Just got done reading through this thread and have enjoyed it all and have actually liked some of the ideas. I'll be adding them to my project eventually. I've actually used a method of feeding oil from the bottom and i'll tell you how i did it and how it did.
I started working on my oil burner last fall. What i had was an old pellet stove the previous home owner left in the garage when i bought our current house. I did use pellets for awhile but got sick of the hassel and actually having to buy a "fuel" to burn. So i started researching waste oil burning and eventually turned my old pellet stove into one. In the pictures, you'll notice i have an old gas tank for my oil resevoir which i currently use a syphoning method to supply the oil to my "oil carb". But when the tank is empty i plan on welding a threaded bung on the bottom so i can use gravity instead. (I also need to add a filter to the setup) I then wrapped my supply tubing around my flue to pre heat my oil before it goes to a ball valve on the side. From there it goes through a pipe, that used to house the pellet auger i gutted, into the stove. The supply line then threads onto my "oil carb".
On the other side of my stove is a induced fan that supplies air up through the bottom of the stove that once fed a pellet fire box....basically a box with holes in it to help burn the pellets cleaner using induced air. I removed that box and used tin with a 2" hole in it to cover the hole so i could narrow the air supply to a small 2" pipe. I feed my oil through a hole in the side of the 2" pipe and then up onto an upside down stainless sink strainer/plug. The strainer wedges perfectly onto the 2" pipe in which i also thread a nut onto the supply tube to help hold the strainer on. To help start the fire and catch any excess oil i used a 4" ducting cap that i cut slightly smaller than size of the strainer and then pushed it down ontop of the strainer. This method has worked great for me and has burned quite clean. I do get clinkers and once in awhile some soot. Which is usually due to my air/oil ratio being a little off (i also added a damper on my exhaust flue to help hold more heat in which has helped create a cleaner burn). The clinkers are easy to clean, as i just pull the cap off and dump them out.
To start the fire i put a lil gas in the ring edge of the cap. Light it and turn on my oil about 1/4 notch (no air yet). When the oil starts to boil on the strainer, i'll cut my exhaust damper to about 2/3 close and i'll kick on my induced fan. I plan on adding a dimmer switch to help control the fan. Right now it has a plate over the opening, which isn't very precise. After about 30 min. and a few adjustments, my stove will generally run all day with no problem. Once in a while i'll get a plug at my ball valve or the fire will stuff itself out for some reason and fill my stove with oil.
One thing i found that is very noteworthy was that i couldn't get a very consistant clean burn at first, nor could i keep it "cadillac-ing" all the time. Either it would get too hot or snuff itself out. What i fould was that i needed some backpressure on my "oil carb". I had a left over proto-type box style carb i had made out of tin that i placed over the 4" cap, opening down. It didn't cover it completely, which is what i wanted, It held just enough flame in, to increase the internal temp and a "box pressure". that it would burn alot cleaner and alot more consistant, whether i had an oil or air swing or not. These are all the pics i have now. I'll post some more when i get 'em.
