Elliptical leg

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Hi,
I need (well, would like) one elliptical leg for the end of an elliptical table. The other end will be attached to a wall, so it only has one leg.
I have several ideas how to make one, layering lots of pieces of bandsawn wood (or plywood) and then shaving and sanding until I'm blue in the face.
Is there a simpler solution? The leg doesn't have to be tapered, just a piece of wood with a elleptical profile, about 6 x 10 centimetre (2 1/2 x 4 inch) inches thick.
Or should I order it from somewhere where they have a spindler moulder and the required profile(s)? Or a CNC cutter. I only need one, and don't want it to cost me an arm as well.
--
mare

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mare wrote:

This wood be better in r.c.woodturning. I just crossposted.
Most look here -- but might miss it.
Some do some pretty fancy stuff.
There are some specialty sites on this type of ornamental turning. DAGS on it. (ornamental turning that is)
-- Will R. Jewel Boxes and Wood Art http://woodwork.pmccl.com The power of accurate observation is commonly called cynicism by those who have not got it. George Bernard Shaw
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WillR wrote:

How about a router carriage, the length of the spindle, with an adjustable edge guide. The blank is held between centers in a lathe-like setup (or a lathe itself, if possible) with an elliptical template attached to one end. Use an end-cutting bit in the router, whose depth and positon is set to the template. It would be necessary to lock the blank in position, while making the cut the full length--then move the spindle a few degrees each time, adjusting the depth and lateral position of the router so it cuts tangent with the curve. Round the facets off with a sander.
Ken Grunke
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Ken Grunke wrote:

Ken:
Forgot about that idea. It's in the Router Magic book -- or sumpin like it. If the guy is interested in the idea I can dig out at least one plan.
--
Will
Occasional Techno-geek
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Turn The leg on two offset centers at 180 degrees with the center point equal distant from the center.
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Ralph wrote:

I guess I'm missing something. How does this form an ellipse? Aren't the ends going to be circular rather than elliptical in section? Unless the lathe moves the center while rotating as is possible with some ornamental lathes the section can't be elliptical.
Roger
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On Wed, 20 Apr 2005 20:18:51 -0400, Roger

I think he means that an ellipse has two "centers", or focal points. However, it won't work, as you suggest, since the ellipse is nowhere "circular", and no matter where the center, the cut will be circular to that center. I think no matter his choice of methods, each has its problems. The closest solution might be the one suggested to cut on the TS or bandsaw to rough shape then plane/sand to taste. The difficulty would be stabilising the already cut part while cutting the rest, but a wood channel and well-placed clamps should do it.
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It may not be truly elliptical but it will look more like an ellipse than a circle.
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No, this won't form an ellipse, but with proper layout it can form a reasonable approximation. I did a quick sketch in AutoCad to see what could be done. Start with a cylinder 4" in diameter and offset it ~1.3" at both ends and turn .75" of material from the highest spot. Have extra length and do NOT turn all the way to the ends , because the offsets are outside the finished ellipse. Now offset if again 1.3" from the original center but in the opposite direction as the first offset. Again turn .75" material from the highest spot. This will leave 4 lines the length of the "ellipse" where the original cylinder and the two offset turnings intersect. These lines are about 0.035" proud of the true ellipse and should be easier to hand sand to blend the curves. This is still not a true ellipse, as you go from the major diameter to the minor diameter the piece is a bit shy, with the maximum deviation being about 0.05". This might be good enough for his purposes. Hope this helps Martin
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Interesting idea. Seeing your note spurred me to do the same thing with another approach. Starting with a 2-1/2" x 4" rectangular blank, and with the table saw blade or band saw table set at 30 degrees, cut an elongated hexagon with sides tangent to the ellipse. The resulting points to plane off vary from slightly under 1/8" to slightly under 1/32" proud of the ellipse, with the worst ones being on the flat side. Cut four 15-degree bevels with the stock vertical before moving to the 30-degree bevel, and there is really very little planing to do.
As someone else said, lots of good approaches to this one.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

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I believe the problem can be solved throught the use of a spindle drum. construct a drum to proper specifications of the leg, length. place recesses in each end plate to hold the stock then add a second end plate. Mount the number of legs you wish to turn in the drum attaching with a screw through each end. The drum should contain spacers between each of the mounting points. you turn you turn down to the spacer prior to mounting the legs. You can use stock of any size as long as the recess is properly constructed. I am being simplistic in my description but I am sure there are people out there who could help..
To turn an ellipse turn the stock to the desired thickness and shape. then remount each leg by tuning it over once. 180 degrees. the circumference of the drum will dictate the curve. Old europe spindle turners used this technique often and keep a variety of drums and sample patterns on hand.
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That's a elegant solution, especially if you need more than one spindle. You didn't say, but it should be noted, that the two end plates are firmly attached to each other by a central shaft. It will make a bobbin shape. This insures that the end plates travel in unison. The bobbin shaped drum is turned between the centers. Actually, I'd use a face plate attached to the drive side plate. Dan
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Consider a circular cylinder.
Consider what you get if you slice that cylinder at an angle.
Now, construct a cylinder perpendicular to that angled cross-section slice.
You have, obviously, and elliptical cylinder.
It should be "obvious to the casual observer" that you can take an angled slice of _that_ cylinder in a manner that will yield a circular cross- section. That cross-section is perpendicular to the minor axis, and at an angle to the major axis such that the 'diagonal' is the same length as the major axis. Mathematical "proof" gets a little messy, but is fairly straightforward -- take the equation of an ellipse, parameterized as a function of the major and minor axis lengths, set the two lengths equal, and "reduce".
"A quantitative answer is left as an exercise for the student." *GRIN*
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wrote:

Right, ... so far, so good.

You just broke my brain.

Or, he could just make a template, turn it close-enough, and fine tune it to fit.

Hm. Sometimes, "close enough" is, well, close enough.
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He just makes it sound tough. Shine a flashlight straight down and it lights up a circle. On an angle it's an ellipse; has to do with trig if anyone insists. It still doesn't solve the probelm. Beside most layout is based on some hefty math, but the layout is to make it all easier. That's what got perspective geometry into the game, making tough to impossible jobs relatively simple. An ellipse can be drawn using two concentric circles and lines form the center ...etc..
But this doesn't in any way make "turning" a rectangle into an ellipse over a length of material any easier. There might be some giant industrial shaper around that would do it. The ellipse is symmetric ...the same in four sections... so only one section needs to be dealt with at a time, then times four. Baring an industrial machine, I'd go for approximate cuts on an oversize piece using the table saw, then hand plane then sand as was suggested earlier.
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snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote:

True, but irrelevant to what I understood to be suggested. I think the offset idea was to turn two circular arcs of relatively large diameter, which combine to form an elongated curved pointy-ended shape that then can be further worked with planes, scrapers, sanders, etc., to approximate an ellipse. As I understood it, both ends of the leg were going to be offset in the same direction, thus the concern for caution with inherent imbalance.
I think what you are talking about can be used to cut a circle in a single slanted plane, which will be useful as a gauge cut for the ellipse. But the ends of the leg will have to be offset pretty darned far from the lathe center if the leg is of any length.
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I was thinking of exactly the same process, with different tools: a bandsaw to cut the rough facets, and a plane to bring to final shape ( and a flexible card scraper if the tiny flats still left by the plane are undesirable).
Same idea--just whatever tools you have available and are most comfortable or prefer to work with.
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There are no simple solutions to turning an ellipse, or an oval for that matter. You might get some ideas from these websites. Dan
My oval turning lathe nearing completion http://www.claycritters.com/lathe /
The Elliptical Turning Association http://www.elliptical-turning-association.co.uk /
THE SOCIETY OF ORNAMENTAL TURNERS (U.K.) http://www.the-sot.com /
ORNAMENTAL TURNERS INTERNATIONAL (AMERICA) http://www.turners.org /
THE OLD SCHWAMB MILL http://www.oldschwambmill.org /
More Woodturning has had oval turning articles http://www.fholder.com/Woodturning/woodturn.htm
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Impressive video. Would such a Volmer type lathe be also of use with a longer piece of wood? Say 75 cm (30")? Or would you need a similar contraption on the other end, linked/synced to the one closer to the lathe?
--
mare

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thanks! Yes, you'd need something on the other end for spindle turning unless you were OK with it gradually turning from an oval to a circle by using a standard dead center.
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