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    1. Kit: , by (Active Member) bills69camaro is offline
      Builder Last Online: Jan 2021 Show Printable Version Email this Page
      Model Scale: 1/8 Rating:  Thanks: 3
      Started: 03-07-12 Build Revisions: Never  
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      This is the tire I will be molding & casting Molding & Casting a Rubber tire it's a Dunlop SP Sport 8000.
      The RTV Molding & Casting a Rubber tire I like to use is a clear platinum base. It's easy to see what you're cutting around and you can cast regular resin Molding & Casting a Rubber tire , clear resin Molding & Casting a Rubber tire , and rubber parts.




      Here I glue a styrene gate to the tire and glued the tire to a foamcore base. It's hard to see because my shot is over exposed. The gray rod is PVC I bought at a industrial supply house and turned it to size on my lathe. The reason for the pin is to make it easier to cut RTV core (shown later on).





      The box with all the elements in place ready for RTV to be poured. The box measures 3" W x 5 1/4" L x 6" H. I cut a piece of foamcore 6" x 17" and score it at the 3" and 5 1/4" dimensions and fold to make the box. I then hot glue the corners for extra strength, and also glue the box to the base.





      I mix the RTV and vacuum it to get the air out. Thats a must if you want a nice mold.<br>The formula I use to mix the right amount of RTV, L x W x H divide by 16 x .625.

      3 x 5 1/4 = 15.75 x 6 = 94.5 divided by 16 = 5.906 x .625 = 3.691 lbs. To convert .691 to ounces, multiply .691 x 16 = 11.056 ounces. I add a couple of ounces extra for waste. Total amount of RTV&nbsp; 3 lbs 13 oz.





      The RTV degassed and poured into the mold.





      After the mold is poured I place it back in the vacuum chamber. The tire is hollow so air will be trapped in the top inside of the tire, the pocket of air will be taken out so we can have a nice clean hollow tire.





      The mold out of the box and the PVC pin taken out, cutting the mold open begins. The mold is cut in the center down to the tire on all four sides. While cutting I wiggle the blade, that makes a jagged cut. When you're ready to cast and put the mold together the jagged cut will act as a lock and keep the
      mold halves from sliding and insuring a clean part.





      Here the mold is cut all around and opened so you can see the master. The mold core still needs to be cut and is keeping the mold from being open all the way.





      With the sides cut we start on the core. If I didn't make a center pin this would be solid RTV and very difficult to cut open. With the pin out there is a void and the RTV is a lot more flexible, making it easy to cut. It has to be cut down to the rim of the tire for the mold to be opened.





      The core is cut allowing the mold to be opened. The tire master is still on the core, unfortunately the master has to be cut off the core.




      Here it is cut in half and off the core.



      The mold is together , the pin in place, and taped with 2" clear packing tape to make it air tight. I then make a paper funnel and hot glue it to the mold, the rubber resin is poured into the funnel. The paper is heavy card stock 110 lb. I then place the mold in the vacuum chamber to be degassed. This takes 2 or 3 minutes. After it's degassed I open the valve on the chamber and let air back in the chamber, the rubber is drawn into the mold cavity. The mold is placed in a pressure pot for curing.


      After a 3 to 4 hr. curing time the mold is opened to show the newly cast tire.



      The tire is flexible and is pulled off the core.



      Nice flexible tire



      I hope my explanation was understandable.

      Bill

      Sorry I posted a pic twice and missed one all together. Not sure how to delete pics and add new ones.



      Molding &amp; Casting a Rubber tire
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  1. bills69camaro's Avatar Active Member
    Name
    bill
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    Feb 2010
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    81
    Hello Shiggy. For the mold I used G T 2135 Compound RTV Molding &amp; Casting a Rubber tire Silicone Clear. I don't know who makes it, it was purchased
    from BCC Products , Inc.
    2140 Earlywood Dr.
    Franklin, IN 46131
    317-736-4090

    The material used for casting Molding &amp; Casting a Rubber tire the tire, F-42 A/B 42 shore A polyurethane elastomer.
    Purchased from BJB Enterprises, Inc. 714-734-8450 you can see all the products on their website.
    Hope this helps.


    Molding &amp; Casting a Rubber tire
    QUOTE QUOTE #17

  2. Shiggy's Avatar Member
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    Chardonnay
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    Sep 2013
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    Thank you for your response!
    QUOTE QUOTE #18

  3. RAT23's Avatar Active Member
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    TOM
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    Jan 2014
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    29
    Hi bill,
    great tutorial!
    What would you say the difference is between the styrene Molding &amp; Casting a Rubber tire pins od & the tires id?

    Thanks, tom
    QUOTE QUOTE #19

  4. rickparis's Avatar Member
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    rick
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    Jan 2021
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    I hope I can find an answer here as it has been a few years since you posted on this thread. I love what you did here. I do not understand how the silicone got into the center portion of the tire? Did you do two pours? I don't understand why you had to cut the original tire in half, did it not stretch enough to get it off the center? I do not want to make a mold of two halves, as most people do. Thanks!
    QUOTE QUOTE #20

  5. rickparis's Avatar Member
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    rick
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    It also seems the piece you turned for the axel center needs to be smaller than the tire rim diameter? so you can cut it out? I see there is some white around the old tire edge, did you use some kind of spacer?
    Thank you!
    QUOTE QUOTE #21

  6. MODEL A MODEL's Avatar Yearly Subscriber
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    don
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    Feb 2017
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    That's a good question!

    Look at the second photo, the "Gate" is the faint off-white / grey square shape under the tire pattern. When pouring the RTV Molding &amp; Casting a Rubber tire this "Gate" is the support for the pattern and is at the bottom of the mold box. It supports the pattern and the PVC pin passes through the center of the tire pattern, but does not touch it. The pin is attached to the mold box walls but not the pattern. Allowing the RTV Molding &amp; Casting a Rubber tire to enter the inside of the tire.

    Later the whole mold is turned upside down, with the "Gate" now at the top.

    I assume that when the mold is in the vacuum, the air that had been in the mold, has to bubble-up through the resin Molding &amp; Casting a Rubber tire ? The resin Molding &amp; Casting a Rubber tire being in the reservoir attached to the (NOW) top of the mold. That being the case, the reservoir's walls need to accommodate the temporary rise of the resin Molding &amp; Casting a Rubber tire .

    Interesting!
    Last edited by MODEL A MODEL; 01-31-21 at 01:41 PM.
    -craftsmanship is a lifelong project of
    self-construction and self determination
    QUOTE QUOTE #22

  7. MODEL A MODEL's Avatar Yearly Subscriber
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    don
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    Making a two part mold this way is the best way.

    When you carefully cut through the RTV Molding &amp; Casting a Rubber tire , it creates it's own "Keys", and creates a net / net fit. A perfect fit.

    And when he opened the valve, allowing the ambient air to enter the vacuum chamber, the resin Molding &amp; Casting a Rubber tire is drawn into the vacuum that still exists inside the tire mold, and, it is being pushed by the returning air.

    He probably had to cut his pattern, because it was a rigid part. A sacrificial pattern, which had served it's purpose.

    The white you see is the pattern. Some rigid plastic? Styrene Molding &amp; Casting a Rubber tire or PVC? Cut in half.
    Last edited by MODEL A MODEL; 01-31-21 at 01:52 PM.
    -craftsmanship is a lifelong project of
    self-construction and self determination
    QUOTE QUOTE #23

  8. MODEL A MODEL's Avatar Yearly Subscriber
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    don
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    Notice the pliers that he is using? These are available in auto parts stores, I own two but can't remember what they're actually designed for? When you squeeze them, they open up. Very useful when cutting into a mold like this.
    Last edited by MODEL A MODEL; 01-31-21 at 01:53 PM.
    -craftsmanship is a lifelong project of
    self-construction and self determination
    QUOTE QUOTE #24

  9. rickparis's Avatar Member
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    rick
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    Thank you!!
    QUOTE QUOTE #25

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