Top to base ratio

[mgilley]

Hello,
Does anyone happen to know how to figure the top to base ratio for a round table? The top is going to be a 54 inch roung glass. I was planning on a 30 inch base.
Thanks,
Mike

[bleeth]

Mike: That should be fine. There is no "fixed" ratio that I am aware of. If your pedestal is "solid" then you can see that you will have only 12" of knee and/or chair space under the table. It is generally more comfortable to have a few inches more (14-16) but of course you need to be concerned about the tipping factor. That is affected by the weight of the glass. The thicker the glass, than the less it will want to move.You still should be safe with a base 50% of the glass size which get's you to 13 1/2" knee space. I personally believe that glass top tables of that sort should be a minimum of 1/2" thick and 3/4" is better (besides looking so much better).
The overall design of your pedestal can also assist greatly. You can always put a base and subtop on it which is wider than the cylinder which gives you higher safety and a lighter appearence. Alternately your pedestal can have an "hourglass" shape. Another option is "outrigger" legs and/or struts.
You can accomplish much by designing the pedestal in such a way that it looks smaller than it is.

[mgilley]

Thanks Dave
Here is a rendering of the base the top is going to be 1/2 in. The top is 32 in dia and the base is 30 accross the base.
6466

[bleeth]

That looks gorgeous and quite functional. What materials are you planning on?

[mgilley]

I'm using Pecan lumber for the whole project. I am going to stain and glaze it and spray a laquer finish. I'm having trouble with the sphere in the center. I can't seem to get the acanthus leaves to lay on the surface like I want them.

[bleeth]

Mike: Check your mail.

[beacon14]

Your effective base size is only 24", you have to measure to the tipping point of the base which is a straight line between the feet. I still think the top will be stable enough unless someone tries to sit on one edge adjacent to one of the tipping points.


6467

[wberminio]

I agree with Dave.Also,think of a method to weigh the base.I've used sand in the past.The last thing you want is the table to tip, when someone puts some weight on an edge.

Erminio

[mgilley]

After talking to the customer, she said that they would plan on using a 48 inch table. This should be alot safer, don' you think?
Mike

[mgilley]

Thanks, David and Erminio.

Dave,
Here is what I drew for the sphere, but I think I shouls have the leaves turned 180 degrees. It is sort of hard to see at such a low res.
thanks,
Mike

6468

[bleeth]

Mike: Your design is looking seriouser and seriouser!! In comparison to the Hemisphere the carving of the legs is a piece of cake. I'm thinking now you would need to cut this part on an indexer unless you were thinking of making a leaf mold, casting the parts in pliable rubber and faux painting them. There is a line of applied moldings that I used a long time ago that were made of horse-hair and some kind of bonding agent (sort of hide-glue like) that you would steam and they would become pliable. The natural color of them was medium dark wood and after you glued them in place and they dried you could stain and finish them with the same product as the wood. I don't remember where they came from now though and an online search isn't helping.
How to machine this and with what software is a subject unto itself unless you have a five axis mill.
James, Brian-what do you think?
(BTW-I like the leaves oriented the way they are)

[mgilley]

Dave,
I have an indexer but I thought it might be simpler to cut the sphere in quarters, make a jig with a 45 degree angle to hold it and cut the leaf. I am using Rhino 4, Rhino Art and VisualMill 6 for this piece. The customer made it clear not to use applied carvings.
Thanks,
Mike

[bleeth]

Mike: You may wish to consider rotating your quarters so the highest point of the sphere is the center of the leaf and not the bottom. You will lose less detail that way at the point. Regarding the sides of the leaves laying on the surface-Artcam came out a few versions ago with a "fade relief" feature that is made for this. It can eliminate those straight cuts at some edges. On the other hand some careful undercutting by hand or dremel after machining would really make it pop.