Spray Foam?

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#1

First let me take this opportunity to thank all of the contributors on this forum for providing a portal for those of us that are learning. Thanks!
Now to my question or questions.

I am building fiberglass intake manifold runners for prototype testing purposes. Think of a pipe but with changes in geometry throughout the length of the pipe. It is approximately 12" long with changes in the X, Y, and Z axis throughout the length of the pipe. It also changes in size from one end to the other. For this reason I made a plug from fiberglass that mimics the interior shape.

My questions are on the easiest or proper way to make these runners.

My first plan is to use my plug to make a two part female mold. With this mold I would make male foam cores that I could layup with fiberglass. I would then disolve the foam to yield the finished part. This would yoield a nice interior runner with no seam line. Is this feasable?
If so what type of spray foam do I use and where do I get it?
The spray foam from the home improvement stores seems to stick to everything.
What would be the proper way or material to use to disolve the foam from the runners after layup?
I had planned on using plaster for the female mold maybe I could use silicone instead to avoid the sticking? What would everyone advise for this?

The other option I was contemplating was to make the two part mold and make the manifold runners in two pieces with a flange to join them together afterwards. Of course then I have the cleanup of the seam lines on the interior as well as the exterior cutoff and smoothing of the seams. I could do this but would prefer the first option for it’s smooth interior.
I would appreciate any help or advise you guys could give.
Thanks!

#2

Boy, where do we start here…

Is this a single tube or multi port runners? Carb or EFI (Duh…)? how is this going to be fasten to the engine?

My thinking is a rapid prototyper would be a better choice. I have an adult student that does this…

PS (Polystyrene) foam will melt out with acetone but there was a post on here about lost foam castings that use water.

#3

Thanks for the reply.
We have done some rapid prototyping with a few fairly simple parts using the Dimension plastics system. The CAD does not currently exist for this intake manidfold design. I would prefer not to create the CAD till the design is proven as there are several variables to this intake manifold design.
We have full CNC machining capability and already have the flanges programmed as well as injector ports. The basic idea was to attach the runners to the flanges using a two part epoxy or equivalent. Each of the runners is seperate from the other. They all terminate in a central plenum that we have not designed yet.
I have confidence in my ability to create this part but need some assistance to the previously mentioned questions.

I will do a search on lost foam polystyrene. Thanks for the heads up!
Any further assistance is appreciated!:slight_smile:

#4

On the EPS (Expansion Polystyrene) make sure you get the freshest possible as if it gets old, it doesn’t expand. Try my link to Delivies Plastics in Utah in suppliers. Get their catalog for the step by step instructions or ask for them too.

With PS foam, you have to use Epoxy resins, but at those temps, yu will need a hight temp rating resin.

#5

Thanks for the link! The polystyrene balls appear to be just what I was looking for.

#6

polystyrene balls? what were you gonna do with them. I have used them in the past but nomrally you use them in a bead expanding mold. Steam hits the mold and expands the beads forcing them against the mold and one another. Then cold water cools the beads so they stop expanding.
This is how coolers are made.

#7

Welcome back Doogie!:smiley:

#8

polystyrene balls? what were you gonna do with them. I have used them in the past but nomrally you use them in a bead expanding mold. Steam hits the mold and expands the beads forcing them against the mold and one another. Then cold water cools the beads so they stop expanding

I was going to use them in a mold that was clamped on each side probably like the bead expanding mold you are describing. I need the beads to expand against each other and the mold to reproduce the interior of the female mold effectivly giving me a male part to work with.

Do you have another idea?

#9

Since someone else brought up an old post along this disscusion:

http://www.compositeforum.werksberg.com/showthread.php?p=10081#post10081

#10

Or check this site out too:

http://www.mci.i12.com/carbon/lost_foam.htm