A Quick Guide to The Operating Principles of Spike's Heater.
Home Assembling Photos Pg1 Photos Pg2 Photos Pg3 Photos Pg4 Contact Me      


Basic Principles of Operation.

The most basic rule of Combustion states that to maintain combustion we need three things.

(1). Fuel. - .............Our fuel is going to be Sump Oil or Waste Oil, to the Americans.
(2). Oxygen -......... Provided by the addition of air, and
(3). (Heat. -........... Without sufficient heat the fuel will not attain suficient temperature to further gasify the fuel and the process will become "endothermic"'. Which in laymans's language means it will just "go out". We need our reaction to be "exothermic" meaning that it must give off more heat than is necessary to maintain combustion. It is this surplus of heat that will provide draft to ensure a supply of fresh air to our flame and most importantly it will be radiated into the surrounding air to warm out tootsies.

Having provided the three things listed above, we need one further condition. Our flame needs to burn cleanly, which will ensure that we do nor stink up the neighbourhood with smoke and smell. We can achieve this by making sure we have enough oxygen present to ensure complete combustion, AND  that it is well mixed with the fuel.

Draft.

Because this heater does not have a forced draft fan, it is most important that we have plenty of draft or airfow, generated by the differential in air column density. This is bought about by the vertical column of air within the heater and flue, being far less than the ambient pressure outside the heater body resulting in a strong airflow from outside, into the heater through the air holes. Air entering at other points will destroy this draft and affect the air/fuel mixture causing black smoke.


Cautions.

It does have some drawbacks, anongst which, the greatest is, that any soot that forms is soft and very very black. A small amount of which will go a long way if smeared. We have our living room carpet professionally cleaned every spring, as there are always a few small spots that seem to escape the primary burner pan when it is being removed for cleaning. The best advice is that if you do see a small spot of soot, do NOT touch it as it will crumble and stain whatever it is resting upon. Wherever possible use a vacuum cleaner to suck up the offending particle from a small distance and dump it. Stains are able to be removed with soap and warm water or any of the commercial cleaning sprays. Read the Instructions.

There is a very slight smell from this heater, but if we maintain a good ballance of fuel and air and ensure that they are very well mixed together it will be nothing like what most people will have experienced when they have previously smelt burning sump oil, it is in fact only very slight and is reminiscent of a newly laid bitumen road. Twenty feet down wind of my flue, it is so dilute as to be almost un-detectable, and certainly much more pleasant than that of a smoky wood fire. So long as the flue is above the roof of your house, your neighnours will never even be aware of it.


Safety Considerations.
Be aware, that although this project is not difficult in itself, and has been successfully undertaken by at least 14 persons that I am aware of,.... The safety aspect is very serious matter especially if you are going to use it for heating a dwelling or inhabited workshop etc. Do not ever underestimate fire as a safety hazard, nor combustion gasses. All of these risks can be minimised by paying some attention to the construction and installation of your heater, with particular attention to, Isolation, insulation and good venting of the flue gasses.

The History. (For those of you who have not read it before)
Sometime circa 1998, several local farm machinery mechanics and I, were discussing the feasibility of a home handyman being able to develop a heater capable of burning waste oil (sump oil) without smoke or smell. We were aware that there are several commercial models of heater available, but all of these are both expensive and require the use of electric pumps and fans for combustion. I wanted to avoid the use of electricity, so that my heater could go on working in the event of a blackout. After a lot of discussion I could not convince my detractors that it was possible, so being a determined type of bloke, I set out to prove my theory that any carbonaceous fuel will burn properly so long as it has enough heat and air, with the air having to be properly mixed with the fuel. All I had to do was work out how to achieve it.

     The first working prototype took about three months to build, as firstly I had to decide on the method of combustion and then work out what materials I had at hand to make the parts out of.

     To ensure that it would withstand the heat generated I decided to use cast iron and cast steel wherever possible and found that this was easily and cheaply found in the junk heap of a local trucking company. Worn out brake drums were found that fitted together with an almost airtight seal, and an old clutch plate and cylinder liner just about completed my list of parts. All that remained was a pan in which to burn the oil and a cover for it, for this I used an old cast iron camp oven and a spring steel disc plough shear. There was not a lot of thought needed to put these things together in such a way as to give me the type of combustion that I wanted and also make it reasonably easy to assemble and pull apart for maintenance, so I just built it "by the seat of my pants".

     The resulting "contraption" worked almost faultlessly right from the first test burn, with only a little bit of experimentation needed to decide the best size, number and location for the air inlet holes in the secondary flame tube. I ended up making up an extension for the drill so that I could actually drill the holes in the tube while it was burning, any mistakes were simply welded over with a nickel electrode, this ended up making the tube rather untidy looking, so once it had been determined what was needed I simply counted the holes and made a new tube with the holes drilled in a neat diagonal pattern.


The First Test Run, Inside.      

After this experimental stage I wanted to see if it worked in an enclosed environment, so much to the dismay of my wife, I removed our slow combustion heater from the living room and attached the oil heater to the existing flue, then drilled a 15mm hole in the wall, through which I then plumbed the oil line which was temporarily attached to a tank holding several gallons of waste oil outside.

     On the night that I got everything set up, it was quite cold and miserable by South Australian standards with an outside temperature around 4 to 6 degrees celsius. After a warmup period of about 30 minutes the heater started to radiate a considerable amount of heat so the oil valve was closed slightly and I sat back to see what would happen. At this time I was still not aware of all of the burning characteristics of the heater which when being tested outside seemed to be quite docile in it's performance. Perhaps it was just that the build up of heat was much more apparent inside, perhaps it was the extra length of flue on the chimney, but on this night I discovered why it is not wise to let too much oil accumulate in the oil pan, It just got hotter and hotter, I turned off the oil supply completely but it continued to burn the oil that had accumulated in the pan, by this time the flame tube was glowing a rosy red along with the bottom 10 centimetres of the heater body, the pyrometer fitted to read the exhaust gas temperature was fast approaching 1100 degrees. At about this time I had vivid imaginings of what the operators of the Chernobyl reactor must have felt like as it ran out of control, things were getting desperate. Shirley, my wife was opening the windows and doors in an effort to reduce the heat buildup in the living room and kitchen area, even I was worried to the point where I used a broom to push open the manhole access into the roof in a last ditch attempt to get rid of the heat. After a few minutes the the residual oil burned off and the heat started to subside, and it was only then that I noticed that the radiant heat from the now glowing heater had "crazy cracked" the plaster on the stone wall 50 cm behind it and melted the coaxial cable going to the TV,.... it had been a near thing.

     

The next trial inside was conducted on the following night after having made a few adjustments to lessen the possibility of a repeat of the previous night. I had covered several rows of secondary air inlet holes, and only opened the oil enough to keep the heat well under control. Meanwhile, Shirl stood 10 metres away at the far end of the kitchen wearing her best "You'll never learn" expression and looking like she was ready to bolt out of the door at the first sign of trouble. It was a slower start taking about 40 minutes to get up to the desired temperature resulting in almost a perfect run, although I found that I still needed to close off a few more rows of secondary air inlet holes to enable it to burn cleanly at lower heat.

     The heater has continued to work virtually without any problems ever since. Even Shirl' has come to accept it, realising how much time, effort and money it saves us every winter, not to mention the trail of wood chips and dirt tracked inside every night. To ensure clean burning the ash needs to be chipped out of the pan almost daily, I say "almost" as it will burn quite well for two days, maybe three without smoking, but the ash becomes thicker and forms an insulating layer which allows a sticky bitumen like residue to form in the bottom of the pan under the ash crust. Daily cleaning keeps the ash layer thin which allows the radiant heat to vapourise the tarry residue whereupon it is burnt prior to the ash being removed.

 


Materials.

Wherever posible I have used parts mafe of cast iron or cast steel, both of these materials are very resistant to burning and warping. My heater is 12 years old and only the bottom half of the secondary burner has been replaced due to the effects of excessive heat. This secondary burner also had more 6mm holes around the top. (It's upside down in the photo) You will notice that over the years the metal has crazy cracked and swollen from the effects of heat and compression. To get around this, the pan is held unde the secondary burner by spring tension from under the supporting strongback rather than screwed up into place with bolts, without provision for expansion.

This burner worked quite well, but I find that fewer larger holes give a wider clean burning temperature range, although it is slightly noisier, I feel that this is due to better mixing of the fuel and air due to higher inlet air velocity.

The secondary burner seen hera at right, was not discarded, but merely cut offalong the second to lowest row of holes and re used, it can be seen being re drilled on the next page in paragraph two. We scroungers never throw anything away, you can never tell when it may come in handy. If we do you can be sure that it is really just "Junk" and useless for anything other than it's scrap value or its weight.





© Perseverance