[Art Ransom]

I am doing a table base from wood. Part of it is a 19" sphere with a 17" spherical viod. I want to mill three 8" holes centered on the equator. In order for them to look round they will have to be elipitical. How do I figure what the axis' for the hole?

[HuFlungDung]

Art,
Any way that you can come up with a quick sketch of what you want to do. I read it forwards and backwards and still could not imagine it

[turmite]

Art is this what you are talking about?

[Art Ransom]

yes that is it!

[turmite]

Art do you need a model of it? I didn't save it but it won't take long to make it again.

Mike

[HuFlungDung]

Where does the requirement for an ellipse come in? That's the part I don't grasp.

[turmite]

Where does the requirement for an ellipse come in? That's the part I don't grasp.

Hu, it is one of them there elliptical illusions!

When you look at the 8" holes from an angle there is the illusion that it is an ellipse.

Mike

[HuFlungDung]

Okay, I'll bite What is the correct viewing angle for a 19" sphere with 8" holes in it? How high should it be off the floor, and what is my ideal height and distance from the object?

[Geof]

Hu, it is one of them there elliptical illusions!

When you look at the 8" holes from an angle there is the illusion that it is an ellipse.

Mike

That may be correct, but if you figured out the elliptical shape needed to make it look circular from one vieiwing angle it would look circular only from that viewing angle; all other views would be decidedly strange I think.

[turmite]

Okay, I'll bite What is the correct viewing angle for a 19" sphere with 8" holes in it? How high should it be off the floor, and what is my ideal height and distance from the object?

HU, you of all people should know that! The "right" side!

Geof I agree. This isn't my thread, I'm just trying to help Art!

Mike

[ger21]

I think the best way to make it look round is to cut a round hole.

[harryn]

I am not positive about this, but I think the general approach is to take the 8 inch circular cut out and "wrap it" around the larger sphere in one direction, and flat in the other.

If you measure 4 inches up and down along the circumference, this should give you an "actual hole" which is eliptical. Width wise, you just measure straight (not along the curvature) to make the other axis.

It would be a good idea to double check this idea before cutting.

[HuFlungDung]

I've heard that good artists (ones who can really paint realistic pictures) have a certain 'literal interpretation' of what they see. For them, looking at a hole off axis may actually look elliptical, but for the average non-artist (like myself), automatic interpretation of the object by my brain renders the ellipse into a circle because I assume it is a circle.