Introduction: Easy Dual Fuel Furnace Burner

Picture of Easy Dual Fuel Furnace Burner

Want to melt metal?

Want to melt metal for free with recycled oil?
Hell yeah!!

Here's an easy-to-make burner that can use either propane or oil (veggie or motor). It will heat a furnace up to aluminum melting temperatures with no problem.

Step 1: The Burner

Picture of The Burner

Safety talk- Yes, we're playing with fire here. Use your head. OK?

Parts for the burner:

A blower- I got mine from a surplus place. The more air it moves the more fire you can produce. Anything around this size will work. Mine's rated at 100 cfm (cubic feet per minute)

1 1/4" dia. steel pipe 18"-24" ish long. The dimensions aren't crucial. I wouldn't go with a smaller dia. though.

30" of 1/4" dia copper pipe

Hose clamp (optional)

1 male propane quick release fitting. Get this from a propane supply. Don't just use an air hose quick release.

Other stuff that you'll need:

Propane tank w/ an adjustable regulator & hose w/ female propane quick release

5 gallon bucket

Plastic valve w/ 3/8"" fittings

Clear poly tubing 3/8"

Teflon pipe tape


Drill & bits

Tap for the propane fitting

Torch & brazing rod. Doesn't have to be big, even a jewelers torch will work.

Metal cutting saw

Assorted hand tools

Step 2: Build the Burner Tube

Picture of Build the Burner Tube

Drill a hole about 2/3 back from the front of the steel pipe large enough to tap for the propane fitting.

Thread it and screw in the connector. Use teflon tape or pipe compound to seal it.

Now drill a second hole 90 degrees from the propane fitting that is wide enough to insert the copper tubing. You may want to file it into an oval shape to help the copper slip through. The better the fit the less brazing you'll have to do. Feed the copper tubing though until the end is flush with the front of the burner pipe.

I put a hose clamp on to secure the copper tubing and provide strain relief.

Seal the copper tubing to the steel pipe. I'd recommend brazing but you could probably get away with solder or even silicone. Only the tip of burner gets really hot.

Step 3: Attach the Blower

Picture of Attach the Blower

Now you need to attach the burner to the fan. How you attach it depends on the fan you get. For this fan I cut a piece of wood that fit snugly in the end of the fan and then drilled a hole in it that matched the outer diameter of the pipe. I put a couple screws into the block to hold it to the fan housing but just left the burner pipe as a friction fit.
I also made a sheet metal damper for more air control

Step 4: Optional Choke

Picture of Optional Choke

You need to fire the refractory cement in a furnace very slowly the first time you use it so I made a choke to cut the air way down for a very small flame. If you want one on your burner cut a slit across the top half of the burner tube with a chop saw right next to where it meets the blower. Then cut a damper out of plywood to slide into it. I only used this for the first firing. After that I took the damper out and slid the burner tube back enough so that the slot was covered by the wood block to keep air from leaking out.

Step 5: Fuel Supply

Picture of Fuel Supply

Oil needs to be vaporized in order to burn. Some burners use oil pumps, tiny nozzles and high pressure air to vaporize the oil before it goes into the furnace. We're not doing that because then I would have to change the title of this 'ible to Complicated Dual Fuel Furnace Burner.
This burner takes the lazy approach. We use propane first to get the furnace hot enough to vaporize the oil. Once the furnace is up to temperature we turn on a gravity feed of oil to the burner. The oil drips out of the end of the copper tube, vaporizes from the heat and ignites. Once the oil burner is going you can turn the propane off and just use the cheap/free stuff.

Supplying Fuel

Propane side

Use a propane tank with an adjustable regulator. A BBQ tank is fine but the non adjustable regulators that come with them don't work well for this. I use a flexible hose with a quick release to the burner. You could also just plumb it together with steel pipe.

Safety First People! Make sure you use equipment that is designed for gas!

Don't cheat and use an air hose. Propane can degrade air hoses and nobody likes a gas leak.

Oil side

Drill and thread a hole in a 5 gallon bucket for the 3/8" valve.. I also made a "nut" out of masonite to secure it on the inside. Attach a piece of clear tubing. If you're lucky the tubing will fit snugly over the copper tubing. If it doesn't get the right plumbing hardware and connect the two.

Fill the tank with used motor or vegetable oil. Strain it through a cloth as you pour it in. You just don't want any big chunks clogging the valve.

As long as the oil tank is higher than the burner it will feed oil to the burner nicely.

Step 6: Make Fire

Picture of Make Fire

Now that we have all the parts together to get our combustion on, let's mix some hydrocarbons and oxygen and generate a nice juicy exothermic reaction.

I use a torch to fight the furnace. That way I can be far away fiddling with the controls rather than sticking my face and hands near the burner as it ignites.

First turn on the fan.

Light the torch ( I use a rag soaked in WD-40 tied to a metal rod with wire) and stick it in the furnace.

Open the propane tank. Adjust to a flame that is coming out of the furnace some but not a lot. You can tell by the sound when you have a happy flame.

Once the furnace is glowing a dull red open the valve (just a little) to the oil tank. There will be quite a bit of flame from the two fuel sources. Turn off the propane tank and adjust the oil flame. There should not be any smoke if you have the oil feed adjusted correctly.

Play with your fire until you run out of oil.

Step 7: Use It!

Picture of Use It!

Here are a couple of projects I've made w/ my metal casting furnace.

This was my first instructable: Entwined Valentines Hearts

The other picture is a big drill guide I made when I worked for the National Park Service

Plus some action shots

Metal casting is great fun. You should do it.
It hardly costs anything to melt metal when you're using this burner to burn waste oil.

Go here to learn how to build the rest of the furnace....

Like projects? Check out our blog- Mike and Molly's House where we chronicle our mighty projects on our mini farm.



MattW1989 (author)2016-02-09

for burning oil, how do you regulate it?

i assume you do somehow becuase the idea of an open tube just makes me envision a stream of fuel just draining out, or does it need that much?

spike3579 (author)MattW19892016-02-10

There is a small petcock on the bucket that the fuel line connects to. I adjust it so there is a steady drip but not a flow coming out of the tube.

th3_v1k1ng (author)2014-05-31

I've gone thru the comments trying to see what kind of fan your using, but cant see.
You say you got it a surpluse store, your in the USA or Canada.
So surplus stores are way different than here in the UK, England.
we dont have cool things like that in our stores.. here..
So, what is it, what was it from.

spike3579 (author)th3_v1k1ng2014-06-06

It's a squirrel cage blower probably from the '40s or '50s. I couldn't find any info about it online. The fan cage is 4" dia by 2" wide. I found a fan on Grainger'sthat is close to those dimensions and would probably work fine. It costs $86.75 new whereas I think I paid $20 for the used one which is rated at twice the cfm. I would look in discarded appliances and try and find one that way if there are no sellers of used stuff near you. Some people use hairdryers or the exhaust from small vacuum cleaners but they are kind of noisy. Another route is to try a 12v blower from a car.

The MadScientist (author)2013-09-22

Hi Spike I've been planning on converting my charcoal furnace to a vegetable oil furnace for a while to melt steel and I was planning on doing something very similar to what you have with the oil drip. The exception to my plans are that instead of using propane to heat up the furnace I will use charcoal and I will only use a hair dryer for an air blower. Do you think this method will still work with those changes?

I think preheating w/ charcoal should work. A hair dryer will work to a certain point. I think they are OK for experimenting with but they aren't made to have long duty cycles or put out as much air as an industrial blower. as far as melting steel that takes a lot of heat. Aluminum melts at 1220° f (an orange glow) while steel melts at 2700° f ( a strong white glow) that's a significant amount of heat to produce.  It should work in theory. I've seen glass furnaces using this type of burner and they typically run at 2200°  f.  Just make sure your furnace can handle the hi temps.  I don't know if a hairdryer will get you hot enough.  Try it and post your results!

I've found that a hairdryer will work fine for long periods of time, I just tape the cool button down so it's not using copious amounts of energy on the heating elements.

Thankyou for your help I'll be sure to tell you about my results when I get the time to do it.

neon238 (author)2012-01-09

why you aren't wearing any PPEs?... molten metal is so dangerous bro...

spike3579 (author)neon2382012-01-09

You're right. I should be.

Dave8{) (author)2011-12-24

You suggested using "regular" white Teflon tape. There is special yellow Teflon tape used for gas connections. It is thicker and seals better as well as being required by code for many gas connections.

Will white tape work properly? Of course, and it probably will never be an issue, BUT, if there is an insurance claim, using the white tape may result in the insurance company denying the claim. Better safe than sorry for $2.76 (see for where I got that price.)

cryophile (author)2011-11-10

Metal five gallon buckets have been difficult for me to find. Where did you get yours?

spike3579 (author)cryophile2011-11-11

I got mine from a salvage place. You could try car mechanics. They get grease and what not in small barrels.
Junk yards....
You could also use a square shape for the shell just cast the inside cylindrical.

chazr (author)2011-11-11

Great job Spike.
I have been wanting to build one of these for a long time, but I am stumped on the refractory part. I am wondering where you will post this part? Will it be here in this post or a seperate one?
Thanks and regards.

spike3579 (author)chazr2011-11-11

I'm going to do the rest of the furnace in a separate post. Hopefully in the next week or so. Stay tuned!

soundmotor (author)2011-11-10

Favorite Worthy!

Ortzinator (author)2011-11-07

I think burning motor oil may be illegal in California.

worker ant (author)Ortzinator2011-11-09

Who cares, everything is illegal in California; just work in a well ventilated area. They donot have used motor oil police

bajablue (author)worker ant2011-11-09


spike3579 (author)Ortzinator2011-11-08

You can always use used cooking oil.
Just have to beat out the biodiesel folks for it.

robbtoberfest (author)2011-11-03

lol, "fight the furnace" Just picture it :)

spike3579 (author)robbtoberfest2011-11-09

Yeah, fight fire with fire ;)

jack8559 (author)2011-11-08

What do you use as a crucible to melt the aluminum in? I know it needs to be something that won't melt, or you would have a mess inside the furnace - cast iron? steel? or is it a special metal crucible like titanium since it takes an extreme heat to melt?

spike3579 (author)jack85592011-11-08

I use 4" steel pipe.
Check out my response to anode505 for details.

anode505 (author)2011-11-08

The crucible, what are you using? I've been pondering building a furnace for a while, but the Crucible is whats holding me back (Mainly for aluminum)

spike3579 (author)anode5052011-11-08

Aluminum melts at about 1200 degrees F

Bronze @1560ish

Steel doesn't melt till 2600 so steel it is.  

I use a section of 4" steel pipe w/ 1/4" plate welded to the bottom.

My crucible cost a couple dollars and lasted 20 melts before it was too oxidized and flaky to keep using.  

You can buy commercial graphite crucibles but they need to be pre-heated and cost more $.  I think about $100 for one that fits my furnace.  

I like steel ones.  Even though they break down the price is right and the surface tension of the aluminum seems to keep any steel flakes out.

You can also cut the top off a used propane torch tank (be careful) for a quick crucible.  It will wear out faster because the metal is thinner but it's quick and easy.  

You can also cast crucibles with high temperature refractory cement (not the same as portland!!) although I've never tried it.

tacamaral (author)2011-11-07

In Brazil, we can say "profissa" when something is so very good it looks professional. For you, man, "profissa". : )

Loved the 'ible. Will do it as soon as I move into a house (hate apartaments).

spike3579 (author)tacamaral2011-11-08

Thanks! I appreciate that.
Yes, get a house w/ a little space for projects.
in the meantime here's some inspiriration.

sconner1 (author)2011-11-07

Good use of waste oil and nice way to make a burner.
I was hoping to also learn to build the whole furnace though and how/where to source parts like the cylindrical ceramic insulation.
How about fireplace brick, or even red bricks?
What's the crucible made from?

spike3579 (author)sconner12011-11-07

I'll get on posting the rest of the furnace next & talk about refractory materials. You don't want to use red bricks. They'll just break down.

karst45 (author)2011-11-07

It also interresting to add a "flame arrestor" to prevent flashback. I know most propane tank are equiped with such safety but if you put on anoter regulator the "flame arrestor" would also protect this part.

sspence (author)2011-11-07

How about a step on casting the cement in the metal pail to make the furnace, or is that documented elsewhere?

spike3579 (author)sspence2011-11-07

It needs to be its own post but it is on my to do list....

sspence (author)spike35792011-11-07

Cool, can't wait!

mikeasaurus (author)2011-11-02

Cool furnace and I like the addition of the choke. I would think having a choke is mandatory with something like this, not optional?
Also, what kind of temperatures have you got with the oil-only fuel, and what metal are you melting?

(Combustion is a type of exothermic reaction and would totally qualify for the Chemical reactions Challenge!)

spike3579 (author)mikeasaurus2011-11-02

I usually use the damper on the outside of the fan if I need to lower the flame.  I generally run it full speed.

more air = more fire = more fun

I've been melting aluminum car wheels but I've seen similar burners melting brass and I think you could do cast iron too. 

There's plenty of energy stored in the oil, more than propane, you just have to get enough air mixed with it.  

Thanks for the heads up. I'm off to enter the chemical reactions contest...

Chicken Girl (author)spike35792011-11-03

You should add a pic. of what you made of the melted aluminium....I'm just sayin'!

spike3579 (author)Chicken Girl2011-11-03

Gotcha & done! added step 7

About This Instructable




Bio: I have a compulsion to make stuff, all kinds of stuff. I'm glad to be here...
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