More fun with Carbon Fiber - Lost Wax Barrel?

This was just a small piece to test the concept, but it's got me a little pumped up about the possibilities.

The idea is to make a carbon fiber barrel, with a built in enclosed track. Furthermore, to do it without the use of syntactic foam, which can make a small barrel a little too heavy. My thought was to use the "lost wax" process.

So here we go. First, a form to pour the wax blank that will ultimately form the shape of the barrel inside diameter. I did it on a mill, but a router would work. Just two opposing halves cut in a 2x4.

I used cheap paraffin wax, which has a melting point of around 125-130°F. This caused some problems later on, but it also has the drawback that it shrinks a lot when it cools, which makes it hard to get a complete casting. After a few trials, and the addition of an aluminum rod down the middle to help hold it together, I got a good casting. The tin foil didn't work very well, as it leaves wrinkles, but Vaseline makes a great release agent, and the casting popped right out. After I got a reasonable core, I cut a groove down the top which would later encapsulate the track.

Sorry I couldn't take pics while I was laying up the layers of epoxy, but this was the setup. I put a single bi-axial sleeve on first. Then two wraps with uni-axial. I then slid a small biaxial sleeve around a delrin rod, and pushed that down into the groove. You can just see the black delrin rod in the first pic. Lastly, a biaxial sleeve around the outside, with heat shrink tubing to cinch it all down.

When it was cured, I had this what you see in the first pic. Then I used a straight router bit, and a ball end cutter to cut out the delrin rod:

Then, into the oven at about 180°F for a few minutes to melt out the wax:

The finished barrel came out just under 1-3/8" in diameter, and right about 3/32" wall thickness

A few lessons learned:

Paraffin won't work. I didn't show the other end of the test piece that collapsed from the heat of the heat shrink gun and curing epoxy. But it obviously is close, since most of the piece worked out. I've ordered a small block of casting wax, which melts at about 155°F, to give that a try. Before starting to lay up the carbon fiber, I put the wax core in the freezer for a little while, hoping that would help resist melting from the curing epoxy. It just caused cracks.

But overall, I think it might be workable. I'm pleasantly surprised that I haven't run into any serious "show stoppers" yet.

Think it could work for a full length barrel? The biggest problem that I see would be melting out the wax. My thought was to put it inside a steel pipe with a cap on the bottom, and fill with boiling water. That should be hot enough to melt the wax, without damaging the tube. Or stand the pipe up in a bed of charcoal like a big dutch oven.

Stay tuned . . .

Quote from seaweed

Melt the wax?

Connect the inside rod to a battery terminal.

Maybe you can rig up some sort of resistance wiring around the rod that will help when pouring and getting wax out.

I thought about some sort of resitance heater, but figured it would only melt what was close to the rod, and might not get the wax adhering to the walls. But maybe worth a try.

The only problem with a larger metal rod, is that it would have less resistance to the flow of electricity, right? I might find myself needing a very high current to sufficiently heat it.

The heat gun might work well, as long as could keep the molten wax from dripping down on the gun.

I've got to give you credit for thinking outside the box. But you are familiar with the K.I.S.S. principle, right?

Regarding electrical heating, don't overlook temperature control. Once melted, waxes can boil just like any other liquid, potentially creating a pocket of trapped pressure looking for a way out. Some waxes are also flamable.

But I like the ideas. Keep 'em coming.

Looking forward to trying some of the more complicated shapes we discussed. This carbon fiber stuff is fun, it opens up a whole new area of challenges and opportunities to make out of the box stuff.

Yep. That's pretty much what I had in mind, and is the main reason that I ordered a casting wax that melts around 155°F. The large diameter aluminum tubing inside also has the added benefit of keeping everything straight during the molding process.

Quote from seaweed

Try leaving it out in the sun. Might just melt the interface a bit and let the wax slide out.

If sunlight is enough to slightly melt the wax, then the heat of the heat gun and curing process probably would too, which would cause problems.

Do you mean making the inside form out of some other material instead of wax? No, I havent tried anything besides the syntactic form. For a straight cylinder, like this sample, that might work quite well.

The real advantage to something like lost wax, I think, is that the shape is only limited by your imagination. If you want to make it thicker in the middle (like some of the elaborate CF euro guns) then you can do so without regard to whether the inside form can be withdrawn. You could just as easily start with a 2" by 2" by 60" block of wax, and carve the most elaborate shape you could think of. As long as the wax has a way out.