Nobody Special Posted September 11, 2013 Share Posted September 11, 2013 Got the casting bug again this weekend. Thought I'd throw together a little "coffee can" furnace in a little metal drum, about 7 gallons. Using lump charcoal to start, then probably build a naturally aspirated burner when cash flow improves. (Wish I'd read frosty's forum comments on them before my last one. It worked but bet I could have done a lot better.) Mud goes in tommorow. Variation on the backyard metal caster recipe that has worked well for me in the past. I know, could spend the money on satanite and kaowool, but I LIKE this one, and it worked fine without much patching. In fact, it's my forge liner now. Refractory's thick, about 2.5 or 3 inches, haven't decided, so the chamber will be 8 inches across by 10 high. Big enough for my level of casting. Also a picture of my dog, Charlie, who was unimpressed by all of this. Quote Link to comment Share on other sites More sharing options...
Justin Caradoc Posted September 12, 2013 Share Posted September 12, 2013 What mix for the refractoy do you use? or should ask how is it diffrent? Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted September 12, 2013 Author Share Posted September 12, 2013 Well, Lionel's recipe was take, by volume, 1.5 parts portland, 2 parts sand, 1.5 parts perlite, mix well dry, then mix in another 2 parts fireclay, then add water a little at a time until well mixed into mixture, not a lot of water, you don't want it soupy. I've tried it and it worked fine for casting. Definitely not as well as an industrial refractory, but it had the distinct advantage of being cheap and the parts coming in 100 lb bags, so patching, if needed (rarely in my case) was also cheap. Most of my casting was aluminum temps or lower, but it worked fine with brass or bronze........but if you let it go much hotter than needed for that, the portland starts to slag out of it a little, and it eventually will need patching. Definitely wouldn't recommend it for playing much with steel. It also eventually got crumbly and had to be replaced after a couple of years, but again, was cheap and easy. I'm certain it's less efficient than industrial stuff and kaowool overall, but I can always go thicker (of course the mix takes longer than kaowool to heat up and cool down), and I only do occaisional casting, not using it on a consistent basis. Basically it's a backyard hobby furnace, it works pretty good, and it can afford not to work perfectly. If I was doing a lot of casting, or going big, I'd probably spring for the good stuff. Only bad experience was failure to ram the mix properly the very first time I tried it, left a little pocket that water pooled in, fired it up nice and slow after it had cured four or five days......and BAM!!!!!! blew a small hole in the side. (it was covered, and i had put a little distance so no harm done except for the heart attack) Easily patched and back up and running. My version (ran out of dang perlite so tried this) was to take out the perlite, and add back in around 1 part sawdust or very small wood shavings. (I read in a couple of homemade versions that you could do this and it would burn out, leaving it honeycombed and the miniscules holes/air pockets served to insulate the mix somewhat. I have no idea if it worked the way it was explained, but it didn't blow up and the refractory worked okay the last time i tried it. Way too long of a response, but I anticipate the "you can't use the cheap crud" comments coming out of the woodwork. Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted September 12, 2013 Author Share Posted September 12, 2013 Starting with some of my homemade lump charcoal and forced air (you guessed it, a hairdryer on a rheostat). Next month probably build a naturally aspirated propane burner. Had built one before, but my ex-wife "misplaced" it. S'alright, after reading some of Frosty's posts on them,I think I can do a better one this time. I'll make a couple of steel crucibles to start and will be ordering some fused silica. (money's tight the last six weeks, ac went out, minor wreck, tire went, septic stopped up......and on and on.......) Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted September 18, 2013 Author Share Posted September 18, 2013 Whee! Casting furnace worked GREAT! Fired it up low for about 10 minutes to see if the refractory was gonna pop, then decided forget it. Turned the air off, put in a gallon or so of lump charcoal, looked around.....crap. Didn't make a crucible. One quick improvised steel crucible later, added a pound or so of aluminum, turned the air back up........and two or three minutes later I saw aluminum running out the drain on bottom. Whoops. Bottom of the steel crucible melted away. Guess it was a a little warmer than I thought........ :D I'm thinking maybe tommorow a better crucible, turn the air down a little and melt some copper or brass. Quote Link to comment Share on other sites More sharing options...
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