This instructable will take you through he steps necessary to constructing a waste oil forge and lighting it. The forge takes in oil, atomizes it, and injects it into a combustion chamber along with a steady stream of air (provided by an electric leaf blower in my case). The oil will vaporize in the combustion chamber and ignite generating enough heat to melt aluminum, brass, iron, and potentially hot enough to fuse low-temp ceramics. The beauty of this machine is it’s almost as cheap to build as it is to run. I was able to construct mine out of some scrap metal and about 30 dollars worth of hardware supplies, no welding required! Additionally this forge should be able to accept a wide range of fuels, I primarily ran mine off of used fryer oil I collected from the bins behind restaurants, but I’ve found that this thing will readily burn; used motor oil, hydraulic oil, melted candle wax, even warm bacon grease. While some fuels work a little better than others, as long as it’s a liquid hydrocarbon this forge will eat it and give you tons of heat.
WARNING: This beast is dangerous! Your dealing with hot oil and temperatures exceeding 2700 degrees Fahrenheit, so, do it outdoors away from structures and anything flammable. Never leave this thing running unattended even for a minute, don’t even turn your back on it. Keep in mind, WATER MAKES OIL FIRES WORSE! Way worse, so have a fire extinguisher ready. Wear dense clothing you can take off quickly. And lastly, keep your distance when your not working with it, of course you’ll have to mess with it some while its running, but limit your time around it and you’ll limit your chances of getting a burn.
Step 1: Necessary Parts
-A Steel container: for the body of the forge, I used a scrap L-joint from a metal fireplace duct. The inside must have a diameter of about 1 foot doesnt even need to be cylindrical as long as it houses the combustion chamber with plenty of room for insulation
-A Blower: I used an cheesy electric leaf blower bought from ebay for like 3$ no good for yard work but perfect for this project
-Threaded metal pipe 1-1.5 in dia (it must fit the blower’s exit-tube diameter) must be at least 2 feet long.
-Another threaded pipe same diameter between 3 and 5 in long
-A two-ended threaded female connector to fit the pipes
-Materials for paper mache (newspaper, glue, cardboard, etc.)
-An Atomizer: something to create a constant spray and will accept oil, I used a generic garden sprayer, an airbrush tip gravity fed from a raised tank would work fine.
-Refractory: at least 2-4 square ft. depending on the size and shape of your forge. this is the heat proof material that is poured and sets like concrete, there are several options for getting refractory, the easiest and more expensive option is to simply buy a refractory mix, either from a fireplace supply store or an online supply. It needs to be rated to withstand temperatures of at least 3100 degrees Fahrenheit. You can also make your own refractory, there are several DIY pages that can walk you through this step.
-Funnel and cheese cloth: you use this to filter the waste oil before it goes into the sprayer (fryer oil tends to have "chunks") the debris will quickly clot spray nozzle otherwise
Step 2: Modeling Combustion Chamber
While building the form keep these things in mind-
- It cannot be straight, whatever body you choose the entrance hole must have at least a 45 degree angle in relation to the exit nozzle. In other words if you were to look through one side of the forge you should not be able to see out the other. The bend in the combustion chamber allows any unspent fuel to slow down and burn before it gets to the nozzle. Otherwise a straight chamber would result in all the burning material to be ejected out the nozzle at once and no combustion cycle would take place.
- The papermache form will have to withstand quite a bit of weight from all sides as you pour the liquid refractory around it. It also must be leak proof so the more layers of paper mache you add the better, you need to be able to throw it around with out it falling apart or breaking.
- Once you’ve got a strong paper mache form, you’ll need to water proof it so it doesn’t disintegrate before the refractory hardens, I used spray silicone on every inch of it but latex paint should work the same. It’ll all be burnt out of the forge as soon as you light it for the first time.
Step 3: Suspending the Form
Pouring the refractory could be difficult depending on the shape of the body you’ve picked. Refractory by definition is very light and foamy if you’ve picked a commercial mix it’ll generate bubbles as it begins to harden. These bubbles will rise and you need to make sure they have a way to escape the form, otherwise they’ll gather and create large pockets which weaken the forge and have no insulating value to them. I cast mine on a little bit of an angle such that any bubbles would make their to the surface. My L-joint body was certainly not designed to hold a liquid, I found that as I poured, the leaks started in places on the L-Joint I was not expecting. It good to have a lot of towels and duck tape handy to keep it sealed as you pour. You’ll want to allow the form to dry for up to two weeks. While the combustion chamber will harden in a few hours after pouring, itll still have quite a bit of water in it, store it in a warm dry place until your sure there’s no residual moisture left. Any moister remaining will turn to steam and break the forge as soon as you light it.
Step 4: Finishing Construction
Step 5: Starting the Forge
What you decide to do with this heat source is up to you what I used it for primarily was to melt down tons of aluminum cans into a cast iron pan then forming them into ingots.
Important! when you want to shut it off make sure you disconnect the fuel first DO NOT TURN OFF THE BLOWER. suddenly turning the blower off at any point while the forge is at temperature will result in the white hot flames from the combustion chamber to reverse their direction and rise up into the plastic components of the blower, destroying it. after disconnecting the fuel leave the blower on for at least five minutes to allow the last of the fuel to burn up and begin to cool down the forge.