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pedestal table base size10/16
A client has requested a pedestal table for a breakfast nook. The table will be 28 x 60, but there's a specific request for a single pedestal.
I've built both single- and double-pedestal tables before, but none with these oddball dimensions. I'm concerned about the tip- over potential, and am soliciting advice on how large to make the base. Tip-over isn't an issue in the short dimension; it's the long dimension I'm worried about.
I told my clients that the best thing would be to use two pedestals, but they're insisting on one so they can maximize seating. Bolting the table to the floor is out of the question.
What size base should I use?
We use 50% as a rule of thumb here and have never had an issue in 34 years.
As pictured looks fine to me but...mock it up. i.e. cut a piece of ply or something to the foot dimensions intended and see is it is tippy.
If the table has 2 pedestals, it would have more weight to lift and less flex in the top. Pushing down on the long end with a single connection at center vs 2 connections and connection closer to the long end means less flex. It's the flex/wobble that could be less than desirable. Put all this in your proposal and let them sign. just mck it up and the answer will become apparent. Might just be plenty stout. We worry so much, it's exhausting
After posting my question, I dug around the internet for a couple hours and found some interesting stuff. More importantly, I found that a single pedestal with a cross-shaped base would not work for this table. Read on:
It seems there's a generally held rule that says a table's base should be 75% of the tabletop size to minimize tip-over potential (this equals a 12.5% overhang at each end and side). The correct way to find the "tipping moment" uses calculus and physics, and involves wood density, calculating the center of mass, etc. The 75% rule is pretty standard, though. My 28X60 table top would then need a 21X45 base.
A cross-shaped base takes care of that, but only if downward force is applied at the middle of the end or middle of the side of the table. If someone were to put pressure on a corner, the table would tilt over very easily. The effective overhang at the corners is roughly 30%. I've attached a drawing to illustrate. There's a diagonal line between the base parts - that represents the effective corner overhang.
In the end, I gave my client three options:
1) use the base as drawn, but bolt the table to the floor. As this project is for a house and not a restaurant, this option was out.
2) go to an x-shaped base which moves the base closer to the table corners. This option was nixed as the base would interfere with a chair no matter where it was placed.
3) redesign the table and use two bases, one at each end of the table. My client went with this option.
Excellent problem solving and that is a clear presentation of what you learned.
Force applied at the corner had not dawned on me, but now that you mention it that is probably a very common occurrence.
Another solution might have been to use a 500 pound base, but as with bolts, probably not acceptable to the customer.
Hello fellow craftsmen!
I read this thread, as I have read many, many, many over the years, always learning so much from all of you, and just couldn't wait to post about just how far we pushed the ratio of tabletop to base size on this last table project.
My thought is that you apply what you know, seek to learn more and push the envelope.
With each project I research the heck out of means and methods, physical limitations and study ways to transfer load. We consider the lumber, the design intent, frequency of use, where in the world the piece will end up and of course reasonable end user maintenance.
We build many pieces that are used in high end, high volume hospitality settings. Jokingly, and seriously, we consider somebody or somebody's living it up and abusing our pieces, or rather, using them for something other than their intended use and build accordingly. . . . .
This piece was subject to all of the above consideration.
The table counter balances itself, it will not tip easily or at all. I will admit that you could force a bounce at the other end when all of the leaves are in place, but really, when is the last time any of us tried hard to heave mightily on a dinner table?
Point is folks: this piece breaks the rules, but it works, very well. I always push the boundaries to see just how far they extend, and each time I learn so much.
-Black Limba solids and veneers, MDF top core material, Finger jointed/hand shaped solid edging, lots of iron, brick laid and veneered base.
-60" x 26" x 2.5" base (iron plates to connect the base plinth to the table base itself via a huge housed tenon)
-Plate steel at top of base to connect LVL platform for top to slide upon. LVL also includes a continuous groove (both sides) to engage waxed maple runners attached to table tops
-59" x 132" top dimension, 59" x 182" when extended. Top is also 3.5" thick, back cut from a 1.375" presented leading edge (this to hide the operating hardware)
This thing was a one-off and a blast to build. The included pics here (I hope) are of the piece before built up edge and finishing, the base after finish and the assembled table right before shipment. Of course, and as usual, we didn't have time before crating to take great pics, and will beg (again, as usual) the client to share their photo shoot pics with us.
I hope you like, and find yourself encouraged to push the boundaries too.
I was thinking that an ellipse might be a good shape for the top, but it never once occurred to me to bolt the table to the ceiling. Well done!
Good humor there Zero Grav. Ya know, Ive always wondered why a photo would come through like that. Case in point the first two photos are upright and the third is defying gravity.
Your post really made me think @John! I'm really quite impressed with the solutions you came up with and this makes me really appreciate being a part of this community even more every time I come in and read the threads! Especially being in the moving business, I get questions from customers every once in a while about carpentry and I'm sure you guys will be able to help me out the next time I need some friendly advice!
Really good looking table man