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The external dimension's are 5 1/4" wide by 4" high with out the lid. With the lid it is 6" high. I have been using a large set of pliers to remove the lid, but I would prefer a handle of some sort made into the lid. If I were to make a new one some of the things I would add would be a handle for the lid, only one opening for the burner, brazed connections instead of silver solder, and make it bigger. I am sure there will be others as I go but it is all a learning process. I would like to make one in a gallon sized can dimensions just for more true smelting type tests.

0825161406.jpg
 
OK that is a little puppy! Nice job though. See there is a definate use for a beer can for reference in photographs.

When I make cast lids I like to have a ring of metal around the perimeter. One way to do this would be to cut a metal can of the proper diameter down so it is as thick as you want the cover and cut off the end so you just have an empty "pipe" made from the walls of the can. Then get 4 screws and nuts and put one screw in every 90 degrees and put the nut on the inside to tighten it. when you look down the "pipe" you will see 4 screws stopping about an inch from center. These support the refractory so it doesn't fall out of the ring when you pour the cover. If I were making a furnace this small with walls as thin as you have made I would use a 2 inch length of black iron pipe of the same OD as the furnace body on the lid, and a longer length for the body of the furnace.

If you add extra nuts to two screws opposite each other so about 1/2" of the bolt head sticks out, you can make a bail type handle which makes removal easy. Just make sure it can swing down and not stand tall and get heated by the flame.

For the hole in a furnace that size I would use a toilet tissue tube in the form to cast the hole which should make it about one inch. And it burns out in the first heat!

Please post the details of the burner as a furnace this size could be a popular build for forum members. And which refractory cement did you use?

Nice job!
 
Burner orifice from a King Kooker cast iron burner assembly Model #WKAF2B. (I got mine at Academy Sporting Goods)
A 1/4" to 1/2" Copper reducer.
A 1 inch long piece of copper tubing.
A 6" piece of black iron pipe.
A 3/8" gas line cut off valve. Optional but I am liking it since I added one to mine.
A 8" x 3/16" steel brake line.

Using the orifice, I silver soldered the 1/4" x 1/2" copper reducer to the small end. (orifice end) The orifice is just about right to reach the wider part of the reducer without extending into the the wide area. I then silver soldered the 1 inch copper pipe into the reducer. Once done I drilled four 1/4" holes at right angles through the reducer right in front of the orifice. Take the 1/2 inch black pipe and test fit the copper tubing into it. It should be very tight, almost an exact fit. With a round file I worked the inside of the black pipe to open it up some. I worked the out side leading edge of the copper tubing only slightly, just enough to get a compression fit between it an the black pipe. Don't make it permanent just yet. I drilled a 1/4" hole 1 1/2" in front of the air holes in the copper reducer (this hole is in the black pipe). I cut both ends off the brake line and bent the last inch or so at an angle where the center line of the tubing is centered inside of the black pipe. Then I silver soldered it in place. I cut a strip from a drink can just wide enough to cover the holes in the reducer when lighting it. Once it warms up a little, I uncover the holes and turn the air compressor on.

There is one last piece, an air supply. I tried my small 2 gallon compressor but the regulator on it would not go down low enough. The next best thing I had on hand was a nebulizer. It works great, it is actually what I used in the video. When the air is turned off, the furnace runs completely silent. (I hooked the air line into the brake line.)

As for the furnace, another member, JHS, made it. He had sent it to me quite some time back but health issues had kept me from working with it. I know he has been down in health for the last few days, but maybe he can post up the mix he used for the refractory.
 
Let's see if I can word this right. If I understand correctly, the crucible needs roughly 1/4 or 25% of the crucible diameter as clearance around the crucible body when heating. This should insure better heat transfer to the material to be melted. This 25% should be measured from the top portion which should also be the widest part of the crucible. So a crucible with a 4 inch wide measurement (at the top) should have roughly a 1/2 inch clearance from the inside of the furnace all the way around. Since my furnace has a 3 1/2 inch opening the crucible should be in the neighbor hood of 3 inch's. Since 3" was unavailable from the local supplier, I went with a 2 1/2 inch diameter crucible. I could have ordered 3 1/8" graphite crucible, but went with the fused silica with a clay bond since he had these in stock. Now the real question is does all that sound about right? Also am I right in thinking that an undersized crucible would be preferred over one that was slightly to big?

Edit for clarity
 
Made a little progress today, but still have more to do before I am satisfied. After trying three different burners today, I am close. If I can melt copper, I will be happy. Here is the heat almost at it's limit earlier today and it would not quite melt copper.

Not Quite there.jpg

Late this evening I got the copper to melt, but just barely. Changed burner to the third version which helped greatly. It still needs a bit of tweaking.

SANY0093.JPG

Last test for the night.

SANY0094.JPG

Finally some little success. Poured copper from a piece of pipe and legs from IC's.

SANY0095.JPG

Still a ways to go yet, but I am happy with most of the progress so far.
 
Shark,

Take some bricks and close in the top of your furnace to to about half the size of the opening to retain more heat and it should solve part of your problem. Your hole in the top of your furnace is much larger than it needs to be and you are loosing a lot of heat from it. Once you find that this works better for you then you can have a metal plate made for it or make another top for it.
 
Yea, I agree. Use some fire clay and make a round puck a little larger than the vent hole. You can slide it across the hole until you have just the right gap. You will know because it will leave a blue flame shooting up through the gap that you may be able to see in the daylight.
 
I agree guys, the opening can stand to be a lot smaller. The skillet I poured into is one of those ash tray cast iron skillets. I had used it to partially cover the opening and the change was drastic. The color inside went from a orange-red to a yellow-white color very quick. I need to get better set up to control the air flow, and I think a high pressure regulator for the gas would make the move to a fully working furnace. (although quite small) I have been using a regulator from a gas grill, and powering the air from dual nebulizers. I do have an adjustable gas valve but it doesn't seem to give quite the control it needs.
 
Shark said:
I agree guys, the opening can stand to be a lot smaller. The skillet I poured into is one of those ash tray cast iron skillets. I had used it to partially cover the opening and the change was drastic. The color inside went from a orange-red to a yellow-white color very quick. I need to get better set up to control the air flow, and I think a high pressure regulator for the gas would make the move to a fully working furnace. (although quite small) I have been using a regulator from a gas grill, and powering the air from dual nebulizers. I do have an adjustable gas valve but it doesn't seem to give quite the control it needs.
Click to expand...

Are you using propane or natural gas for your furnace? I will get you a picture of my furnace posted when I get a chance. It is a similar design to the furnace you have except for the burner assembly and it will eliminate the need for the nebulizer you are using.
 
I am using propane. I have changed the burner out to one of the Reil(?) type burners, but it still needs air assist to get hot enough. This is the current burner assembly I am using, it seems to work the best of the three. I scaled everything but the orifice size down by 1/2" to fit the small size of the furnace. My original worked great up to aluminum but that is about as far as I could seem to push it.

SANY0100.JPG

Notice the paper still on the burner pipe. That paper stayed there after a continuous 4 hour burn and I could still hold my hand within 4 inch's of the furnace with out being uncomfortable.
 
You might want to try a larger reducer. I can't tell if that's a 3/4" to 1/2" or a 1" to 1/2", but I'd suggest a 1-1/4" or 1-1/2" to 1/2". As close as the gas inlet pipe is to the 1/2" pipe, it may be restricting the air that is able to pass around the gas pipe.

Dave
 
Locally the largest single reducer I can find is 3/4 to 1/2. I had thought about using two to achieve a bigger opening but wasn't sure that would help. I just changed the regulator to a high pressure type and heating it up with no added air. I should know pretty soon what the effects that has on it pretty soon.

Edit: fix miss spell check, :D
 
Shark said:
My original worked great up to aluminum but that is about as far as I could seem to push it.
Click to expand...
I made a Gingery Furnace once upon a time that did aluminum really well, and that was with charcoal and a blowdryer ;)

Shark said:
Notice the paper still on the burner pipe. That paper stayed there after a continuous 4 hour burn and I could still hold my hand within 4 inch's of the furnace with out being uncomfortable.
Click to expand...
That sounds like good insulation and nice tight tolerances--good job!
 
Here are some pictures of the furnace I use. It is about the same size and setup as yours. It is capable of holding a #6 crucible but I use a #4 in it.


In the first photo you will see that the exhaust opening is a lot smaller than in your furnace. The opening is 2" across and the two side slot are 2" long as well. Most of the time when I am running the furnace I will put a brick over the side slots just to retain heat and not use as much fuel. It doesn't really make much of a difference when I close the side slots off on how the furnace operates.

photo 1 (2).JPG

In this second photo you will see that my burner pipe is a 3/4" pipe with a 3/4" x 1-1/2" bell reducer on the end of it for the inflow of air for the fuel mixture. I have seen these furnaces also setup with an added air supply from a compressor or other source to generate higher heat temperatures. But I don't feel that is necessary for this furnace at this point with everything I have used it for

photo 2.JPG

In the third photo you will see that the burner inlet is a little bit more to the side of the furnace than your is but I don't think that will have much of a difference on your furnace. The reason for the side inlet where it is is so that it will create a vortex motion of the flame in the furnace. I think yours is fine where it is.

photo 3.JPG

In this fourth picture you can see a #4 graphite crucible next to a 300ml beaker for size comparison. This furnace will reach an operating temperature hot enough to melt this crucible full of copper powder in roughly 30-45 minutes from a cold start. Once it reaches its melting temperature the copper can be poured and another load added to the crucible and melt the charge in about 10-15 minutes. The furnace does not have to be run at maximum out put to accomplish this. When my furnace is operating you can not touch the sides because of the heat generated, you have to use gloves even when using the handles to remove the top.

Another tip on the crucible is to not use a cheap clay one when running this furnace, if you look at the picture looking down into the furnace you can see that I used a couple of cheap crucible and they failed during the melt. Go ahead and spend the money to get a graphite crucible. The one in the picture is a salamander crucible I purchased on ebay for about $20.00 if I remember correctly.

photo (6).JPG


1. I think you need to upsize your burner pipe to a 3/4" with a bigger bell reducer on the end for incoming air flow.

2. You need to reduce your exhaust opening.

3. I'm also not so sure that your gas pressure might need to be increased at your burner pipe. I am guessing that the propane is being supplied by the tank that you use on your house and that you are running this at the same pressure that the appliances use inside your house. If this is the case I would look at separating the two lines and using a higher pressure regulator for the furnace than what is used for your house.

4. You should consider making a metal band to go around the lid of your furnace that has handles on it. This can easily be done by taking a piece of a metal can and cutting it the same height as your top on your furnace. Attach a couple of handles on it similar to what mine has with rivets or screws. Then take and drill 4 - 6 holes in the metal band and mark on the cement top where the holes are and then drill these out smaller than the screws that you can take and drill into the metal to attach to the top. This will make it a lot safer to deal with the top when you want to remove it.
 
I will have to try those suggestions. From all I have studied not many people seem to build them this small, that is why I went with a 1/2" build for the burner. I have the pipe here, but need the 3/4" to 1 1/2" reducer. I am running this one from a 20Lb bottle and have just changed to a high pressure regulator. I now have a cold spot in the crucible where the burn makes initial contact. I think I will wait and try to get the 3/4 burner going before fooling with it much more.
 
Frank, what is the size tubing you used for the orifice? It looks like 1/4 or 5/16 brass.
 
The orifice for propane is normally around a #55 (0.040) to #60 (0.052) drill bit, depending on the burner size.

You can find plans for that burner and many others on the internet. The simpler burners like that one work well if properly tuned.
 
For decent prices and a wide variety of black iron and brass pipe and fittings, check http://www.zoro.com. My local big box stores only stock the stuff that would commonly be used. Zoro has a much wider selection. I've bought 1-1/2" to 1/2" and 1-1/4" to 1/2" from them. Be sure to look at all the different listings. Sone of the reducers are quite short and "blunt". Others are longer and more gradually tapered, and are much better for this use.

Dave
 
Thanks Dave, I could use one of those stores closer to home. It will help on another project I have rambling around in my head.

I did find a 1 1/4" x3/4" reducer yesterday and managed to get it set up with a 3/4" pipe. I used 3/8" copper tubing and a 3/64 drill bit for the orifice. It seemed a bit fussy on start up but worked great once it warmed up. After sitting in the furnace for over an hour without melting copper pipe, it hit me why it wasn't melting... :oops: . I was running the gas at 1.5 PSI. There is a reason for using a gauge on the adjustable regulator, I just forgot about it at the time. As soon as it hit 5PSI, the copper melted in about 1 minute. Now I am wishing I had cleaned the ash tray of the previous attempted pour as the second attempt of the day would have been nice by its self.

SANY0101.JPG


The second attempt was very liquid and poured easy and smoothly. I need to make/buy myself a small mold and learn some more about melting and pouring metal's harder than lead.

Edit: correct measurement
 

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