- Two tools needed but not entirely necessary for this job are a plasma torch and a wire welder (MIG). If you don't have a plasma torch, see if you can either borrow one or have someone make the cuts to separate the tanks and cut the door opening and chimney holes. This makes this job go so much easier and makes a nice cut that is also easier to weld back together again. Last resort, have a weld shop do it for you and trade him a six-pack or two for his time, as it doesn't take long to do. An oxy-acetylene torch just doesn't make a nice clean cut for this job. Last, but not least, you could use a saber or jig saw. There is a fair amount of welding on this project as well, so if you don't have a MIG welder, looks like you should get a few cases of beer for that welding shop to do the work. Of course, the beer is for AFTER the welding has been completed.
- Materials needed. Two discarded hot water heaters. One gas (20 to 40 gallon) and one electric (40 to 50 gallon) would make the project go faster as the gas heater already has the down tube in the center of it. Choose the gas tank to be a smaller diameter than the electric one, as the smaller must be fitted to the inside of the larger. If you have to, you can weld in a piece of pipe to the center of an electric one. Other supplies include the parts for the burner assembly. I used old electric motor steel bands.
- Strip all the outer sheet metal and insulation off of the heater tanks.
- Cut and separate the center tube from the bottom of the tank. Be careful when doing this, as you will have to weld the center tube back in place later.
- Next, scribe a line around the tank, approximately 12 - 14 inches down from the seam on the top of the tank, and cut it away from the bottom. The following picture shows the tank after cutting the tube free from the bottom, and cutting the bottom off the tank. It is sitting on it's top.
- Now cut the bottom free from the rest of the tank, leaving approximately 1 - 2 inches of material as in the next picture. Don't throw away the center section yet. You can use some cut off strips of that tank to make the lips for the door, a cap for the top and a piece for the chimney flange as explained later.
- As one may suspect, the next step would be to weld that upper section back onto the lower section.
- I started by just tacking it at each 90 degree part around the outside, making sure that the two halves fit together well. You will IMMEDIATELY see why the plasma cuts are much better here when you begin to weld these two pieces back together. Next tack at the half way points between the 4 at the 90 degree places giving you a total of 8, and next between them until you can see that the whole thing will go together without big gaps etc. Then start to stitch weld between the tacks, skipping to ever other one or every third one. This helps keep the warping to a minimum.
- Once you get that seam welded, you can now weld the bottom tube back to the bottom of the tank.
- Once all the welding is done on this assembly, now would be a good time to put water in it and check for leaks. Remember, it is a discarded water heater for a reason. See if you can locate the reason why it was scrapped in the first place. This would be the time to fix them or just cut around any bad spots when you get ready to separate top from bottom etc.
- After leak testing, and repairing them by welding, proceed with the electric tank.
- The first thing I do is cut the door opening while the tank is in one piece. It stays solid and will roll about easier while you cut the thing. I made a jig out of some old wood, but a bent piece of sheet metal for the horizontal cuts and any straight edge for the vertical cuts work just as well.
- The door is located about 6 inches above the bottom seam. Decisions on if you will hinge the door, or use my cheapo attachment method can wait for now. Just try not to warp or distort the door if you can help it. A better fitting door is just better for everything.
- Next I cut in the hole for the 6 inch stove pipe adaptor. I placed it about 3 inches from the top seam on the stove.
- Next I cut the top of the tank off, with the cut line going approximately thru the center of the stovepipe hole. I figured, less welding that way.
- You may as well check for holes at this point, although it is not as important as having a leak in the water tank.
- Next, cut out a larger hole in the middle of the electric tank top to accommodate the gas water tank. It is approximately 4 inches in diameter, but may have some shape interfere with the fitting. You may have to jossle it around a bit to get it to fit. Also, if you have two different manufacturers of heaters, the inlet and outlet holes may be in different locations. For mine, it just so happened that they lined up the same. I cut out the two holes to fit the inlet/outlet nipples thru at this time too.
- Weld them together, and weld a plate on top of the large hole for the center. 1/8" is plenty thick for this, or a piece cut from the discarded center section of the gas heater would work too.
- At this time, you should have an assembly that looks like the following picture. I have already installed a ¾" piece of pipe in one of the nipples.
- Next, drop this assembly back down on top of the electric tank, and tack it in several places, just as with the smaller water tank.
- As before, tack several places making sure of the fit, and then weld between them.
- Make the chimney flange from a part of the discarded gas tank center section. A roll former works best for this, but you can do it by hand just as well. The criteria are that it fits inside the elbow that is mounted on the stove, and gets welded to the electric tank to be airtight.
- Cut some 1" long strips from the discarded center section of the gas heater long enough to fit inside the door opening. You will need two vertical and two horizontal strips. Cutting them from the old tank will give you approximately the right curve to them to allow the door to fit on better, and a tight fitting door is essential to the burning of the stove, not to mention keeping the noise of the fire down. Oh, I didn't tell you about the noise the burner makes.
- Drill approximately 4 - ¼" holes on each side of the door opening, in ½" from the edge.
- Clamp the fitted pieces to the inside of the door opening
- Plug welds hold all four pieces to the inside of the door opening. Now is a good time to test fit the door. It should drop on like it grew there and fill the hole nicely.
- Weld on some legs. I used some 1" square steel tubing. I like to use three as it sits on an uneven floor better than trying to place 4 legs evenly. Spay them out at approximately 5 degrees. This helps prevent the stove from tipping over. Put a layer of sand in the bottom of the stove. This helps soak up any oil that you may spill inadvertently, and helps keep it bottom heavy.
Oops... wrong picture. But it helps having a beer getter. It's a long trip from the couch to the fridge, this just gets me there and back faster.
The burner assembly
I have used this burner assembly on several stoves that I have built. It is the evolution of several months of trial and error and I feel that it works far superior to anything else I have tried, and I have tried several. 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 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 that 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 would prefer to use vegetable oil as in the rare occasion you DO get a whiff, it makes you hungry.
- I start with a couple steel bands. Fortunately I have a scrap yard that has a ton of these old electric motors, and just slipping the stator assembly out of them is not a difficult job. I also try to use stainless for at LEAST the inner band, as it will get hot, but for the amount of money and time you will have invested in this, it isn't critical.
- The outer band is approximately 9" in diameter and the inner is approximately 7". The relationship between them is only necessary to form an air chamber or plenum, so that you introduce air into one place and it comes out the drilled holes in the inner wall.
- First step in construction is to drill a series of ¼" holes evenly spaced around the inner 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 place 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.
- Now create an inner ring, to fit between the outer part of the inner band and the inner part of the outer band. The next picture is a little out of sequence, but 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.
- Fit this inner ring to the outside of the inner ring. A die grinder helps a bunch here for this.
- 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 (after cutting a hole large enough for it) 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 incorporated it into this burner. It appears to keep the soot buildup to a minimum inside this assembly.
- I then cut a hole in the outside can to match the shape of a bent piece of auto exhaust pipe.
- Weld all these pieces together
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- Position this outer band around the outside of the inner band on the bottom place, while fitting the inner ring on. Remember to leave room to weld them together. I found that trying to weld two edges together is time consuming. Doing a fillet weld takes much less time.
- How's this for a burner assembly sitting inside the stove? Oh, maybe I should have mentioned, you need to make the door large enough to get this 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.
- That second piece of auto exhaust pipe is a slip fit over the one welded to the burner, then welded to the stove. It is actually the connection point for the blower assembly connected to it on the outside. As you can tell, I spared no expense on a connector system between the output of the blower and the input tube to the stove. Those long winter nights had to be supported by some Icehouse beer somewhere along the line. That aluminum can with the top and bottom cut out and a couple hose clamps work well.
I have included the very first post I placed on "otherpower.com" discussion board. Several other people have tried this variation and seem to be happy with it as well.
After that post, I did get to converse with Bruce from Canada via email, and we exchanged a few ideas, but in the end, I feel that this design is superior. Without going into comparing apples and apples, lets just leave it at that. You can find his modifications by googling the MEN stove.
Posted 6Jan2003:
This is a variation on the MEN (Mother Earth News) waste oil stove from 1980. Many of you may have seen that article and the subsequent postings from that guy in Canada. I gotta tell you, I tried the original design, and the Canadians mods, and what I ended up with is far superior to any of them. Attached is a quick sketch. Let me know if you need more detail. The burner assembly I made from two stainless steel electric motor housings (cans) with the guts (windings) removed. Gotta be stainless, or you will be making a few of these assemblies. Not that they are hard, just time consuming. One is just a larger frame size than the other to obtain the "plenum" around the inside "can" which I call the burner. There are a series of 1/4" holes drilled around the inside of the inner can, approximately 16 of them, and then a few at the bottom in about the location shown on the sketch. Drill these before you weld the cans to the bottom plate. Then fabricate a ring to enclose the top of the two cans, from inside to outside can. Weld the 1 1/2" pipe to the outside can after cutting the appropriate size hole for the exhaust pipe. I made the pipe leading into the tank out of a size, which slips over the one used on the burner assembly. No airtight necessary here as when it's burning, it is a positive pressure so you don't have to worry about fumes coming back out the blower. Since it slip fits into the pipe leading in from the blower,, it is extremely easy to remove, chip out the residue left from the burning oil (and you WILL have residue) and slip it back in. I used an adjustable orifice (kind of like a gate valve) for the valve instead of a needle valve, it keeps the clogging to a minimum. Also, it is placed AFTER the pre-heated oil.... much easier to adjust the heated oil rather than the sludge that is going into the pre-heater coil made from 3/8" copper line that is wrapped around the chimney pipe. Lets see... what other tips can i give you... oh yah.... make sure you have some speed adjust capability to the blower. The one that was out of the car works just fine for me. I usually throw a piece of oil soaked paper towel (not dripping wet) in the burner assembly, turn on the drip feed to a good rate, light the paper on fire, and the blower on low speed. As soon as it's going at a good clip, turn the blower on medium speed and Katie bar the door. The outside of my stove gets up over 550 degrees F, and keeps my 1200 sq ft shop toasty by having the gate valve open only a half turn. I can make the outside of the heater glow red, but it will chase me out of the shop. Now lately it's been pretty warm here in Arkansas, but today it dipped down pretty far. It'll be a good test of the critter here tonight. I still don't trust it going all night without attendance, because I am still pondering filtering the oil to prevent clogging of the supply line. I don't want to come into the shop in the morning with a puddle of oil on the floor. Although, the saving grace here is that if the fire does go out... the flow rate slows severely. that's about it for now...unless anyone has any more questions...I think I already mentioned that my local junk yard is missing a few GM blower motors (heh heh) rj
