Topic: Stikum

[bwaller]

Can anyone suggest a clay type material that will harden enough to work with a die grinder or dremel but still stick to bare aluminum? (in a clean combustion chamber)

I have some Crayola "model magic" but it doesn't harden fully or stick well enough to work.

[slikwilli420]

Something like an epoxy? I use Devcon aluminum putty. It's resistant to a bunch of chemicals and dries extremely hard.

[gschuld]

Marine Tex is also good, high heat version available if needed.  Also epoxy based.

George

[FunJimmy]

+1 on the epoxy putty.
I found a nice epoxy putty at the local marine supplier.
The format was a round rod with the two components in the same extrusion.
Just cut a piece off and nead like dough. Place before it sets and grind when cured.

[bwaller]

Thanks guys but I need something I can completely remove afterwards. The same kind of stuff we'd check squish clearances with but that hardens enough to "shape" with a grinder. I want to knead it into place in a chamber, let it set-up then grind into the shape I want, but still be able to remove easily afterward.

The Crayola stuff doesn't quite measure up but the epoxy may be too tough to remove.

[754]

What are you checking or trying to?
Real modeling clay can be carved and cut and shaped with exacto knives or other tools... They used it a lot to model car bodies.

[bwaller]

Experimenting with a squish shelf in a combustion chamber. If it works out with putty first then the chamber can be welded and the shape duplicated...or that's the plan!

The modelling stuff I have is ok, but didn't stick well so I need to try something different.

[gschuld]

You could try west system epoxy mixed with a very large proportion of 410 fairing filler.  It is very lightweight, sands easily, and should stick well enough.  The large proportion of 410 filler will also make it substancially softer and easy to sand than the aluminum, so something like a 3M Roloc 2" disc on an air grinder in medium or fine will remove the epoxy/filler without tearing into the aluminum hardly at all.

George

[FunJimmy]

Brent,

If your chambers are clean apply PVA fibreglass mold release and let dry.
Then fill the desired area with an epoxy putty and cure completely. Once cured, make an alignment mark with a sharpie before pulling the cured epoxy plug out. Wash the plug and the combustion chamber to remove the mold release agent. Now you can contact cement the plug back using the alignment marks to locate the plug and grind away. You should be able to pry the plug without the need for solvents but they're always there if needed.

[turboguzzi]

brent, do you need to dettach those castings in one piece after your "sculpting"? if not, just heating them with a propane burner will soften them

[Captain]

 Get hold of any of the major names in custom pistons. (CP, Diamond and the like) They all have these combustion chamber molding kits  or at least their own versions. Not expensive and very easy to use as it is very easy to pour and all that is needed for use as a mold release is either WD40 or Silicon spray (which I prefer).

 Captain

[bwaller]

Thanks guys, good ideas. I like the chamber kit too Captain, I'll use that later.

[RAFster122s]

Could you use a thin layer of plastic wrap for your epoxy filler mix. You can use microballoons (tiny glass spheres to build bulk) or Cabosil (a thickening agent for epoxy)...there are others out there. The thing about clay is it often shrinks when it hardens. Not sure if Sculpty shrinks or not, regular modeling clay definitely does. Epoxy will not shrink or expand very much when subjected to "normal temperatures".
Are you forming chamber molds to accurately determine the volume of the combustion chamber using water displacement in a finely graduated beaker or container for your "plug(s)"?


The Plug made could be carefully cut to give you cross-sections for templates you could make out of metal or other hard material to guide your progress, orienting them either on a grid or using radial lines marked on the head and repeated on each cylinder combustion chamber.


Granted the time tested method of CC'ing a cylinder with a glass or plexi plate with a buret  ?spelling? to measure the volume of the combustion chamber is the more conventional method of determining volume of the cylinder.


Local public library in Kingsport TN about 17 miles from my residence offers free 3D scanning and they are very reasonable on 3D printing now. I don't know the resolution of the their equipment yet. I haven't taken advantage of that service they are offering patrons.  They help or do the scan cleanup of the object you wish to 3D replicate or provide them of a 3D file input used to create the drive instructions for the 3D printer they use. They will even teach you how to do some of it.  It is pretty cool.


David