I want to build a charcoal forge to melt aluminium, then use that to cast segments of a giant parabolic dish which will be used for a multitude of things including making a solar forge.
The charcoal forge is going to be the simple "plaster+sand insulated container with an air feed and a steel crucible" design popularised on YouTube.
However, forges are things I have no experience with, anything I should know that a complete amateur almost certainly wouldn't?
Oh, also, are fire extinguishers typically made of steel?
I'm hoping I can get hold of a used up disposable extinguisher and lop the top off to use it as a crucible.
Although it wouldn't work for a solar forge if it got to steel-melting temperatures. Pity there's not really any way I can make a crucible for melting steel.
Interesting questions OP. Pinned this one.
>>929935
>giant parabolic dish
you can get a giant satellite tv dish from craigslist for cheap and line that with mylar. Boom solar forge.
>>930278
I'd be surprised if they're actually parabolic, because abbreation probably wouldn't matter for a satellite dish and spherical dishes are easier to make from what I hear.
Also, I live in NZ, so there's a very limited supply of random junk.
>>929935
Somebody pointed out here that you can make a smooth surface by using a barrel of some sort, cover one end with mylar and then pump some air from the barrel. Atmospheric pressure will push in the mylar forming a parabolic surface. Or close.
>>930343
Exactly parabolic is preferable, so I wish to cast one.
>>930340
Christchurch?
I have such a dish. previous owners were asian.
you can have if you're in Canterbury
>>930209
Spend $20 and get a grsphite crucible off of Amazon.
Sorry for the late responses, was away for the weekend.
>>930839
Hold on, is this the 6-segmented dish I tried to buy before which was advertised as being in Auckland(where I so happened to be headed) but actually turned out to be in Christcurch?
Thay would be amusing.
>>930909
Graphite crucible?
What's the melting point, and does it provide other advantages such as being less liable to be stuck to?
Also bear in mind that NZ is isolated and has a tiny population, so buying online is tricky and expensive unless by some miracle it's available domestically without a massive markup.
>>931899
It'd be tiny though.
I want the sort of mirror that if you fired the resulting beam at bare rock, it would quickly vaporize.
Although directing the beam could be an issue, since a mirror reflecting only 90% of light is absorbing 10% of a ridiculous amount of heat energy.
Maybe there's a way to do it with lenses, but the simulation would be tricky to setup.
R8 h8 dont b8.
All sourced from stuff i found. Literally $0.00 invested so far, included the chevy fly wheel my brother gave me for the plate. Still looking for about 30 more bricks for the top.
>>932929
tremendous
>>932931
You like it? I gotta say I'm pretty pleased with myself. I'm not sure if i should buy some mortor or just slatjer the sides in mud everytime i use it.
Heres one with the plate on it. I think i need to do some adjustments on it to get the plate off the walls so i can build the top.
>>932934
>>929935
>plaster+sand insulated container with an air feed and a steel crucible
I've heard people shit talking the plaster/sand mix here on /diy/ before. Supposedly this isn't particularly durable, and it's better to use a mixture of actual refractory cement. Does anyone have experience using either in a forge build that they want to share? is legit refractory cement worth the 3-4x cost?
>>933001
Yes, it is.
I don't know much but I know that utilizing heat more efficiently will always pay for itself with enough time.
>>933004
>utilizing heat more efficiently
we are talking about using fucking charcoal as a fuel source. Shit's dirt cheap, so efficiency isn't really an issue. I'm more concerned about durability.
>>930209
>>931846
graphite crucibles and clay crucibles. they don't contaminate the metal slightly like steel crucibles will.
However, you could probably make an obsidian crucible if you really wanted to, to cast steel in. Just use solar forge to make lava in the top of a rock, use tongs to pick up and pour before you've melted all the way through, bam, rock crucible for steel.
https://www.youtube.com/watch?v=hHD10DjxM1g
Watch king of random stuff. He looks like a rat.
>>931846
>6-segmented dish
Nah never advertised, it's about 3m diameter copper mesh with steel spokes.
for picking up asian TV I imagine, it's mounted round at my mates house doing fuck all.
What kind of mold would hold up to aluminum or other low heat metals a charcoal forge could melt?
I know a steel muffin pan will, but for casting a shape. I know silicone can deal with an oven at 400,F but I doubt it could take the 1000+ of liquid metal. Maybe a type of fiberglass or ceramic clay of some kind?
>>933574
clever fucker though
you don't cast metal in a forge you dumb niggers
