Hello, have been struggling with a pedestal table build for a client. It’s a single pedestal supporting a 1.5” thick Alder top 52” L x 39” W. The design was mutually chosen in order to fit into a small breakfast nook area. The first base I built was made from Sugar Pine. I started out with a 6”x6” block and cut out the shape on my old band saw. But as it was a new design I removed too much material and left some areas too narrow. With this original base the table top jiggled whenever you hit the corner. Also the diameter of the feet was not nearly big enough and the table was prone to tipping. So I built a second base. Luckily I had purchased a new band saw around that time so I went with all Alder wood for the base. This time I left a lot more material and the new pedestal goes from 3.5” thinnest to 6” at its thickest. I increased the foot diameter from 25” to 33” which along with added weight took care of the tipping issue. However the table still has a slight jiggle to it. Seems to start from the narrowest part of the pedestal which is up near the top. Wondering if there’s anything I can do to remedy this and stabilize the top jiggle just a bit more. Or if there’s any recommendation on a pedestal size that would work. Any advice would be appreciated, thank you.
Replies
By "jiggle" do you mean the commonly-found shaking of the top in the horizontal plane when the top is clonked on it's edge?
Such jiggles are a feature of single pedestal tables - a behaviour inevitable to some degree, given their design. There's no automatic counter-force to knocks on the top, as there is with a three or four-legged table, in which knock forces get distributed evenly around the top by the three or four legs, with the push back up the legs from the floor serving to quickly dampen vibrations.
There must be several factors that influence the amount of jiggle in a single pedestal table, including the inherent stiffness (or lack of it) of the wood used in the pedestal, it's effective diameter (probably the narrowest part, as you describe) but also the weight and diameter of the top. Heavier tops of larger diameter will tend to acquire and shed more angular momentum than lighter tops of smaller effective diameter, when knocked on their edge or corner.
I suspect that you may have to live with the jiggle - unless you want to redesign the table to not-jiggle as the primary or only attribute. In that case - give it four legs. :-)
But a more practical solution would probably be to greatly lighten the top. You could reduce the thickness to 3/4 but give the impression of a weightier top with a thicker rim, for example ..... . Counter-intuitively perhaps, less mass in the top will mean less rather than more jiggle.
Lataxe
That's a fairly large top. Two pedestals with three feet would probably work better.
The video was helpful. As Lataxe says, reducing the weight of the top would help. A thicker pedestal would also help. Building the pedestal as a box instead of cut from solid stock might add rigidity also.
This may be too late for what you're asking, but Tim Rousseau, one of my (many) favorite FWW teachers has an excellent video series on just this, how to build a pedestal table that is strong, sturdy, and not tippy or wobbly. Like you, I had to modify the size of the table to fit the breakfast nook for my son and his young family.
https://www.finewoodworking.com/videoworkshop/2015/07/pedestal-dining-table
I love to build more than design, so am always happy to use designs that others have worked out if they appeal to me. I may tweak them to make them mine, but appreciate the designs of others who have worked out the structural engineering.
Wow thank you all for the insightful responses this helps immensely.
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