Wendell, the best thing is to go to this web site
and read up on the different (and there are many) different formula for two part
castable polyurethane resins. The Prototype menu will take you there I
believe. http://www.smooth-on.com/proto.htm
Of course there are many companies that sell similar stuff - but, this one sells
are you need. I use the Featherlite resin for my molds - so light it will
float on water. But there are some that mimic aluminum to the point you
can machine it much the same, etc.
But, basically you need a mold (I make mine
out of foam sheets) to pour the mixed resin into and some cores (silicon rubber
is used - also at this website) to put in the mold to provide a Hollow area
(when you pull them out) for your runners. Then you cut an opening for the
throttle body down to the runner holes in the casting.
I mount my plastic TB/Plenum to a 3/16" thick plate
of 6061t6 aluminum which I have cut holes in for the tubes to go through
(naturally you need to insure the holes match the holes in your plenum). I
then machine (carve) a slight concave ring around each runner hole in the
plastic (for an O ring).
I drill holes in the plate and put inserts in the
plenum. When I tighten those bolts down it draws the plastic down on the O
ring squishing it against the aluminum tubes and the 3/16" plate effectively
sealing the tubes to the plenum.
Here are some photo of one of my molds
with the two silicon rubber cores to give you a better ideal. I pour with
the mold upside down and the cores suspended from the bottom of the mold to
dangle in space inside the mold. The plastic fills everything but the
cores and within 45 minutes (or less) you have a plastic plenum. The
photos were of an older plenum, I now use a simpler mold. I cut a half
moon out of a 3" sheet of foam and the put a 1" sheet on each side. The
hollow is my now my mold.
Hope this helps.
Ed.
----- Original Message -----
Sent: Thursday, May 05, 2005 10:19
AM
Subject: [FlyRotary] Re: Duct Nearly
Finished
Would you give instructions for making the plastic
manifold?
Wendell
No! Steve!, No! Never! {:>).
Actually, I have come a ways since I made my first horrid attempt at
fiberglass work. I used to spend a week on the mold, Paint it with
mold separator, wax it, etc. Then mainly because of the shapes ended
up having to destroy the mold to get the product. First breakthrough
was use of duct tape - but still ended up with foam mold mainly destroyed.
So know I use a type of "tan" foam that epoxy does not destroy, carve the
shape with rasp and a brush with stiff brass bristles and slap the
fiberglass directly on the foam. For ducts, its nice because then I
can shape the foam internally to get exactly the curve I want.
Fiberglass does have advantages in many cases.
But, don't think a large scale composite
project is even on the distant horizon {:>)
Ed
----- Original Message -----
Sent: Thursday, May 05, 2005 7:04
AM
Subject: [FlyRotary] Re: Duct Nearly
Finished
Ed,
It sounds like you're becoming quite handy with fiberglass.
You may be ready to start a composite project.
Steve Brooks
Got the new duct nearly finished.
Just need to pop rivet the hinge halves on it, sand some of the worst
bumps off, paint it and put it on. Then ready to go fly and try
out the new duct and engine. Took two days, to make the mold,
fiberglass the outside and contour the inside for that trumpet shape -
it would have taken me two weeks 5 years ago - but still prefer metal
{:>).
Now just have to whip up a combination
filter holder and Plenum and I'm done with mods for the summer (I
think).
Tracy got the apex seals for
analysis but just headed out to Colorado like he had planned rather
than postpone his trip to play with the seals - just don't know about
some folks {:>).
Sure makes me wonder why airline builders
use all of those expensive circuit breakers rather than cheap fuses -
must be something I'm missing. Fortunately, we have the right to
make the choice that suits our preferences (and pocket
book).
Ed
Ed
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