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Backyard Foundry - oil burning furnace - moulding and casting a spider

this is the start of my dads youtube channel

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Dave Wilson 408/12/2021 11:02:54
6 forum posts

My dad casts a lot of parts for his steam engines but due to a shortage of solid fuel here we are switching to oil/diesel. This is our burner at experimental stage, hope you enjoy

Testing an waste oil burner

Moulding a spiders body from a carved pattern

Casting the body in zinc

Engine related casting to come

Luker08/12/2021 11:55:40
160 forum posts
116 photos

Hey Dave, Nice videos! Glad to see other foundrymen on the site! Some humble advice for your burner... If you ignite the oil in the furnace and combine it with the vacuum inlet you'll get better and cleaner combustion. The furnace will also run much hotter. For anything with a melting point below cast iron you probably don't need any diesel. Here's a section of a video with my setup... hope I've done this right.

Dave Wilson 408/12/2021 12:02:27
6 forum posts

Cool video Luker! Very nice editing.. We are intending to use it for cast iron once its tuned a little more.


Edited By Dave Wilson 4 on 08/12/2021 12:13:10

Luker08/12/2021 13:10:03
160 forum posts
116 photos

Thanks Dave... videos aren't really my thing, was actually for a FEA conference I presented at.

There's quite a step in heating requirements for cast iron compared to zink and the brasses, but with diesel added you shouldn't have any issues. Please keep us updated!

noel shelley08/12/2021 14:18:41
1298 forum posts
21 photos

Dave , It is good to see people trying foundry work, it's not the black art some would have you believe, as you are proving ! As Luker has said feed the air in with the fuel, it will burn both cleaner and much hotter. The yellow flame indicates unburn carbon. The amount of heat you will need for cast iron is many more times that for zinc. Will your furnace lining take white heat for may be an hour ? The burner should be at a tangent, causing the flame to swirl round the crucible. Use a needle valve to control the oil flow and filter the fuel to avoid blocking valve or jet. DO NOT use the same crucible for different metals and for cast iron a crucible will only last may be 6 or 8 melts before it will have wasted/ burn away to such an extent that it will be unsafe to use. For the size of the pattern the mold box was almost to small leaving little room for your runner or any gating as the runout on the casting indicated. Fitting handles to the mold boxes will make them much easier to work with. Since you seem to be going in for this I would recommend that you buy parting power (as the cornflower may cause blow holes as it burns) and for what it costs the bag that is used with it. When ramming the cope place the runner form in the required position, allowing for any gating and ram round it, there is less risk of damaging the mold if done after ramming, and open up the top to form a funnel to aid pouring. NEVER work on concrete , slabs or stone when using molten metal, any spills will cause and explosion under the molten metal that will shower all with droplets ! Ideally a sand floor but otherwise wood. Place the crucible on a ceramic surface to skim and the molds on the ground, NOT a bench or table ! For an improved chance of success in the non ferrous metals ( below 1200c) the use of a pyrometer will repay you handsomly. A handheld display and K type thermocouple is all you need. See you tube - Dubious Engineering- melting brass in a spin drier. You will see some of the above there. Keep us posted of developments. Good luck and best wishes Noel.

clogs08/12/2021 14:47:58
626 forum posts
12 photos

following with interest......

is gas, ie propane hotter than D fuel or not.....certainly cleaner to use.....

I want to cast bronze items.....getting close to serious about this.....

we do have a place near but they only work during the tourist season.....they manufacture small castings to go with/ display their custom glass works of art........

Luker08/12/2021 15:23:00
160 forum posts
116 photos
Posted by clogs on 08/12/2021 14:47:58:

following with interest......

is gas, ie propane hotter than D fuel or not.....certainly cleaner to use.....

I want to cast bronze items.....getting close to serious about this.....

we do have a place near but they only work during the tourist season.....they manufacture small castings to go with/ display their custom glass works of art........

Hi Clogs, there's more than flame temperature to consider in the mass transfer equations. Specific heat etc. Big melting temperature difference between cast iron and bronze. Bonze will melt no issue with propane, can be done in a ceramic fiber lined dustbin with a blow torch if you want to. Very difficult to get poor bronze castings if you do the basics right...

Oil fired furnaces shouldn't be dirty, mine runs clean. Certainly no smoke...

SillyOldDuffer08/12/2021 15:56:54
8516 forum posts
1915 photos
Posted by clogs on 08/12/2021 14:47:58:

is gas, ie propane hotter than D fuel or not ...

Propane, Butane and Methane all burn at a little under 2000°C. It's quite easy to get the flame up to temperature because the burner only has to mix gases in the correct proportion.

Too much air cools the flame, too little air and fuel is unburnt.

Diesel burns at between 1000 to 1400°C, so cooler than gases. As Bronze melts at 950°C, it can be seen Diesel won't work unless the burner is carefully adjusted to maximise flame temperature. Harder to do than with gases because liquid diesel has to be mixed efficiently with air before ignition, typically as an atomised spray or by vaporising it. Oil burners are more complicated to make and control.

Coke burns at about 1100°C but the temperature can be driven up to about 2000°C by blowing air through it. For foundry work, Coke has the advantage of storing heat in the solid, which means the temperature is less likely to drop when cold metal is added, or when extra latent heat is needed to convert from solid to liquid form.

They will all work, but I think Coke is easiest, gas a bit harder, and Diesel on the awkward side.

I'd steer clear of petrol: it has all the disadvantages of diesel plus spillages carry high risk of flash fires and explosions. Nasty stuff!


noel shelley08/12/2021 16:01:10
1298 forum posts
21 photos

Hi Clogs, as Luker has said Bronze no problem with propane. Needs about 100c more than brass, so 1150c or there abouts . If you see the youtube I listed you'll see brass being melted. Remember that to pour the metal it will need superheating to WELL above the melting point, which for brass is limited to about 1050c MAX. The problem with brass is that the zinc boils at 907c, hence the white smoke - zinc oxide - not good to breath and also the limit on super heat. Copper and tin boil at over 2000c so not an isue, though all copper alloys will with increasing temperature absorb oxygen - and the need for degassing sometimes. The burning temperature of the fuel can be raised by the addition of a small amount of oxygen, but now we're drifting out of the back yard !!!  Noel.

Edited By noel shelley on 08/12/2021 16:11:12

Edited By noel shelley on 08/12/2021 16:35:11

Luker08/12/2021 16:50:10
160 forum posts
116 photos
Posted by SillyOldDuffer on 08/12/2021 15:56:54:
Posted by clogs on 08/12/2021 14:47:58:

is gas, ie propane hotter than D fuel or not ...

Diesel burns at between 1000 to 1400°C, so cooler than gases. As Bronze melts at 950°C, it can be seen Diesel won't work unless the burner is carefully adjusted to maximise flame temperature. Harder to do than with gases because liquid diesel has to be mixed efficiently with air before ignition, typically as an atomised spray or by vaporising it. Oil burners are more complicated to make and control.

Dave you need to be careful interpreting information from the internet. Flame temperatures vary depending for what application the specific tests were done. Adiabatic flame temperatures of diesel can exceed 2300DegC if you run slightly lean. These tests were specific to diesel burners used in large industrial smelting furnaces. Diesel will most certainly melt bronze, in fact it melts pig iron, cast iron and I have even melted BMS in my furnace.

My burner is incredibly simple, with no nozzle and the diesel is fed by gravity. i.e. no compressed air. The fuel air mixture is easy to get right with a simple gate valve. I have melted using propane, waste oil, diesel and a few other fuels. You would be hard pressed to melt cast iron in a gas furnace without freezing the valve (depending on the ambient temp).

We need to be careful not to steer people in the wrong direction based on internet searches, especially when it comes to foundry work which is inherently very practical. The heat and mass transfer also requires an in depth understanding of the governing equations and not only the flame temperatures...

Dave Wilson 409/12/2021 15:56:31
6 forum posts

Thanks guys for all the comments and suggestions made in this thread!. The mixed feedback has inspired us to make more videos when we get the time. He has spent a lifetime filling cabinets with model steam boat and train engines, I'd like to see if we can get them running in future episodes.

My Dad also read this thread last night and took on board all of the feedback. He doesn't really like computers (whaa!?) So it takes time to post anything back. He sent one message but did it privately as he would like to remain as anonymous as possible... so thats why theres not much talking on the videos.

Dave Wilson 419/12/2021 23:27:27
6 forum posts

Part 3 of the spider tutorial is up, i know its not model enginering as such but some of the techniques may be useful to others.

Dave Wilson 402/01/2022 20:41:54
6 forum posts

For anyone following here is part 4

PatJ03/01/2022 08:15:40
334 forum posts
407 photos

I have been casting gray iron since 2012, and have tried a variety of fuels and burner types.

I use a siphon nozzle burner with diesel, but am converting to a similar pressure nozzle with gear pump to avoid having to have an air compressor for atomization air.

Cast iron can be melted with propane if you have a sufficiently large tank, or you carefully warm (without overheating) the tank as the gas is being used. The vapor pressure inside of a 20 lb propane take will drop too much as the tank cools, and so it is difficult to maintain enough pressure to melt iron (without tank heating).

I use diesel exclusively since it does not contain heavy metals, and it lights easily with a siphon or pressure nozzle type burner, without using propane.

I have started and run my siphon nozzle burner on diesel at 30 F.

Most I know mix at least 20-30% diesel with their waste oil to assist in starting and operating the burner.

The red hot burner tube type burners don't last long. A siphon and pressure nozzle burner tube run cool to the touch if operated correctly.

It is easy to melt cast iron, brass, bronze, or aluminum using diesel.

Generally a #10 crucible full of iron requires about 1 hour to bring up to pour temperature, which is extimated to be about 2,500 F.

A #10 crucible holds a little less than 30 lbs of iron.

Most folks I know run their oil burners at about 2.7 gal/hr, and the combustion air blower is adjusted to accomodate this fuel flow, using either a variable speed blower motor, or a dump damper to get rid of the excess blower air.

My casting videos are on Vimeo.

I will try to post a link here; hopefully it will work.

Good luck with your metal casting. I must say I really enjoy metal casting, and it creates unlimited opportunities as far as the engines you can make.

Hit the "scroll down" or "load more" at the bottom of the Vimeo page to get to my casting videos.
Note that the Elliot Bay Triple Expansion build videos are by a fellow named Randall Marquis.
The remainder of the videos are mine.

Edited By PatJ on 03/01/2022 08:16:13

Edited By PatJ on 03/01/2022 08:18:14

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Edited By PatJ on 03/01/2022 08:20:32

Edited By PatJ on 03/01/2022 08:21:13

Edited By PatJ on 03/01/2022 08:23:41

Edited By PatJ on 03/01/2022 08:24:32

noel shelley03/01/2022 10:34:00
1298 forum posts
21 photos

Hi Pat, Good to see another foundry man here ! I'm a propane man, but most of my work is in brass and an A6 will take about 20 mins. In the workshop I would connect 3 X 47Kg cylinders to avoid the bottles freezing and loosing pressure - it also enabled me to empty a bottle completely - my gas man would run his heating all winter on the contents of other peoples returned bottles ! When/or IF I ever get round to it I was going to use a redundant central heating burner as the heat source, running on diesel because it is a self contained unit only needing fuel and electric power. The only thing that might need changing would be the nozzle and adjustment of the air. I would hope that it would be efficient and clean, more so than the home made burners, and I have one. Are You in the UK ? Best wishes Noel.

PatJ03/01/2022 17:08:56
334 forum posts
407 photos

Hey Noel-

I am trying to get lots of people into making their own iron castings, but so far have only roped one into it, but he is doing it successfully.

The central heating unit is the same configuration that I am going to change to, except mine will not be a packaged unit, but will consist of the same parts mounted separately, to be more modular, and because I don't have a spare central heating unit.

Central heating units use a gear pump with pressure nozzle, generally operating at about 100 psi (that is where I will operate mine on diesel). And the beauty of them is that you don't need an air compressor, which is really what I am after. The siphon nozzle and pressure nozzle operate the same, except one uses compressed air for atomization and the other uses pressure from a gear pump.

I have tried a drip-style burner, an Ursutz which is a precombustion chamber type burner, dual nozzle burner, propane, etc. The siphon or pressure nozzle burner is the most reliable and infinitely controllable/stable burner that I am aware of, and no degredation over the life of the burner (which is infinite). Both of these burner types do need clean fuel that is well filtered, which is why I use diesel. Waste oil can be used, but generally it is thinned with diesel, and it must be filtered clean.

I use about 10 psi pressure on my diesel fuel tank with my siphon nozzle, but when I convert to a pressure nozzle, I will not pressurize my fuel tank.

Pouring iron is not much more difficult than pouring brass/bronze, and easier in many respects since you don't run into the zinc problems that brass has.

Using good heat shields on the skimmer handles and pouring shank is a must with iron, to prevent overheating the gloved hand. And gas welding goggles are required to shield the eyes from the intense IR that comes off the furnace and crucible.

If you want to pour iron, and are not exactly sure how to do that, I can save you a great deal of grief.

It took me six years (on and off) to master the iron process.

I am across the pond, but with the internet, we are all close, and brothers in casting for sure.

There is nothing like pulling fresh iron castings coming out of the sand mold (when all goes well that is).

Note, leave iron castings in the sand overnight to cool, else you will get hard spots in them.

Pat J

Edited By PatJ on 03/01/2022 17:14:10

Edited By PatJ on 03/01/2022 17:16:05

Edited By PatJ on 03/01/2022 17:16:51

PatJ03/01/2022 17:25:18
334 forum posts
407 photos

I meant to mention that I have seem some use packaged heating units for a foundry furnace.

The output burner tube on a packaged unit is generally about 4 inches diameter, which is a bit large, and may or may not impinge flame on the side of the crucible (which must be avoided).

I am installing my pressure nozzle inside of a 2.5" diameter thinwall stainless burner tube, and that diameter works well with my furnace, which has a 13 inch interior diameter, and a 14 inch interior height.

The burner tube entry should be at the junction of the top of the plinth and the bottom of the crucible.

I generally elevate my crucible on a plinth as high as possible in the furnace, leaving about 1.5" between the top of the crucible and the lid.

PatJ03/01/2022 17:36:16
334 forum posts
407 photos

I am still working out the exact details of my new pressure nozzle burner, but this is my progress to date.

The fuel line on the output of the pump is rate for 100 psi continuous, and I think is automotive injector fuel line.

I hope to get this unit operational this year.

Note that my initial rough sketch is not quite complete, so don't use it literally.

Fuel flow will be adjusted using the needle valve to about 2.6 gal/hr, and then the combustion air blower tuned for that fuel flow.  My combustion air blower is a varialbe speed Toro leaf blower running on its lowest speed.
















Edited By PatJ on 03/01/2022 17:38:15

Luker03/01/2022 18:08:29
160 forum posts
116 photos

Hi Pat,

Many ways to make a furnace… My furnace uses a simple atomization tube, and gravity to feed the fuel with a simple gate valve to control the flow. If the furnace is designed properly the tube should never get red hot and should only run a little over the vaporizing temperature of the fuel (the supply air keeps it cool). Most of the combustion should occur at the bottom of the furnace. When I started I used normal MS tubing and this lasted around 5 heats, with each heat roughly 5 hours (I tend to plan my castings to get a batch done). When I changed the tube to stainless it lasted until I broke out the furnace for a reline recently (three trains later) and the lining glassed.

Generally I run waste oil for anything with a melting point below cast iron; the tank has a simple strainer from a French press coffee maker. For cast iron I mix 50/50 with diesel although I have melted cast iron with straight waste oil. You do need a little extra heat if you making the cast iron from scratch using pig iron.

Nice to see the different ideas!


MikeK03/01/2022 18:40:50
226 forum posts
17 photos

I'm curious...How quiet can these furnaces be made to run? I would love to try casting, but live in the city with close neighbors who may complain.

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