Hey bob,
I've been meaning to ask you something and I keep forgetting. Are those castings lost foam or do you have a pattern made up for them? I've been reading up on metal casting and will probably get into casting later but I want to do a lot of reading and research before I play with molten metal.
I really like my toes and other body parts where they are and want to make sure I have a damn good idea of what I am doing before I play with that.
We went through several different patterns.. Made them out of nylon... The last pattern is actually a plate with all the runners and risers and other stuff on it. Bang one side
up, bang the other side up. Take the plate out and go to town... You see can videos on youtube, and see how they do production sand casting... Its what we were trying to
replicate... A straight up pattern is fine for a few, but having to cut the runners and risers and all that is a PIA.
We were using some type of petrobond, oil based sand... Not the green sand with the clay and the water... When we got the stuff, it just wouldn't stick... Adding more
oil didn't do it, water didn't do it.... Took a bit of research, and I didn't believe it when I saw it, but I didn't have anything left to lose.... Rubbing alcohol... mixed it up
real good, and it was nice and sticky and stayed together... That was when we figured we needed a muller, and we actually found an old used one, they are not very common.
Back up plan if we didn't find a muller... And I didn't realize it then.. But now I do... Cement mixer with some steel balls in it... ROCK CRUSHER!!!!!
I built the furnace... Refractory cement is a ***** to work with.. You are supposed to use a "high shear" mixer... Ended up making a glorified paint stirrer on a drill... The amount
of water needed is also a pain... Requires very very little water, and a very precise amount of it.. I think it was 4cc's per pound... And the refractory cement is expensive... There
are all kinds of home brewed fire brick concoctions out there, I just wanted a furnace that would last and last and last... If I had to do it over again, I would not have made all the bricks
out of refractory cement, I would have just made 1" or so thick hot face, and done the rest with the stuff from Home Depot, would have saved about $400... I did the base like that..
The refractory is also super sticky... Had to slather the molds with vaseline, and then parchment paper over that... And the stuff takes forever to set up enough so that you could take the mold off...
Burner wise, made that too. Lots of designs on line... Basically just pipe... Tricky part is the flare on the end, and the nozzle size... I didn't get a perfect double cone,
but it was close enough, it works... Ended up using a mig welding tip for the nozzle... It'll run as low as 2psi of propane(makes fantastic burgers at 2psi),
and once its warm it'll go up to 55psi before flaming out. At 30psi it will melt 30 pounds of aluminum in under 45 minutes... I don't know if that is good or not..
Honestly, casting sucks.. Its probably not bad with something small, but banging up a big mold really sucks, those castings are 8 or 9 pounds, and each flask when full weighs over 140lbs..
Not the easiest thing to move around....
Casting is almost a black art.. The design of the molds, the runners, risers, blind risers, gates, flow restrictions blah blah blah... I bought a couple of books and it made my head spin..
And then what temp do take your material to, the fluxes, there can be Argon involved, hydrogen embrittlement... There is a lot more to it than I thought there was... I just scratched
the surface of it, so much more to learn... And I don't care to learn it.
And some pics.
Muller:
Brick Molds:
Test fitting.
Almost finished product... Painted the stand after that, and a cut up 55gallon drum goes around it... The lid is designed to float slightly so it sits flat,
And its counter weighted so it opens and closes really easy.
My burner.
And this pic is just for fun... Guy down the street builds chile processing equipment, commercial size.. He was building a GIANT chile roaster, and we made the
burners.... What a pain in the ass that was... For a furnace you are trying to tune the burner to give you a nice pretty cone... In a chile roaster you want a
big giant spread out flame... We got the length of the flame he wanted, but fell a bit short on diameter of it, played with it for a while also... The trick..
Instead of using a welding tip to get a smooth gas flow... Grease fitting, pull out the ball and spring, and the gas comes out all turbulent... These flames
are about 6 feet long and about 26 inches or so in diameter...(have you ever tried measuring the size of a flame??). They flamed out at about 58psi....
Just the two of them running sounded like sticking your head in a jet engine... The giant roasters he is making have 12 of those burners...
And since this is TREASUREnet... In the GOLD prospecting forum... I was down at the chile guys shop yesterday, and found out that his Dad was a professional gold miner...
Up by Caballo reservoir, before Caballo was there.. They used to pump water up out of the Rio Grande to run their sluices, then when they made the reservoir they couldn't
use the water anymore and had to go with giant dry washers... I thought that was pretty interesting.
Oh... And the pic of the chile roasting burners. That's 2 of them running.
