Solar Foundry?

[motoman465]

Hey, I just had an idea...planets must be aligned or something.  I have been wanting to do a little aluminum casting but have yet to even start on a foundry.  I remember reading on a site somewhere about a guy that covered an old satelite dish with reflective mylar and it melted an automotive heater core.  Do you think it would be possible to make a reflective parabolic dish and melt aluminum in a steel crucible?  It sounds good in my head, but do you think it would actually work in the real world?  Thanks!

Todd

[Ungrounded Lightning Rod]

Yes.

You might also look into cheap plastic or glass mirrors - a bit smaller across than the crucible - to tile the dish.  That will give you a better focus.

Mirror tiles may be available at your hardware store.

Or get some inexpensive glass hall or door mirrors totaling about the area of the dish and a glass cutter.  B-)

Check with your local window dealer.  Bet he's got some mirrors, too.

[tecker]

I did good scrounging at two glass companys for broken mirriors the pieces look good . I haven't made much progress but it's on my must do list .If you like puzzles it's ok.

[Capt Slog]

I made a solar panel a couple of years ago.  For the collector I needed a large sheet of metal, and knew that copper would be best as I wanted to solder onto it.  I managed to cadge a thrown-out domestic hot water cylinder.  I cut the ends off this and then cut and opened up the cylinder bit to make a flat sheet, but that's another story.

The point of this post is that I was left with the cylinder ends.  The bottom end was concaved.  I smoothed the surface with some fine emery paper and then polished it to a mirror finish with metal polish.  The result was an 18 inch (or so) mirror that when put in the sunlight could burn holes in piece of wood.  I never tried to melt metal with it, but I can see no reason why it shouldn't.  Not upto smelting standards I know, but great fun all the same.

What you really need is one of these..

http://en.wikipedia.org/wiki/Image:The_City_of_Nottingham-_Summer_04_088.jpg

This cost £900,000 apparently, and has to be coverd at certain times in case it instantly barbeques pigeons flying past it

[motoman465]

Thanks for the input!  Guess I have another thing to add to my list..LOL!

Todd

[cyplesma]

did you need the link to the guys site that does the back yard casting?

http://www.backyardmetalcasting.com/

.

[Bobbyb]

Hi,

If your internet connection allows it u might one to check out this episode of mythbusters Episode 46: Archimedes Death Ray.

If u don't know the show check out http://dsc.discovery.com/fansites/mythbusters/mythbusters.html

In short it's a entertainment science show.  In this show they try to burn a live size wooden boot using only mirrors and the sun.

Don't remember if they burn down the boat but there are some small scale test with great result's (burning wood).

As for melting metals, also collect all the wood as u search for those mirrors, burning that is a good plan B .

good luck!

[electrondady1]

i saw that episode and the boat did catch on fire.

i am unshure if there is much of an upper limit to the potential energy.

the sun does get fairly toasty

the only restriction i see  would be the size of the reflective surface

[ruddycrazy]

On noticing this Diary entry I just had to look

The melting temp for aluminuim is 660C (1220 F), now a solar reflective parabola may well provide this temperature or even greater. But to really melt ali,steel etc it needs to be soaked above that temp for all the solids to dissolve. Personally unless your living in the sahara desert in mid summer, I don't think you'd get enough energy to melt anything worthwhile before a cloud came over and the lot cooled quicker and you ended up with a solid mass of junk. When I was doing my engineers diploma we did some ali casting and I remember we thru some pill into the mix and i do remember the teacher saying without this little pill forget any chance of a casting. It's been that long I can't remember what the pill consisted of but some research will surely find it.

All in all I'd luv to be proved wrong but using solar to melt ali,stell etc wont happen unless the sun visits earth I reckon.

Cheers Bryan

[Ungrounded Lightning Rod]

Personally unless your living in the sahara desert in mid summer, I don't think you'd get enough energy to melt anything worthwhile before a cloud came over and the lot cooled quicker and you ended up with a solid mass of junk.

In the absence of significant obstructions that block or filter the light the temperature you'll approach is just the temperature of the sun times the fraction of the "sky" the crucible "sees" as being "sun" after the mirrors get done distorting the image.

There are lots of places where cloud cover is nearly nonexistent for hours at a time.  I'd have no problems with this in northern California anywhere east of the coastal range, or in Michigan summers for days at a time.

Of course the Nevada place is ideal:  No clouds almost all the time, thin air (above 47% of the atmosphere) yielding little filtering OR air cooling, etc.

[ULR]

... the temperature you'll approach is just the temperature of the sun times the fraction of the "sky" the crucible "sees" as being "sun" after the mirrors get done distorting the image.

Actually, higher.  (The above approximation treats the rest of the sky and the ground as being at absolute zero.  In fact the apparent radiant temperature of the sky is 4 degrees absolute plus some more because of the "greenhouse gasses" - mainly water vapor, while the radiant temperature of the earth is whatever the local ground temperature is.)

[ttgrthomas]

Todd,

First, view the 1400mm diameter Solar Cooker at www.sun-and-ice.de

I calculated the BTU's per hour on a typical sunny day anywhere south of a Salt Lake City latitude. in North America; spring, summer or fall seasons especially. I got about 14,000 BTU's per hour with my 4.5 ft. diameter reflector/concentrator dish.  

The focal area on that solar cooker was about as big around as a dinner plate. Maximum temperatures are in the 425-500 F range. The focus on the www.sun-and-ice.de solar food cooker is designed WEAK/DIFFUSE so that even if you leave it unattended & forget that there's liquid in the cooking pan, it won't just all boil off and burn a hole clean THROUGH the pan. This is a good safety feature for cooking, yes.

HOWEVER, if you really WANT aluminium melted down inside a crucible, the focus must be sharper .... say about the size of a teacup saucer.

All I can say at this point is that a PARABOLA design is optimal.

The larger the diameter of this parabola, the more raw BTU thermal power you'll have .... on the presumption that your Solar Micro Foundry Dish is built closer to machine shop specifications and we distance ourselves much further away from the poor quality of a garage-based weekend hobbyist.  

If you're interested in getting a business going where all manner of ordinary metals is melted-down with VERY high temperature parabola dish focused sunlight, contact me at 480.528.0632 in Phoenix, Arizona.

Gary