[TheForge] eliptical rings on a cone mandrel?

[kim george]

coudn't you also do it on a bollard?


At 09:45 AM 11/17/2006 -0500, you wrote:
>I don't happen to have a cone mandrel, so can't try this myself.  I'm
>hoping someone can give it a quick try and let the rest of us know how
>it works:
>
>Those of you who suffered through algebra are aware of the "conic
>sections" - shapes that can be derived mathematically from a cone.  The
>circle, for example is a horizontal slice through a cone.  Blacksmiths
>make use of this by using a cone mandrel to make perfectly circular
>rings.
>
>What is not so obvious is that the elipse, the parabola, and the
>hyperbola are all also conic sections.  If look at a cone from the side,
>it's a triangle.  (Mathematically, it's two triangles, one upside down
>atop the other, but we don't have to bother about that.  One "half-cone"
>will do.)  Draw a horizontal line through this triangle (i.e., of the
>cone), and, as I said above, you've got a circle on the cone.  Draw
>vertical line through this triangle and you have a parabolic curve on
>the cone - interesting, but probably not too useful.  (And the hyperbola
>is even worse.)
>
>But an elipse is also possible.  An elipse arises from an angle between
>horzontal and vertical.  And they're really cool shapes.
>
>So, make a ring.  Round it up on the cone.  Then take it off the cone
>and hammer it from the side to make it somewhat oblong.  Put it back on
>the cone and hold it at an angle (say, 30 to 60 degrees from horizontal)
>and "elipse" it up on the cone.  Got that?
>
>If some interested folk could try this out and report back, I'd like to
>hear about it.
>
>(I suspect the trick to make this practical might be to make it
>narrower than wanted on the anvil, as the thing will tend back to round
>on the cone.  It also may be necessary to take it off the cone
>occassionally to flatten the plane of the ring against the anvil.)
>
>Bruce
>NJ
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Kim George

       "Why for you burry me in cold,cold ground?" Taz