Structures

This week Invention Squad built strong and stable structures. We looked at a variety of designed structures to see whether they were formed of linear (rods, bars, sticks etc.), planar (sheets) or block components.

Then we gave the kids a pack of playing cards and a pair of scissors each. Their task was to build any structure they wanted to- tables and chairs, houses and bridges and test them for their load bearing properties. Since we deliberately did not provide any glue or tape, one aspect of this design challenge involves exploring joints.

Here are some simple structures made by card slits that form potential support units for our structures.

These can be used to support a planar sheet made of multiple cards- which creates a (somewhat shakey) table,

or the first storey of a house,

or a beam bridge with two piers…

As everyone knows, the funnest part of building a structure can be demolishing it.  We tested our structures to see if they could support an elephant. This is a chance to observe how compression and tension forces act on a structure:

image taken from http://www.pbs.org/wgbh/buildingbig/bridge/beam_forces.html

It's also an opportunity to spot the weak spots in a structure, as it's collapsing.  The central point of a beam bridge (furthest from the piers) is always the weakest point.  This woven bridge (below) works quite well to add strength to the beam.

Enterprising use of card boxes and some trussing on the piers on this bridge (below).

Whoops! Back to the drawing board.

 How can we make that beam more sturdy? What would make those piers more stable and supportive?