What to use to make a mold?

[AK]

I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if mold material can
withstand 500 degrees Fahrenheit so I can pour lead into it and then
cover it by fiberglass. Alternatively I would use the mold to create a
fiberglass container first and fill it up with lead pellets. So my
question is what do I use to make a mold, gypsum if so what kind,
anything else?

Andrzej

[sisu1a]

On Mar 22, 5:23*pm, AK > wrote:
> I want to make a small mold I would later use to create a fiberglass
> container to hold lead weight. It would be nice if *mold material can
> withstand 500 degrees Fahrenheit so I can pour lead into it and then
> cover it by fiberglass. Alternatively I would use the mold to create a
> fiberglass container first and fill it up with lead pellets. So my
> question is what do I use to make a mold, gypsum if so what kind,
> anything else?
>
> Andrzej

High temp RTV rubber can withstand up to 1000deg F. It's not cheap
stuff, but it will work quite nicely...

If you use gypsum or plaster products, just make two molds, (after
your first mold is made make a male model from it to cast new females
off of...) as it would be difficult to get out your lead w/out
breaking it, assuming it survives the thermal shock of the pour. Heat
up your plaster mold in an oven to within 100deg of your pour first to
avoid that pitfall, but you must very slowly heat the plaster up since
it may have micro water in pores that will superheat and make it crack
as the steam exits. Take at least 4 hrs to bring your mold up to temp
(after 24 hrs minimum cure) , ramping up 100deg/hr until at
400ish... plaster is cheap and easy to work with, so it will
probably be most practical. note-plaster expands 1-3% when cured, so
take this into account for allowances if you have critical tolerances.

If you need precision plaster/gypsum there is a product called
Ultracal (in 30 or 60 minute cure versions) made by US gypsum that
does not expand or shrink. it's cheap enough to use too at like
$30/50# . It feels and mixes just like plaster of paris but is
gypsum based so it cures like cement. Phenomenal product actually...

There's always the option to just trap your lead shot in epoxy
thickened with cabosil or microballoons etc, which seems much easier
but will obviously not provide the same density as a solid block...

-Paul

[Eric Greenwell]

sisu1a wrote:

> There's always the option to just trap your lead shot in epoxy
> thickened with cabosil or microballoons etc, which seems much easier
> but will obviously not provide the same density as a solid block...

It does avoid the breathing of lead vapors, something even a pilot
should avoid.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Steve Leonard[_2_]]

For a single pour mold, you can even carve it out of wood, like a 2 by 4.
It will smoke, burn the wood (you can blow out the fire), but it will hold
up for a single lead weight making. How heavy a weight are you trying to
make? And about how big?

You could then make the glass cup from the lead part, or even from a block
of foam that you cut to about the same shape.

A friend once got in trouble with his wife by using one of her frying pans
to make lead disks for putting in the seat pan of our old club two place!

One thing to watch out for (may not be this way with the gypsm stuff that
Paul mentioned), but anything that used water in its making, can trap
water inside. Put molten lead in it, and it can be a bad thing.

Happy slug making!

Steve Leonard

[Ian Burgin]

At 02:30 23 March 2009, Steve Leonard wrote:
>For a single pour mold, you can even carve it out of wood, like a 2 by 4.

>It will smoke, burn the wood (you can blow out the fire), but it will
hold
>up for a single lead weight making. How heavy a weight are you trying
to
>make? And about how big?
>
>You could then make the glass cup from the lead part, or even from a
block
>of foam that you cut to about the same shape.
>
>A friend once got in trouble with his wife by using one of her frying
pans
>to make lead disks for putting in the seat pan of our old club two
place!
>
>One thing to watch out for (may not be this way with the gypsm stuff
that
>Paul mentioned), but anything that used water in its making, can trap
>water inside. Put molten lead in it, and it can be a bad thing.
>
>Happy slug making!
>
>Steve Leonard
Lead has a melting temp of about 500 degrees C commercial moulds for
casting batches are usually cast iron as are some pans.
If you make a mould using sheet steel this would then encapsulate the lead
after pouring and prevent the soft lead from deforming under pressure from
the fastening bolts.

[[email protected]]

On Mar 22, 5:23*pm, AK > wrote:
> I want to make a small mold I would later use to create a fiberglass
> container to hold lead weight. It would be nice if *mold material can
> withstand 500 degrees Fahrenheit so I can pour lead into it and then
> cover it by fiberglass. Alternatively I would use the mold to create a
> fiberglass container first and fill it up with lead pellets. So my
> question is what do I use to make a mold, gypsum if so what kind,
> anything else?
>
> Andrzej

sand

[sisu1a]

On Mar 23, 8:28*am, wrote:
> On Mar 22, 5:23*pm, AK > wrote:
>
> > I want to make a small mold I would later use to create a fiberglass
> > container to hold lead weight. It would be nice if *mold material can
> > withstand 500 degrees Fahrenheit so I can pour lead into it and then
> > cover it by fiberglass. Alternatively I would use the mold to create a
> > fiberglass container first and fill it up with lead pellets. So my
> > question is what do I use to make a mold, gypsum if so what kind,
> > anything else?
>
> > Andrzej
>
> sand

http://en.wikipedia.org/wiki/Sand_casting not quite that simple in
practice and would also req the purchasing of some specific setup
materials which are not found at Home Depot etc...

You should go the wood or plaster route.Wood is dead simple if your
shape is not to complex. I saw that Steve quite rightly mention of
worry of plaster and residual water/steam being an issue... hence
the very specific directions I layed out for preheating/drying your
plaster mold BEFORE lead is poured in. If it survives the 4 hr
incremental ramp up to 400deg, it will not break from the pour since
all the water will have been evacuated by then. If in doubt, leave it
in the oven for an extra hr or 2 at 400ish...

I dabble in investment casting, and the same methodology applies for
pouring 1700-2100 deg metal (bronze, slver, gold, etc) into a plaster
mold, except the heatup/dryout process brings it up to 1000deg over a
5, 7, or 12 hour ramp up (usually spending some an hr or 2 at 1300deg
to vaporize out the wax remnants before ramping back down to
1000ish).

-Paul

[AK]

On Mar 23, 12:12*pm, sisu1a > wrote:
> On Mar 23, 8:28*am, wrote:
>
> > On Mar 22, 5:23*pm, AK > wrote:
>
> > > I want to make a small mold I would later use to create a fiberglass
> > > container to hold lead weight. It would be nice if *mold material can
> > > withstand 500 degrees Fahrenheit so I can pour lead into it and then
> > > cover it by fiberglass. Alternatively I would use the mold to create a
> > > fiberglass container first and fill it up with lead pellets. So my
> > > question is what do I use to make a mold, gypsum if so what kind,
> > > anything else?
>
> > > Andrzej
>
> > sand
>
> http://en.wikipedia.org/wiki/Sand_casting* not quite that simple in
> practice and would also req the purchasing of some specific setup
> materials which are not found at Home Depot etc...
>
> You should go the wood or plaster route.Wood is dead simple if your
> shape is not to complex. * I saw that Steve quite rightly mention of
> worry of plaster and residual water/steam being an issue... * *hence
> the very specific directions I layed out for preheating/drying your
> plaster mold BEFORE lead is poured in. If it survives the 4 hr
> incremental ramp up to 400deg, it will not break from the pour since
> all the water will have been evacuated by then. *If in doubt, leave it
> in the oven for an extra hr or 2 at 400ish...
>
> I dabble in investment casting, and the same methodology applies for
> pouring 1700-2100 deg metal (bronze, slver, gold, etc) into a plaster
> mold, except the heatup/dryout process brings it up to 1000deg over a
> 5, 7, or 12 hour ramp up (usually spending some an hr or 2 at 1300deg
> to vaporize out the wax remnants before ramping back down to
> 1000ish).
>
> -Paul

Thank you a lot to all who responded, especially to Paul for the
details he provided and Steve for the safety warning.
I was already aware of safety issue, but I appreciate you mentioned
it.

[jb92563]

For safety in an accident I would use the lead pellets
and make a containter.

Plus you will be able to make adjustments to your weight if you use
pellets in a containter.

A big chunk of lead could become a very dangerous projectile in a hard
landing or crash.

Ray

[The Real Doctor]

On 23 Mar, 02:01, Eric Greenwell > wrote:
> sisu1a wrote:

> It does avoid the breathing of lead vapors, something even a pilot
> should avoid.

Is the sublimation rate of lead at room temperature significant?
Church roofs seem remarkably resistant to evaporation after hundreds
of years, as do the 120 year old lead water pipes in my house.

Ian

[The Real Doctor]

On 23 Mar, 07:45, Ian Burgin > wrote:

> Lead has a melting temp of about 500 degrees C ...

It might be worth thinking about using plumber's solder instead. It's
a lead-tin eutectic alloy, which means it melts at a significantly
lower temperature (183 degrees C), but still has a high density (84%
that of lead).

Ian

[The Real Doctor]

On 23 Mar, 00:23, AK > wrote:
> I want to make a small mold I would later use to create a fiberglass
> container to hold lead weight. It would be nice if *mold material can
> withstand 500 degrees Fahrenheit so I can pour lead into it and then
> cover it by fiberglass.

I'm a little puzzled here. When you have filled the mould with lead
and covered it with fibreglass, won't the mould still be in there. Is
that OK?

How big is this thing? How complicated is the shape?

Ian

[AK]

On Mar 24, 12:26*pm, The Real Doctor >
wrote:
> On 23 Mar, 00:23, AK > wrote:
>
> > I want to make a small mold I would later use to create a fiberglass
> > container to hold lead weight. It would be nice if *mold material can
> > withstand 500 degrees Fahrenheit so I can pour lead into it and then
> > cover it by fiberglass.
>
> I'm a little puzzled here. When you have filled the mould with lead
> and covered it with fibreglass, won't the mould still be in there. Is
> that OK?
>
> How big is this thing? How complicated is the shape?
>
> Ian

Ian, I create a mold first then I pour lead into the mold. Later I
break the mold up and I use fiberglass to cover the lead so it is
trapped and I am not exposed to lead dust.

[AK]

On Mar 24, 10:53*am, jb92563 > wrote:
> For safety in an accident I would use the lead pellets
> and make a containter.
>
> Plus you will be able to make adjustments to your weight if you use
> pellets in a containter.
>
> A big chunk of lead could become a very dangerous projectile in a hard
> landing or crash.
>
> Ray

Good point, that is why the lead weight is going to be under my rear
end and it will be properly secured. Obviously I want the lead weight
as small as possible (vertically) so I don’t loose much of head room.

[AK]

On Mar 24, 12:24*pm, The Real Doctor >
wrote:
> On 23 Mar, 07:45, Ian Burgin > wrote:
>
> > Lead has a melting temp of about 500 degrees C ...
>
> It might be worth thinking about using plumber's solder instead. It's
> a lead-tin eutectic alloy, which means it melts at a significantly
> lower temperature (183 degrees C), but still has a high density (84%
> that of lead).
>
> Ian

Do you know of good source for this alloy (I don't know if I want to
go to Radio Shack to buy 40 lb of solder? My wallet would be way too
light and then I would have to buy even more of the alloy.

[Craig[_2_]]

On Mar 24, 4:05*pm, AK > wrote:
> On Mar 24, 12:26*pm, The Real Doctor >
> wrote:
>
> > On 23 Mar, 00:23, AK > wrote:
>
> > > I want to make a small mold I would later use to create a fiberglass
> > > container to hold lead weight. It would be nice if *mold material can
> > > withstand 500 degrees Fahrenheit so I can pour lead into it and then
> > > cover it by fiberglass.
>
> > I'm a little puzzled here. When you have filled the mould with lead
> > and covered it with fibreglass, won't the mould still be in there. Is
> > that OK?
>
> > How big is this thing? How complicated is the shape?
>
> > Ian
>
> Ian, I create a mold first then I pour lead into the mold. Later I
> break the mold up and I use fiberglass to cover the lead so it is
> trapped and I am not exposed to lead dust.

Sheet lead is usually available from a good hardware store or from a
roofing supply place. I picked up a roll approx. 300 mm wide by 4mm
thick. You can easily cut it with tin snips and some judicious
forming with a mallet against a sand bag will get it to whatever shape
you want. Multiple layers can be kept together with double stick
carpet tape.
Craig

[Darryl Ramm]

On Mar 24, 4:05*pm, AK > wrote:
> On Mar 24, 12:26*pm, The Real Doctor >
> wrote:
>
> > On 23 Mar, 00:23, AK > wrote:
>
> > > I want to make a small mold I would later use to create a fiberglass
> > > container to hold lead weight. It would be nice if *mold material can
> > > withstand 500 degrees Fahrenheit so I can pour lead into it and then
> > > cover it by fiberglass.
>
> > I'm a little puzzled here. When you have filled the mould with lead
> > and covered it with fibreglass, won't the mould still be in there. Is
> > that OK?
>
> > How big is this thing? How complicated is the shape?
>
> > Ian
>
> Ian, I create a mold first then I pour lead into the mold. Later I
> break the mold up and I use fiberglass to cover the lead so it is
> trapped and I am not exposed to lead dust.

Unless you are planning on eating you lunch off the lead I would not
be too worried by the minuscule exposure. Is this a club ship where
people are going to be moving the weights in and out all day long,
without washing their hands etc? If you are worried by lead exposure,
be careful in venting the area when you cast the lead. And the
exposure to chemicals and fiberglass fibers while encapsulating the
lead in fiberglass may be a larger minuscule health risk than the
small miniscule lead exposure :-) (says man who is hypersensitive to
epoxy).


Darryl

[AK]

On Mar 24, 8:11*pm, Darryl Ramm > wrote:
> On Mar 24, 4:05*pm, AK > wrote:
>
>
>
> > On Mar 24, 12:26*pm, The Real Doctor >
> > wrote:
>
> > > On 23 Mar, 00:23, AK > wrote:
>
> > > > I want to make a small mold I would later use to create a fiberglass
> > > > container to hold lead weight. It would be nice if *mold material can
> > > > withstand 500 degrees Fahrenheit so I can pour lead into it and then
> > > > cover it by fiberglass.
>
> > > I'm a little puzzled here. When you have filled the mould with lead
> > > and covered it with fibreglass, won't the mould still be in there. Is
> > > that OK?
>
> > > How big is this thing? How complicated is the shape?
>
> > > Ian
>
> > Ian, I create a mold first then I pour lead into the mold. Later I
> > break the mold up and I use fiberglass to cover the lead so it is
> > trapped and I am not exposed to lead dust.
>
> Unless you are planning on eating you lunch off the lead I would not
> be too worried by the minuscule exposure. Is this a club ship where
> people are going to be moving the weights in and out all day long,
> without washing their hands etc? If you are worried by lead exposure,
> be careful in venting the area when you cast the lead. And the
> exposure to chemicals and fiberglass fibers while encapsulating the
> lead in fiberglass may be a larger minuscule health risk than the
> small miniscule lead exposure :-) (says man who is hypersensitive to
> epoxy).
>
> Darryl

I agree with you that epoxy is not friendly to our bodies. I have
paint booth I build in my garage for hobbies. I just completed my tail
dolly renovation with major epoxy work. Working in a paint booth with
the exhaust fan working no one could smell anything in the garage. I
also have a fresh air supply by Hobby Air so I am all set. Working in
such conditions is actually fun.

Maybe the exposure is not great, but I still like to have the lead
enclosed.

[AK]

On Mar 24, 7:56*pm, Craig > wrote:
> On Mar 24, 4:05*pm, AK > wrote:
>
>
>
> > On Mar 24, 12:26*pm, The Real Doctor >
> > wrote:
>
> > > On 23 Mar, 00:23, AK > wrote:
>
> > > > I want to make a small mold I would later use to create a fiberglass
> > > > container to hold lead weight. It would be nice if *mold material can
> > > > withstand 500 degrees Fahrenheit so I can pour lead into it and then
> > > > cover it by fiberglass.
>
> > > I'm a little puzzled here. When you have filled the mould with lead
> > > and covered it with fibreglass, won't the mould still be in there. Is
> > > that OK?
>
> > > How big is this thing? How complicated is the shape?
>
> > > Ian
>
> > Ian, I create a mold first then I pour lead into the mold. Later I
> > break the mold up and I use fiberglass to cover the lead so it is
> > trapped and I am not exposed to lead dust.
>
> Sheet lead is usually available from a good hardware store or from a
> roofing supply place. *I picked up a roll approx. 300 mm wide by 4mm
> thick. *You can easily cut it with tin snips and some judicious
> forming with a mallet against a sand bag will get it to whatever shape
> you want. *Multiple layers can be kept together with double stick
> carpet tape.
> Craig

Good idea, I guess this is another way of doing it.

[The Real Doctor]

On 24 Mar, 23:20, AK > wrote:
> On Mar 24, 12:24*pm, The Real Doctor >
> wrote:

> > It might be worth thinking about using plumber's solder instead. It's
> > a lead-tin eutectic alloy, which means it melts at a significantly
> > lower temperature (183 degrees C), but still has a high density (84%
> > that of lead).

> Do you know of good source for this alloy (I don't know if I want to
> go to Radio Shack to buy 40 lb of solder? My wallet would be way too
> light and then I would have to buy even more of the alloy.

Builders' merchants used to sell it by the kilogram, but it's banned
or about to be banned for domestic use so may be harder to find in the
UK now. Dunno about where you are.

Ian

[The Real Doctor]

On 24 Mar, 23:05, AK > wrote:

> Ian, I create a mold first then I pour lead into the mold. Later I
> break the mold up and I use fiberglass to cover the lead so it is
> trapped and I am not exposed to lead dust.

I don't think you need worry about lead dust. I used to fly a Club
Libelle (not a Libelle owned by a club) which had a 1/4" sheet of lead
under the pilot's seat - if that's the sort of thing you need then why
not glue a thin layer of energy absorbing foam to each side and make
yourself a very heavy cushion?

Ian

[Z Goudie[_2_]]

At 15:03 25 March 2009, The Real Doctor wrote:
why
>not glue a thin layer of energy absorbing foam to each side and make
>yourself a very heavy cushion?

And have it hit you hard in the back of the legs under high g if you plant
the glider?

Always a good idea to have any necessary forward of CG ballast in front of
the pilot.

[Andy[_1_]]

On Mar 25, 11:15*pm, Z Goudie > wrote:

> Always a good idea to have any necessary forward of CG ballast in front of
> the pilot.

That may depend on whether the objective is to adjust CG, or to
increase flying weight.

Andy

[The Real Doctor]

On 26 Mar, 06:15, Z Goudie > wrote:
> At 15:03 25 March 2009, The Real Doctor wrote:
> why
>
> >not glue a thin layer of energy absorbing foam to each side and make
> >yourself a very heavy cushion?
>
> And have it hit you hard in the back of the legs under high g if you plant
> the glider?

He has said elsewhere, I think, that this is for placing under him.
And he could fasten the cushion down.

> Always a good idea to have any necessary forward of CG ballast in front of
> the pilot.

In general yes, but surely it depends entirely on the glider's weight,
balance and limits?

Ian

[Martin Gregorie[_4_]]

On Tue, 24 Mar 2009 19:20:32 -0700, AK wrote:

Is this for a private glider of for use in a club glider?

IOW, what are your options for placing the weight and for securing it?

- if you have to sit on it then sheet bent to match the seat pan
would minimize its effect on your headroom, but securing it
properly could be difficult.

- putting a block of lead in the nose is safest (its on the scene of
the crash before you get there), and securing it may be somewhat easier,
particularly if you use sheet lead and the securing bolts also hold
the sheets together. Last but not least the forces you need to
anchor it against would be less (launch acceleration, sliding back
during a winch launch)


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Z Goudie[_2_]]

At 14:35 26 March 2009, The Real Doctor wrote:

>He has said elsewhere, I think, that this is for placing under him.
>And he could fasten the cushion down.

I would be worried about the design strength of any fastenings to flimsy
seat pans during high g impact decelerations.

>In general yes, but surely it depends entirely on the glider's weight,
>balance and limits?

If it's for C of G positioning then the further forward the less mass
needed. You may exceed the all up weight limit with sufficient mass at
the seat lever arm for CG positioning; also I'd not be particularly happy
about speed performance ballast I couldn't get rid of in the air if I
ended up low and scratchy!

[The Real Doctor]

On 26 Mar, 21:00, Z Goudie > wrote:
> At 14:35 26 March 2009, The Real Doctor wrote:
>
> >He has said elsewhere, I think, that this is for placing under him.
> >And he could fasten the cushion down.
>
> I would be worried about the design strength of any fastenings to flimsy
> seat pans during high g impact decelerations.

I'd be concerned about doing them right...

> >In general yes, but surely it depends entirely on the glider's weight,
> >balance and limits?
>
> ... I'd not be particularly happy
> about speed performance ballast I couldn't get rid of in the air if I
> ended up low and scratchy!


Having spent 5 hours 4 minutes sitting on a 1/4" lead sheet in a Club
Libelle below 2000' in France, I can assure you that "low and
scratchy" takes on a whole new meaning.

Ian