[TheForge] eliptical rings on a cone mandrel?

[Bruce Freeman]

No, that misses the point.  Those of you who've had the pleasure of
making a ring using a cone mandrel understand completely what a
difference this is compared to even making one over the anvil horn
(which is not typically round).  The ring almost magically forms itself
round - you can't miss!

What I'm shooting for here is a comparable experience in making an
eliptical ring, WITHOUT making a special eliptical cone mandrel (a
possibility, but not practical).  

BTW, I've reviewed the math.  Indeed, a cone intersected (through its
axis) at an angle yields an ellipse - a symmetrical ellipse.  (If any
one cares to see the math, I'll post it.)

Unfortunately, I got no time at Marshall's forge.  He has a small cone
mandrel I could use, when I get time.  (I do too, but can't find it. 
GOT to get my shop in order, already!)

Happy turkey day,

Bruce
NJ

>>> rick at smokyforge.com 11/17/2006 7:06 PM >>>
You could form half, the turn it around and form the other half.  That

should work.

|8^)>
Rick Crawford at Rafter Lazy C
  Home of Smoky Forge and Lem the Wonder Mule
   In the middle of Northern Illinois

    http://www.smokyforge.com 
     rick at smokyforge.com 




----- Original Message ----- 
From: <wmullett at bright.net>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Friday, November 17, 2006 3:23 PM
Subject: Re: [TheForge] eliptical rings on a cone mandrel?


> The ellipse formed by a cone is not symmetrical.
>
>>
>> From: "Bruce Freeman" <FREEMAB at pt.fdah.com>
>> Date: Fri Nov 17, 9:45 AM
>> To: <theforge at mailman.qth.net>
>> Subject: [TheForge] eliptical rings on a cone mandrel?
>>
>> 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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