First Melt

The time has finally come to see if my furnace will melt anything. Gingery's book calls for a double layer of charcoal on the bottom to get started and add to it as needed to maintain heat. I will start with that but I am doubtful that I will get enough heat going to melt anything with just a double layer on the bottom. I built my furnace twice as large as the furnace described in Gingery's book so my guess is that it will take quite a bit more than that. Keeping that in mind I have also decided to try melting some aluminum scrap first beacause of the lower temperature requirements to melt aluminum.

Here is the furnace layout all ready to get started.

To get the furnace ready I added a triple layer of charcoal on the bottom of the furnace and let them burn until they had all turned white. Just as you would to get a grill ready to cook on. Once those were going I set the crucible on top of the coals and added some additional charcoal along the sides of the crucible. Then I added several crushed aluminum cans to the crucible, turned on my shop vac, adjusted the flow down low and put the lid on the furnace That is when the waiting game started. After 20 minutes I noticed that the bottom of the crucible was glowing a dull red but after poking around on top of the cans it didn't appear that they were beginning to melt.It also appeared that most of the charcoal on the bottom had been used up so I lifted the crucible out of the furnace and added more charcoal and put the crucible back in place. I put the lid back and placed a small brick made out of leftover refractory mix on top of the vent hole. I didn't completely cover the vent, maybe about 90%. After it appeared that the new coals were going I increased the air flow a little bit in an attempt to bump the temperature up inside the furnace. That seemed to work and I finally noticed the aluminum starting to melt in the crucible, which was surprisingly exciting to see. It may have taken about 30 minutes longer than I had expected but it was working! Once the melting got started it seemed to melt all of the cans that I had placed into the crucible quite quickly so I removed the lid, skimmed off the slag, added more cans and closed the furnace up again. Once again the cans melted quite quickly and I also discovered something new. Aluminum cans leave have a LOT of impurities to remove as they melt. I was unsure of how much slag to expect and what it would look like etc. but once I saw it, it was obvious. So after reloading the crucible three times and skimming the slag I stirred the aluminum up to try to get a feel for it's consistency.

Here is a little tool that I made to skim slag from the melt. I also used it to stir the melt. It worked but I do think that I will buy a carbon rod to use for stirring.

Ultimately I finished up the night getting three melts in. I had stolen on of my wife's muffin pans to make ingots which seemed to work quite well for aluminum and I think the ingots gave me a good head start on removing the impurities of the cans. I hope that the  various other non-can scrap that I have will not create so much slag.

Crucible Modification

Seeing a problem with my design I realized that I needed to rethink my method of pouring. As you can see from what I came up with the first time around, aside from wishing I had noticed the upcoming issue before I completed all of the work, I knew that I had to figure out how to come up with a method of poring that maintained stability of the crucible as it was set aside after removal from the furnace while I attached a handle to the bottom of the crucible. The original design gave good control of the crucible while being poured but had lousy stability for the crucible while setting. Plus it was not the best or safest stab ility while installing the handle.

Notice how the assembly sits. Not stable at all.

The first thing I did was to trim the posts that I had extending from the lower corners. Then I added the posts shown above. I really only need to have one of the posts but I figured, while I am at it, put two on, one on each opposite corner so that I might have quicker access to hooking up the pouring handle. As I only used re-bar for the posts and had just cut through the re-bar a little over 3/4 of the way through to bend the re-bar, I welded the posts at the bent corner to add some material and strengthen the posts.

My next step was to redesign the handle itself because the change in post position changed the angles I needed to have at the pouring handle. Here is what I came up with:

 

An easy fix! I just cut the re-bar at the base of the plate, bent it to the angle I needed and welded it up to add some strength.

Crucible

Finally getting back to work on my furnace project it is time to produce some sort of Crucible so that I can get started melting some metal! Winter will be setting in here in Montan and I am quickly running out of time. The items I need to finish up as quickly as I can are: a crucible, some lifting tongs, something to allow me to pour the metal from the crucible. I figure I will make a crucible first and then figure out the other items as I go along.
Here is my initial design for a crucible:

I found this 4.5 inch square tubing in the scrap pile at the local metal supply shop. It has 3/16 wall thickness so it should be reasonably durable for melting aluminum and pot metal. I also found a 3/16 thick piece of cold rolled flat that fit the width of the tube very nicely so I was able to get a nice bottom plate welded onto the tube. I cheated and strayed from my practice to date of trying to use only basic tools such as  power drill. I used a power hack saw to cut the tube and the bottom plate. There was no way I wanted to cut those pieces by hand using a hand hack saw! I have a buddy that has restored an old power hack saw. It is a piece of history. Over 100 years old and he has restored it to near showroom condition. He was kind enough to offer it's use up to me and saved me a ton of work.

 

Here is the bottom. My idea is to use the longer corners as a point to hook onto to help with pouring the metal from the crucible. I have since rethought this approach.

Next item I needed to come up with was something to lift the crucible. I wanted something that would give me a very positive grip on the crucible and since I am not going to be using a standard shaped crucible I had to rethink

This should give me a positive grip on the crucible. Just spread the lifting tong a bit and slip over the posts welded onto the crucible. These holes are 1/16 oversize so they should fit easily enough.

Nice fit!

The next item I need is something to help control the crucible while pouring. The crucible that I have made will hold well over 1 quart of aluminum. That could be a handful to try to rotate to pour being so heavy. My thought is that controlling each end and just having to lift instead of rotating would be easier as well as safer. The above handle would be used to grab onto the lower post welded to the crucible after the crucible has been removed from the furnace using the lifting tongs.

I saw a problem with my design right after I made this piece.