I now use this burner assembly on all the stoves that I build. It is the evolution of nearly three winters of trial and error and I feel that it works far superior to anything else I have tried, and I have tried several different variants. My criteria was to keep it simple, inexpensive and without some formal control system. The drip method seems to be the simplest method to meet these needs. No pre-filtering to speak of is necessary other than screening out the cigar butts and speedy dry when you put it in your holding tank.
I start with a couple steel bands or hollow tubes. I have chosen to use used electric motor steel bands because I could get them, but two bands of steel, anywhere from 3/32” to 1/8” thick would work. I also make the inner can anywhere from 1” to 2” taller than the outer can if you can, which just makes it easier to weld together. I have a scrap yard nearby that has a ton of these old electric motors, and just pounding the stator assembly (copper wire) out of them is not a difficult job unless the band is staked (outer band punched into the copper assembly) to the stator. I also try to use stainless for at LEAST the inner band, as it will get hot and self-destruct. But for the amount of money and time you will have invested in this, it isn't critical. Some have tried to use thicker steel for this burner, and the only problem I have heard about was that it was difficult to get up to temperature. But, once it did, it behaves just as the burner made from thinner steel. I have had people tell me they used brake drums and all kinds of other devices for this, all working equally as well. I started with old motor housings and since it works for me, I really didn’t look much further for anything else.
In my burners, the outer band is approximately 7" in diameter and the inner is approximately 5". Although this relationship between them is only necessary to form an air chamber or plenum that you introduce air into one place and it comes out the drilled holes in the inner wall. If all you can get is 7” and 9”, the thing will work just as well. I have built so many of these now, out of several different sizes experimenting with each one, and haven’t found much difference between the sizes.
The first step in constructing the burner is to drill a series of ¼" holes evenly spaced around the inner (smaller diameter) band. I usually place them up about 2 inches from the bottom. Marking them is not rocket science either. I usually start by drawing a line around the circumference of the band. Then mark one place on the top and spin it to the bottom, marking the top again, essentially at the 180-degree place. Then spin it 90, and then 180 again to give you 4 marks. Now put one in-between them, and then in-between them again until you get 32 marks.
Drill them. And if you have used stainless, get ready to sharpen your drill bit a few times. Stainless eats up cheap drill bits.
Cut out a bottom plate from some 1/8" steel slightly larger than your outer band diameter. Remember to leave something to weld to. Weld the inner, drilled band to this plate, centering it. Complete the welding all the way around the bottom so as to prevent the oil from wicking into the space between the inner and outer cans. It will coke up and eventually clog things, so just go ahead and fillet weld the inside can to the bottom plate now and be done with it.
Now create an inner ring, to fit between the outer part of the inner band and the outer band. Actually, by hanging over the outer band by a quarter inch or so makes it easier to do a fillet weld at this interface.
This shows both the bottom plate and the inner ring. Peeking from behind is the piece of exhaust pipe that will later be welded to the assembly.
Trial fit this inner ring around the outside of the inner can first. A die grinder helps a bunch here for this, but a big rat-tail file works just as well. Remember, the better fit this is, the easier and better weld you will get. Assemble these parts to the inner band and bottom by first evenly placing the outer band around the inner band, then slipping on the ring, which forms the top of the chamber between the two. I usually make the ring a larger diameter than the outer can so that I can do a fillet weld where they meet. This is easier than trying to corner weld them together. Tack all these parts together then weld the outer can to the bottom and the ring to both parts. You now have a burner assembly less the air inlet tube.
This is a picture of an earlier burner, but you should get the idea of what a finished one looks like. I drilled many holes on different levels inside this version. I would put a band of sheet metal inside to cover up different holes to see what the result was. In the end, a series of holes near the bottom seems to produce the best results I’ve seen to date.
I have tried different ways to get the air into the burner. My first attempt was to put a piece of auto exhaust pipe welded to the outer can perpendicular or straight into the can. But I found that the incoming air cooled the can at the point of which it was aimed at, and soot built up there. I happened across another design on the Internet (The Turk Burner) and the net effect was to swirl the air inside the pot. So, I tried it on one burner by welding a curved piece of exhaust pipe to the outside of the can.
Net affect was not what I had hoped, but the swirling did keep the soot buildup down on the inlet side of the burner. It didn’t eliminate the soot buildup, it just moved it to a different location inside the pot. So swirling the air yes/no? More labor and welding than needed in my opinion. Feeding it straight in works ok if you have to remove and clean the burner anyway.
I now cut a hole in the outside can to match the shape of a piece of auto exhaust pipe. I have changed this design and gotten away from using round tubing coming out of my blower assembly, but that’s because of the blower I chose. If you can only get a hold of an old hair dryer, then using old exhaust pipe may be the perfect solution for you.
This may be a bad time to mention this, but you need to make the door large enough to get the burner assembly in and out, as you will have to clean out the crud periodically. That's the whole reason for making it removable by the way. You WILL get crud buildup. I have found that it is easy to clean though as most anything that will burn in this burner will mostly disintegrate. Whatever is left behind can't be nice stuff.
Try and round up your tubing first before welding stuff together. I like to choose two different diameters that have a slip fit to them. Reason being is that I weld the larger piece to the stove so that the burner can be slipped in and out of it for removal. Also, locating this tubing so that the burner assembly sits up off the floor, will keep it hotter for more complete burning. I use to put feet on the burner until I tried this. This pipe welded to the stove is actually the connection point for the blower assembly connected to it on the outside as well.
When using the drip variation, I take the oil out of the holding tank via 3/8" copper line, putting at least three turns around the chimney of the stove then thru a valve. The lower viscosity of the heated oil is much easier to control. The output of the valve is fed into the top part of the tube, which is in the center of the stove. It only protrudes in about 2 or 3 inches. The reason for this is that if the tubing were extended down to just above the flame in the burner, the oil would tend to cook and solidify in the tubing. I tried moving the tubing all the way up, but without the shielding effects of the center tube running down the middle of the stove the turbulence of the fire inside the stove would scatter the droplets all over the place. So the combination of dripping from a distance away from the burner (atomization via pre-heating and dropping from some distance) makes the oil burn better. I have put transmission fluid, hydraulic oil and vegetable oils thru this unit, and they all work equally as well.
I feed the oil from a height that would break the stream up into droplets as it fell after being pre-heated by wrapping the copper feed line a few turns around the chimney. I still think that getting the viscosity of the oil down improves things as it makes it easier to control the flow. The problem with dropping the vegetable oil from heights in this stove is that the flame is so violent with the induction of air into the burner and the rising heat front, it tends to spray the droplets all over the place and sometimes misses the burner. I first used this design (drip method) to burn most anything in it, and I started my experiments with crankcase oil. Even heated, it doesn't get to the lower viscosity that vegetable oil gets to, so this stuff (vegetable oil) presents a different problem. Due to the dropping oil going everywhere inside the stove, this is when I came up with the down tube. If the top of the tube is closed off, and only the hole for the oil feed is going into it, air won’t be passing up thru the tube to affect the droplets. I positioned the end of the tube above the burner. Eventually the flame will eat all the carbon out of the steel and it will just crumble away, but it will normalize to somewhere at about 4” to 6” above the top of the burner which will work just fine.
Here is what I came up with. I now inject the oil into the burner in the same tube with the airflow going into the burner. It appears that it does a couple things.
By being in the air flow, It keeps the oil from clogging in the 1/4" steel brake line (not copper) by adding some cooling effect to the tube, and places the oil in the bottom of the pot without splashing it all over the place.
The interface of the one piece of exhaust pipe inside the other, a slot and one more hole drilled in the inner can, allows for the removal of the line. Lighting this couldn't be easier either. Put a paper towel or a half sheet of newspaper in the can and turn on the flow of the oil. As soon as the paper towel appears to be getting saturated, throw in a match and let it begin to burn. As soon as it looks like it's burning good, start to feed it forced air. I like to start it on slow speed (with a multi speed setting blower) until I am sure that the flame will self sustain, and then turn it up gradually to where it's burning white. I have had no appreciable buildup in this setup either.
I have also had success in just letting this arrangement gravity feed to with a valve for adjusting the flow. No pre-heat is necessary either for the vegetable oil as it is already less viscous than crankcase oil.
Here is a drawing of the style burner I now use for just about everything. I find it easy to light, easy to clean and burns just about anything I put in it. [The line drawing doesn't shrink well, so click on the small image below to see the full-size drawing.]
The only thing I do different than in this drawing is that I’ve made the air inlet a rectangular tube instead of round. The main reason for this is the blower I’ve selected. I chose to use a GM heater motor style squirrel cage motor/blower. The first one I made, I enclosed it in another motor can used as the housing, with just a piece of auto exhaust pipe coming out of it. The pipe was about 1/3 the size of the length of the squirrel cage fan blades, so I know I wasn’t getting much out of it. The evolution of getting more air out of the blower and using less energy to do it now lent itself to making the outlet tube more rectangular, so hence the shape of the tube as you can see in the next series of pictures:
This shows the combination of burner and blower, both of which are inserted into the tube that gets welded to the stove. Now I can take out either the blower or the burner by itself.
Any questions? Lets build the blower.
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