requires a fraction of the electricity/power that an air compressor does.

I am told that the key to successful gear pump operation is to use a good spin-on fuel filter ahead of the pump, and have also been told that the slightest dirt in the fuel will lock the pump.
I have a spin-on filter that I will use.

Do you have a feedback needle valve with return line to the tank, for flow control?

The opposite is true here about diesel and kerosene.
Kerosene in this part of the country is treated like some sort of rare commodity, and is about 4 times more than diesel.
I think heating oil in other parts of the country may be somewhat less expensive.
This part of the country is natural gas in the city, and propane in rural areas.

.

 

[creast]

My setup is rough and ready at the moment as I wanted to see if it worked before finalising.
The gearpump is tiny, I used gears from a small planetary gearbox and they are only 10mm OD x 6mm wide. The pump is approx 1" dia and about same in length and has a capacity of 0.18cc/rev giving 0.65 l/min at 3600 rpm.
However I don't run it that fast and usually under 1000 rpm, just fast enough to provide the 100psi required by the nozzle. Speed control of the DC motor enables some flow control but dropping below 80psi affects nozzle performance.
Power consumption is a mere 7W.
I put the basic design on GrabCad but for this actual unit I dropped the shouldered shaft/keyed drive gear and simply soldered the gear to the shaft which working fine at present.
https://grabcad.com/library/micro-gear-pump-1
A pressure relief valve ensures max pressure set to 120 psi and discharges in the reservoir. I am sure the pump will go higher but there is no need and also I am running through nylon pneumatic fittings rated 150psi max.

The pump has no seals so is mounted vertically so any external leakage from shafts etc simply drips back into the reservoir.
I have not fitted a strainer as yet to the inlet since I am using clean diesel in a clean stainless reservoir but probably will do later.
The blower is from a cordless vacuum cleaner and again is controlled by variable DC unit. All power is from a repurposed AT computer supply at 12v.

I am still unsure whether to fit a swirl vane to the nozzle, again I was impatient to get an actual test done so I will put it on the list

 

[Len6163]

Today I was testing my new home built diesel fuel burner for the furnace which itself is working a treat.
I melted half an A2 crucible of brass scrap in just 5 minutes which pleased me no end and duly poured it into a muffin tray as normal as two nice ingots.
Then I decided to melt some copper pipe scrap which took a little longer and poured the muffin ingots.
That was a big mistake!
Unlike Aluminium and Brass muffins which just fall out when cool the copper ingots bonded to the tray itself and I had to chisel them out complete with steel skin bottoms!
Doh!!

I would just like to offer a suggestion in regards to releasing pours from molds, many years ago I worked for a mining company in western australia and was involved in the gold pouring and to assist with releasing the ingots from the molds we would prep them doing the following. Using the bottom third of a metal 44 gallon drum with a sheet of steel mesh on top (size is not important so long as it supported the molds, then took a steel bar and wrapped the end with cheese cloth having an approx 100mm wide wrap on the end which was wired in place. the end of the torch was soaked in diesel and ignited the now flaming torch was them placed in the drum under the molds. the inside of the molds would become covered in soot. a few minutes would do the trick a thick layer of soot would coat the inside of the molds. The soot acts as a release agent and I never had an ingot stick in a mold that had the soot treatment. Hope that helps someone.

 

[GreenTwin]

Creast-

That is a very sophisticated setup, and very clever design.

I am using a more low-tech approach.

I have been using stock heating unit parts, such as a Suntec gear pump, and Delavan pressure nozzle.
I am going to run the pump at 7 gph, and just bleed the extra fuel back to the fuel tank via a needle valve.
My furnace only needs 2.7 gal/hr.

I am looking foward to not having to use an air compressor anymore.
It takes a little time to build a pressure burner, but I think it will be worth the effort.

My motor is 1/3 hp, which is far larger than it needs to be, but is what I ended up with.
The main thing is portability.
I sometimes transport my furnace to art-iron shows, but they have to have a good air compressor.

The pressure nozzle burner will allow me to operated with just a very small 120V circuit for the gear pump, and a little more 120V power for the leaf blower.

.

Edit:
I have tried spin vanes, and no spin vanes, and I have never been able to tell any difference in furnace operation.
So these days I don't use a spin vane.
I think the spin vanes are more for the benefit of discharging the burner into a large open heating unit combustion chamber.
For a furnace, the burner discharge is immediately swirled around the inside of the furnace, and so there is really little time for a spin vane to work, but that is just my guess.

 

[creast]

I would just like to offer a suggestion in regards to releasing pours from molds, many years ago I worked for a mining company in western australia and was involved in the gold pouring and to assist with releasing the ingots from the molds we would prep them doing the following. Using the bottom third of a metal 44 gallon drum with a sheet of steel mesh on top (size is not important so long as it supported the molds, then took a steel bar and wrapped the end with cheese cloth having an approx 100mm wide wrap on the end which was wired in place. the end of the torch was soaked in diesel and ignited the now flaming torch was them placed in the drum under the molds. the inside of the molds would become covered in soot. a few minutes would do the trick a thick layer of soot would coat the inside of the molds. The soot acts as a release agent and I never had an ingot stick in a mold that had the soot treatment. Hope that helps someone.

Yes!! I completely forgot about that method.
I guess I got just so complacent doing Brass and Aluminium but 'sooting' would benefit all metals. Thank you!

 

[creast]

Creast-

That is a very sophisticated setup, and very clever design.

I am using a more low-tech approach.

I have been using stock heating unit parts, such as a Suntec gear pump, and Delavan pressure nozzle.
I am going to run the pump at 7 gph, and just bleed the extra fuel back to the fuel tank via a needle valve.
My furnace only needs 2.7 gal/hr.

I am looking foward to not having to use an air compressor anymore.
It takes a little time to build a pressure burner, but I think it will be worth the effort.

My motor is 1/3 hp, which is far larger than it needs to be, but is what I ended up with.
The main thing is portability.
I sometimes transport my furnace to art-iron shows, but they have to have a good air compressor.

The pressure nozzle burner will allow me to operated with just a very small 120V circuit for the gear pump, and a little more 120V power for the leaf blower.

.

Edit:
I have tried spin vanes, and no spin vanes, and I have never been able to tell any difference in furnace operation.
So these days I don't use a spin vane.
I think the spin vanes are more for the benefit of discharging the burner into a large open heating unit combustion chamber.
For a furnace, the burner discharge is immediately swirled around the inside of the furnace, and so there is really little time for a spin vane to work, but that is just my guess.
View attachment 144415

I wouldn't say it is sophisticated, more like a 'Heath Robinson' lash up as we say here.
However, I am pleased so far and will pursue it further and maybe do a vid at some point... early days yet
Your setup is somewhat more demanding due to the scale of melt quantities etc and I wish you success in its development.

I am like minded about swirl vanes too so I am not too concerned at this stage.

Rich

 

[awake]

Rich, thanks so much for sharing the design of the gear pump! Very interesting indeed.

 

[creast]

Rich, thanks so much for sharing the design of the gear pump! Very interesting indeed.

No problem.
In hind site I would probably shift the collar feature on the shaft outboard with a retainer/ thrust bearing washer just to remove any potential face leakages of the gears and I would also change the key method of the drive gear to a cross pin and scallops in the gear if you get me?
I did work on similar pumps during my apprenticeship around 50 yrs ago! Just trying to remember details.. lol!
As I said in earlier post, my prototype has a simple plain shaft with the drive gear fixed by soldering. A helical coupling ensures no axial loading and it works.
Rich

 

[GreenTwin]

Siphon nozzle burners can be scaled up or down over a pretty wide range.

You can operate them with or without combustion air.
They will naturally aspirate and draw in their own combustion air, but for iron melts, or faster AL/Brass/Bronze melts, people use a combustion air blower.

For larger furnaces, they can be stacked one over the other on the side of the furnace, separated by perhaps 10 inches vertically.

I have also seen them used in a 180 degree dual burner fashion with good success.
I tried a duel 180 degree burner a few years ago, but unfortunately at the time I was ignorant of how to correctly tune an oil burner, and so I did not realize what a promising configuration this was. At some point I will to back to a dual 180 degree configuration on my furnace.

There are a several drip-style oil burners used online to melt iron and other metals, and there is much to be said for the simplicity of a drip-style, but for fine and accurate/immediate control, the siphon or pressure nozzle is unparalleled.

Beautiful work Rich, and an inspired design in my opinion.
Thanks for sharing that.

Pat J

 

[awake]

Pat or Rich, I am slowly working on a furnace, and once it is complete will be working on a diesel burner. I am curious about how much air flow you find that you need. Would something like a hair dryer produce enough, or does it need to go all the way up to a leaf blower, or ... ??

 

[L98fiero]

I would just like to offer a suggestion in regards to releasing pours from molds, many years ago I worked for a mining company in western australia and was involved in the gold pouring and to assist with releasing the ingots from the molds we would prep them doing the following. Using the bottom third of a metal 44 gallon drum with a sheet of steel mesh on top (size is not important so long as it supported the molds, then took a steel bar and wrapped the end with cheese cloth having an approx 100mm wide wrap on the end which was wired in place. the end of the torch was soaked in diesel and ignited the now flaming torch was them placed in the drum under the molds. the inside of the molds would become covered in soot. a few minutes would do the trick a thick layer of soot would coat the inside of the molds. The soot acts as a release agent and I never had an ingot stick in a mold that had the soot treatment. Hope that helps someone.

When I first started machining in the 70s the foreman trained me to pour Babbitt bearings, that was the release agent there, too. The difference was that it was just put on with a very carburizing, little to no oxygen, oxy-acetylene flame.

 

[GreenTwin]

Pat or Rich, I am slowly working on a furnace, and once it is complete will be working on a diesel burner. I am curious about how much air flow you find that you need. Would something like a hair dryer produce enough, or does it need to go all the way up to a leaf blower, or ... ??

I will start a separate thread so as not to sidetrack Rich's thread.
I am sure Rich will have his own response.

https://www.homemodelenginemachinist.com/threads/how-to-tune-a-foundry-oil-burner.34966/
.

 

[rutzen]

Hi, I would like to ask if anyone has tried using a conventional oil central heating boiler burner for a furnace? I am in the UK and can get kerosene for central heating easily. I have successfully used a waste oil burner in the past [Colin Peck's design] and cast a set of wheels for a 5 inch gauge locomotive, also bronze cylinders. However this is very messy stuff to burn and I would like a cleaner setup. I already have such a burner which is why I ask the question.

 

[creast]

Hi, I would like to ask if anyone has tried using a conventional oil central heating boiler burner for a furnace? I am in the UK and can get kerosene for central heating easily. I have successfully used a waste oil burner in the past [Colin Peck's design] and cast a set of wheels for a 5 inch gauge locomotive, also bronze cylinders. However this is very messy stuff to burn and I would like a cleaner setup. I already have such a burner which is why I ask the question.

Yes. I tried one at first but the burner diameter was way too big for the scale of furnace I intended and the fuel consumption very high.
A work colleague did use one for melting scrap aluminium (cylinder heads) into ingots.
Personally I would go either siphon nozzle or better still a scaled down equivalent of the central heating burner.

 

[creast]

I will start a separate thread so as not to sidetrack Rich's thread.
I am sure Rich will have his own response.

https://www.homemodelenginemachinist.com/threads/how-to-tune-a-foundry-oil-burner.34966/
.

Thanks Pat.
I think the answer lies in just how big a furnace you need and the method of fuelling.
Siphon nozzles work well and from my experience they need only a little extra air since compressed air is being blasted in too.
My problem with siphon nozzles was the compressor continually cutting in and very noisy. My regulator also dropped during the compressor recharging and was constantly having to be readjusted.
This furnace used an old car heater blower on variable speed 12v supply and worked well.
My latest uses a fan from a cordless vacuum cleaner, again on variable supply 12v and is plenty good enough for the job and quieter.
Leaf blowers seem overkill unless you have massive furnace and doing iron.
My first furnace with car blower is here

 

[awake]

Thanks Pat.
I think the answer lies in just how big a furnace you need and the method of fuelling.
Siphon nozzles work well and from my experience they need only a little extra air since compressed air is being blasted in too.
My problem with siphon nozzles was the compressor continually cutting in and very noisy. My regulator also dropped during the compressor recharging and was constantly having to be readjusted.
This furnace used an old car heater blower on variable speed 12v supply and worked well.
My latest uses a fan from a cordless vacuum cleaner, again on variable supply 12v and is plenty good enough for the job and quieter.
Leaf blowers seem overkill unless you have massive furnace and doing iron.
My first furnace with car blower is here

Looking at this video, and comparing Pat's "tuning" instructions in another thread - does the height of yellow flames here suggest that it could use a bit more air, or is this about what one should look for?

 

[creast]

Andy,
To be honest I really didn't have a clue what was correct when I made that short clip as it was experimental.
I do know that when I overdid the air it made the burn seriously cooler. In fact I was misguided that it should burn with a blue flame like propane and soon found this is not the case with oil fired burners.
Pat's tuning info is very useful and I will endeavour to do tests on my setup but no way would I use a 2-3 gal/hr setup with UK diesel costs, mine is only 1/2 gal/hr .
If you look at domestic boiler burners they do run with a yellow flame to enable complete burn of the oil droplets so it was a bit of a learning curve which I didn't really follow too long before going back to propane or electric.
The furnace was way quicker than the others but a bit of a faff to run i.e compressor, heating waste oil etc .
I am not sure, for what I cast, if I will use the diesel burner that much but it is something I have pondered on for years and enjoy the challenge to scratch my head and see if I can. As they say 'it's the journey, not the destination'.
Another point of concern is the event of a flameout which is possible for several reasons and can result in oi/diesel being sprayed into a hot furnace resulting tons of toxic smoke and more seriously a potential explosive re-ignition.
This has only happened to me once but did cause quite an arse nipping sensation!
Rich