Frank, I searched for plaster and got this g-mail for 50% plaster/
50%starch and the link for the commercial grade
Aquacore.
george grimes
www.rotaryeng.net/carbon-intake.txt
http://www.aero-consultants.ch/_files/file.php?id=267&name=Flyer_AB-Aqua.pdf
That is no longer on the web site as it was too much to expect from
home builders. It was in the context of casting your own epoxy
intake manifolds. As such it required core boxes. The p-port is much
better and much easier.
It was still on the server and that where the search engine found it.
It is now gone from the server as well.
Here it is from my files.
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How to Make Carbon Fiber Intake Manifolds by Marinus B. (Ben) Bosma
I want to make the runners that go from the intake plenum to the
throttle body. This requires a 180 degree sweep. Can anyone tell me
how to approach such a project. Or recommend a good book on the subject.
Jerry Hey
The idea is to create a tool that "disappears" inside a locked
shape. We use various types of mandrels but the most common
technique is to make a water soluble mandrel. There really is no
limit to the shapes.
Here is a good source for the water soluble plaster.
http://www.acrtucson.com/
Aquacore is about $100/5gal bucket as I recall. I think it's corn starch
w/plaster... shhhhh
Another really cool technique is to make the tooling from Z-corp 3D models
and forget to reinforce the model with infiltrant. Since, they are bound
with a water soluble material you can wash out the tool in a bucket
of water. We've made tube junctions and high temperature manifolds
using this technique. Both these methods can withstand the 14.7PSI
force of a vacuum bag and the rigors of autoclaves.
With the 3D printer create an internal geometry that easily washes
out like a lattice work. That saves in weight and material.
http://zcorp.com
You should've seen the Northrop Grumman quality manager when I
pulled a perfect carbon fiber plenum out of the sink. The biggest
problem with "BIG AEROSPACE" is that they want to catalog all the
tooling and cataloging a tool that went from 3D model to water
soluble part was documenting it. Where's the tool? I told him it
was that milk in the sink!
I think there is a potential for someone to formulate a moldable
water soluble material. Something that a ham fist like me can shape
into a shape
(play doh?) allow to harden, mold onto and wash away.
The water soluble plaster takes on the same finish as the mold in
which it was created meaning that the INSIDE of the part has a great
finish as well. That's what we want isn't it? I, too have washed
out foam but it left a very rough finish on the inside that's not
conducive to good airflow.
Attached are a couple of pictures of a real part done using this technique.
We have applied for a patent on this "technology" but, I'm not real hopeful
given how mundane it is and the prior art out there. I'm not
showing the internal structure of this tool because that's the
technology we're struggling to protect. The tool is about 80% air
and can still hold the forces of the bag. God developed this a long
time ago when He designed chicken bones. Great engineering role model.
I don't recommend autoclaving. We autoclave at 300deg
F and pressurize at 125PSI. That's very serious composites that are
structural and highly consolidated. We make microwave components
that go into space and they have to be super light, can't outgas and
have to be strong enough to carry several hundred dollars worth of
electronics on a Delta II ride.
My recommendation is to use a wet lay-up and a simple vacuum bag.
For something like a plenum:
3K twill weave, 3 plys (you don't need to orient them that way).
Huntsman(tm) epoxy resin for infusion (I forget the part number, I'm
at home). Use the Freekote(tm) release on permanent tooling or a
sealer on soluble tooling (polymer of some kind from Lowe's).
Prime paint (2-part epoxy like Polane) over the tool. This is
much lighter than gel coat and gives you a contrasting color on the
inside of the part. I recommend white because it shows any leaks,
drips and other evidence of stuff you don't want in your part. The
primer becomes the inside layer of your part. Mix up a small batch
of epoxy by weight and stir in some Cab-o-sil (silica) if you want a
little more viscosity. Paint the entire tool over the cured primer
and lay-up the 3K like you were putting on a plaster casting.
Strips work better than big sheets. Lay-up 3 plys the same way and
have a Pepsi(tm).
At this point there are tons of options but for the vacuum bag lay-
up put your peelply over every square inch of the part (it will
stick), put breather (baby blanket) over the peel ply and bag over
all that.
Suck out the air with your vacuum pump (Seal-a-meal works great) and
leave the pump on for at least 8 hours. The Huntsman(tm) infusion
resin doesn't gel for 1:50 which is good if you're infusing since
you need it to run for a long time. Also, it's very thin. Silica
is a good thickener but it makes it harder to penetrate the fibers.
With a 1:50 gel time you can start over a dozen times on a part the
size of a manifold and still not have a cure going.
Having said all that, you can use practically any resin/fiber combination
you are comfy with. There are numerous grades of carbon fiber and
even more glass. If you're going for a high temperature application
like an intake manifold the epoxies tend to work better than the
polyesters. We use epoxy exclusively because all our parts fly into
air or space.
I'm a strong believer in creative composite work. This forum is
good for sharing however, there are as many ways to do something as
there are members who participate in this forum and the those who
lurk here. Try your system on a flat piece of nylon cutting board
first. Almost nothing sticks to them. The idea is to get resin to
kiss 360degs of each fiber. The 3K stands for 3,000 fibers per tow
which is what you'd normally call a thread. 3K fabric is pretty
light. Getting epoxy to wet out into that is a piece of cake. When
you look at your wet lay-up with your Pepsi in your hand you will
think it's too dry. When you hookup the vacuum the resin will
squeeze out into the peelply and fill the breather full of excess
resin. You'll wonder where it came from. The result however is beautiful.
Here is a great link to a guy who, like us homebuilders, is too
cheap to spend thousands of dollars tooling up a one of a kind part.
http://www.jcrocket.com/kitchenbagging.shtml
While, I've got the floor:
I think there are other creative ways to get a shape into a
composite. We've talked about soluble tooling which is fertile
ground for you geniuses out who still remember Jr. High Chemistry
class or home ec. What are some other materials that will become
rigid yet can easily be removed? Cardboard? Biscuits dough? Play
Doh? Ever consider making a rubber shape, filling it with sand and
sucking the air out of it? Notice how rigid that assembly is? Ref:
coffee bags at the grocery.
What about mixing materials? Nomex veil + Carbon + epoxy? What
resins cure up and are able to withstand exhaust temps? Is there
anything? What happens when a fully cured composite is torched?
Will the carbonaceous char still be durable enough for a pipe?
Who says you can't prefabricate a flange and glue it to a soluble
tool and glass around it?
Well, you get the picture...
Autoclaving is not for the weak at heart. We use a lot of pressure
and a lot of heat. Sometimes we even use argon because it has a
better heat coefficient than air and doesn't oxidize parts and
tooling under pressure.
Vacuum bagging is sort of a poor middle ground between a wet layup
and that nasty autoclave.
eBay is an excellent resource for vacuum pumps (food sealers). I purchased
one a couple of years ago on eBay for less than $20 including
shipping and after cleaning the dried veggies and funk off of it was
able to draw
28.5inches of vacuum. That is exactly what we got on our central
($$$$) vacuum system here.
Do I need to tell you what happened, I mean happens, if you draw
resin into the kitchen pump? A little resin trap is a good idea.
Again, mason jar
(cans collapse, oops I keep showing my mistakes) with a tube in and
a tube out.
Hobby Lobby is another good source for layup materials. The
polyester quilting batting works exactly like the breather material
you buy from a composites supplier because it is exactly the same
dang thing!
I'm still looking for a poor man's peel ply. I think there is
something at the fabric store that works. I just haven't found it
yet. The peel ply we use is supposedly Teflon(tm) woven into a
fabric. It has to breath some but won't stick to the resin. It
looks like lingerie material although, I'm NO EXPERT on lingerie
(whew!).
The shiny blue tape you see the pros use to seal to the tool is
designed for high temperatures. Clear packaging tape from the
hardware store works just as well and is 10% the cost.
We have a room full of bagging films some of which I'll never use again
because they don't work. The best stuff is nylon but it doesn't
stretch so we use it for flat layups, mostly. For the kitchen layup
use laundry bags, painting drop cloth.
Now, here's a hot tip. If you want to make a conformal bag, there
is a product out there that works like a charm. It's called liquid
latex and is also available from Hobby Lobby as Castin' Craft Mold
builder. It's designed to be painted, rolled or poured onto
something you need to replicate. In it's shipped form it's a little
heavy but it can be thinned with a homemade solution of 50/50
ammonia and water. Use distilled water because if your tap water
is a little hard you'll precipitate that out and it will cause lumps
(ask me how I know that.) Ben
Tom Weber Wrote:
I then went to our local plastic supply house and purchased 2" ID.
clear acrylic tubing. You can heat the tubbing to form what ever shape
you need, IE 180, 90 270 what ever, You have to be diligent and
careful but you can make pretty tight bends without kinking the acrylic.
Once you have your final shape cut the acrylic tube in half so you can
split it apart length wise. Coat the inside of the tube with
silicon or mold release. Then I took a 2.25" bicycle inner tube
coated the out side of the tube with silicon spray for mold release.
I've never tried the Carbon sleeve but it may work just fine for
the next steps. I took S glass and epoxy cut to size length wise
add a little length. The width should be pie times the Diameter so
3.1415 X 2" = 6.2813" times the number of wraps. I used three wraps
so 18.85" long. Lay the material on wax paper, pour the resin on
the material, cover with plastic wrap (like the stuff you use to
cover a bowl for the refrigerator). Use a rod to roll over the
plastic wrap to distribute the resin and push out any excess. peel
the plastic wrap off and wrap it around the partially inflated tube.
Lay the whole mess into your acrylic mold. Place the top half on and
use heavy rubber bands or hose clamps to keep it together. Then
inflate the tube so you have the material pushing against the inside
of the acrylic mold. Let the whole thing cure and split it apart.
clean up the end and viola you now have a light weight complex
intake manifold. Like I said I think this process has some merit
and I'll work more on it later. T.W.
Tony LongEZ wrote:
Paul and friends Just some FYI I talked to Acrtucson the web site
that Ben posted they have a sample pack you can purchase for $30+S&H
the woman to talk to is Halina Pender very nice lady (520) 434 6342.
Apparently they have two types they have a pour type for casting and
a more solid type for machining one is called aquacore and the other
is aquapour. Also in the sample pack is a quart of both and a filler
to make the mold smooth and a release agent. I have a kit on the way,
it'll take about a week to get here.
Tony
Here is the first design using your technique. The core box
for casting the soluble plaster is on the right. The soluble plaster
core is on the left. You hand lay up around the plaster core and
you have six bell mouths, six runners, a plenum and a 3 inch throttle
body for an RX8. It is designed to be used with the lower
RX8 stock manifold as in this picture. You tig weld a flange
on top of the stock manifold and layup a carbon flange around
the bottom of the runners to form a mating system.
Paul Lamar ...No rotor no motor.
I think what Ben is relating is a method my grandfather used to copy tea
cups. He would make a mold of a cup he liked or that one from a set was
broken. The cup was taped around the top to be able to fill higher than the
cup itself. then plaster of Paris was poured in and allowed to set. This
center then had the tape removed and pulled from the cup. Being a machinist,
he then cut a half round ring around the top of this. It was then put back in
the cup. A box was partly filled with plaster of Paris and the cup assembly
half submerged in it with the handle only half in the plaster. He had also
made three tapered dowels from a broom handle with flat ends. He set these
into the plaster away from the cup. When the plaster hardened he could remove
the dowels. The the box was filled with plaster. Of course a release agent was
used to ensure clean separation. The the box was removed from the outside and
the mold could be taken apart to remove the cup. The cast in dowels and the
ring held the parts in alignment. A tapered hole was scratched/filed in to
allow filling the mold with clay which was very liquid. You did not totally
fill the mold the first time. A stopper was held in with a rubber band and the
mold also held together with bands. The plaster wicks the water away and after
a day you could carefully take it apart and pull out the new cup. At this
stage it is very delicate and needs to be fired.
This could be used to make the intake. Partly fill the mold and shake to coat
the inside of the mold. Repeat until built up to 1/4" to 3/8" thickness. Use
the water soluble casting material. If the mold was made of potters clay and
fired without glaze, it is quite tough and will wick the water. The cast could
be plaster. When done it would be ready to mold the carbon on the outside for
the manifold.
Dale Davies
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