More fun with Carbon Fiber - Lost Wax Barrel?

    Do you know of a plaster that is water soluable after it is set? I doubt that you would ever get a hardened plaster core out of a gun length barrel section. Now if it could be dissolved out with warm water or something, then you definately have my attention!

    I'm actually looking into it as we speak. I believe it is soluble in that in could be soaked and, being that a tube has two open ends, it could run out. Give me a bit to read up a bit more. I, too have been interested in the idea for use in forming parts out of composites.


    I'll get back to you.


    Mark.

    Well so far between what I've read and what I can remember from my experiences with it (a long time ago) is that is will begin to dissolve in water. I think the biggest concern would be time to set up. It may feel dry shortly but in that type of thickness might take a few days. But if you've got the time....
    try picking up some, the smallest quantity you can buy, or come across, and do a small scale trial.
    If I come up with anything further I'll let you know. In the mean time, if you get a chance to try it before I do, let me know how it works.


    Mark.

    plaster is always vulnerable to chipping and vibration...i be it you could hit the tube with a mallet every six inches and most likely knock it out...

    i like to spear fish

    If it is that vulnerable, then how will I cut the radius on the corners, and the groove for the track, etc.?


    Also, plaster tends to be a little porous on the surface, doesn't it? If it is, then the epoxy will soak in and there is no way you will extract it from a tube 60" long.


    I think the core has to be made of something that can either be dissolved, or melted, or chemically removed.

    We have a 3d printer at school. Basically, it sprays glue like an inkjet printer on special sand then lays down a new single layer of sand and does the same thing again and again until the piece builds up. The glue ink is water soluble.


    I have used it to make this which encases ball bearings. I 3d printed the negative of it with ball bearings as one piece, then I soaked it in melted petroleum jelly. I poured in some dental resin, then boiled the peice until the mold dissolved and was left with just the blue part where I could pop in the bearings.


    Perhaps you can use a water soluble glue with some sort of filler to make a machineable core.

    Did you know carbon fibers contract when heated and expand when cooled along the fiber direction?


    Making a core out of aluminum with a very smooth surface finish and waxing it good perhaps it might come out when cooled water is passed through the core.

    Davie Peguero

    Quote from seaweed

    Did you know carbon fibers contract when heated and expand when cooled along the fiber direction?


    Making a core out of aluminum with a very smooth surface finish and waxing it good perhaps it might come out when cooled water is passed through the core.


    Intersting, and counter intuitive. I didn't know that. But the whole point of using wax or something similar is that the core can be any shape, as complex as you can sculpt, and still be easily removed. Any rigid core would limit you to perfectly straight sections.


    I like the water soluable glue thing. But what's the size limit on that printer?

    Quote from Tin Man

    I like the water soluable glue thing. But what's the size limit on that printer?


    12x12x4 not big enough to make a gun, all the bigger things are printed in sections then assembled. That's why I suggested just making the core out of a glue and filler.

    Davie Peguero

    Hi
    I saw your project and joined the board. I don't know if you considered using styrofoam and acetone in place of wax and heat. Shape the core from styrofoam and then dissolve it out with acetone. Airplane modelers and surfboard shapers use a fine grain(bubble ) foam that can be hot wire formed/machined(sp?) and shaped with wood working tools. For a smooth surface a wax or epoxy coat on the plug can be used and it will remain in the gun after the foam is dissolved.


    The reason I brought this up is that foam is stiffer than wax and doesn't bend out of shape with the heat of handleing (body temp) although heating the wax might be a part of your post cure to strengthen the composite.


    Really looking forward to seeing more of this project

    Thanks Derryck. I did consider the foam / acetone approach, and even played with it a little. I wasn't satisfied with the results, but I probaby didn't stick with it long enough, nor was I aware of the fine grane foam that you referred to.


    On the gun that I am laying up now, I poured the wax with a piece of steel rod inside the mold, which made it exceptionally strong and stiff. I have had no issues with heat from handling or machining softening the wax so far. One thing that I particularly like about the wax is that it is easy to repair samll chips or dings if you damage it. Not sure how that would be handled with the foam?


    Do you have any pictures of the foam process that you could post? I would really like to see how that is done, and what a typical part looks like!


    I should have the CF stock for my "concept gun" ready to show in a couple more days, if all goes well.

    Jeff,
    How about shaping the core from Balsa like we did in the old days... Just introduce a bunch of termites
    after the CF has cured.;):D:D A new spin on Soluble Core Technology.:D


    There was a US Pat# 529043 for a water soluble resin, but that was for injection molding.
    Honestly I wish I could be of more help but my background is with metal and ceramics.;)
    Cheers, Don

    "Great mother ocean brought forth all life, it is my eternal home'' Don Berry from Blue Water Hunters.


    Spearfishing Store the freediving and spearfishing equipment specialists.

    The wax actually worked very well, once I learned to conrol the shrinkage, and how to remove it easily from the mold. One of the nice things about wax is that the properties can be tailored across a wide range of hardness, melting temp, etc, and it's reusable. But even the cheap parafin works well, and $10 at the local grocery got me all I needed for this gun.


    I'll start a thread soon, when I'm done laying up the CF on this gun.

    Jeff,
    Could you make the mold (plug) out of aluminum instead of wax and use a release agent to pop it out? I bought some CF tubes for a pole spear a few years back and i believe that was how they made them. I apologize in advance if it has already been discussed.


    Mike

    Edited once, last by ladvr ().

    Tin Man--- :thumbsup2:I can't wait to see this new gun :thumbsup2:
    Ill need as least 2 120cm guns. Thank you for all your time and effort. :toast:
    I've wanted an enclosed track pipe [or close to pipe] gun for years an years.

    Quote from ladvr

    Jeff,
    Could you make the mold (plug) out of aluminum instead of wax and use a release agent to pop it out?


    Yes, and no. That is the technique that seems to be the most common if the tubular shape is of constant cross section, especially circular. It works fine on a circular section, because you can twist the mandrel to help break it loose, and as you withdraw it.


    The problem is that if you have an enclosed track, or a square shape, or anything else that keeps you from twisting the mandrel, it can be much harder to remove. At least, that's what I've been told. And obviously the mandrel approach won't work if you have something in the middle of the gun (like a high mount handle) that would be a geometric impossibility to remove if the core is one solid piece.


    Hau - Take heart! I have found that this gun is giving me some trouble at the high mount handle, and the flaired butt section. But the straight section is a piece of cake. It should work very well for a Euro barrel.

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