[Images: Fallingwater cantilevered via wikipedia; amnesta.net /Artwork: designslinger]

In yesterday's post I wrote about three residential projects whose architects used the cantilever
as an integral part of their design. Frank Lloyd Wright's, Fallingwater is probably the most recognized house in America, and the most popular use of the cantilever in architecture.

[Images: Diving board; Alvar Aalto chair, akahnvexgala via flickr /Artwork: designslinger]

How did he get all that concrete to hang out over the waterfall without collapsing into it?
The principle is really pretty simple. If you want to suspend something into space, just make sure that it is attached solidly to something that can handle all the stresses placed on it. (The red arrows). Think of a diving board as one of Wright's balconies. A diving board is firmly attached near the rim of a pool, yet it hangs in space and can support the weight of a human being. It has much more spring (blue arrows) in it than a balcony, but even something as solid as concrete has to have a little give, or it will crack. The same idea applies to the chair because the seat is cantilevered from the frame base.

[Images: Sequoia tree via wikimedia; Cantilever rock, trekearth.com /Artwork: designslinger]

Tree limbs cantilever out from their trunk. The trunk provides the first line of support, the area
where the limb projects from the trunk is next in line. If you've ever climbed a tree, you feel most comfortable standing in the pocket where they join together. As you climb out on to the branch, you still feel pretty secure because you're halfway from the trunk and the branch is still fairly thick. But, the farther from the trunk, or the thinner the branch, the more likely it will break and down you'll go. This is one of the dangers when building a cantilever, making sure that your support structure can sustain the weight and flex of the overhanging structure.

The rock that seems to defy gravity is located in Glyder Fawr, Wales. It extends 25 feet beyond
the cliff face and doesn't fall over because it is perfectly balanced in relation to the rock below it. Because nature created this balancing act, the rock is not secured by, or to, anything but is in perfect alignment and can support itself along with the weight of the thousands of tourists who walk out to it's edge.

After reading this post, if you are inclined to create your own cantilever project, I suggest you
start with something modest, like two small pieces of wood. Place one end of the first piece on a flat surface like a table top. Stand it up in a vertical position and take the second piece and place it on top of the first. Hold the vertical piece in one hand and slowly slide the top piece out until it falls. As long as it stayed suspended in air, it was cantilevered. Unless you are an architect or engineer, or very well acquainted with the ins and outs of construction, I don't recommend attempting anything beyond the two pieces of wood experiment because it may end in a messy pile of debris.