vjaqua wrote:
Something to consider for this application is "lost styrofoam" casting. You sculpt your
part
from easily removed blue foam, and ship it off to a casting house. The foam is vaporized
by the incoming melted aluminum. Good detail, and no fancy cores - the downside - you
have to make a new sculpture for each pour. - Vance
I think I might try that Vance. That sounds like it might work.
How would you make a hollow runner? Just carve it out from two
pieces and glue it together? Perhaps John Lynch can 3D machine
the styrofoam runner halves from a program. Can the foundry
stuff sand down in the runner with out breaking the foam?
Yes the foudry can stuff sand into holes, and some the core techniques
can probably be used such as resin etc for more structral integrity.
You could probably carve most of the passages with a ball burr, and
fairly long shaft, and the foam pices can be assembled, if required. Vance
Is blue foam the best to use or perhaps some other finer grain
foam? I think in production they use a mold and steam expanded styrofoam
beads that give a smoother surface finish.
The "blown" foams have the advantage of a lower density and are easier for the aluminm
to vaporize, as well as being more suited to series production and smoother
surface than carved.
The lost wax is a great process - tho more costly. You coat the wax with a refractory
plaster, which is fired, vaporizing the wax before the metal is poured. The lost foam
just uses sans.-Vance
There has certainly been a lot of work on this topic! I still believe that a very reasonable solution would be to have a 90 degree lower intake manifold out of aluminum (or perhaps mild steel), similar to but much lighter and better configured than the stock manifold. Then make the upper manifold in carbon fiber.
I think the best technique would be to build a "plug" out of foam or wax from the lower manifold to the throttle body. Shaping blue foam into the upper 1/2 of the runners with a flat surface around/between each pair of tubes, then finishing the foam with micro filler would allow the upper 1/2 of a mold to be pulled. The flat surfaces would be a mating flange around each tube -- very strong! The contour could be any shape necessary, such as winding around the front and back of the engine and around to a throttle body. If you exceed 180 degrees, then a 2-piece mold would be required on top - no big deal.
After the top mold has been pulled, a lower 1/2 plug would be built inside the upper mold, following its contours. Then cast a lower mold off this combination. Vacuum-bag in 2-3 layers of carbon fiber with hi-temp epoxy (overkill) into each mold half, pop 'em out and you have two parts to bond together to create a low-profile intake manifold. The flanges could be G10 phenolic (300 degrees). Depending on the location, alignment and style of the throttle body (and injectors), one additional box or mold might be needed for the dynamic chamber and its flange. After it is done, you have a mold from which dozens of manifolds could be produced. Probably would weigh around 1 lb.
Depending on the precise length needed, options might include wrapping the tube so a relatively small throttle body was on top of the crankcase, or a longer length with the T.B. dropped off the side.
I'm happy to work on this (upper) end of such a project, but need a lower intake manifold to start with and a reasonably close design. Cutting down the stock manifold still results in the center tubes too close together, so I'm still evaluating my options for a new version. Seems like it would be much better to run the front two tubes close together, and also the rear tubes together. This means the lower intake manifold needs to start out in the right direction. The upper manifold would also be a lot simpler this way -- just two pairs of tubes running independently between the flanges.
So the bottom line is, if there are few or no restrictions on the shape of the upper manifold, what is the most ideal design? I'm pretty good with composites and molds, but not a welder (no Henrob, yet). Anyone interested in this scenario?
Scott Gettings
Yes. I am looking at making a pattern for just the bottom 90 degrees.
If I could only figure out how to get the cores in the mold.
I now understand core boxes, core prints, drags and copes.
I still don't fully understand curved parting lines.
I need to take a trip up to the foundry and have a look around.
Paul Lamar
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