I would like to cast some aluminum--could a plaster mold be used
safely?

Thanks

Tut

wrote in message
oups.com...
I would like to cast some aluminum--could a plaster mold be used
safely?

Marginally, but only with great difficulty. Plaster is difficult to
completely dehydrate. Hot metal will rapidly drive off steam from any
remaining water, and cause the mold to either break (FAST!) or vomit up its
contents of molten metal.

Aluminum melts very near the decomposition temperature of calcium sulfate
(the primary constituent of Plaster of Paris), so the mold will be damaged
immediately upon pouring. You'll certainly lose features, and some of those
may be those of your face, if you're not careful.

Get some casting sand, and learn to make simple foundry molds. Metal
casting is one of the "high casualty" activities of amateur metalworkers.

LLoyd

Lloyd,

Your comments, please, on the feasibility of melting aluminum in a crucible
from the heat of an oxy-acet rosebud heater.

Thanks,

Bob Swinney
"Lloyd E. Sponenburgh" wrote in message
...

wrote in message
oups.com...
I would like to cast some aluminum--could a plaster mold be used
safely?

Marginally, but only with great difficulty. Plaster is difficult to
completely dehydrate. Hot metal will rapidly drive off steam from any
remaining water, and cause the mold to either break (FAST!) or vomit up
its contents of molten metal.

Aluminum melts very near the decomposition temperature of calcium sulfate
(the primary constituent of Plaster of Paris), so the mold will be damaged
immediately upon pouring. You'll certainly lose features, and some of
those may be those of your face, if you're not careful.

Get some casting sand, and learn to make simple foundry molds. Metal
casting is one of the "high casualty" activities of amateur metalworkers.

LLoyd

Lloyd E. Sponenburgh wrote:
wrote in message
oups.com...
I would like to cast some aluminum--could a plaster mold be used
safely?

Marginally, but only with great difficulty. Plaster is difficult to
completely dehydrate. Hot metal will rapidly drive off steam from any
remaining water, and cause the mold to either break (FAST!) or vomit up its
contents of molten metal.

Aluminum melts very near the decomposition temperature of calcium sulfate
(the primary constituent of Plaster of Paris), so the mold will be damaged
immediately upon pouring. You'll certainly lose features, and some of those
may be those of your face, if you're not careful.

Get some casting sand, and learn to make simple foundry molds. Metal
casting is one of the "high casualty" activities of amateur metalworkers.

LLoyd

LLoyd,

Thanks for the info--I was invited once many years ago to observe a ME
class cast Al for a class project and they used casting sand with good
results--thanks for saving my skin from hot metal. ;-))

VR

Tut

On Thu, 18 May 2006 09:56:07 -0500, "Robert Swinney"
wrote:

Lloyd,

Your comments, please, on the feasibility of melting aluminum in a crucible
from the heat of an oxy-acet rosebud heater.

Thanks,

Bob Swinney

It works for small melts, but fuel cost is very high.

Make yourself one of the self-aspirated propane-air burners described
at
http://www.abana.org/ronreil/design1.shtml

These are very inexpensive to make out of plumbing parts and a $2 MIG
nozzle. You'll need a regulator capable of about 20 PSI and a 20 lb
propane bottle as from a gas grill. I also highly recommend the
stainless conical 1:12 flare nozzle from Larry Zoller for under 10
bux.

You'll also want a few firebricks to make a little housing to surround
your crucible. Such a setup will melt a pound or two of aluminum
in a few minutes. You can gather everything you need for less than
the cost of one oxy and acet refill, and propane refills are
comparatively very inexpensive.

There's a photo of the flame from my first Reil burner at
http://www.abana.org/ronreil/burner2.jpg

I later built a side-arm burner that works even better, probably
produces about a quarter million BTU/hr.

There are those who have melted iron with these burners in a
refractory enclosure.

Lloyd E. Sponenburgh wrote:

wrote in message
oups.com...

I would like to cast some aluminum--could a plaster mold be used
safely?


Marginally, but only with great difficulty. Plaster is difficult to
completely dehydrate. Hot metal will rapidly drive off steam from any
remaining water, and cause the mold to either break (FAST!) or vomit up its
contents of molten metal.

Years ago I toured a plant in East Oakland, Calif
that did nothing but thin-wall plaster-cast AL.
Absolutely gorgeous work.

But as you said, lots of baking, lots of very careful
mold design.

Aluminum melts very near the decomposition temperature of calcium sulfate
(the primary constituent of Plaster of Paris), so the mold will be damaged
immediately upon pouring. You'll certainly lose features, and some of those
may be those of your face, if you're not careful.

Yup. One-time molds and one-time use of plaster. I
think they said they went through a railcar of plaster
every month. Also tall risers to get enough pressure
for good detail.

Get some casting sand, and learn to make simple foundry molds. Metal
casting is one of the "high casualty" activities of amateur metalworkers.

LLoyd

Are you sure that was plaster molds and not investment casting ceramic
slurry? Very thin wall is the key tipoff. The foundry I visit does
aluminum all the way to stainless steel. The molds are fired at 1800F or
so, are pulled directly from the kiln and filled with hot metal within
20 or 30 seconds, never cool off.

Jim Stewart wrote:

Lloyd E. Sponenburgh wrote:

wrote in message
oups.com...

I would like to cast some aluminum--could a plaster mold be used
safely?



Marginally, but only with great difficulty. Plaster is difficult to
completely dehydrate. Hot metal will rapidly drive off steam from any
remaining water, and cause the mold to either break (FAST!) or vomit
up its contents of molten metal.


Years ago I toured a plant in East Oakland, Calif
that did nothing but thin-wall plaster-cast AL.
Absolutely gorgeous work.

But as you said, lots of baking, lots of very careful
mold design.

Aluminum melts very near the decomposition temperature of calcium
sulfate (the primary constituent of Plaster of Paris), so the mold
will be damaged immediately upon pouring. You'll certainly lose
features, and some of those may be those of your face, if you're not
careful.


Yup. One-time molds and one-time use of plaster. I
think they said they went through a railcar of plaster
every month. Also tall risers to get enough pressure
for good detail.

Get some casting sand, and learn to make simple foundry molds. Metal
casting is one of the "high casualty" activities of amateur metalworkers.

LLoyd

RoyJ wrote:

Are you sure that was plaster molds and not investment casting ceramic
slurry? Very thin wall is the key tipoff. The foundry I visit does
aluminum all the way to stainless steel. The molds are fired at 1800F or
so, are pulled directly from the kiln and filled with hot metal within
20 or 30 seconds, never cool off.

Positive. One-time plaster molds.
I can't imagine why they'd be using
a boxcar of plaster a month if the
mold were ceramic slurry.

Jim Stewart wrote:

Lloyd E. Sponenburgh wrote:

wrote in message
oups.com...

I would like to cast some aluminum--could a plaster mold be used
safely?




Marginally, but only with great difficulty. Plaster is difficult to
completely dehydrate. Hot metal will rapidly drive off steam from
any remaining water, and cause the mold to either break (FAST!) or
vomit up its contents of molten metal.



Years ago I toured a plant in East Oakland, Calif
that did nothing but thin-wall plaster-cast AL.
Absolutely gorgeous work.

But as you said, lots of baking, lots of very careful
mold design.

Aluminum melts very near the decomposition temperature of calcium
sulfate (the primary constituent of Plaster of Paris), so the mold
will be damaged immediately upon pouring. You'll certainly lose
features, and some of those may be those of your face, if you're not
careful.



Yup. One-time molds and one-time use of plaster. I
think they said they went through a railcar of plaster
every month. Also tall risers to get enough pressure
for good detail.

Get some casting sand, and learn to make simple foundry molds. Metal
casting is one of the "high casualty" activities of amateur
metalworkers.

LLoyd

On Thu, 18 May 2006 13:57:57 GMT, "Lloyd E. Sponenburgh"
wrote:


wrote in message
roups.com...
I would like to cast some aluminum--could a plaster mold be used
safely?

Marginally, but only with great difficulty. Plaster is difficult to
completely dehydrate. Hot metal will rapidly drive off steam from any
remaining water, and cause the mold to either break (FAST!) or vomit up its
contents of molten metal.

Aluminum melts very near the decomposition temperature of calcium sulfate
(the primary constituent of Plaster of Paris), so the mold will be damaged
immediately upon pouring. You'll certainly lose features, and some of those
may be those of your face, if you're not careful.

Get some casting sand, and learn to make simple foundry molds. Metal
casting is one of the "high casualty" activities of amateur metalworkers.

LLoyd


lloyd's comments are bang on the money. I'll give you my experiences.
I was trying to make a casting for a mills 0.75cc model diesel engine.
this is no bigger than a matchbox so I made the mould by lost wax in
plaster. after a week of curing and drying I heated the mould enough
to melt out the wax. I then microwaved the hot mould to boil off all
of the moisture.
it seemed pretty damned dry and hot to me so I melted a crucible of
alumimium alloy for the pour.
the mould was carried out to the shed in a cooks heat mitten and it
was weighted down.
when I completed the pour the aluminium started to boil up in the
pouring sprue. I put the crucible back in the furnace and stepped away
just as a geyser of molten aluminium erupted from the floor up to the
ceiling of the workshop.

despite all that drying and heating there was still enough moisture in
the mould to cause mischief.

in the middle of all this bubbling up the mould disintegrated.

you can make a mould in cast iron or steel. just leave paper thickness
gaps between each piece of the mould and use a mould release spray.
or
make the mould in greensand.

the other thing that will bite you if you dont understand it is
hydrogen embrittlement. in the moulten state aluminium can dissolve
prodigious amounts of hydrogen, but in the solid state none can be
held in solution so it comes out of solution during cooling just like
co2 in a shaken up softdrink. the source of the hydrogen is
dissociated moisture. start with clean dry aluminium chunks and avoid
casting on humid days. aluminium chloride pills will purge out the
hydrogen gas as hydrogen chloride (one wiff will clear the lungs and
nasal passages like nothing else on earth :-) ) but they often arent
needed.

if you want a nice strong alloy stir the aluminium with a piece of
copper pipe. the copper pipe will dissolve into the aluminium with
astonishing speed. aircraft alloy is copper aluminuim alloy.

Stealth pilot

I would like to cast some aluminum--could a plaster mold be used
safely?

US gypsum makes "Metal Casting Plaster" which is formulated for
Non-ferris metals. There are others, which are made with plaster and
other refractory ingredients. Regular casting plaster will crack and
crumble when baked at 500 F which is needed to remove the water. Before
ceramic shell became popular, many lost wax bronze foundries made their
own "investment" by adding refractories to casting plaster.

--
Billy Hiebert
HIEBERT SCULPTURE WORKS
Small Part Injection Molding
http://www.hieberts.com

Billy and Stealth Pilot--thanks both of you for your input.

Stealth Pilot--say hi to T Gossling next time you see him. ;-))

Tut

Billy and Stealth Pilot--thanks guys for your inputs.

Stealth Pilot wrote:

if you want a nice strong alloy stir the aluminium with a piece of
copper pipe. the copper pipe will dissolve into the aluminium with
astonishing speed. aircraft alloy is copper aluminuim alloy.

Stealth pilot

Sorry Stealth Pilot, I can't walk away from this one.

Aircraft Alloy.

This is erroneously perpetuating the biggest pile of hokey crap that
ever got passed off on the buying public, the myth that there is some
mysterious supernatural properties to something used to build aircraft.
In this day and age, the only thing really mysterious is "where the hell
did those certifications sheets go that were with the metal when it came
in?" Other than certs, it's the same old crap that is available anywhere
you can buy aluminum sheet goods. Different alloy are used in different
parts for different needs.

I'm done ranting now. I promise I'll play nice. Mostly. If anybody is
looking.

FWIW it would be more correct to say that "Some of the alloys commonly
used for aircraft building use copper as an alloying agent" or some
such.

The 2000 series alloys contain copper as their major alloying agent.
Makes for a decent piece of sheet metal with good hardening
capabilities.
The 7000 series use zinc. Cuts really nice, crisp even. Heat treatable
to get even more strength out of it. In the wrong environment it will
rot while you watch.

Etc., etc....

If you dissolve some copper into the aluminum pot, the castings have to
sit a while before they have hardened up, until then they machine a
little more like pure al., similar to chewing gum. If you have access to
a decent temp controlled oven, and some phase diagrams for similar
alloys ('cause, face it, the likelihood of getting a analysis of the
cast is pretty slim), you can artificially age the parts to speed the
process along. Then they machine nice. Or they might not, the nature of
home foundry work, eh!

Cheers
Trevor Jones

Trevor--

It would appear that a small percentage of copper in Al (3-5%) does
increase the strength of sand cast AL--as much as 2-3 times depending
on percentages and in some cases other trace elements. Ref--"Manual for
the Design of Ferrous and Non-Ferrous Pressure Vessels and Tanks"--by
Karl Siemon 1940.

I assume that aircraft manufacturers would want the strongest Al alloy
possible--although I have no experience in aircraft production.;-))

Once again I appreciate everyones inputs--thanks.

Tut

wrote:

Trevor--

It would appear that a small percentage of copper in Al (3-5%) does
increase the strength of sand cast AL--as much as 2-3 times depending
on percentages and in some cases other trace elements. Ref--"Manual for
the Design of Ferrous and Non-Ferrous Pressure Vessels and Tanks"--by
Karl Siemon 1940.

I assume that aircraft manufacturers would want the strongest Al alloy
possible--although I have no experience in aircraft production.;-))

Once again I appreciate everyones inputs--thanks.

Tut

The copper alloy that I see the most of is 2024, usually in T3
condition. The copper goes into solution when heated and allows a great
deal of work to be carried out. It is then allowed to age on its own, or
it is aged artificially, causing the copper to precipitate out of
solution. It is by no means the strongest of the alloys used, but it is
dead common, as it is strong enough and reasonably corrosion resistant.
Solution heat treatment and precipitation hardening of formed sheetmetal
parts is a fairly regular occurence in the shops I have been working in.

With proper heat treating, 7075 can be brought to strengths exceeding
many of the steel alloys.

The aircraft manufacturers want the best overall material for the
particular part, and choose their materials accordingly. These parts may
be cast, forged, machined from solid, or built by various methods of
sheetmetal work. Many alloys are used, chosen for their attributes, for
the method they must be worked, or cost.
There is some pretty low grade **** that ends up as airplane parts. But
it is low grade **** that has been deemed acceptable for the purpose it
is used for. All is not equal, and that which carries the moniker of
"aircraft grade" or "aircraft alloy" is a pig in a poke unless there is
a fair bit more info attached.

Cheers
Trevor Jones

Thanks Trevor,

If I melt down an Al head from an auto salvage yard what type of alloy
would you guess I might get?

Tut

I don;t recall off ohand what alloy it would be, but rthere is a few
different types in use by different companies. It is good material to
sand cast with. I treat aluminum from vehicle parts like heads,
manifolds, trany cases etc as I would 356.1 alloy


On 20 May 2006 18:10:22 -0700, wrote:
Thanks Trevor,

If I melt down an Al head from an auto salvage yard what type of alloy
would you guess I might get?

Tut

Roy,

Thanks for the info--it looks like 356 has no copper in it so I guess I
won't be stirring it with a copper pipe. ;-))

Tut

I buy ingots from a supplier not to far from me. The info he gave me
wsa that virtually all the aluminum found in automotive wheels, head
cases etc can be treated as 356 alloy, and everythng should work ouyt
just fine. There are some odd ball propreiatary alloys used by some,
but treat it as if it was 356.

The smelter that I buy from on occasion uses automotive andother
precast junk as hie main ingredients for 356, and IIRC is it 380
alloy. Heck I can't remember my own age anymore yet alone aluminum
alloys I do not use anymore. I tend to stick with what can be used in
356 applications.

On 20 May 2006 18:31:37 -0700, wrote:
Roy,

Thanks for the info--it looks like 356 has no copper in it so I guess I
won't be stirring it with a copper pipe. ;-))

Tut

Roy,

Thanks again for your info. I was thinking, how does one tell Al from
magnesium at the salvage yard? I don't need a fire in my garage. ;-))

Tut

wrote:
Roy,

Thanks again for your info. I was thinking, how does one tell Al from
magnesium at the salvage yard? I don't need a fire in my garage. ;-))

Tut



You are going to HAVE to have a fire to melt all this stuff...

wrote:
I would like to cast some aluminum--could a plaster mold be used
safely?

As others have said, it's a bit hot for plaster.

I just poured my first-ever cast yesterday: old auto pistons for the
metal, and 90/10 sand/modelling-clay for the mould.
The part was essentially a Y-junction in pipe, so I made the core first,
& fired it in an electric kiln. Then coated it in wax, & coated the
whole thing in more sand mix. Poked several holes from the top with
0.9mm wire, to provide air vents.
After several false starts, I found the secret to baking that mould
without cracking it: dry it thoroughly at room temperature first. Then
into the kiln, & a very light heat to melt the wax, which is then poured
out. Then ramp up heat slowly (over 3 hours), until it's incandescent.
That burns all the wax out.
Melted the metal in the same kiln, & poured. Looked good. Now I erred:
it took so little metal that I thought something had stuck. So I tapped
the mould: cracked it! Metal ran out the crack: I stopped it with sand,
& poured in more metal.
However, the first pour had evidently skinned before the second went in:
they didn't unite. Lesson 1: pour once only... Apart from that, it came
out quite well.

On Fri, 19 May 2006 19:45:27 -0600, Trevor Jones
wrote:

Stealth Pilot wrote:

if you want a nice strong alloy stir the aluminium with a piece of
copper pipe. the copper pipe will dissolve into the aluminium with
astonishing speed. aircraft alloy is copper aluminuim alloy.

Stealth pilot

Sorry Stealth Pilot, I can't walk away from this one.

Aircraft Alloy.

This is erroneously perpetuating the biggest pile of hokey crap that
ever got passed off on the buying public, the myth that there is some
mysterious supernatural properties to something used to build aircraft.
In this day and age, the only thing really mysterious is "where the hell
did those certifications sheets go that were with the metal when it came
in?" Other than certs, it's the same old crap that is available anywhere
you can buy aluminum sheet goods. Different alloy are used in different
parts for different needs.

I'm done ranting now. I promise I'll play nice. Mostly. If anybody is
looking.

FWIW it would be more correct to say that "Some of the alloys commonly
used for aircraft building use copper as an alloying agent" or some
such.


agreed
I suppose I should have taken more time to post but I didnt have it.

what I was trying to convey was that the aluminium can be increased in
strength if you stir in some copper.
alooominum has a melting point around 300 degrees and copper around
1500 degrees so it seems difficult to conceive of a method of getting
the two mixing.
just stir molten aluminium with copper and you'll get a surprise at
how fast the copper vanishes/dissolves in. it turns out to be easy.
Stealth Pilot

On Sun, 21 May 2006 03:16:31 -0800, David R Brooks
wrote:

wrote:
I would like to cast some aluminum--could a plaster mold be used
safely?

As others have said, it's a bit hot for plaster.

I just poured my first-ever cast yesterday: old auto pistons for the
metal, and 90/10 sand/modelling-clay for the mould.
The part was essentially a Y-junction in pipe, so I made the core first,
& fired it in an electric kiln. Then coated it in wax, & coated the
whole thing in more sand mix. Poked several holes from the top with
0.9mm wire, to provide air vents.
After several false starts, I found the secret to baking that mould
without cracking it: dry it thoroughly at room temperature first. Then
into the kiln, & a very light heat to melt the wax, which is then poured
out. Then ramp up heat slowly (over 3 hours), until it's incandescent.
That burns all the wax out.
Melted the metal in the same kiln, & poured. Looked good. Now I erred:
it took so little metal that I thought something had stuck. So I tapped
the mould: cracked it! Metal ran out the crack: I stopped it with sand,
& poured in more metal.
However, the first pour had evidently skinned before the second went in:
they didn't unite. Lesson 1: pour once only... Apart from that, it came
out quite well.

you cannot interrupt the pour for a moment because they will never
unite.
if you are doing a multi ladle pour the subsequent ladle must be
started before the previous one has completed pouring.

....and "better a feather than a flitch"
Stealth Pilot

On 20 May 2006 19:20:59 -0700, wrote:

Roy,

Thanks again for your info. I was thinking, how does one tell Al from
magnesium at the salvage yard? I don't need a fire in my garage. ;-))

Tut

it always burnt brightly for me :-)

you can make your own greensand btw.

take any fine quartz sand and put it in a bucket.
squish a hose into it and let the bucket overflow until all the white
clay component has washed away.
then get 5% of the volume of the sand in bentonite clay. moisten the
sand with no more than 5% water (ratio to the amount of sand) and nead
your hands throught the sand clay misture.
the aim is to coat each sand grain with a coating of bentonite and you
do this by neading and rubbing the sand through the clay.
when it is all coated and moistened it takes on astonishing strenght.

bentonite is such a unique clay that it is available from minerals
suppliers. it loses one water bond when you dry it pre casting.
it loses the second bond during casting and it is this that creates
the gas pressure in the sand which prevents permeation into the samd
of the metal. it loses the final water molecule at over 1500 degrees.
after an aluminium casting you let it cool then replace the lost
moisture and you are back in business to make the next mould.
Stealth Pilot

wrote:

Thanks Trevor,

If I melt down an Al head from an auto salvage yard what type of alloy
would you guess I might get?

Tut

Could be anything, but 356 is fairly likely according to what I have
read. I have a couple heads around for the same thing, though it's not
happening fast.

Whatever alloy it is, it will be a sandcasting alloy, most probably.

Cheers
Trevor Jones

wrote:

Roy,

Thanks again for your info. I was thinking, how does one tell Al from
magnesium at the salvage yard? I don't need a fire in my garage. ;-))

Tut

You need a pocket knife and a couple packets of vinegar from a fast
food restaraunt (convenient and portable, no other reason).

Scrape a spot clean with the knife blade, apply vinegar. It will bubble
and turn a smutty purpleish brown if magnesium. A known magnesium
sample, like one of the firestarters with the flint down the side of it
will give you a good reference. If you are dealing with thin castings, a
large hammer will tell. Al. parts will break up easilly, magnesium parts
will rebound the hammer right back at you.

I know this from experience, and should have figured it out BEFORE I
worked myself to a full sweat breaking up those cast oil pans I found in
the dupster. Sigh
They were about 1/8 inch thick, and on a concrete surface when I hit
the first one with an 8 pound sledge. The damn hammer almost got me on
the rebound.

Cheers
Trevor Jones

cavelamb, David, Stealth Pilot, and Trevor

Thanks everyone for the input--Trevor your hammer incident brought a
smile to my face.

Best Wishes

Tut

wrote:

cavelamb, David, Stealth Pilot, and Trevor

Thanks everyone for the input--Trevor your hammer incident brought a
smile to my face.

Best Wishes

Tut

Well, it almost put a divot in mine :-)

There's a surprising amount of exercise in a couple truck oilpans.
sigh.

Cheers
Trevor Jones

356 is likely the most common aluminum sand and permanent mold casting
alloy, especially due the the automotive industry. It is rarely used
"as-cast". The "as-cast" temper is called "F". In F temper it would have a
tensile of about 20 ksi and 3% elongation. It can be "aged" at 440 degrees
for 7-9 hours which improves tensile to about 24 ksi this is called "T5"
temper. It can also be brought to a temper of "T6" by heating to 1000
degrees, holding for 6-12 hours, quenching in water and then aging at 310
degrees for 3-5 hours. Tensile goes to 25+ ksi, yield strength is 18 ksi
and elongation perhaps 3.5%. 356 casts easily. It is an aluminum with a
nominal 7% silison content. Copper is considered an impurity.

319 is a common casting alloy, with slightly less silicon than 356 (about 6%
silicon) but also about 3.5% copper. The aim of this alloy is to produce a
cast aluminum alloy with fair strength as cast. It is a little more
difficult to cast without internal shrink problems and is generally used as
cast.

201, 204 and 206 are aluminum alloys containing 4 to 6% copper. 201 also
contains some silver, (only a tiny amount) but the price is higher. These
alloys should all be used after a heat treatment. The procedure is a more
complicated heat treatment involving slow heating to about 980 degrees, with
a water quench. With good quality material the aging may be eliminated but
a lot of designers wish to "over-age" the casting because it will be
dimensionally more stable than in the t^ temper. This overaging is called
T7. These alloys are often used in military applications.

535 aluminum is an alloy of aluminum with magnesium plus other elements. It
is difficult to cast but has the advantage of an alloy which is of good
strength as cast. Heat treating is not done. This alloy is very bright on
surface appearance and polishes well. It also will anodize very nicely and
has good corrosion resistance, even in seawater.

713 aluminum is an alloy of aluminum with about 7% zinc. It is reasonably
easy to cast, a bit more difficult than 356 or 319 but develops its strength
naturally. It is called a "naturally aging" alloy. It will develop full
strength 21 days after casting at which time is machines easist. If
machined immediately after casting it will be gummy and machined surfaces
will be rough. To speed up the process if can be given a T5 treatment of
aging at 250 degrees for 12 hours.

There are many other aluminum casting alloys but these are some of the more
common ones.

Mark


"Roy" wrote in message
...
I buy ingots from a supplier not to far from me. The info he gave me
wsa that virtually all the aluminum found in automotive wheels, head
cases etc can be treated as 356 alloy, and everythng should work ouyt
just fine. There are some odd ball propreiatary alloys used by some,
but treat it as if it was 356.

The smelter that I buy from on occasion uses automotive andother
precast junk as hie main ingredients for 356, and IIRC is it 380
alloy. Heck I can't remember my own age anymore yet alone aluminum
alloys I do not use anymore. I tend to stick with what can be used in
356 applications.

On 20 May 2006 18:31:37 -0700, wrote:
Roy,

Thanks for the info--it looks like 356 has no copper in it so I guess I
won't be stirring it with a copper pipe. ;-))

Tut

Mark,

Alot of great info in your post--thanks much.

My plan is to cast a 50 inch dia wind generator blade from one I'm
currently using. Had thoughts of copying it from wood but decided to
give casting a try as new learning experience.

Thanks to all for hopefully keeping skin on my bones. ;-))

Tut

wrote:

Mark,

Alot of great info in your post--thanks much.

My plan is to cast a 50 inch dia wind generator blade from one I'm
currently using. Had thoughts of copying it from wood but decided to
give casting a try as new learning experience.

Thanks to all for hopefully keeping skin on my bones. ;-))

Tut


Solid cast blades?

Wouldn't that be a liggle heavy?

cavelamb,

1 inch at the tip, 3 inches at the base. 50 inches long and about .5
inches thick--rough weight approx 3x50x.5x.5 x (.0978 lbs/cu in)= 3.7
lbs ;-)

tut

On 23 May 2006 07:02:18 -0700, wrote:

cavelamb,

1 inch at the tip, 3 inches at the base. 50 inches long and about .5
inches thick--rough weight approx 3x50x.5x.5 x (.0978 lbs/cu in)= 3.7
lbs ;-)

tut

Whoa! Time Out! Sanity Check time...

That's all well and good, but I wouldn't try making your own blades
without some serious engineering studies - remember that when a
propeller or turbine blade is spinning at 3K - 5K - 10K you have a
rapidly multiplying amount of force working on that blade. And DIY
Metal Casting doesn't give you a lot of control over the internal
grain structure and alloy composition of that blade.

And when one blade breaks off the hub, the rest are going to go into
a severely imbalanced condition and follow in rapid succession - and
where they fly and where they land, nobody knows...

REALLY easy to kill someone that way - they just have to be standing
in the wrong place. Just because you /can/ cast your own propeller
blades doesn't mean you /should/.

This is the time you go buy the factory made part that you can be
fairly certain will work properly and safely. Even with homebuilt
aircraft running modified automotive and snowmobile engines, they buy
a factory built propeller. Save the DIY stuff for the not-so-critical
parts.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.

Bruce,

Thanks for your comments. If I were talking about making 15 foot blades
I would agree--but for a 50 inch blade I think I'll be safe. If I ever
get around to casting and testing, I'll let everyone know how it turns
out.

Tut

In article , Bruce L.
Bergman wrote:

On 23 May 2006 07:02:18 -0700, wrote:

cavelamb,

1 inch at the tip, 3 inches at the base. 50 inches long and about .5
inches thick--rough weight approx 3x50x.5x.5 x (.0978 lbs/cu in)= 3.7
lbs ;-)

tut

Whoa! Time Out! Sanity Check time...

That's all well and good, but I wouldn't try making your own blades
without some serious engineering studies - remember that when a
propeller or turbine blade is spinning at 3K - 5K - 10K you have a
rapidly multiplying amount of force working on that blade. And DIY
Metal Casting doesn't give you a lot of control over the internal
grain structure and alloy composition of that blade.

And when one blade breaks off the hub, the rest are going to go into
a severely imbalanced condition and follow in rapid succession - and
where they fly and where they land, nobody knows...

REALLY easy to kill someone that way - they just have to be standing
in the wrong place. Just because you /can/ cast your own propeller
blades doesn't mean you /should/.

This is the time you go buy the factory made part that you can be
fairly certain will work properly and safely. Even with homebuilt
aircraft running modified automotive and snowmobile engines, they buy
a factory built propeller. Save the DIY stuff for the not-so-critical
parts.

Yeah - what he said. I've made a hell of a lot of stuff in the past and
hope to in the future, but I'd *never* do this. Subjectively, I'd rate
the risk of failure as pretty high, and the *consequences* of failure
as potentially fatal.

Cast aluminium in thin long sections has lousy resistance to vibration
induced stresses. It's not just the tensile strength.

PDW

I've used a Ron Reil design for a number of years - on and off.
I use "green sand" - and have mixed results with some Al.

I used propane and the heating is done by the IR from the walls that
the torch got hot in the first place. You don't heat with the flame.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member
http://lufkinced.com/



Don Foreman wrote:
On Thu, 18 May 2006 09:56:07 -0500, "Robert Swinney"
wrote:


Lloyd,

Your comments, please, on the feasibility of melting aluminum in a crucible

from the heat of an oxy-acet rosebud heater.

Thanks,

Bob Swinney


It works for small melts, but fuel cost is very high.

Make yourself one of the self-aspirated propane-air burners described
at
http://www.abana.org/ronreil/design1.shtml

These are very inexpensive to make out of plumbing parts and a $2 MIG
nozzle. You'll need a regulator capable of about 20 PSI and a 20 lb
propane bottle as from a gas grill. I also highly recommend the
stainless conical 1:12 flare nozzle from Larry Zoller for under 10
bux.

You'll also want a few firebricks to make a little housing to surround
your crucible. Such a setup will melt a pound or two of aluminum
in a few minutes. You can gather everything you need for less than
the cost of one oxy and acet refill, and propane refills are
comparatively very inexpensive.

There's a photo of the flame from my first Reil burner at
http://www.abana.org/ronreil/burner2.jpg

I later built a side-arm burner that works even better, probably
produces about a quarter million BTU/hr.

There are those who have melted iron with these burners in a
refractory enclosure.


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wrote:

Bruce,

Thanks for your comments. If I were talking about making 15 foot blades
I would agree--but for a 50 inch blade I think I'll be safe. If I ever
get around to casting and testing, I'll let everyone know how it turns
out.

Tut

A 50 inch airplane proppeler cast at home?

No need to tell us about that. It WILL majke the news, unless you live
a long ways from any witnesses.

Do you have a video camera? Tripod for it?

Enquiring minds want to know.

Learn to laminate maple and carve a prop if you HAVE to do it yourself.

Cheers
Trevor Jones

Trevor Jones wrote:

wrote:

Bruce,

Thanks for your comments. If I were talking about making 15 foot blades
I would agree--but for a 50 inch blade I think I'll be safe. If I ever
get around to casting and testing, I'll let everyone know how it turns
out.

Tut

A 50 inch airplane proppeler cast at home?

No need to tell us about that. It WILL majke the news, unless you live
a long ways from any witnesses.

Do you have a video camera? Tripod for it?

Enquiring minds want to know.

Learn to laminate maple and carve a prop if you HAVE to do it yourself.

Cheers
Trevor Jones

OK

Wind generator blade. Not so much a threat to life and limb.

For that size, you would be happier with one made of composites,
methinks.

Cheers
Trevor Jones

I learned lost wax casting in college using silver and bronze, (not
quite as hot as aluminum) The investment mold material was similar to
plaster. You heated the mold to burn not melt out the wax. I don't recal
the burn out temp on the kiln, But it had to be hot enough to burn off
the carbon residue because the mold was clean white in the cavity. You
pour with the mold hot from burn out.