Casting and building the Compac Super GK blaster scope - A tutorial

Discussion in 'Replica Props' started by adamata, May 16, 2015.

  1. adamata

    adamata Sr Member RPF PREMIUM MEMBER

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    As many members know, I have been molding and casting the Compac Super scope used on the Han Solo "Greedo Killer" blaster for quite some time. I was able to get a correct version years ago (with the accurate front lens). I have had a few people ask me how I made these so accurately lately with almost no cleanup and I wanted to share how I do it and the process I go through.

    I have been struggling with casting this thing for years. Trying to mold a perfect cylinder that has to have a perfect flat area on the ends is been a PITA.

    I have actually molded this this about 5 times trying to find the perfect method, and then it hit me. Cast it in parts and assemble it like they did when they made the real ones.

    So, I wanted to share how I make these an why I don't have them available all the time. :)

    First off, all three parts are molded individually. The two scope body parts are done in a dump mold so that the lens ends do not have any seams. The knob assembly is done with a 2 part mold. This is what they look like right out of the molds
    gkt01.jpg


    I grind the ends down with a disk sander to make sure they are flat
    gkt03.jpg


    I use a center square to find the center of each part and score lines using a dental tool
    gkt05.jpg

    If you dont have one of these, shame on you!

    You can get one from Micromark:
    http://www.micromark.com/center-square-5-inch-capacity,8433.html


    With scored lines to mark the centers
    gkt07.jpg


    Here they both are in a custom made jig used to keep them vertical and to keep the lenses damage free during the process.
    gkt09.jpg


    I used a 1" flat bit to hollow out the bell end so it will accept the main tube. This is why having a perfect center hole is important (You will see more why further down)
    gkt11.jpg



    It gets a little hairy doing this
    gkt13.jpg


    When done, this is what the bell end looks like. I also drill a hole in the main tube as well.
    gkt15.jpg


    I test fit them, to make sure they are aligned right, then add a double ended screw into the bell end
    gkt23.jpg

    If the holes are off center even a little, when trying to screw them together, this will happen :-(
    gkt40.jpg


    Then add some super glue inside where they will meet and screw the main body parts together
    gkt17.jpg


    I put the scope on a V-block and drill out a small hole for the knob assembly to fit into. You can see the underside of the assembly in the first pic. This makes sure the part is in the exact spot it should be in
    gkt19.jpg


    I sand the flash off the knob assembly and drill out the top screw (and countersink the hole)
    gkt21.jpg


    I check the fit of a real brass screw to make sure it will fit
    gkt22.jpg


    I drill a smaller pilot hole into the mail body for the screw to fit into
    gkt25.jpg


    and then screw the assembly into the mail body.
    gkt30.jpg


    And that is basically it. There is no flash or sprues to clean up, and just a little seam work and main body sanding.

    So, That is how its done. I hope that answers any questions and if you are interested in one, I am going to post soon in the JY :)
     
  2. Prefect42

    Prefect42 Sr Member RPF PREMIUM MEMBER

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    Brilliant tutorial. Not only for a scope but for anyone wanting to make a mold.

    Cheers!

    Ted.
     
    adamata likes this.
  3. Striker

    Striker Member

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    Are your molds "Open Molds"?
     
  4. adamata

    adamata Sr Member RPF PREMIUM MEMBER

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    Yes, the two main parts are. I will take some pics and post them

    scope_molds.jpg
     
    Last edited: Jul 9, 2015

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