I want to use a nice set of legs I recently acquired to make a table to use in my show. The legs are the kind that the center of the leg is at a 90 degree angle from the top. They're about 29-1/2 inches high; so the top of the table would be around 30 inches high. I only need the table to be about 18 inches wide to hold the props I need it to hold; but this would make the front legs only about a foot or so from the back legs.

Would such a table be reasonable stable? If somebody were to accidentally bump it in the wrong place, would it be prone to falling down? Is there some kind of formula for figuring out this sort of thing?

Thom
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The secret to table legs is that they have to be at the extreme edge of the corners. If they are not french design where the knee and foot stick out beyond the table top, then place closest to the corners as possible. Next there cannot be any play in the leg attachment. Meaning they do not move, they are solid in their place. If they are not very stable, then cross braces would be needed toward the bottom of the legs, to keep them from moving inward.

The table would still scoot if bumped, but not fall over. The props may go flying though.

Pick up an expensive books on table or google tables on the Internet. If they are the screw type of table legs from the Home depot, then attach with the plates sold for them or use T-Nuts to attach, that way they can be removed for transit.

This has been my experience.

If the table is 18" wide, why can it not be up 18" deep? I have one table that is 16" square at the top, and maybe 32" high, and it sits just fine.



One other tip is to pay attention to the center of gravity. Too much weight up high will make it unstable.

Thank you, gentlemen.

I'm afraid I mis-spoke (or mis-wrote). The table would be about 40 inches wide but only about 18 inches deep. Is there a way of determining if it will be top-heavy before I build it? How do I determine where the center of gravity will be?

Nice table, Michael.

Thom
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That really does not have anything to do with the table being steady. It all has to do with the legs holding up the top. It does not matter if it is narrow or square.

I'm sure there are scientific/mathematical methods for determining the center of gravity, but that's beyond anything I'd personally do. You can develop a sense for the basic physics, and the ratio between height and width. The taller the object in question, the wider the base needed to support the weight, unless the weight is lowered toward the bottom, rather than the top. I'm sure this doesn't help much, but as a general rule, follow Bill's advice and position the legs as close to the corners as you can.

The table I show above works just fine, but if it were twice as high and no wider than it is now, it would probably tip over easily.

Sometimes you won't know these things without first building a prototype.

Once the center of gravity falls past the legs, the table will fall over. Determining where the center of gravity (COG) is, is pretty difficult if not impossible without building the table! I guess it will be about where I've shown it on the attached sketch, but if the legs were heavy and the top light then the COG would move down, if the top is heavy and the legs light then it would move up. Also, placing stuff on the table will probably move the effective COG up.

..... then of course, a heavy table would be harder to "knock" while a light one would be easy...... but once the heavy one starts moving the momentum is likely to keep it going! - It's not an easy question!!!!

Click here to view/download attached file.

You could try building a scale model of it first which might allow you to get some idea of the center of gravity. It would be beneficial if your model materials matched what you would ultimately use, but doing a rough 1/40 or 1/25 scale model may not be too much work.

What you could do is to make a very thin aluminum "cross" type supports that extend in front and behind the table--they would look like this shape -- # (but perpendicular), and to the sides as well. You could use pieces of sheet aluminum, extending at least a foot in front and to the sides of the table. These aluminum pieces would be about 4" wide, crossing where the table legs will go.
You could have them marked, and quickly bolt them together before the show (to make them easy to transport).
This could be covered by a small carpet.

These bolts would stick up where the table legs are. You would drill the table legs (are they wood?) from the bottom up, to fit the diameter of the bolts.
So, when you go to a show, you take the flat aluminum supports together, arrange them in this shape --#--but at right angles, put them on the floor, and bolt them togther, with the bolts up. You would cover it with a dedicated carpet (would have to have holes for the bolts), and put your table over it. You would not have to worry about the table tipping over and making a mess of your props and possibly your show.
This way, you could have a table as narrow as you wanted, without worrying about the table tipping over easily.

I am no expert in building tables, but in a theater I once worked with a very narrow and tall table which we made very bottom heavy by having pieces of lead inside the legs at the very bottom. Granted, it was heavy to lug around but it really stayed put! I guess technically we lowered the center of gravity.

And there's your solution.

Here's the quick and dirty on stability.

1) The wider your table, the more stable.

The way it will be easiest to tip is always towards the shorter side. So if one side is 40 inches and the other side is 20 inches, it will tip more easily towards the 20 inch side.)

2) The lower the table, the more stable.

This is only because you are lowering your Center of Gravity (CG). So the post I quoted above is a correct solution for a very tall table. If you put all the weight in the bottom of the legs, then you can make your table very high without much risk of tipping over. Consider the child's playtoy - the punching bag with a sand bottom that always "rights" itself after being punched. The reason is because of the very heavy sand in the rounded base. Effectively, it has a CG on the floor which means the bag will always return.

So what you can do, with set dimensions, is build your table just as you want it. Now see if it tips over easily. If not, you worried for nothing. If so...you can fix it in one of three easy ways.

A) Place a "heavy" brace on the legs (so a cross piece that runs from leg to leg or even an extra "shelf") towards the bottom. The heavier this brace/shelf, the better balanced the table will be.

B) Hollow out the inside of the legs and place iron or some other heavy material in the bottom of the legs. It won't budge.

C) Screw the legs to your stage floor. Hey, I'm presenting solutions ... I didn't say they were all created equal!

Using a tripod helps also. As three legs are more sturdy on uneven ground than four.