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Pedestal table stability3/21
I have read some discussions about pedestal table stability and designing to minimize tipping over. I have built pedestal tables before, but I want a more scientific way of calculating the parameters. In my CAD program it is easy enough to determine the center of gravity using oak density to determine table weight and putting a 250 Lb. person on the edge. Putting weight in the base shifts the CG to a better place. The question is whether the CG needs to absolutely be inside the base, or if it is outside when does it become unstable. This is a good head scratcher ! I have attached a model for argument's sake. The top is 42" square and the base is a pyramid.
It would be nice to be more scientific, but what are you going to use for loads calculations on the top? My wife puts a lot of load on a table since her knees are shot (and she's not a small gal anymore either. she never reads this site, so I'm okay here!) Most people put enough load on to just stabilize themselves. You are going to have to do some measurements, then go from there.
How about this as a parameter:
If a 288 lb person decided to sit on the edge of that 42" table, he will get exactly what he deserves, a lesson in respecting objects. People are not completely stupid - or at least we cannot design for total Idiocracy.
If someone - anyone - sees a large farm type table with four stout legs and substantial aprons and a thick top, they may be tempted to lean against it - or perhaps even sit on it. They read it as able to withstand that 'use'.
If they see a 42" round table, even with that monstrous base, they read it as lighter and more fragile, and would not sit on it. This is pretty basic stuff, I know. But if they do not understand that, it is not your responsibility to design for their lack of common sense.
Beyond that, it is all about form vs function, with the sense of an artist. The 11" overhangs on the drawn table are knee knockers, not enough room for comfortable sitting - OK for casual use.
What is wrong with following historical precedent? Has not all this been worked out before? You don't need to have 18th century details to see that the designs of a Hepplewhite double pedestal table will solve many of the goals of table stability, appearance of stability, and leg/foot room.
I can understand the desire for input on pedestal design. My wife has an old table handed down in her family (that it wasn't high end is obvious). When you add even one leaf and the people at the ends lean on it, as one normally would, it rocks a little. Add the second leaf and it becomes part of a circus act.
The obvious solution would be a pedestal which splits when the table is pulled apart, moving the supports out as each leaf is installed.
What David said. Common sense cannot be taught. You got it or yer..