Winter Activity

After doing some research on my own and getting feedback from some fellow Gingery builders on the "gingery machines" yahoo forum, folks who have quite a bit of experience casting. I have discovered that I can in fact cast and pour metal in the winter and not expect some sort of major disaster or meltdown. So, especially with the weather being so mild in Montana this winter, mid 20's and 30's instead of our average low teens, I will begin casting after getting back from my next work tour. That is so cool! I thought I was done until next spring!
My worry was two fold, one of which is still a concern, but not a dangerous situation. That concern is getting the pour completed without losing so much temperature in the melt that it does not flow well. I am willing to work around that as best as I can. My primary concern was that with the green sand being to cold I ran the risk of some sort of explosive event when the metal met the green sand. Everything I have heard indicates that this is not an issue. In fact one of the forum members is in Alaska and thinks that the frozen green sand may add strength during the casting process. Now, he is using a home made green sand and I will be using Petro Bond, which is uses an oil based binder, while his mixture used water as a binder.
Hopefully in a month or so I will be back with details of my first castings, which should be lathe parts!

Second session of melting

Well I didn't get any photos but I did get around to melting some more scrap aluminum. During my first melting session I noted that due to the size of the furnace I had made that it was evident that I needed more heat to get things moving along so I made that adjustment this time around. I started out with a good solid layer of charcoal on the bottom of the furnace four deep and got that burning. While that was getting started, I got some additional charcoal started in my fire pit and set the crucible into place in the furnace to start pre-heating the crucible. Once all of the charcoal was going good I added charcoal around the sides of the crucible about two-thirds of the way up. As soon as I accomplished that task I added scrap to the crucible, set the lid in place and got my air flowing into the furnace.

I checked on the progress after about 20 minutes and found a nice pool of molten aluminum in the bottom of the crucible! At that point I turned off the air, removed the furnace lid and spooned off the slag then added more scrap. Filling the crucible with a bunch of crushed cans the first thing I noticed was that the cans caught fire and melted within no more than 30 or 40 seconds.............NICE!

I repeated that cycle once more and found that I was losing heat and the melting process was slowing down so after yet another addition of scrap I put the furnace lid back on and got the air flowing again. Within a few minutes I had the temp back up and was melting scrap very easily again. I kept this cycle going until I had melted down an entire bag of crushed aluminum cans, which sounds like a lot of aluminum but there is also a lot of slag in the cans and my guess is that I got about a quart of aluminum melted from the one trash bag of cans, which I poured into a muffin tin to make ingots. It was only 12 degrees or so outside and by the time I poured the last of the crucible I was losing the heat in the metal. My hope is that I am cleaning up the scrap in making the ingots so that when I melt them again to pour a project I won't have so much slag to deal with.

After melting the bag of aluminum cans I decided to see how tin cans would melt, so I added charcoal to the furnace and got the heat up again. I loaded the crucible with tin cans and checked on them after 20 minutes or so in the furnace. They were glowing but no where near melting so I opened up the air and gave it a good blast, which in very short time only succeeded in blowing a hole in my crucible! In adding that much air I oxidized the mixture and killed my crucible. Kind of impressive for a charcoal powered furnace, but not what I was looking for!

So now I will have to wait for the weather to warm up and make another crucible before I can resume converting my scrap into ingots........................ I wonder what I would get if I added some tin cans to the melted aluminum.............Hmmmmmmmmm

until next spring then!

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.

Air flow metering valve test parts

After getting caught up on some work around the house I finally got to getting some work done on the furnace. I made up test parts for my idea about varying the air flow my furnace is getting from a shop vac. I could just buy a cheap hair dryer and be done with it, but I already have the shop vac.
I took the pipe that fits into the tuyere and added a small stop so that it would slide in but not protrude all the way into the furnace. Then I cut an opening into the pipe, made a small sheet metal finger that would fit into the opening in the pipe, obstructing a lot of the airflow up and out before it gets to the furnace. It seems to work so far. So far I have only roughed this together. After testing during a firing of the furnace I will clean up the design and construction, if it works as I expect it to.
Here is what I have done so far:

 

Air flow

After spending my 14 days at work I arrived home to a small amount of snow on the ground, which was a bit of a drag since October had just arrived a few days ago. That's a month or so early. Plus it was cold (3 deg. F) which is an even bigger problem as I want to try to start making some ingots while I am home.
I have been thinking of a way to cut down on the airflow I get from using my Shop-Vac as an air supply to my furnace. Since I can't easily reduce the output at the Shop-Vac, the flow needs to be reduced at some point along the connection to the furnace. So what I have come up with is cutting an opening in the supply pipe that slips into the tuyere, as well as fabricating a deflection valve to divert a portion of the air flow up and out of the opening. Since I am trying to use only some basic tools, cutting the opening will take a bit of time. I will put a picture of the modification out when I get the opening cut and the deflection valve fit. Then it will be time to try melting some of my scar pile and making some ingots! If the weather cooperates.