I’m hoping someone can help me with some questions to know whether or not the table can be supported by this design and how to calculate the length of the support runners and the width necessary to prevent tipping/rocking along the width as well.
Table length and width ~90" x 36"
Angle of the cantilever arm (terminology?) either 130 degrees or 50 degree
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Which of the two designs from the elevation view would provide better support (could I use either as long as runners are long enough?) Which would require shorter runners [longer overhang]?
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What would the minimum width between the two support arms would I need to prevent horizontal tipping
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How do I calculate tipping weight on the end of the table (opposite of the support)
Material is wood. I found some figures for “E = modullus of elasticity” and for the wood I’m using it’d be between 1.6-1.7 and the user posted this note: units of measure are psi, values must be multiplied by 10^6.
This is all beyond my math skills, but am willing to try and learn! Thanks!
Michael, as a ChE. I’m not the right kind of engineer, but as a furniture builder I offer the following:
Which base is stronger: I think they are the same. You are squeezing the base between the top and the floor. Since the shape is the same, the forces should be the same as well.
Preventing tipping: I have always been conservative and tried to make the base at least 2/3rds of the dimension of the top. That said, is your table sitting on the floor and can it have a wider base plate that the cantilever arms attach to? Same for the arms attaching to the bottom of the top? You can give the appearance of a skinny support if you have attachment systems that actually spread the top and bottom load (and obviously, a strong enough “skinny” part). Almost all single pedestal tables are built in such a way.
Anyway, my thoughts.
One other point I didn’t address: While the strength of the support should be the same with either orientation, the tipping avoidance should be better with the top orientation. That one has more equal weight distribution applied to the floor arm.
If at all possible I’d like to not have arms that extend width wise for the upper or lower, but if need be I can definitely consider it.
Between the two cantilever arms on the floor will be a stretcher of minimal length to connect the two, but I would very much not like to have it extend past the runners.
2/3rd length wise or width wise? Length wise I can definitely do; however, width wise it would impede on the rolling a chair underneath and from an aesthetics POV imo.
If you’ve got other questions let me know.
Thanks for the advice.
I may just test this on Pine and see what happens. It’s got a lower modulus of elasticity but also a much lower Janka rating (wondering how these two affect one another for a project like this).
I just calculated the weight of various woods and the table top ranges from 55-75 lbs. I’m confident in the cantilever supporting this weight, but would ultimately want the weight of 200+ lbs on the opposite edge be able to be held up.
Just not at DMS since the woodshop committee has banned Southern Yellow Pine from the general stationary power tools
The old fashioned answer is scrap wood and a scaled mock up.
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Plywood it is then. I’m finding a MoE of 1.0-1.29 for plywood which is close to the woods I want to use. I figure if it can do what I want on plywood it’ll do what I want on the hardwoods
Just vectors.
Lots of vectors.
Zzzzzzz…
for reference: 
Strength is a funny word. It applies to a lot of things that get over simplified to “strength.” Design 1 is less tippy to the right, design 2 is less tippy to the left. The limitation in both designs is the moment on the joints:

90" is really long, you’re putting a lot of weight ~45" out. I have no idea how to analyze whatever joint you’re planning on using at the corners of the ‘c’. I would be impressed if you can beef it up enough to eliminate sagging and/or joint separation. Certainly not impossible.
I would make the width of the support a minimum of 1/3 of the width of the table.
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It could be made such that it sags into shape. The frame would basically be preloaded by the weight of the table top.
Another option would be use a clear polycarb leg, creating an “invisible” leg on the table to add strength.
If you are married to the cantilever beam concept I would also explore doing the lower joint like this:

By having a cable in tension with a turnbuckle you could adjust the tilt of the table top. The torsional load on the lower joint is also eliminated/minimised. You would also want some way to lock the joint in so when someone leans on the short side of the table it will not tip.
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