My 6 year old son built this structure with three supporting columns
on the bottom. When time came to destroy it in a spectacular
fashion, I suggested pulling out the middle column so that it
would crash inward. he did just that, but it did not crash. I have
no idea how it may be still standing, but photos prove that it did
There are absolutely no hidden gimmicks, chewing gum secretly holding
things together, etc. This post is NOT a joke.
It would appear to, but the right hand stack bears on the lower
horizontal block and uses the tapered corner as a fulcrum 'prying up' on
it, at least that's my guess. You could probably never build that by
It's a Linux world....well, it oughta be.
I still haven't started that project! I've got one paying and two
'freebie' jobs to run across the lathe before I can tear it down to do
the retrofit. I've got it all imagineered though...
It's a Linux world....well, it oughta be.
The outside blocks on the third level are also outside the line of the
cylinders on the second level, so there is a lifting effect against the
3&4 level center posts as well.
The dark Blue block has just enough width to keep the orange from falling.
More important, in this same regard, is that for the center flats on the
top two levels to be able to fall down in the center (aka put pressure on
that middle cylinder), they would have to lever up the bottom horizontal
flat using the inside edge of the those two cylinders they are resting on.
Because there are two columns of outside edge flats and only one column in
the middle, this fulcrum effect only has to allow each outside column to
lift 1/2 the weight of the center. So to be balanced, the fulcrum holding
up the bottom flats needs to be 1/3 the way from the outside edge. But the
inside edge of the cylinders are both more than 1/3 of the way in, so it
can't fall from the center.
In other words, if you pull out that middle cylinder on the second level,
the top still won't fall as far as I can tell. Is the structure still
standing? Try pulling out that middle cylinder and see what happens. I
bet it all still stands. Or, just push down on that center cylinder a
little bit and see if it separates from the blocks above. If it does, then
you should be able to pull it out. If not, you might have to slide that
red cylinder in just a little bit more towards the center and then it
So this means the angle blocks don't need to hold up the entire top
structure. They only need to hold the weight of that center white
Looking at the left two cylinders (white and blue) you see a fairly strong
stack and with the help of the added weight of the entire top structure.
For the orange block to fail by falling down, it would create a fulcrum on
the right (inside) edge of the blue block below, and lift the column on the
left edge of the orange block. That looks like it's creating about a 3 to
1 ratio by my measurement. But since all it has to hold up, is the 1/2 of
the center white cylinder and the outside column has the weight 1/2 the
entire top structure, a 3 to 1 ratio is far more than what is needed to
keep it from falling. It could probably keep standing with a 6 to 1 lever
Same sort of thing for the right side with red cylinder. Becks of the
position of the red angle board, it's actually got a bit more leverage on
the outside, but also has to lift from the far end of the red board which
is farther, but I still calculate about a 2.5 to 1 ratio. So again, the
weight of the outside column still has far more leverage on the red board
than what is needed to hold up the center white cylinder by my calculation.
As far as I can see, you can pull out that center white cylinder and it
will still stand.
The thing that makes it all work is just what Stuart said. The top two
levels of flat blocks is positioned on the cylinders so that the center
support isn't needed at all. As such, there's no need for the center to
hold any real weight.
It's deceptive looking because we tend to look at the center of the
cylinders to judge how the structure is balanced, but to analyze how it
fails, you have to look at the outside or inside edges of the cylinders
which would the fulcrum when it started to fall. So in your mind, replace
those thick cylinders on the second level with thinner blocks positions
near the inside edge of the cylinders, and you can get a better visual
image of how the top is balanced so that there's little to no weight on the
center cylinder. And without the need for the center to hold up the weight
then you can understand why it didn't fall down when you removed a center
At first glance, it sure looks like it shouldn't be standing. :)
Interesting! The blocks remind me of my childhood when Santa would bring us
kids a big box of wooden building blocks every year for Christmas. We built
stuff for days upon days for years upon years. Many, many years later I
found out the fabulous blocks were firkin' brush blocks!
That is interesting. Some others have pointed out what I was thinking, but
it also reminds me of one of the things I saw in a beginning engineering
class decades ago, which showed the strange behavior (to us) of some ancient
architectural structural designs. If you analyze a dry-laid stone-block
wall, you eventually see that it's far more stable than you might think,
because of the same effect that is making your son's toy project stay up.
In the row of three round columns, the downward force on the outer two is
considerably more than that on the center one, based on how the weight is
distributed above them. On the bottom row, the actual length of the lever
applied from the two round columns is longer than you might think. On the
right (red) one, it extends roughly from the outside edge of the round
column. That's the one that's probably holding up most of the weight. But
any contribution from the other one helps.
On Sun, 26 Aug 2007 19:06:28 -0500, Ignoramus19259
At the second row the red column on the right is hanging over the edge
of it's support. The row above notice how the columns are outside of
the columns below them. That is helping transfer the load to the
outside. In order to rotate down those red and orange horizontal
blocks have to raise up at the outside up against the weight of
everything above. If you start taking pieces off the top it'll
That kid is going to own you at Jenga ;)
I'm working on a huge set of blocks for my niece right now. Well,
part of it anyway. It's gonna be a while before she gets it all, but
she's only 5 months old so I've got some time.
- That kid is going to own you at Jenga ;)
Speaking of Jenga...
I was camping in the infield for the NASCAR Bud at the Glen many years
A group of guys camping near us had brought a Jenga set in the back of
a pickup truck, along with a few step ladders.
The Jenga set was made of 4 x 4 PT posts, cut to ~ 3 ft lengths.
They'd put their beer down, grab a 4 x 4 and climb up the step ladder
to put up it on top. I don't recall any serious injuries, but like I
said, it was long time and a lot of beers ago.
Indeed. But, looking at it, I think I see what's happening.
The two orange pieces at lower-right are the key, I think. The weight
that the orange cylinder is bearing, is pushing down on the far end of
the orange trapezoid. So that gives an up force to the other end of it,
because of the way the right end of the orange trapezoid then tries to
pivot on the top of the blue cylinder. If the orange cylinder was 1/4"
further left, the whole thing would have collapsed to the center as
expected, I think. Working off of this image, anyway:
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