IES Gómez-Moreno – Departamento de Tecnología 1st year ESO – Structures: cubes project

Construction and evaluation of structures

Structures can be made from a wide range of materials, from steel to paper. Each material has advantages and disadvantages.

Once you have chosen the appropriate material for the structure you want to build you must think about the loads and forces it will have to support, the resistance of the material, its price and durability, and the aesthetic qualities it will bring to the project.

In this section you will learn how to build frame structures (very light structures using bars or beams) from different materials. You must choose materials that are easy to find and use, such as paper, cardboard and plastic.

You must build two cube-shaped frame structures (with 10 cm. edges). They must be made at home and brought them to class before the day ______. Don’t forget to put your full name and class (you have to invent a way to put it in the structure). You can choose the material you prefer between paper, cardboard and plastic (see the following pages to know how to work with each of these materials)

A: Cube with no extra bar between corners / B: Cube with extra bar between corners. You will build a triangulated frame structure (truss). A triangle is a shape that cannot be deformed. Using triangles results in more rigid structures, that is, structures that cannot be easily deformed.

You can even build a more rigid frame if you build the sides with two extra bars like in the picture on the bellow. It is a little bit more difficult to construct, but it is worth the effort!

So, you have to build

·  One cube with no extra bars

·  One cube with one or two extra bars per side.


Paper

Paper structures (recycled paper, if possible) are made by turning normal sheets of paper or newspaper into resistant bars:

1.  Roll each sheet starting at one of the corners

2.  Glue the end to the centre part of the rolled tube

3.  Cut off the ends (they are weaker)

Tricks to get perfect structures

·  The thinner the paper, the easier it will be to roll. You can roll several sheets together to make it thicker and more resistant.

·  To join several bars, you can put them inside each other or glue together smaller tubes at the end.

·  Sometimes to join two bars it is useful to squash the ends first so they are flat.

·  In some joints you will have to cut the ends first into a bevelled edge (triangle-shaped cut) so that they fit perfectly.


Cardboard

Cardboard has an interesting property: its resistance changes depending on the direction of the internal folds. It is more resistant to compression if it is folded lengthways.

With cardboard it is possible to build triangular or square shapes, make L-shaped rods or simple strips with which to make the structures.


Plastic

You can use plastic straws (like the ones you use to drink from a tall glass) to build structures. They are cheap and easy to find.

You can use cardboard triangles on the corners. It is very easy and it makes the joints stronger. To do it, cut small triangles of cardboard and glue them to the straws that form the joint.

To make a longer straw by joining two together, put glue inside the ends of the straws you want to join and put a tube of paper inside them. To make an angle, you can bend the tube of paper.

If you want to tie the straws forming a cross you can use a piece of string, tying a knot that will hold the two straws together.