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Re: [hobbicast] The bad and ugly, not so much good :(

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  • James (Jim) Buchanan
    Chris: From what I can see you are pouring to HOT. Big and heavy pieces don t need to be much above the melting point of aluminum to pour. Check the edge of
    Message 1 of 14 , Jun 1, 2003
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      Chris:

      From what I can see you are pouring to HOT. Big and heavy pieces don't
      need to be much above the melting point of aluminum to pour. Check the edge
      of the melting aluminum and the crucible to see that the meniscus is turned
      down. Or, pour as soon as the charge is melted.
    • Chris Boyer
      Jim Ok now I m learning something. Had to look up meniscus :) 3. The curved upper surface of a nonturbulent liquid in a container that is concave if the
      Message 2 of 14 , Jun 1, 2003
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        Jim

        Ok now I'm learning something. Had to look up meniscus :)

        3. The curved upper surface of a nonturbulent liquid in a container that is
        concave if the liquid wets the container walls and convex if it does not.


        You may have a point. The mold was not quite ready when the AL was melted.
        So it had to sit about 5 minutes. I upgraded the breakers on the kiln so I
        could turn it on high. Cuts the melt time to about 2 hours instead of 6.
        Also haven't gotten a pyrometer fixed up yet. No less than 6 meters here
        and not a single one has a k thermocouple :(


        > Chris:
        >
        > From what I can see you are pouring to HOT. Big and heavy pieces don't
        > need to be much above the melting point of aluminum to pour. Check the
        edge
        > of the melting aluminum and the crucible to see that the meniscus is
        turned
        > down. Or, pour as soon as the charge is melted.
        >
        >


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      • James (Jim) Buchanan
        For large parts try to pour as cool as possible. It will definitely show convex when it is cool and will wet the crucible as it heats up.
        Message 3 of 14 , Jun 1, 2003
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          For large parts try to pour as cool as possible.

          It will definitely show convex when it is cool and will wet the crucible as
          it heats up.
        • viscoyl
          ... get the carriage done. BIG headache, still have it. ... 1 more time. Open for suggestions on how to stop the shrink !!! ARGH !!!! and other words I bet
          Message 4 of 14 , Jun 1, 2003
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            --- In hobbicast@yahoogroups.com, "Chris Boyer" <boyercl@a...> wrote:
            > Well I updated my latest attempt at the headstock casting. Didn't
            get the carriage done. BIG headache, still have it.
            >
            > Its on its own page now under Gingery Lathe - headstock. Will try
            1 more time. Open for suggestions on how to stop the shrink !!!
            ARGH !!!! and other words I bet you can figure out ;).
            > Some wanted more pictures of molds rammed and set up. I didn't get
            them done either.
            > Hope tomorrow is better. Have some AL wheels tranny and misc
            engine parts coming. NO, not quite free. I have to take the truck
            apart to get them and I believe I got suckered into replacing rear
            wheel bearings in a T-Bird ??
            >
            > http://users.adelphia.net/~boyercl/hobbies.htm
            > Chris (CB)
            >
            >
            >




            I had to cast the headstock twice to get a good part back when I
            built my lathe. Some of Gingery's molding methods seem questionable
            to me, but anyway, I eliminated the shrink at the r. end of the
            headstock by using a 1 1/2" dia. riser at each corner. This is
            probably overkill, if I was doing it again I would use two risers at
            the right end only, and gate into both risers.
            Mike.



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            > [Non-text portions of this message have been removed]
          • Ron Thompson
            If you attach the riser with gates, the gates need to be large so they don t solidify before the casting. I always thought risers went on the thick sections of
            Message 5 of 14 , Jun 1, 2003
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              If you attach the riser with gates, the gates need to be large so they don't solidify before the casting. I always thought risers went on the thick sections of the part.

              Ron Thompson
              On the Beautiful Mississippi Gulf Coast
              USA

              Email me for current special offers on items from http://www.plansandprojects.com

              Grave yards are full of people who thought the law could, should and would protect them.
              ----- Original Message -----
              From: Chris Boyer
              To: hobbicast@yahoogroups.com
              Sent: Sunday, June 01, 2003 11:11 PM
              Subject: Re: [hobbicast] Re: The bad and ugly, not so much good :(


              See below



              > --- In hobbicast@yahoogroups.com, "Chris Boyer" <boyercl@a...> wrote:
              > > Well I updated my latest attempt at the headstock casting. Didn't
              > get the carriage done. BIG headache, still have it.
              > >
              > > Its on its own page now under Gingery Lathe - headstock. Will try
              > 1 more time. Open for suggestions on how to stop the shrink !!!
              > ARGH !!!! and other words I bet you can figure out ;).
              > > Some wanted more pictures of molds rammed and set up. I didn't get
              > them done either.
              > > Hope tomorrow is better. Have some AL wheels tranny and misc
              > engine parts coming. NO, not quite free. I have to take the truck
              > apart to get them and I believe I got suckered into replacing rear
              > wheel bearings in a T-Bird ??
              > >
              > > http://users.adelphia.net/~boyercl/hobbies.htm
              > > Chris (CB)
              > I had to cast the headstock twice to get a good part back when I
              > built my lathe. Some of Gingery's molding methods seem questionable
              > to me, but anyway, I eliminated the shrink at the r. end of the
              > headstock by using a 1 1/2" dia. riser at each corner. This is
              > probably overkill, if I was doing it again I would use two risers at
              > the right end only, and gate into both risers.
              > Mike.
              >

              If I under stand correctly there were 4 risers? How big was the headstock?
              Mine is about twice the AL as in the book. I know the risers go to the
              casting. Did you connect the risers together as well? How big were the
              gates?

              1.5" spru is in the plan and at least 1 riser on each end. Hmm might have
              to go 2 risers on the heavy end? I was using about 1/2" deep x 3/4" gates
              about 1.5" from the casting.

              Thanks Chris


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              [Non-text portions of this message have been removed]
            • Chris Boyer
              See below ... If I under stand correctly there were 4 risers? How big was the headstock? Mine is about twice the AL as in the book. I know the risers go to
              Message 6 of 14 , Jun 1, 2003
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                See below



                > --- In hobbicast@yahoogroups.com, "Chris Boyer" <boyercl@a...> wrote:
                > > Well I updated my latest attempt at the headstock casting. Didn't
                > get the carriage done. BIG headache, still have it.
                > >
                > > Its on its own page now under Gingery Lathe - headstock. Will try
                > 1 more time. Open for suggestions on how to stop the shrink !!!
                > ARGH !!!! and other words I bet you can figure out ;).
                > > Some wanted more pictures of molds rammed and set up. I didn't get
                > them done either.
                > > Hope tomorrow is better. Have some AL wheels tranny and misc
                > engine parts coming. NO, not quite free. I have to take the truck
                > apart to get them and I believe I got suckered into replacing rear
                > wheel bearings in a T-Bird ??
                > >
                > > http://users.adelphia.net/~boyercl/hobbies.htm
                > > Chris (CB)
                > I had to cast the headstock twice to get a good part back when I
                > built my lathe. Some of Gingery's molding methods seem questionable
                > to me, but anyway, I eliminated the shrink at the r. end of the
                > headstock by using a 1 1/2" dia. riser at each corner. This is
                > probably overkill, if I was doing it again I would use two risers at
                > the right end only, and gate into both risers.
                > Mike.
                >

                If I under stand correctly there were 4 risers? How big was the headstock?
                Mine is about twice the AL as in the book. I know the risers go to the
                casting. Did you connect the risers together as well? How big were the
                gates?

                1.5" spru is in the plan and at least 1 riser on each end. Hmm might have
                to go 2 risers on the heavy end? I was using about 1/2" deep x 3/4" gates
                about 1.5" from the casting.

                Thanks Chris


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              • viscoyl
                ... headstock? ... to the ... were the ... might have ... 3/4 gates ... Yes, 4 risers, not connected together except by the casting itself. The gate was about
                Message 7 of 14 , Jun 2, 2003
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                  > If I under stand correctly there were 4 risers? How big was the
                  headstock?
                  > Mine is about twice the AL as in the book. I know the risers go
                  to the
                  > casting. Did you connect the risers together as well? How big
                  were the
                  > gates?
                  >
                  > 1.5" spru is in the plan and at least 1 riser on each end. Hmm
                  might have
                  > to go 2 risers on the heavy end? I was using about 1/2" deep x
                  3/4" gates
                  > about 1.5" from the casting.
                  >
                  > Thanks Chris




                  Yes, 4 risers, not connected together except by the casting itself.
                  The gate was about 1" wide and 1/4" deep going into each of the
                  risers on the R. end, coming from a tapered sprue about 3/4" dia. at
                  the base and 7/8" at the top. My headstock pattern was about 1"
                  larger in height from parting line to top and 1/16"-3/32" thicker
                  than the one in the book, otherwise I followed Gingery's dimensions.
                  Also, I deepened the raised area between the clamp pads in an effort
                  to prevent too abrupt a change in cross section area.
                  Mike.
                • viscoyl
                  ... they don t solidify before the casting. I always thought risers went on the thick sections of the part. ... Yes, they are supposed to. As I said, if I was
                  Message 8 of 14 , Jun 2, 2003
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                    --- In hobbicast@yahoogroups.com, "Ron Thompson" <thom1486@b...>
                    wrote:
                    > If you attach the riser with gates, the gates need to be large so
                    they don't solidify before the casting. I always thought risers went
                    on the thick sections of the part.
                    >
                    > Ron Thompson
                    > On the Beautiful Mississippi Gulf Coast
                    > USA
                    >



                    Yes, they are supposed to. As I said, if I was doing it again, I
                    would put two risers at the heavy end and gate into them. I cast mine
                    about 15 years ago when I knew less about such things than today, and
                    the first attempt had a big shrink area at the intersection of the
                    base and the r. end. I don't know if it would have seriously affected
                    the strength of the casting, but it didn't look good.
                    Mike.
                  • regor2morts
                    Sounds like we all had the same shrink problem. I fixed mine on the second casting by putting a piece of Styrofoam over pattern in the area where the cavity
                    Message 9 of 14 , Jun 3, 2003
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                      Sounds like we all had the same shrink problem. I fixed mine on the
                      second casting by putting a piece of Styrofoam over pattern in the
                      area where the cavity formed. That forced the shrinkage to come out
                      of the metal that filled the foam area. The foam was roughly double
                      the volume of the original cavity and far enough from the wear pads
                      to be removed with a file. I can't say my casting was pretty but the
                      cavity was minimal.
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