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Re: gates and sprues

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  • Lyle
    Well then it s a big misunderstanding on my part - sorry. The original problem still has not been resolved with his casting I think it s got something to do
    Message 1 of 53 , Mar 6, 2007
      Well then it's a big misunderstanding on my part - sorry.
      The original problem still has not been resolved with his casting I
      think it's got something to do with how he did his molding. Someone
      offlist emailed me the dimensions of the lathe bad pattern and I
      think the guy would get better results if he cast it upside down with
      the main body of the pattern in the drag, the part where he got
      shrinkage would have the most hydraulic pressure and be fed from the
      rest of the casting. He would still need to put risors in but they
      would feed the bottom of the lathe bed and take advantage of the full
      depth of the cope rather than just partial advantage because the
      pattern is not sticking up into the cope. Personally I'd stick the
      risors right next to, but not directly into the pattern shape.


      --- In hobbicast@yahoogroups.com, "Dave" <odd_kins@...> wrote:
      > Lyle the internet is really a bad place to have any kind of
      > conversation. The response to George's post was suppost to add info
      > that I feel was left out, the only thing I disagreed with was not
      > using a clamp or weights on your mold. I'm sure if the same
      > conversation happened face to face things would have been different.
      > Somethings I take for granted, like looking at the web sites I
      > posted and reading all the way thru. The 1:4:4 ratio or any ratio
      > would be worked from the ingate backwards to the sprue, this is why
      > i gave you these sites. as far as number crunching I do it from the
      > sprue forward because i've done it for about 30 years. As far as
      > further explaination when i say the ratio is a starting point, that
      > would take more than a book to explain, as people in the foundry
      > business still argue about. I reread the post to George and have
      > to find anything that says his comments wouldn't work. the most
      > important thing to me is give people enough information to do the
      > research, then they can deciede how thay want to do things.
      > I'm not offended by anyone, but maybe sometimes offend. We all have
      > that problem.
      > So George, Lyle and anyone else who may have been offended, I am
      > sorry.
      > --- In hobbicast@yahoogroups.com, "Lyle" <creepinogie@> wrote:
      > >
      > > Dave,
      > > Do you know what the Reynolds number, hydraulic radius, or N
      > factor
      > > is? And what they are used for? I do. We're talking home casting
      > > here. And I doubt anyone, certainly not me, is going to be
      > > numbers. I make my gating system based upon experience and
      > sometimes
      > > it takes a few times to get things right. So do your ratios if
      > they
      > > are supposed to be "starting points." When asked for some further
      > > explanation of it your answer didn't make sense (when you said
      > > ingates were larger than the sprue). Then you linked to a bunch
      > > other people's websites. Shouldn't the size of the gates and
      > risors
      > > be based on the size and greatest cross sectional area of the
      > casting
      > > and not all based on some sprue size? Nowhere is there anything
      > > the 4:1:1 ratio that talks about thickness of the casting and
      > total
      > > size. Maybe I should join a particle physics group and when
      > someone
      > > poses a question, I can pipe up and when asked to explain, give a
      > > bunch of links to other peoples sites.
      > >
      > > The reason I came into this thread is because George was trying
      > > give the guy some advice when you piped in with all sorts of
      > reasons
      > > why they wouldn't work. You mentioned porosity in core sand
      > (nothing
      > > to do with the original question) and gave some ratios with no
      > > further explanation. One of George's points was that much of the
      > > resources out there was for cast iron and therefore not always
      > > applicable to aluminum. Now I don't always agree with some of the
      > > things he says, but I do for all his answers to the guy who asked
      > the
      > > original question. It is not condusive to a group to give someone
      > an
      > > answer and have another contradict it with some vague response.
      > Yes,
      > > there are always exceptions. But this guy is pouring a lathe bed
      > > which I assume is a realatively bulky and thickwalled casting. I
      > > could be that enlarging the gates, is going to compound his
      > problem.
      > > He didin't mention if his casting was cast concave side up - or
      > down
      > > which is certainly going to affect his gating and there's no rle
      > ever
      > > that's going to cover all cases.
      > >
      > > The guy's real problem (without actually seeing a photo) is
      > probably
      > > a combination of sprue, risor, and gating size as well as their
      > > locations. I would really like to see a photo of what the guys is
      > > talking about.
      > >
      > > I'm not trying to prove you don't know what your talking aobut
      > I
      > > would like to point out that there's some things you bring up
      > > aren't right either.
      > >
      > > I invite anyone who is pouring lathe beds to come to my shop in
      > > Northern MN and we can pour some aluminum together and maybe
      > > something. That's what's so neat about this hobby. You can't
      > > everything from a book. I am a college educated engineer and
      > > %95 of the stuff I do comes from doing - not reading. And there's
      > > lots of books and websites with some dubious explanations.
      > >
      > > LL
      > > PS don't be too offended by me, just certain things set me off.
      > But
      > > I'm still learning too after 5 different homemade crucible
      > furnaces,
      > > 3 commercial furnaces and about 30 years on and off doing foundry
      > > stuff (30 molding and last 15 has been melting and pattern) and
      > I'm
      > > nowhere near an expert.
      > >
      > > --- In hobbicast@yahoogroups.com, "Dave" <odd_kins@> wrote:
      > > >
      > > > This quote is from page 3
      > > >
      > > > "In general, the entire path of molten metal, within the gating
      > > > system as well as the mould
      > > > cavity, is turbulent in most castings. This can be readily
      > > > ascertained by calculating the
      > > > value of Reynolds number for a typical casting. A major purpose
      > of
      > > > the gating system
      > > > (instead of pouring metal directly into the mould cavity) is to
      > > > reduce the turbulence,
      > > > though it cannot be completely eliminated."
      > > >
      > > > The closest thing I said may have been gating into a riser
      > rather
      > > > than the casting. by that I mean you still use a gating system,
      > > same
      > > > ratios apply but you can eliminate some of the cleanup on the
      > > > casting by doing so. I did not mean that you pour down the
      > riser.
      > > > which by the way I have done because the amount of metal I can
      > pour
      > > > is limited, and it does give you a crappy casting. but they
      > > for
      > > > my flasks and they work. When I get setup for a #10 crusible I
      > > won't
      > > > have that problem.
      > > > Instead of trying to prove that I don't know what I'm talking
      > about
      > > > why don't you go to the shop and try the ratios giving by me
      > > > others on your next casting and see if it works;-)
      > > >
      > > > --- In hobbicast@yahoogroups.com, "Lyle" <creepinogie@> wrote:
      > > > >
      > > > > I was talking about gating directly into the mold cavity not
      > the
      > > > > ratios. I think you were the one that said that. Right?
      > > > > maybe I'm wrong but someone here said that a day or so ago.
      > > > > LL
      > > >
      > >
    • Dave
      Ok you can turn your monitor the right way up now. Didn t even think about rhe angle the pictures were at. ... look like. ... photo editing ... that way ... to
      Message 53 of 53 , Mar 10, 2007
        Ok you can turn your monitor the right way up now. Didn't even think
        about rhe angle the pictures were at.

        --- In hobbicast@yahoogroups.com, "joe" <jalign@...> wrote:
        > Nice pictures Dave that gives me a better idea of what the risers
        look like.
        > I noticed the pictures are sideways, I downloaded a different
        photo editing
        > programfor my computer to rotate the pictures before I post them,
        that way
        > I don't have to tip my monitor on it's side to look at them. (grin)
        > Joe in PDX
        > --- In hobbicast@yahoogroups.com, "Dave" <odd_kins@> wrote:
        > >
        > > Joe I'm adding some pictures to my album that might help. I had
        > > double role the mold as the cope would drop out when pulling the
        > > cope flask off. This casting is 8"X4"X2.5" so about the same as
        > > of your pockets. I poured the mold cold, with 6061alloy, but the
        > > gating system is not what I wanted. Tried to force the pattern
        > > gating into too small of a flask, the gate was only 5/8 away
        > > the pattern and it broke.
        > >
        > >
        > ===snip==
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