Joined: September 01 2010 Location: United States Posts: 47
Posted: September 13 2010 at 6:38pm | IP Logged
I decided to build a backyard charcoal foundry, the specs I've seen use a paint bucket, but I figure an old charcoal smoker already in my backyard would be better.
The specs use concrete as the insulator, why is that? I thought concrete crumbles around 900 degrees. Would I be better off just springing for that Fiberfrax Durablanket? it defeats the purpose of a cheapo, but durable foundry. One guy said he's had his foundry (insulated with concrete) for over 10 years.
what s the melting bucket thing made of? the thingymajig that holds and pours the metal?
could a small, but powerfull fan be used as the blowamahopper?
Joined: October 26 2009 Location: United States Posts: 270
Posted: September 13 2010 at 8:16pm | IP Logged
Don't use concrete. Use refractory cement. The melting bucket thing is called a crucible. Check out backyardmetalcasting.com. There are many furnace designs that should give you some ideas.
__________________ Proverbs 18:2 "A fool does not care whether he understands a thing or not; all he wants to do is show how smart he is."
Joined: September 01 2010 Location: United States Posts: 47
Posted: September 14 2010 at 3:00am | IP Logged
why pay for something when I can find it free, that flowerpot furnace threw me off, as you need to buy the booklet to find out how to do it, I'll just look harder. What temperatures can cement handle?
Joined: October 31 2006 Posts: 402
Posted: September 14 2010 at 7:22pm | IP Logged
Dave Gingery's books aren't expensive and will save you a lot of money in the long run. http://www.lindsaybks.com/dgjp/djgbk/index.html
You're dealing with very high temps and molten metal here, it's worth a few bucks to get the right information. This stuff can hurt you bad if you don't treat it right.
Joined: February 14 2008 Posts: 423
Posted: September 15 2010 at 2:35pm | IP Logged
For a crucible, I'm using a 4"x4" steel square tube, 1/4" wall, with a 3/8" plate welded on the end. This is plenty for zinc and seems to be adequate for dozens of pours of aluminum, but I wouldn't try brass (and of course I can't melt steel in there!). Most fluxes are salts that will corrode a steel crucible very quickly.
If you can find a fireplace or pottery shop that will sell you a few dozen firebricks, I think I'd just stack a furnace from those--they're quite cheap, will withstand ridiculous heat, and are easy to rearrange for a bigger or smaller fire. Getting the fuel packed tightly around your crucible, and preventing big air gaps, seems to be the trick for fast efficient melting. You really don't need much air; something like a hair blowdrier would be plenty. Too much air just cools off the crucible.
I echo the safety recommendations! I usually pour wearing face shield, leather everything, and behind a short sheet metal "blast curtain", since molten aluminum is wicked hot and will stick to you.
Joined: August 24 2011 Location: United States Posts: 7
Posted: August 24 2011 at 6:37am | IP Logged
yes you can use a brake drum and a blow dryer, or like I did was i used a keg as the furnace, portland cement, refractory clay, sand, perlite, and as little water as necessary to get it workable, it is very little water, have had great success in melting a variety of metals but not steeel or iron, i used a combination of burners put into one to get the most wide range of heat, my cucible is a 6 inch pipe about 5 inches high witj 1/4 plate welded for the bottom, if it wasn't raining here i would post pics, but very easy to build with minimal tools
Joined: December 15 2006 Location: United States Posts: 19
Posted: January 02 2012 at 12:06pm | IP Logged
I would go with Holloway and use a refractory cement for the furnace itself.
Both concrete and refractory cement are mixed with water and poured into some king of mold to give it the shape you want (Sono-Tube would work, around a large potato chip can). A primary concern here it the AMOUNT of water used. Follow what ever directions you find on the subject. Both materials will shrink as they cure. You want to minimize that by using very little water. Additionally, the concrete may hold water (concrete in a floor will take 28 days or longer to cure, Hoover Dam is probably still not fully cured). Water pockets of any kind are not desirable in furnace. When the furnace is fired that water expands and turns to steam. If it cannot escape it will explode.
Steel crucibles will work for a while for zinc and lead. I expect they might work for a while for aluminum. You can also find and buy crucibles through Foundry suppliers. I have a small one that is about the size of a coffee cup. The ones that I use at school will hold 16# of aluminum or 40# of bronze. That might equate to about 1.5 gallons volume
As I said - follow the directions carefully for a safe furnace.
You can also search the web for "back yard casting" and find lots of information from people that have been there and done that.
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Joined: February 05 2012 Location: United States Posts: 4
Posted: February 05 2012 at 1:13am | IP Logged
The easiest and best way for most people to make a crucible furnace is with a 55 gallon metal drum and line it with 4" of refractory. I use silica glass making sand and lincoln fireclay. It will withstand anything. I have a few that are over 20 years old and have thousands of firings to pure copper heats. Thats hotter than steel by the way.
The easiest and best burner is a oil burner from a home oil furnace.
You can find them used if you live in a oil use area but they are still available new. You only need about 1.5 gallons per hour burner. Not a huge burner. You can burn a mix of deisel and used motor oil if you want and switch to 100-% used oil after it gets hot. Generally it takes about an your to reach a red heat and you can melt 60lb of aluminum every 15 minutes after that.
Joined: December 10 2007 Posts: 95
Posted: February 05 2012 at 11:44pm | IP Logged
Use refractory and then you have to fire it at a low temp to cure it if you dont it can expload in your face from traped moisture.
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Joined: March 04 2015 Posts: 3
Posted: March 04 2015 at 5:30am | IP Logged
I used Plaster of Paris and sand for mine. It only goes to 1500 F max and its only meant for aluminum but I can also do lead and zinc as well. It can be a good way to go. Learned from youtube. Gotta love that site.
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