Metal Casting Zone

Hello,

I am a noob to the forum so take it easy on me.

I just recently decided to build my own aluminum foundry. I have a good idea of what I want to do and I need some help with the burner design. Before that I need to tell you about my foundry:


The foundry is going to be built with a well tank. It's 28" wide by about 48" tall. I decided to make the burner a waste oil burner. I heard that a propane burner will be too expensive for the size of foundry that I am building. My goal is to build a foundry capable of melting about 15-20lbs of aluminum per burn.

The burner:

I am basing my design off this guy's burner, home.comcast.net/~moya034/burner/ . I plan to use a leaf blower as the blower attachment. I will also make some modifications to this design. Since I will be using a leaf blower, I need a larger pipe for the burner, so I will use a 2"x8" or 10" long diameter pipe. Secondly, the oil burner tube will be 1/4" sch80 12" long pipe. It will be fed with a gravity fed waste oil system.
Now, what I don't understand is the propane preheat assembly. I understand it has to be preheated, however, what does it look like, a cutaway of the burner with the propane? This is what I understand...

The top pipe fittings are for propane, when the tube enters the 1" pipe there is a say #58 hole at the end of it. So basically the hole for the propane burner is right where it enters the bigger tube. Is that correct? or does the propane enter the same tube as the oil will be flowing from, but the propane burns separately from the oil, then once its hot enough, turn off the propane and let the oil flow..correct?

Maybe I just haven't seen a good diagram of a waste oil burner?

Thanks for the help guys! I'm hoping my foundry is awesome! I'll post another question in the foundry insulation section as well. I've got a few questions for that as well.

I built a Moya burner and I like it. I still use a seperate propane burner to preheat, then I pull it out and put in the oil burner. I'll put propane into it sometime, probably drill a small hole and use 1/8" copper pipe for it. I think his is going into the outer tube and the blower is forcing it into the furnace. Also, the copper fitting at the back of the tee is drilled out and the stainless steel pipe for the oil is straight through it. I can loosen the nut and slide to spipe in or out to get the best flow at the tip. I also put a small turbine on the end to put a little spin on the air and it hold the tube in the center of the pipe.




This is with the oil burner and I had the oil cranked up. With the flames lower it got really hot.


Welcome to the forum! I see in your profile, you live in Powell. I live near Mt. Gilead and work in Marion.

Welcome! I also use a moya-style burner, mine is built out of 1 1/4" black pipe (plus a few other things) Here's a rather dark pic of my setup:

and the obligatory action shot:

My propane injection is the line you see going into the top side of the burner. The basic idea is you just introduce the propane into the airstream, turning it into a blown propane burner temporarily before you shift over to oil. You don't have to be real fussy about orifice size or placement and all the other stuff that is the bugaboo of normally aspirated propane burners. My injector tube is just a 1/4" soft copper pipe epoxied into a hole in the top of my burner, with the "nozzle" end pinched down to about 1/16" or so. My regulator is a fixed 10PSI one off of a turkey fryer setup, and it provides plenty of gas.
One thing you will want to install if you are going to be using a leaf blower is A: get earplugs and B: build a dump gate to adjust your air supply. This can be as simple as a tee with one side covered by a piece of sheet metal. Too much air and you will just be blowing your heat right out of the furnace, and you will never keep it lit when using propane.

Now I always hear "preheat" what exact is that? Am I preheating the metal tuyrue, the actual foundry, or what before I use the waste oil? I like the idea of using 2 seperate burners. Maybe have a piece of sheet metal for the tuyrue then have basically 2 entirely separate 2" diameter pipes for the propane burner, then the waste oil that I can swap out quickly to get her goin.

Thanks for the T idea. I have to get a blower and I guess the one im going to get is only 2 speed so besides that I wouldn't have much control. I considered putting it on a dimmer switch but I don't think thats a good idea putting a 840watt total motor on a 600watt dimmer switch...

My next question, how exactly do I light the oil? Is there some process to lighting it or what?

Thanks for the help guys!

You preheat with the propane until the inner walls of your furnace are nice and hot, like glowing red. Now, when you introduce your oil into this preheated environment, it will more or less flash to vapor and self-ignite. This is more or less how these burners work. To light mine, I take some cardboard and wrap a piece of wire around it. I soak the cardboard a bit (not much, just enough for ease of lighting) with some thinned oil, or something else flammable. I then hang this in the furnace in front of my tuyere and light the cardboard. I turn the air on low, and ease on the propane. once this catches well and is burning good, I open the lid a bit and pull the piece of wire out. I then heat on propane for 4 or 5 minutes, until the furnace walls are a nice dull red or hotter. The hotter the better, really. I then turn the propane right off and crack open the oil valve, and open up the air a bit. Take it easy on the oil, it's not hard to overdo it and have massive columns of thick black smoke eminating from your backyard. Adjust the oil and air up a bit at a time until you are at the temp you want to be. Easy Peasy.