# Design a hinge pin for a folding clothes line Part 1

Here you will design a hinge pin and wall anchors for a folding washing line.

Here you will design a hinge pin and wall anchors for a folding washing line.

It might help if you download the design specification in the Downloads section below in case you want to refer to it as you go.

This design task has been split into two parts.

The video for part 1 (this step) sets the scene and leads you through the process for designing the hinge pin. As you go, you can do calculations yourself if you like. They involve Free-Body Diagrams and equilibrium in two dimensions. In the end you will select an item from a list.

From this you will get the basic idea of how to use rotational equilibrium to solve a problem in two dimensional forces on a rigid object.

If you just watch the video it will take about 8 minutes. If you do the calculations it will take longer; how much longer depends on so many factors, but allow a total of 30 minutes.

The video for part 2 (the next step) leads you through the process for designing the wall anchors. You will see how different FBDs can reveal different forces – forces that are external on one diagram can become internal forces on another.

If you are running out of time when you have completed part 1, you could just review the video for part 2 to get the overall idea. But this is an important topic and it would be good to study it in detail if you can.

### Talking points

• Did you see the great importance of the extra equilibrium equation we got from considering twist?
• Can you think of other ways the pin joint could fail?