[TheForge] eliptical rings on a cone mandrel?

[Steve Smith]

Why wouldn't it be symmetrical? Not that I've tried it or anything, but 
Bruce has it right--an angled plane on a cone makes an ellipse.

Steve

Rick wrote:

> 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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